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Table of Content
28 July 2020, Volume 28 Issue 7
    Graphene-based membranes for pervaporation processes
    Kecheng Guan, Gongping Liu, Hideto Matsuyama, Wanqin Jin
    2020, 28(7):  1755-1766.  doi:10.1016/j.cjche.2020.04.011
    Abstract ( 198 )   PDF (3293KB) ( 58 )  
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    Two-dimensional graphene and its derivatives exhibiting distinct physiochemical properties are intriguing building blocks for researchers from a large variety of scientific fields. Assembling graphene-based materials into membrane layers brings great potentials for high-efficiency membrane processes. Particularly, pervaporation by graphene-based membranes has been intensively studied with respect to the membrane design and preparation. This review aims to provide an overview on the graphene-based membranes for pervaporation processes ranged from fabrication to application. Physical or chemical decoration of graphene-based materials is elaborated regarding their effects on the microstructure and performance. The mass transport of pervaporation through graphene-based membranes is introduced, and relevant mechanisms are described. Furthermore, performances of state-of-the-art graphene-based membranes for different pervaporation applications are summarized. Finally, the perspectives of current challenges and future directions are presented.
    Fluid Dynamics and Transport Phenomena
    A comparative analysis of unsteady and steady Buongiorno's Williamson nanoliquid flow over a wedge with slip effects
    R. Chandra Sekhar Reddy, P. Sudarsana Reddy
    2020, 28(7):  1767-1777.  doi:10.1016/j.cjche.2020.04.016
    Abstract ( 138 )   PDF (3326KB) ( 55 )  
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    Comparison between unsteady and steady MHD Buongiorno's model Williamson nanoliquid flow through a wedge with slip effects, chemical reaction and radiation is made in this analysis. Thermophoresis and Brownian motion are also considered in this study. Appropriate similarity variables are presented to transmute the governing PDEs into the set of non-linear ODEs. The most widely authenticated finite element method is implemented to analyze these set of ODEs numerically. The behavior of concentration, temperature and velocity sketches for varied values of relevant parameters is numerically calculated and the outcomes are plotted through graphs. The numerical values of dimensionless rates of mass transfer, heat and velocity are also evaluated and depicted through tables. It is noted that with upsurging values of angle of wedge parameter, the distributions of temperature of the liquid intensify in both steady and unsteady cases.
    Mesoporous tablet-shaped potato starch aerogels for loading and release of the poorly water-soluble drug celecoxib
    Akbar Mohammadi, Jafarsadegh Moghaddas
    2020, 28(7):  1778-1787.  doi:10.1016/j.cjche.2020.03.040
    Abstract ( 189 )   PDF (3278KB) ( 73 )  
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    In this study, after determination of the optimal values of the effective parameters in the synthesis using experimental design software, tablet-shaped potato starch aerogels were synthesized at the optimal condition in order to be used as a drug carrier. The celecoxib, as the model drug, was loaded into the aerogel matrix during the solvent exchange step. FTIR (Fourier Transform Infrared Spectroscopy), FESEM and HRTEM (Transmission Electron Microscopy) analyses showed that celecoxib has been successfully loaded into aerogel matrix. Also, XRD analysis showed that most of the celecoxib has been loaded in amorphous form. In vitro studies were performed in both simulated gastric and intestinal fluids. The release kinetics showed that the loaded celecoxib dissolved faster than crystalline celecoxib. At rotational speed of 100 r·min-1, about 26% and 50% and at rotational speed of 50 r·min-1, about 20% and 42% drug was released during the first 30 min of soaking in the simulated gastric fluid and simulated intestinal fluid, respectively. The release of the mentioned drug was increased up to 60% and 98% at a rotational speed of 100 r·min-1 and up to 46% and 93% at a rotational speed of 50 r·min-1 at the end of 5 h in the simulated gastric fluid and simulated intestinal fluid, respectively. It could be concluded that potato starch aerogels can be very useful in many drug delivery applications along with conventional micronization techniques. Modeling of release data showed that the release kinetics follows the Korsmeyer Peppas model, which considers phenomena of matrix erosion and drug diffusion.
