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Table of Content
28 May 2021, Volume 33 Issue 5
    Comparison of catalyst-coated membranes and catalyst-coated substrate for PEMFC membrane electrode assembly: A review
    Bee Huah Lim, Edy Herianto Majlan, Ahmad Tajuddin, Teuku Husaini, Wan Ramli Wan Daud, Nabilah Afiqah Mohd Radzuan, Md. Ahsanul Haque
    2021, 33(5):  1-16.  doi:10.1016/j.cjche.2020.07.044
    Abstract ( )   PDF (4032KB) ( )  
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    Catalyst-coated membranes (CCMs) have gained popularity among membrane electrode assembly (MEA) fabricators for their abilities and advantages compared with those of other methods, such as catalyst-coated substrates (CCSs). CCMs show a profound new analysis for reducing platinum (Pt) catalyst loading. In addition, they increase the total number of reactions that occur on the MEA because of their active area amplification, which leads to an improved catalyst-utilization efficiency rate. Moreover, several characteristics are involved in the MEA fabrication methods. Material-manufacturing effects with regard to catalyst inks and analysis of the overall performance of MEAs prepared by the CCM and CCS methods are deliberated. This deliberation emphasizes the practical approaches in minimizing performance deterioration during the fabrication of MEAs using the CCM method and converses the commercialization of the CCM fabrication method toward developing an end product. Novel research is required for MEA fabrication using the CCM methods to ensure that the fuel cell performance is improved. Therefore, this review is focusing on the pros and cons of both distinguished methods, that is, CCM and CCS fabrication, for better comparison.
    Fluid Dynamics and Transport Phenomena
    Experimental investigation of different brines imbibition influences on co- and counter-current oil flows in carbonate reservoirs
    Pouyan Ahmadi, Mohammad Reza Aghajanzadeh, Masoud Riazi, Mohammad Reza Malayeri, Mohammad Sharifi
    2021, 33(5):  17-29.  doi:10.1016/j.cjche.2020.08.028
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    Imbibition of water, as wetting phase in oil-wet fractured carbonate reservoirs, plays a key role in fluid flow between matrix and fracture system. The type of injected seawater and its chemistry would profoundly influence the imbibition process. In this study, the impact of smart water (a brine that its ions have been adjusted to facilitate oil recovery) and low salinity water on co- and counter-current imbibition processes for oil-wet carbonate cores has been experimentally investigated. The results show an increase of about 10% in oil recovery for co- and counter-currents for smart seawater imbibition compared to that of low salinity seawater. In addition, as a result of the influence of co- and counter-current on each other, by co-current removal from one core face, the countercurrent in the other face would be intensified by as much as about 75%. A close examination of different lengths (5, 7 and 9 cm) of carbonate cores with the same permeability revealed that by decreasing porous medium length, the amount of counter-current producing oil would be decreased so that in the 5 cm core, counter current oil production will not happen. For similar core lengths by increasing permeability, the share of counter current flow would be decreased approximately 18% since the capillary pressure could not overcome non-wetting phase viscous forces. Considering the role of matrix length along with a modified brine (which is designed according to the matrix mixture) strengthen the relevant mechanisms to have more oil production so that the higher thickness of matrix causes the higher amount of co-current oil producing and consequently more total recovery.
    Experimental investigation on the effect of surface characterization of electrodes on the gas bubble dynamics in electrolyte flow and performance of FLA batteries by using PIV
    Saeed Nahidi, Iraj Jafari Gavzan, Seyfolah Saedodin, Mahmoud Salari
    2021, 33(5):  30-39.  doi:10.1016/j.cjche.2020.09.062
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    In the flooded lead_acid batteries (FLAB), gas bubbles are initially formed on the surface of the electrodes, which are produced by electrochemical reactions, and then released into the electrolyte. In the present investigation, the effect of surface characterization of electrodes of FLAB on the gas bubble dynamic parameters in the electrolyte flow at different charging/discharging rates (C-rates) are studied utilizing particle image velocimetry (PIV) method. The results show that the capacity of FLAB have a linear behavior due to changes in each of the two parameters of the surface characterization of electrodes and the Crate. At all State of charges (SOCs) of FLAB cells in different tests, increasing average roughness (Ra) and average wavelength of the roughness (λa) in the electrode surfaces, results in an increase in average bubble diameter and bubble rising velocity. Nevertheless, a sharp decrease in the void fraction of bubbles within the electrolyte was observed due to the increment in λa and Ra. Also, the effect of the rising movement of gas bubbles within the electrolyte on the average electrolyte velocity pattern in the gap between the electrodes by changing the surface characterization of electrodes are investigated in detail.
    Separation Science and Engineering
    Mechanically activated starch magnetic microspheres for Cd(II) adsorption from aqueous solution
    Xinling Xie, Xiaona Zhao, Xuan Luo, Tongming Su, Youquan Zhang, Zuzeng Qin, Hongbing Ji
    2021, 33(5):  40-49.  doi:10.1016/j.cjche.2020.06.003
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    Magnetic starch microspheres (AAM-MSM) were synthesized via an inverse emulsion graft copolymerization by using mechanically activated cassava starch (MS) as a crude material, acrylic acid (AA) and acrylamide (AM) as graft copolymer monomers, and methyl methacrylate (MMA) as the dispersing agent and used as an adsorbent for the removal of Cd(II) ions from aqueous solution. Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM) were used to characterize the AAM-MSM adsorbent. The results indicated that AA, AM, and MMA were grafted to the MS, and the Fe3O4 nanoparticles were encapsulated in the AAM-MSM adsorbent microspheres. The adsorbent exhibited a smooth surface, uniform size, and good sphericity because of the addition of the MMA and provided more adsorption sites for the Cd(II) ions. The maximum adsorption capacity of Cd(II) on the AAM-MSM was 39.98 mg·g-1. The adsorbents were superparamagnetic, and the saturation magnetization was 16.7 A·m2·kg-1. Additionally, the adsorption isotherms and kinetics of the adsorption process were further investigated. The process of Cd(II) ions adsorbed onto the AAM-MSM could be described more favorably by the pseudo-second-order kinetic and Langmuir isothermal adsorption models, which suggested that the chemical reaction process dominated the adsorption process for the Cd(II) and chemisorption was the rate-controlling step during the Cd(II) removal process.