    Separation Science and Engineering
    Enhanced air filtration performance under high-humidity condition through electrospun membranes with optimized structure
    Xue Gao, Sisi Wen, Bingling Yang, Jian Xue, Haihui Wang
    2020, 28(7):  1788-1795.  doi:10.1016/j.cjche.2020.02.025
    Abstract ( 187 )   PDF (3092KB) ( 47 )  
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    The separation stability under high-humidity is significant in practical applications for air filters. Herein, hydrophobic polyvinyl chloride (PVC) nanofiber filters with bead-on-string structure are designed to steadily remove particle matter under high relative humidity of 90%-95%. The developed hydrophobic filters possess comparable separation performance with the hydrophilic one, but greatly enhanced stability. After the introduction of beadon-string structure, the filtration performance can be furtherly improved due to the formed large cavities and hydrophobicity. Such hydrophobic PVC filters can be promising candidates for air purification in practical applications especially in wet seasons.
    Catalysis, Kinetics and Reaction Engineering
    Study of the kinetic behaviour of biomass and coal during oxyfuel co-combustion
    Oris Chansa, Zhongyang Luo, Chunjiang Yu
    2020, 28(7):  1796-1804.  doi:10.1016/j.cjche.2020.02.023
    Abstract ( 111 )   PDF (6559KB) ( 32 )  
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    In this study, the thermogravimetric analysis (TGA) method has been used to evaluate the kinetic behavior of biomass, coal and its blends during oxyfuel co-combustion. The thermogravimetric results have been evaluated by the Coats-Redfern method and validated by Criado's method. TG and DTG curves indicate that as the oxygen concentration increases the ignition and burn out temperatures approach a lower temperature region. The combustion characteristic index shows that biomass to coal blends of 28% and 40% respectively can achieve enhanced combustion up to 60% oxygen enrichment. In the devolatilization region, the activation energies for coal and blends reduce while in the char oxidation region, they increase with rise in oxygen concentration. Biomass, however, indicates slightly different combustion characteristic of being degraded in a single step and its activation energies increase with rise in oxygen concentration. It is demonstrated in this work that oxygen enrichment has more positive combustion effect on coal than biomass. At 20% oxygen enrichment, 28% and 40% blends indicate activation energy of 132.8 and 125.5 kJ·mol-1 respectively which are lower than coal at 148.1 kJ·mol-1 but higher than biomass at 81.5 kJ·mol-1 demonstrating synergistic effect of fuel blending. Also, at char combustion step, an increase in activation energy for 28% blend is found to be 0.36 kJ·mol-1 per rise in oxygen concentration which is higher than in 40% blend at 0.28 kJ·mol-1.
    Quantum chemical descriptors based QSAR modeling of neodymium carboxylate catalysts for coordination polymerization of isoprene
    Shuguang Xiang, Jiye Wang
    2020, 28(7):  1805-1808.  doi:10.1016/j.cjche.2019.07.018
    Abstract ( 118 )   PDF (161KB) ( 17 )  
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    Based on the quantum chemical descriptors and the activities for isoprene polymerization of 12 neodymium carboxylates obtained by authors' earlier work, statistical analysis of data was made and a QSAR model correlating the quantum chemical descriptors and the activity was built with the partial least square (PLS) approach. The model is: A = 51602 εHOMO + 6 σ + 12546, which indicates that the catalytic activity A is positively correlated with the HOMO energy εHOMO and the ligand polarizability σ, with the contribution of σ being larger, εHOMO smaller. The model's coefficient of determination r2 = 0.96 and that of cross validation q2 = 0.94, both being close to 1, which means that its quality is well and its predictive power is strong. Analysis of the modeling process and the resulted QSAR model, together with the interpretation of the model's mechanism, also shows that the model obtained from this study is valid and reliable. According to the QSAR model, the mechanism of catalyst activity can be interpreted as that neodymium carboxylates with higher HOMO energy and larger ligand polarizability are easier to react with the co-catalysts so as to produce more active and stable centers of catalyst, resulting in a higher activity.