    Robust, fluorine-free and superhydrophobic composite melamine sponge modified with dual silanized SiO2 microspheres for oil-water separation
    Ruilong Zhang, Zhiping Zhou, Wenna Ge, Yi Lu, Tianshu Liu, Wenming Yang, Jiangdong Dai
    2021, 33(5):  50-60.  doi:10.1016/j.cjche.2020.06.006
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    Massive oily wastewater discharged from industrial production and human daily life have been an urgent environmental and ecological challenge. Superhydrophobic materials have attracted tremendous attention due to their unique properties and potential applications in the treatment of wastewater. In this study, a novel superhydrophobic/superoleophilic composite melamine sponge modified with dual silanized SiO2 microspheres was fabricated simply by a two-step sol-gel method using vinyltriethoxysilane and hexadecyltrimethoxysilane as functional agent, which exhibited a water contact angle of 153.2° and a water sliding contact angle of 4.8°. Furthermore, the composite sponge showed the excellent oil adsorption performance and the compressive elasticity reaching up to 130 g·g-1 of dichloromethane and 33.1 kPa of compressive stress. It was worth noting that the composite sponge presented the excellent separation efficiency (up to 99.5%) in the processes of continuous oil/water separation. The robust superhydrophobic composite melamine sponge provided the possibility with the practical application for oil-water separation.
    Efficient adsorption to hexavalent chromium by iron oxalate modified D301: Characterization, performance and mechanisms
    Dongmei Jia, Huamin Cai, Yongzheng Duan, Jiangbao Xia, Jia Guo
    2021, 33(5):  61-69.  doi:10.1016/j.cjche.2020.06.031
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    Chromium is a common harmful pollutant with high toxicity and low bearing capacity of soil and water. Excellent salinity resistance, a wide pH range, and high regeneration capacity were essential for qualified adsorbents used in removing hexavalent chromium (Cr(VI)) from polluted water. Herein, iron oxalate modified weak basic resin (IO@D301) for the removal of Cr(VI) was prepared by the impregnation method. The IO@D301 was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Owing to abundant amine, carboxyl groups and iron ions existing on the surface, IO@D301 possesses high adsorption and salinity resistance capacity for Cr(VI). The maximum adsorption capacity of IO301 towards Cr(VI) reached 201.30 mg·g-1 at 293 K and a pH of 5. The adsorption equilibrium was well fitted by the Freundlich model, and the adsorption process was described by the pseudofirst-order kinetics model as spontaneous and exothermic. The mechanism may be identified as electrostatic attraction, coordination, and reduction, which was confirmed by FT-IR and X-ray photoelectron spectroscopy.
    One-step fabrication superhydrophobic sand filter for capillary-driven separation of water-in-oil emulsions
    Bao Wang, Chaolang Chen, Zhaoxin Li, Jianfeng Wu, Xianglou Liu, Jiadao Wang
    2021, 33(5):  70-75.  doi:10.1016/j.cjche.2020.07.012
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    The efficient separation of water-in-oil emulsion is of significance in environment and energy filed, and it has become a world-wide challenge. Herein, we have presented a one-step, facile and low-cost approach to prepare superhydrophobic sands for efficient separation of water-in-oil emulsion. The as-prepared sand layers possessed a water contact angle higher than 151°, demonstrating their superior superhydrophobic property. Besides, the as-prepared sand layers could separate water-in-emulsions with separation efficiency up to 99.7%, which is superior to both traditional and superwettable filtration membranes. The effect of thickness of sand layer on separation performance was also investigated. The results showed that the filtration flux decreased with the increased of filtration thickness while the separation efficiency increased. The as-prepared sand layer proposed by this study is a processing candidate for separating water-in-oil emulsion in practical industry. Additionally, the as-prepared superhydrophobic sand fabrication method also provides an alternative for desert water storage.
    The phase behavior of n-ethylpyridinium tetrafluoroborate and sodium-based salts ATPS and its application in 2-chlorophenol extraction
    Shuai Xu, Qi Zhu, Shaojie Xu, Manjing Yuan, Xuliang Lin, Wenjing Lin, Yanlin Qin, Yuliang Li
    2021, 33(5):  76-82.  doi:10.1016/j.cjche.2020.07.024
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    In this paper, the aqueous two-phase systems (ATPS) containing n-ethylpyridinium tetrafluoroborate ([EPy]BF4), sodium-based salts, and water were studied and the extraction efficiency of 2-chlorophenol was measured to study the ATPS performance in extracting phenolic compounds. The binodal curves of [EPy]BF4 + sodium carbonate (Na2CO3) ATPS and [EPy]BF4 + sodium dihydrogen phosphate (NaH2PO4) ATPS have been determined at 308.15 K, 318.15 K, and 328.15 K and atmospheric pressure. After getting good correlation with Merchuk equation, the binodal curves together with gravimetric method were used to calculate the tie-lines data. Furthermore, the reliability of tie-lines data was verified using Othmer-Tobias and Bancroft equations. Then, the salt influence and temperature influence on the phase behavior were discussed and the results show the salt-outing ability of Na2CO3 is better than NaH2PO4. With the aim of studying the ATPS performance in extracting phenolic compounds, extraction efficiency for 2-chlorophenol at different temperatures were studied and the results show that [EPy]BF4 + Na2CO3 ATPS is preferred than [EPy]BF4 + NaH2PO4 ATPS in applications.
    Experimental and numerical analysis of a demister with vortex generators
    Laishun Yang, Minghai Xu, Jianjun Wang, Lei Song, Jianxing Wang
    2021, 33(5):  83-95.  doi:10.1016/j.cjche.2020.07.045
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    An improved wave-plate demister equipped with vortex generators (VGs) has been proposed for wet flue gas desulfurization systems (WFGD) in this work. Numerical and experimental methods were used to evaluate the effect of VGs on the separation of small droplets. Five types of wave-plate demister with different VGs were analyzed. The vortex generators in question included rectangular plates, semi-elliptical plates, square tubes, round tubes, and triangular tubes, respectively. In order to explain the strengthening mechanism, the distribution of flow field, secondary flow, and droplet trajectory were shown, and the effect of VGs on the flow field in the demister was discussed in depth. The simulation results show that the separation performances of the demisters with VGs were significantly improved over that of the initial demister, and the accompanying pressure drop was small. For the vortex generators studied, the rectangular plate fully demonstrated its superior separation performance, followed by semi-elliptical plate. The strengthening effect of VGs was tested through experiments. Experimental data reveal that the average droplet diameter (D50) at the outlet of the demister with a vortex generator can be reduced to 23.13 μm, whereas this value for the initial demister can be maintained at 32.07 μm. Moreover, compared with the original demister 0.81, the overall separation efficiency of the improved demister was improved to 0.92.
    Enantioseparation of 3-chlorophenylglycine enantiomers using Mandyphos-Pd as chiral extractant
    Xiong Liu, Shuhuan Chen, Yu Ma, Wenjie Xiao
    2021, 33(5):  96-103.  doi:10.1016/j.cjche.2020.08.009
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    Chiral extractant plays a key role in chiral extraction, and considerable efforts have been undertaken for the development of new and efficient chiral extractants in recent years. This work demonstrated for the first time that chiral ferrocenyl diphosphine ligand (Mandyphos-Pd) had considerable ability to enantioseparate 3-Chlorophenylglycine enantiomers with separation factor (α) of 2.64. Mandyphos-Pd concentration and pH had significant influences on enantioselectivity, while operating temperature showed less influence. The extraction experiments can be performed at room temperature (20 ℃) which had the advantage of energy saving. After optimization, the highest performance factor (pf, 0.08376) was obtained at the condition of pH 7.8 and Mandyphos-Pd concentration 1.2 mmol·L-1. According to the experimental results, the possible recognition mechanism was discussed.
    Molecular dynamics simulation of small gas molecule permeation through CAU-1 membrane
    Mingming Zhai, Tomohisa Yoshioka, Jianhua Yang, Jinqu Wang, Dinglin Zhang, Jinming Lu, Yan Zhang
    2021, 33(5):  104-111.  doi:10.1016/j.cjche.2020.08.048
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    CAU-1 is one of aluminum-based amine-functionalized Metal-Organic Frameworks (MOFs). Gas permeation and separation behaviors through CAU-1 membrane were simulated by the dual-control plane nonequilibrium molecular dynamics (DCP-NEMD) method. The thickness of membrane was 3.55 nm. Gases CO2, N2, CH4, H2, He, Kr and Xe were chosen for the calculation in both single component and binary mixtures. The permeation process was calculated in grand canonical (μVT) ensemble with periodic boundary conditions (PBC) in x- and y-directions at different temperatures. The calculated permeance of H2, CH4, N2, CO2 and Kr decreased with increasing temperature in both single and binary system, while that of Xe with kinetic molecule of 0.41 nm increased with increasing temperature. It shows Xe permeation is governed by activated diffusion. The simulated separation factors of CO2/N2 and CO2/CH4 of 4.2 and 1.3 respectively were lower than the experimental ones when only considering van der Waals interaction. Further consideration of electrostatic potential leads to improved calculation CO2/N2 and CO2/CH4 separation factor of 23.0 and 12.9 respectively that were consistent with the experimental ones of 26.2 and 14.8. It suggests the necessity of considering the Coulomb interactions between CO2 and NH2-on the pore wall of CAU-1 for permeation of CO2. For H2/N2 and H2/CH4 the ideal selectivities also keep consistent with our experimental results. Interestingly, the simulated separation factor for noble Kr/Xe reaches infinite, predicting that CAU-1 membrane possesses potential separation properties for radioactive Kr/Xe.
    HPLC and GC methods development for the analysis of key intermediate for synthesis of dicamba
    Zhenming Zhang, He Zhao, Xiaohui Wang, Weiming Ni, Fengsheng Gao, Jianrong Wang, Minjin Liu, Yongli Li
    2021, 33(5):  112-117.  doi:10.1016/j.cjche.2020.09.046
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    The microreactor based hydroxylation process of 1,2,4-trichlorobezene for producing 2,5-dichlorphenol, the key intermediate of dicamba, is energy efficient and cost effective. But the 2,5-dicholorphneol is present in a mixed state after production. The reaction mixture contained the main by-product 2,4-dichlorophneol, low-content by-product 3,4-dichlorophneol, and other impurities. The difficulty in separation and analysis limits the application of this process widely. The current work aimed at establishing effective analysis methods by gas chromatography (GC) and high performance liquid chromatography (HPLC). The GC method was not able to separate 2,5-dichlorophenol and 2,4-dichlorophenol completely, but the developed HPLC method worked efficiently. The linear correlation coefficients of 2,5-dichlorophenol and 2,4-dichlorophenol were both higher than 0.999, and the average recovery was 100.33% for 2,5-dichlorophenol and 100.13% for 2,4-dichlorophenol, respectively. The relative standard deviations from precision tests were both less than 1%. The contents of 2,5-dichlorophenol and 2,4-dichlorophenol were determined with external standard method. The HPLC method has the advantages of simple operation, good separation efficiency, high accuracy and precision, and was successfully applied for both qualitative and quantitative analysis of 2,5-dichlorophenol and 2,4-dichlorophenol of the sample solution.
    Exploring the methods on improving CH4 delivery performance to surpass the Advanced Research Project Ageney-Energy target
    Weichen Zhu, Yuxuan He, Minman Tong, Xiaoyong Lai, Shijia Liang, Xu Wang, Yanjuan Li, Xiao Yan
    2021, 33(5):  118-124.  doi:10.1016/j.cjche.2020.10.035
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    CH4 storage associated with adsorbed natural gas (ANG) technology is an issue attracting great concern. Following the Advanced Research Project Agency-Energy (ARPA-E) targeted deliverable capacity of 315 cm3·cm-3 (STP), hundreds of thousands of materials have been experimentally or theoretically evaluated, while the best results still show a 35% gap from the target. Moreover, recent theoretical research reveals that the target is beyond the possibility that real materials can be designed. To get rid of the awkward situation, we make attempts on investigating the CH4 delivery performance under other operation conditions. Methods of raising the discharge temperature (to infinite high) or elevating the storage pressure (to 25 MPa) have been proved to show limited effectiveness. In this work, it is found that the ARPA-E target can be achieved by using a decreasing storage temperature strategy. By taking 280 CoRE (computation-ready, experimental) COFs (covalent organic frameworks) as ANG materials, when reduce the storage temperature to 190.6 K, the highest deliverable capacity can reach 392 cm3·cm-3 (STP), and 16.1% CoRE COFs can surpass the target. The target is also achievable when storage at 220 K. Structure performance relationships study shows strong correlation between deliverable capacity and void fraction. Hence, 120 hypothetical COFs are generated to ascertain the optimum void fraction. In addition, the performance of 2D-COFs can be greatly enhanced by increasing the interlayer spacings, e.g. CH4 deliverable capacity (storage at 190.6 K) of ATFG-COF can be improved from 239 to 411 cm3·cm-3 (STP) when interlayer spacing is enlarged to 1.65 nm.