    Methane oxybromination over Rh-based catalysts: Effect of supports
    Peng Wang, Lang Chen, Sheng Shen, Chak-Tong Au, Shuangfeng Yin
    2020, 28(7):  1809-1815.  doi:10.1016/j.cjche.2019.09.001
    Abstract ( 196 )   PDF (2713KB) ( 15 )  
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    Bromine mediation has been regarded as one of the most efficient ways to activate and convert methane to useful organics. This article reports the effects of active components (Rh, Ru, Pd and Pt) and supports (SiO2, MgO and Al2O3) on the catalysis of methane oxybromination. Among the prepared catalysts, Rh/SiO2 is the best in performance (CH4 conversion of ca. 20% and CH3Br selectivity exceeding 70%). The results reveal that support type has a notable influence on the catalytic performance of Rh, especially on product distribution. The high selectivity to CH3Br over Rh/SiO2 is attributed to its low propensity for CH3Br oxidation. It was found that Rh small in particle size shows high catalytic activity and CH3Br selectivity. Although silicalite-1 zeolite suffers from a certain degree of structural damage due to the presence of high temperature steam, the use of silicalite-1 as support results in a performance comparable to that of Rh/SiO2.
    Enantioselective esterification of (R,S)-2-(4-methylphenyl) propionic acid via Novozym 435: Optimization and application
    Xin Yuan, Lujun Wang, Panliang Zhang, Weifeng Xu, Kewen Tang
    2020, 28(7):  1816-1823.  doi:10.1016/j.cjche.2019.09.003
    Abstract ( 114 )   PDF (5496KB) ( 18 )  
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    This paper reports on the resolution of (R,S)-2-(4-methylphenyl) propionic acid (MPPA) enantiomers by enzymatic esterification in organic solvent. Novozym 435 (CALB) has the best catalytic performance compared with other lipases. Of the alcohols screened, n-hexanol is the best acyl acceptor and gives the highest enzyme activity and enantioselectivity in n-hexane. Response surface methodology (RSM) was used to evaluate the influence of the factors, such as temperature, enzyme amount, substrate concentration and reaction time on the substrate conversion (c) and enantiomeric excess (ee). The correlation coefficient R2 for enantiomeric excess and the conversion are 0.9827 and 0.9910, respectively, indicating that can accurately predict the experimental results. By simulation and optimization, the optimal conditions were obtained, involving 600 mmol·L-1 MPPA concentration (0.60 mmol), 850 mmol·L-1 hexanol concentration (0.85 mmol), 58 mg enzyme amount, 75 ℃ temperature and 4.5 h reaction time, respectively. Under the optimized conditions, the experimental values of conversion and enantiomeric excess were 89.34% and 97.84%, respectively, which are in good agreement with the model predictions.
    The fouling properties of SiO2-CaO-P2O5 system in high-temperature rotary kiln phosphoric acid process
    Pan Wu, Li Lü, Siyang Tang, Changjun Liu, Hairong Yue, Wei Jiang, Bin Liang
    2020, 28(7):  1824-1831.  doi:10.1016/j.cjche.2020.01.005
    Abstract ( 152 )   PDF (3383KB) ( 42 )  
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    Kiln phosphoric acid (KPA) technology could produce P2O5 with high purity and has been applied in thermal phosphoric acid industry; however the formation of fouling in the high-temperature rotary kiln restricts the stable and long-term operation. In this paper, the reaction of phosphate ores with gaseous P2O5 was investigated in a high-temperature reactor, and the CaO-SiO2-P2O5 ternary phase diagram was analyzed to understand the fouling formation mechanism. The results showed that the low-melting-point products, such as Ca(PO3)2 and Ca2P2O7, are responsible for the fouling in the KPA process. In addition, a small amount of impurities, e.g., aluminum and iron, could facilitate the generation of the low-melting-point products and cause serious fouling. Based on the high-temperature SiO2-P2O5 and CaO-SiO2-P2O5 phase diagram analysis, the control of Si/Ca molar ratio (e.g., Si/Ca = 2.0) was found to avoid fouling formation in the kiln. These results could provide the operation parameters of reaction temperature and feeds composition to suppress the fouling in the kiln reactor for the phosphoric acid production in industry.