    Separation of As and Bi and enrichment of As, Cu, and Zn from copper dust using an oxidation-leaching approach
    Erjun Zhang, Kanggen Zhou, Wei Chen, Xuekai Zhang, Changhong Peng
    2021, 33(5):  125-131.  doi:10.1016/j.cjche.2021.03.016
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    Copper dust with high arsenic content is a hazardous waste that should be treated properly. Herein, the copper dust is oxidized, leached, and separated at room temperature and atmospheric pressure. To separate As and Bi, part of As(III) in copper dust is oxidized to As(V), so that most of the As, Cu, and Zn elements enter the solution and the Bi remains in the leaching residue. Also, the influence of several factors, such as H2SO4 dosage, H2O2 dosage, liquid-solid ratio, leaching temperature and leaching time, on the leaching percentage of As, Bi, Cu, and Zn is systematically investigated. The optimal conditions are obtained as follows: liquid-solid ratio of 3:1, H2O2 dosage of 10 ml/50 g (dust), H2SO4 dosage of 4.5 ml/50 g (dust), leaching temperature of 85 C, and leaching time of 3 h. Under these conditions, the leaching percentage of As, Cu, Zn, and Bi is found to be 97.39%, 96.11%, 97.32%, and 2.40%, respectively. For further recovery of As from the leaching solution, the one-step recycle leaching of the leaching solution is performed to increase the concentration of As in the recycled leaching solution. The concentration of arsenic in the recycling leaching solution is found to be 79.63 g·L-1, which is beneficial for the study on further recovery of As2O3.
    Catalysis, Kinetics and Reaction Engineering
    Influence of extra-framework Al in Fe-MOR catalysts for the direct conversion of methane to oxygenates by nitrous oxide
    Shenglai Li, Lisong Fan, Lina Song, Dangguo Cheng, Fengqiu Chen
    2021, 33(5):  132-138.  doi:10.1016/j.cjche.2020.06.007
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    Iron-containing zeolites play an important role in the selective oxidation of methane to oxygenates by nitrous oxide. A solid-state ion exchange method is adopted to prepare Fe-MOR zeolite catalysts with different amounts of extra-framework Al. EPR spectra and UV-vis spectra show that the percentage of iron ions in tetrahedral or octahedral coordination increases while those of clustered Fe species decrease by the addition of extra-framework Al species. Nitrous oxide titration reveals that more active Fe centers are formed, which promote the nitrous oxide consumption. The number of active centers in the catalyst with the introduction of extra-framework Al is about four times that of the catalyst without the addition of extra-framework Al. Due to this, there is an increase in the methane conversion, total selectivity and yield of oxygenates.
    Formation kinetics of polyoxymethylene dimethyl ethers from methylal and trioxane with little water
    Xiaofei Qin, Sen Lei, Xubin Zhang, Chen Cao, Feng Xin, Honglin Chen, Xiaoming Zhang, Yachen Yin, Guilian Wu
    2021, 33(5):  139-146.  doi:10.1016/j.cjche.2020.06.011
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    Polyoxymethylene dimethyl ethers (CH3-O-(CH2O)n-CH3, PODEn, n>1) can be added to diesel to reduce air pollution caused by incomplete combustion. Driven by this need, a cost-effective and efficient synthetic route is presented and investigated by this work for the production of PODEn, which are formed from methylal and trioxane with low water content (b10 %(mass)) over HZSM-5 catalyst in a batch slurry autoclave at the temperature from 353.15 K to 393.15 K. The reaction rate laws including the PODEn and byproducts of polyoxymethylene hemiformals (HFn), polyoxymethylene glycols (MG), methanol (MeOH) and methyl formate (MF) are developed. The rate constants of propagation step (k6) and depolymerization step (k-6) are assumed independent on polymerization degree of PODEn. The rate of reaction is proportional to the content of the catalyst (Wcat) for the catalytic reaction within the scope of the study. All kinetic parameters were estimated by combining genetic algorithm and least square regression to fit experimental data well. This work is valuable for process optimization and reactor design.
    Strong interfacial charge transfer between hausmannite manganese oxide and alumina for efficient photocatalysis
    Aisha Kanwal, Shamaila Sajjad, Sajjad Ahmed Khan Leghari, Muhammad Naeem Khan
    2021, 33(5):  147-159.  doi:10.1016/j.cjche.2020.09.010
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    Well crystalline manganese oxide (Mn3O4) nanoparticles anchored on gamma alumina (γ-Al2O3) have been successfully tailored via a proficient and cost effective chemical process as an efficient material for photo catalysis. XRD indicated the composite formation of γ-Al2O3 and hausmannite structure of Mn3O4. SEM and TEM revealed that hetero structure of Mn3O4/γ-Al2O3 exhibits an amalgam of aggregated nanoparticles and nanorods. XPS demonstrated the chemical states of binary nanocomposite. The band gap tuning has been performed with γ-Al2O3 nanoparticles by assimilating hausmannite Mn3O4 particles into flower like microstructure of Al2O3. The photoluminescence spectra affirmed the enhancement in charge separation in Mn3O4/γ-Al2O3 binary hybrid photocatalyst. The band gap becomes narrow with the increase in concentrations of Mn3O4. The narrowing of band gap is concorded with crystalline domains of primary aggregated particles. To elucidate the mechanism of the photocatalytic activity linear sweep voltammetry was performed. The results showed that Mn3O4/γ-Al2O3 nanocomposite revealed the enhancement in current density as compared to pure γ-Al2O3 which confirmed the electron transfer from Mn3O4 to γ-Al2O3 through the interfacial potential gradient in conduction bands. The optimum concentration of 6.0% Mn3O4/γ-Al2O3 for hybrid structure showed an excellent photocatalytic activity under visible light due to narrow band gap energy. High degree distribution of Mn3O4 nano architects overlying on γ-Al2O3 induces a significant synergic effect between γ-Al2O3 and hausmannite phase of manganese oxide (Mn3O4). This strong interfacial contact between γ-Al2O3 and Mn3O4 endures the quick transfer of photo generated charge carriers across interface.
    Ionic liquid catalyzed solvent-free synthesis of chalcone and its derivatives under mild conditions
    Qiu Zhao, Gang Wang, Fuxia Liao, Yifan Sha, Fei Xu, Chunshan Li, Zengxi Li, Yijun Cao
    2021, 33(5):  160-166.  doi:10.1016/j.cjche.2020.09.013
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    An ionic liquid (IL) catalyzed solvent-free process was developed for the direct synthesis of chalcone and its derivatives by using substituted acetophenones and benzaldehydes via aldol reaction under mild conditions. A series of acidic and basic ILs were selected and screened. The influences of cations and reaction conditions on product yield and selectivity were systematically investigated. The [Bmim]OH was identified as the optimal IL, with the highest yield and selectivity reaching up to 96.7% and 100%, respectively. A reaction mechanism-based kinetic model was established and regressed with experimental data, revealing the β-Hydroxylketone dehydrolysis with activation barrier of 37.8 kJ·mol-1 was observed as the ratecontrolling step.
    Functionalized metal-organic frameworks with strong acidity and hydrophobicity as an efficient catalyst for the production of 5-hydroxymethylfurfural
    Huan Li, Yao Zhong, Luxi Wang, Qiang Deng, Jun Wang, Zheling Zeng, Xinxiang Cao, Shuguang Deng
    2021, 33(5):  167-174.  doi:10.1016/j.cjche.2020.09.018
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    In the dehydration of fructose to 5-hydroxymethyl furfural (HMF), in situ produced water weakens the acid strength of the catalyst and causes the rehydration of HMF, causing unsatisfactory catalytic activity and selectivity. In this work, a class of benzenesulfonic acid-grafted metal-organic frameworks with strong acidity and hydrophobicity is obtained by the direct sulfonation method using 4-chlorobenzenesulfonic acid as sulfonating agent. The resultant MOFs have a specific surface area of greater than 250 m2·g-1, acid density above 1.0 mmol·g-1, and water contact angle up to 129 . The hydrophobic MOF-PhSO3H exhibits both higher catalytic activity and selectivity than MOF-SO3H in the HMF synthesis due to its better hydrophobicity and olephilicity. Moreover, the catalyst has a high recycled stability. At last, fructose is completely converted, and 98.0% yield of HMF is obtained under 120 C in a DMSO solvent system. The successful preparation of the hydrophobic acidic MOF provides a novel hydrophobic catalyst for the synthesis of HMF.
    A solvent-free, selective liquid phase hydrogenation of nitroarenes to aniline in slurry bubble mode on porous NiMo bimetallic catalyst
    Di Liu, Pengshan Zhao, Hao Zhang, Minjie Liu, Junyan Wang, Guoming Zhao, Qingbin Guo
    2021, 33(5):  175-180.  doi:10.1016/j.cjche.2020.07.018
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    NiMo bimetallic catalysts were prepared by a solid reaction method. On the NiMo catalyst, the selective liquid phase hydrogenation of nitrobenzene to aniline was achieved in slurry bubble mode. And the high yields (98.9%) were obtained under the conditions of 80 ℃, solvent-free and atmospheric pressure. The effect of Mo on the catalytic behavior of Ni based catalyst was investigated. The characterization displayed that the inclusion of Mo could improve the specific surface area and pore volume, and the solid reaction method made metal Mo enrichment on the surface of catalyst. These two aspects should be responsible for excellent catalytic performance of NiMo catalyst. In sum, we described a simple and efficient NiMo catalyst and provided a facile and green procedure for liquid phase hydrogenation of nitrobenzene to aniline.
    Evaluations of physico-chemical properties of TiO2/clinoptilolite synthesized via three methods on photocatalytic degradation of crystal violet
    Raza Ullah, Jihong Sun, Anadil Gul, Tallat Munir, Xia Wu
    2021, 33(5):  181-189.  doi:10.1016/j.cjche.2020.09.045
    Abstract ( )   PDF (3157KB) ( )  
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    Different preparation routes for TiO2-supported natural and synthetic clinoptilolite (TiO2/CP) composites were thoroughly investigated on the basis of sol-gel, hydrothermal, and in-situ hydrothermal methods. The micro-structural features and physicochemical properties of resultant TiO2/CPs were characterized via X-ray diffraction patterns, scanning (transmission) electron microscope images, Fourier transform infrared spectra, inductively coupled plasma-optical emission spectrometry methods, BET-isotherms, UV-visible spectra, and surface charge potential distributions. The results showed that in-situ hydrothermal method led to well dispersions of loaded-TiO2 particles on the surface of leaf-like CP, while obviously aggregated TiO2 on a relatively distorted structure of CP was obtained using sol-gel and hydrothermal methods. Their adsorptive and photocatalytic efficiencies for removal of crystal violet (CV) dye in aqueous solution were also explored under UV-irradiations. The results demonstrated that TiO2/CPs synthesized via sol-gel and in-situ hydrothermal methods presented the excellent performances with 98% removal efficiencies as compare to the bare commercial TiO2 which achieved 53% removal of CV dye. While, the in-situ hydrothermally synthesized TiO2/CPs were the best due to their moderate energy cost, highest adsorption capacities and removal efficiencies. Particularly, the synthetic CPs as supports exhibited synergetic photocatalytic activities for the degradation of CV dye, which is attributed to their high surface areas, better adsorption capability, and fine dispersion of TiO2 particles. Adsorption and degradation kinetics of CV dye were found to follow the pseudo-second and pseudo-first order models, respectively.
    Process Systems Engineering and Process Safety
    Hydrodynamics of air-kerosene bubble column under elevated pressure in homogeneous flow regime
    Bay Van Tran, Son Ich Ngo, Young-Il Lim, Keon Bae, Dong Hyun Lee, Kang-Seok Go, Nam-Sun Nho
    2021, 33(5):  190-202.  doi:10.1016/j.cjche.2020.08.031
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    A multiphase computational fluid dynamics (CFD) model coupled with the population balance equation (PBE) was developed in a homogeneous air-kerosene bubble column under elevated pressure (P). The specific pressure drop (ΔP/L), gas holdup (αG), and Sauter mean diameter (d32) were experimentally measured in the bubble column with 1.8 m height and 0.1 m inner diameter, which was operated at a superficial gas velocity of 12.3 mm·s-1, and P = 1-35 bar (1 bar = 105 Pa). A modified drag coefficient model was proposed to consider the effect of bubble swarm and pressure on hydrodynamics of the bubble column. The Luo breakage model was modified to account for liquid density, viscosity, surface tension and gas density. The ΔP/L, αG, and d32 obtained from the CFD model were compared with experimental data, and the gas density-dependent parameters of the CFD model were identified. With increasing P from 1 to 35 bar, the αG varied from 5.4% to 7.2% and the d32 decreased from 2.3 to 1.5 mm. The CFD-PBE model is applicable to predict hydrodynamics of pressurized bubble columns for gas-organic liquid in the homogeneous regime.
    Simulated annealing-based optimal design of energy efficient ternary extractive dividing wall distillation process for separating benzene-isopropanol-water mixtures
    Min Li, Yue Cui, Xiaojing Shi, Zhishan Zhang, Xiaoxiao Zhao, Xiuyu Zhu, Jun Gao
    2021, 33(5):  203-210.  doi:10.1016/j.cjche.2020.08.041
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    This article investigates the performances of different extractive distillation processes intensified with dividing-wall column for separating benzene-isopropanol-water ternary mixtures. All the processes with ethylene glycol as solvent are optimized with the minimal total annual cost (TAC) as target. In order to get the global optimal solution intelligently, an improved simulated annealing algorithm is adopted, which is programmed in MATLAB and linked to Aspen Plus. The results show that the extractive dividing wall column-solvent (EDWC-S) process consisting of an extractive dividing wall column and a solvent recovery column is the best scheme. It can reduce the TAC by 28.65% and CO2 emissions by 32.84% compared to the conventional triple-column extractive distillation process.
    Neural network-based source tracking of chemical leaks with obstacles
    Qiaoyi Xu, Wenli Du, Jinjin Xu, Jikai Dong
    2021, 33(5):  211-220.  doi:10.1016/j.cjche.2020.12.022
    Abstract ( )   PDF (5341KB) ( )  
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    The leakage of hazardous gases poses a significant threat to public security and causes environmental damage. The effective and accurate source term estimation (STE) is necessary when a leakage accident occurs. However, most research generally assumes that no obstacles exist near the leak source, which is inappropriate in practical applications. To solve this problem, we propose two different frameworks to emphasize STE with obstacles based on artificial neural network (ANN) and convolutional neural network (CNN). Firstly, we build a CFD model to simulate the gas diffusion in obstacle scenarios and construct a benchmark dataset. Secondly, we define the structure of ANN by searching, then predict the concentration distribution of gas using the searched model, and optimize source term parameters by particle swarm optimization (PSO) with well-performed cost functions. Thirdly, we propose a one-step STE method based on CNN, which establishes a link between the concentration distribution and the location of obstacles. Finally, we propose a novel data processing method to process sensor data, which maps the concentration information into feature channels. The comprehensive experiments illustrate the performance and efficiency of the proposed methods.
    Chemical Engineering Thermodynamics
    Simultaneous removal of copper and zinc ions by low cost natural snail shell/hydroxyapatite/chitosan composite
    Abbas Bambaeero, Reza Bazargan-Lari
    2021, 33(5):  221-230.  doi:10.1016/j.cjche.2020.07.066
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    In this work, the snail shell/hydroxyapatite/chitosan composite was prepared as adsorbent. The adsorption potential of the composite was studied for simultaneous sorption behavior of Zn (II) and Cu (II) ions in a batch system. Chitosan and hydroxyapatite (HAP) were extracted from shrimp shell and bone ash, respectively, so this is a low cost natural composite. To prepare the composite, chitosan was dissolved in acetic acid, then HAP and snail shell powders were added to the chitosan solution. The morphology and characterization of the composite was studied by SEM and EDX analysis. Atomic adsorption was used to measure the amount of the ions. Experimental parameters were optimized with Design Expert Software and five parameters such as the concentration of ions, pH, adsorbent amount and contact time were studied at room temperature. Optimized value for the parameters of Zn (II) and Cu (II) concentrations, pH, adsorbent dose, and contact time were 3.01 mg·L-1, 5.5, 0.02 g and 95 min, respectively. The adsorption isotherms for Zn (II) and Cu (II) showed Langmuir and Tempkin, respectively. Kinetic and equilibrium studies showed the experimental data of Zn (II) and Cu (II) ions were best described by the pseudo-second-order model. Studies on thermodynamic show the adsorption process were physical and spontaneous.
    Solubility measurement and thermodynamic modeling of carbamazepine (form III) in five pure solvents at various temperatures
    Wenju Liu, Zehua Bao, Yanmin Shen, Tiantian Yao, Hongjuan Bai, Xinyu Jin
    2021, 33(5):  231-235.  doi:10.1016/j.cjche.2020.09.054
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    In this work, the solubilities of carbamazepine (CBZ) (form III) in ethyl acetate, methyl acetate, ethylene glycol, chloroform and cyclohexylamine were determined by laser monitoring techniques at pressure above sea level, and the solubility data of CBZ (form III) in different pure solvents were fitted by the Modified Apelblat model and λh model. The result shows that the solubility of CBZ (form III) in five solvents increases as temperature rises, and the solubility in chloroform was the largest. The experimental solubility values of CBZ (form III) in ethyl acetate, methyl acetate, chloroform and cyclohexylamine were in better agreement with the simulated fitting values of the λh model. For ethylene glycol, the r value was much larger than the other four solvents, and it can be seen from the λh model that ethylene glycol was closer to the ideal solution system than the other four solvents.
    Biotechnology and Bioengineering
    Split internal-loop photobioreactor for Scenedesmus sp. microalgae: Culturing and hydrodynamics
    Laith S. Sabri, Abbas J. Sultan, Muthanna H. Al-Dahhan
    2021, 33(5):  236-248.  doi:10.1016/j.cjche.2020.07.058
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    In this study, the evaluation of the performance of the split internal loop photobioreactor for culturing a species of green microalgae, Scenedesmus sp. under different operating superficial gas velocity and during a different time of growth (i.e., starting for the first day until end day of the culturing process) was addressed. The evaluation of the performance of the split internal loop photobioreactor was included assessing the density, pH, temperature, viscosity, surface tension, the optical density, cell population, dry biomass, and chlorophyll of the culture medium of the microalgae culturing. Additionally, the hydrodynamics of a Split Internal-Loop Photobioreactor with microalgae culturing was comprehensively quantified. Radioactive particle tracking (RPT) and gamma-ray computed tomography (CT) techniques were applied for the first time to quantify and address the influence of microalgae culture on the hydrodynamic parameters. The hydrodynamics parameters such as local liquid velocity field, shear stresses, turbulent kinetic energy, and local gas holdup profiles were measured at different superficial gas velocities as well as under different times of algae growth. The obtained results indicate that the flow distribution may significantly affect the performance of the photobioreactor, which may have substantial effects on the cultivation process. The obtained experimental data can serve as benchmark data for the evaluation and validation of computational fluid dynamics (CFD) codes and their closures. This, in turn, allows us to develop efficient reactors and consequently improving the productivity and selectivity of these photobioreactors.
    Alginate core-shell microcapsule reduces the DMSO addition-induced osmotic damage to cells by inhibiting cellular blebs
    Chengpan Li, Jing Liu, Qiang Wu, Xiangyu Chen, Weiping Ding
    2021, 33(5):  249-255.  doi:10.1016/j.cjche.2020.10.019
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    In cryopreservation, the addition of cryoprotectant can change the intra- and extra-cellular osmotic pressure, affect the cell morphology, and induce blebs on the plasma membrane. In this study, the blebs of cells microencapsulated in the alginate microsphere induced by osmotic shock were studied, and the effects of microencapsulation on bleb size and cell viability were determined. Firstly, a coaxial co-flow focusing device was applied to generate cell-laden microcapsules using alginate hydrogel in this paper. Then, cellular blebs induced by DMSO with various concentrations under microencapsulation were compared with that when non-encapsulated, and the dynamic process of cellular bleb was investigated. Finally, the qualitative relationship between bleb size and cell viability in the presence of DMSO was built, and thus the effects of microencapsulation on bleb size and viability were evaluated. The results show that the bleb size is smaller and the cell viability is higher, and cell microencapsulation can significantly inhibit the excessively large blebs generated on the cell membrane and reduce the osmotic damage to cells when loading cryoprotectant and then to improve cell viability during cryopreservation. This work can provide insights for optimizing cryoprotectant-loading protocols, offer a new avenue to study cell blebbing, and advance future research on cryopreservation of rare cells and biomaterials.
    Microwave energy inductive fluidized metal particles discharge behavior and its potential utilization in reaction intensification
    Xingang Li, Chuanrui Pang, Hong Li, Xin Gao
    2021, 33(5):  256-267.  doi:10.1016/j.cjche.2020.07.061
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    Microwave-induced metal discharge (MMD) technology offers a novel methodology for efficient gas-phase catalytic reaction due to its unique heating effect, plasma effect and discharge effect. Herein, we successfully used a special kind of uniformly distributed particles with synergistic microwave-induced fluidized-metal discharge (MFD) effect. A lab-scale atmospheric quartz tube fluidized bed reactor was designed. Apparatus like highspeed camera, fiber spectrometer and infrared thermometer were used to record the discharge phenomena. The effects of operating conditions such as gas velocity, microwave power, carrier gas type, and metal type on the discharge behavior were investigated in detail. Subsequently, the MFD was applied into the methane dry reform reaction (MDR) with excellent conversion compared with the conventional heating conditions. Gratifyingly, the metal particles can both be the converter of microwave and the catalyst of the reaction. The reported conclusion provides a novel way to intensification the reaction process and utilize microwave energy.
    Targeting efficient biomass gasification
    Saneliswa Magagula, Jiangze Han, Xinying Liu, Baraka C. Sempuga
    2021, 33(5):  268-278.  doi:10.1016/j.cjche.2020.11.027
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    The sustainability of biomass use as a primary energy source depends on the efficiency of its conversion processes. The key contributing factors are well understood, owing to extensive experimental and theoretical modeling efforts in literature. In this manuscript, we present a systematic study of the thermochemical conversion route that allows us to target desirable outcomes when converting biomass to other fuels and products. Using process synthesis techniques that include material, energy and work balances, we identify the best targets to consider for highly efficient processes given specific constraints. Our analysis shows that by supplying the right amount of oxygen, a 100% carbon conversion efficiency can be achieved for certain applications that require gas as product. If the objective is to obtain a cleaner fuel from biomass, converting it to char is most efficient in terms of carbon and energy conversion. According to our analysis, an energy neutral biomass gasification process is theoretically possible over a wide range of H2 and CO production rates. We demonstrate its feasibility by simulating the process on Aspen Plus®. The simulation reveals that with heat integration, we can achieve the energy neutral target at a hydrogen production rate of 0.9 mol/mol biomass. We further show that even at zero energy requirement, biomass gasification processes can have excess chemical potential, which can be recovered as useful work or conserved by producing more H2. Adding low temperature heat in the form of steam at 102 C gives an 8% gain in chemical potential conservation and increases the hydrogen production rate by 60%. The insights revealed in this work allow for better decision making in early stages of process design, and consequently, more efficient biomass gasification processes.
    Enhanced adsorption of phenol from aqueous solution by carbonized trace ZIF-8-decorated activated carbon pellets
    Xinlong Yan, Yanfang Li, Xiaoyan Hu, Rui Feng, Min Zhou, Dezhi Han
    2021, 33(5):  279-285.  doi:10.1016/j.cjche.2020.06.027
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    Trace zeolitic imidazolate framework-8 (ZIF-8)-decorated activated carbon (AC) pellets were synthesized by a facile wet impregnation technique. After pyrolysis of the above composite material, the obtained carbon had a large surface area and pore volume, with traces of Zn on its surface. Subsequently, the capacity of the ZIF8/AC samples to adsorb and remove phenol from aqueous media was evaluated in both batch and column experimental setups. The equilibrium adsorption capacity reached 155.24 mg·g-1, which was 2.3 times greater than that of the pure AC (46.24 mg·g-1). In addition, adsorption kinetics were examined by pseudofirst and pseudosecond order models, and adsorption isotherms were fitted into Langmuir and Freundlich equations. The adsorbent could be easily filtered from the solution and washed with methanol and water, while maintaining an efficiency N90% after 4 cycles. The above results make it a potentially reusable candidate for water purification.
    In-depth investigation on the factors affecting the performance of high oil-absorption resin by response surface method
    Lei Ma, Hongxia Lv, Haonan Yu, Lingtong Kong, Rongyue Zhang, Xiaoyan Guo, Haibo Jin, Guangxiang He, Xiaoyan Liu
    2021, 33(5):  286-296.  doi:10.1016/j.cjche.2020.07.032
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    A series of high oil-absorption resins with low cross-linking degree were synthesized by suspension polymerization using stearyl methacrylate (SMA), 2-Ethylhexyl methacrylate (EHMA), and styrene (St) as monomers. Response surface methodology (RSM) with central composite design (CCD) was also applied to determine the optimal parameters that are mainly known to affect their synthesis. Thus, the effects of the monomer mass ratio (EHMA:SMA), the rigid monomer (St) dosage, the porous agent (acetone) dosage, and their pairwise interaction on the resin's oil-absorption capacity were analyzed, highlighting PSES-R2 as the resin with the optimum performance. The pure oil-absorption rates of PSES-R2 for gasoline, diesel, and kerosene were 11.19 g·g-1, 16.25 g·g-1, and 14.84 g·g-1, respectively, while the oil removal rates from oily wastewater were 98.82%, 65.11%, and 99.63%, respectively.
    Optimization and evaluation of reduced graphene oxide hydrogel composite as a demulsifier for heavy crude oil-in-water emulsion
    Kin Kit Fong, Inn Shi Tan, Henry Chee Yew Foo, Man Kee Lam, Adrian Chiong Yuh Tiong, Steven Lim
    2021, 33(5):  297-305.  doi:10.1016/j.cjche.2020.08.027
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    The rising production of produced water from oilfields had been proven to bring detrimental environmental effects. In this study, an efficient, recyclable, and environmental-friendly reduced graphene oxide immobilized κ-Carrageenan hydrogel composite (κCaGO) was fabricated as an alternative sorbent for crude oil-in-water demulsification. Polyethyleneimine (PEI) was employed to form a stable hydrogel composite. The conditions for the immobilization of graphene oxide (GO) on PEI-modified κ-Carrageenan (κC) beads were optimized appropriately. An immobilization yield of 77% was attained at 2% PEI, 2 h immobilization activation time, and pH 6.5. Moreover, the synthesized κCaGO is capable of demulsification with an average demulsification efficiency of 70%. It was found that the demulsification efficiency increases with salinity and κCaGO dosage, and it deteriorates under alkaline condition. These phenomena can be attributed to the interfacial interactions between κCaGO and the emulsion. Furthermore, the κCaGO can be recycled to use for up to six cycles without significant leaching and degradation. As such, the synthesized κCaGO could be further developed as a potential sorbent substitute for the separation of crude oil from produced water.
    Sulfamic acid functionalized slag for effective removal of organic dye and toxic metal from the aqueous samples
    Dauda Mohammed, Muhammad H. Al-Malack, Basheer Chanbasha
    2021, 33(5):  306-318.  doi:10.1016/j.cjche.2020.08.047
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    Surface functionalization of blast furnace slag with sulfamic acid (a zwitterion) was performed for the removal of Cr3+ and methylene blue dye (MB) from water samples. The slag functionalization process was optimized using Response Surface Methodology Design. Statistical analysis of the parameters that include the sulfamic acid amount (A), reaction time (B), and temperature (C) revealed that (A) increase had a negative effect on the adsorption of both pollutants by the zwitterion slag, whereas (B) and (C) increase presented a positive impact. At the optimum condition of 2 g sulfamic acid amount, 50 min reaction time and 37 C temperature, the prepared slag showed a removal efficiency of more than 90% for both Cr3+ and MB. Surface characterization by SEM/EDS, FTIR, XPS and surface area analyser, showed an improvement in surface properties and the incorporation of zwitterionic NH2+ and S=O groups of sulfamic acid. Adsorption isotherm and kinetic studies conducted with the zwitterion slag showed the adsorption process was suited to Freundlich isotherm model and pseudo-second-order kinetic model. The thermodynamic study conducted revealed the spontaneity of the process based on the calculated negative ΔG (Gibb’s free energy) values. The prepared zwitterion slag offered easy regeneration with dilute HCl solution and showed a considerable removal (Cr3+: 65% and MB: 80%) for both pollutants even after 3 cycles of usage.
    Effect of sulfate on Cu(II) sorption to polymer-supported nano-hydrated ferric oxides: Experimental and modeling studies
    Wenxiang Ni, Luyang Yang, Xiaolin Zhang, Hui Qiu
    2021, 33(5):  319-326.  doi:10.1016/j.cjche.2020.09.050
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    Incorporating of hydrous ferric oxide (HFO) inside porous supports with large sizes has become an effective way to decontaminate the water from heavy metals. Ubiquitous anions like sulfate are usually present in high concentrations in water, and might greatly affect adsorption behavior of hybrid HFO. Here, a polymer-based HFO-CPS was fabricated by encapsulating nano-HFO inside a chloromethylated polystyrene polymer (CPS) and the reactivity of HFO-CPS with Cu(II) was evaluated in the presence of sulfate ions. Surface complexation theory was firstly employed to describe the effect of sulfate on Cu(II) adsorption edges of hybrid HFO-CPS, where constant capacitance model (CCM) was adopted. The available weak adsorption site Fe(2)OH of hybrid HFO-CPS was found to decrease from 20% Fe to 5% Fe, which might be caused by the pore plugging effect after HFO encapsulation. With the assumption that a ternary complex was formed, the effect of sulfate on Cu(II) adsorption by HFO-CPS were successfully described by CCM using the optimized Fe(2)OH site under different sulfate concentrations (1 or 10 mmol·L-1) and Cu/Fe ratios (0.0042 or 0.0252). It is confirmed that the formation of FeOHCuSO4 ternary surface complexes played an important role in enhancing Cu(II) adsorption on HFO-CPS in the presence of sulfate.
    Influence of synergistic effect of LiNi0.8Co0.15Al0.05O2@Cr2O5 composite on the electrochemical properties
    Yunke Wang, Yongjia Li, Yenan Zhang, Guozheng Zha, Feng Liang, Yongnian Dai, Yaochun Yao
    2021, 33(5):  327-336.  doi:10.1016/j.cjche.2020.09.017
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    LiNi0.8Co0.15Al0.05O2 (NCA)@Cr2O5 composite electrode combines the high rate-capability characteristics of NCA with the stability of Cr2O5, playing a synergistic role in improving the cyclic stability, initial discharge capacity and the security of low cut-off voltage (2.0 V). When the mass ratio of Cr2O5 in NCA is 45% (mass), the capacity retention rate increases from 58.5% without Cr2O5 to 69.3% in the range of 2.0-4.3 V. The initial discharge capacity of NCA@Cr2O5 composite material is 211.4 mA·h·g-1, its first coulombic efficiency is 94.2%, and the charging capacity remains approximately constant when mixed with 15% (mass) Cr2O5. The reason for the improvement of the initial charge-discharge efficiency (ICDE) was explained. Impedance and cyclic voltammetry analysis reveal more detailed reasons of the observed improvements. Compared with NCA cathode material, the NCA@Cr2O5 composite material can provide not only additional stable sites and channels for Li+ insertion/extraction to make up for the loss of active Li+ sites and prevent the accumulation of Li+ in the circulation process, but also protect the NCA electrode from the corrosion of the electrolyte decomposition by the Cr2O5 nanoparticles adhering to NCA interface.
    Zeolite A enhanced chitosan films with high water absorption ability and antimicrobial activity
    Jie Gong, Fei Tong, Bin Wang, Di Ma, Chunyong Zhang, Jinlong Jiang, Lixiong Zhang
    2021, 33(5):  337-343.  doi:10.1016/j.cjche.2020.08.057
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    Zeolite A/CS xerogel hybrid films were prepared by in-situ crystallization method with uniform structure and good strength. The hybrid films prepared from the precursor films dried at 50 C showed zeolite A was well crystallized. The hybrid films show high water absorption, good elastic strength and Young modulus. The antimicrobial ability of the hybrid films was investigated after Ag+-ion exchanged. The Ag+-exchanged hybrid films with 35% (mass) content of zeolite A showed the highest antimicrobial activity, which could reduce the concentration of the microbial to zero after 7 h.