    Application of machine learning to process simulation of n-pentane cracking to produce ethylene and propene
    Weijun Zhu, Xingwang Liu, Xu Hou, Jiayao Hu, Zhenheng Diao
    2020, 28(7):  1832-1839.  doi:10.1016/j.cjche.2020.01.017
    Abstract ( 106 )   PDF (2331KB) ( 24 )  
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    Modeling light olefin production was one of the main concerns in chemical engineering field. In this paper, machine learning model based on artificial neural networks (ANN) was established to describe the effects of temperature and catalyst on ethylene and propene formation in n-pentane cracking. The establishment procedure included data pretreatment, model design, training process and testing process, and the mean square error (MSE) and regression coefficient (R2) indexes were employed to evaluate model performance. It was found that the learning algorithm and ANN topology affected the calculation accuracy. GD24223, CGB2423, and LM24223 models were established by optimally matching the learning algorithm with ANN topology, and achieved excellent calculation accuracy. Furthermore, the stability of GD24223, CGB2423 and LM24223 models was investigated by gradually decreasing training data and simultaneously transforming data distribution. Compared with GD24223 and LM24223 models, CGB2423 model was more stable against the variations of training data, and the MSE values were always maintained at the magnitude of 10-3-10-4, confirming its applicability for simulating light olefin production in n-pentane cracking.
    Photo-reduction of NO by g-C3N4@foamed ceramic
    Rui Zheng, Chunhu Li, Chengzhen Zhang, Wentai Wang, Liang Wang, Lijuan Feng, Junjie Bian
    2020, 28(7):  1840-1846.  doi:10.1016/j.cjche.2020.02.020
    Abstract ( 127 )   PDF (1935KB) ( 46 )  
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    G-C3N4 was supported on the surface of foamed ceramic, and the g-C3N4@foamed ceramic was packed in the photocatalytic reactor in a layered manner. Effects of urea and H2O2 concentration on NO conversion were investigated. Pulse experiments were carried out to investigate the change of NO conversion with time under different concentrations of H2O2. The contribution of each route that NO converted and the selectivities of products were calculated. Results showed that the photo-reduction of NO accounted for 2%, and the photo-oxidation of NO accounted for 14%, and the rest was absorbed by the humidifier. Products include ammonia (NH+ 4-N), nitrogen (N2), nitrite (NO-2-N) and nitrate (NO-3-N), of which N2 accounted for 9%.
    Column breakthrough studies for the removal and recovery of phosphate by lime-iron sludge: Modeling and optimization using artificial neural network and adaptive neuro-fuzzy inference system
    Beverly S. Chittoo, Clint Sutherland
    2020, 28(7):  1847-1859.  doi:10.1016/j.cjche.2020.02.022
    Abstract ( 136 )   PDF (2070KB) ( 35 )  
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    Increases in the treatment of water to meet the growing water demand ultimately result in unmanageable quantities of residuals, the handling, and disposal of which is a major environmental issue. Consequently, research into beneficial reuse of water treatment residuals continues unabated. This study investigated the applicability of lime-iron sludge for phosphate adsorption by fixed-bed column adsorption. Laboratory-scale experiments were conducted at varying flow rates and bed depths. Fundamental and empirical models (Thomas, Yan, Bohart-Adams, Yoon-Nelson, and Wolboroska) as well as artificial intelligence techniques (Artificial neural network (ANN) and Adaptive neuro-fuzzy inference system (ANFIS)) were used to simulate experimental breakthrough curves and predict column dynamics. Increase in flow rate resulted in reduced adsorption capacity. However, adsorption capacity was not affected by bed depth. ANN was superior in predicting breakthrough curves and predicted breakthrough times with high accuracy (R2 > 0.9962). NaOH (0.5 mol·L-1) was successfully used to regenerate the adsorption bed. After nine cyclic adsorption/desorption runs, only a marginal decrease in adsorption and desorption efficiencies of 10% and 8% respectively was observed. The same regenerate NaOH solution was reused for all desorption cycles. After nine cycles the eluent desorbed a total of 1550 mg phosphate exhibiting potential for further reuse.
    A safe and efficient process for the preparation of difluoromethane in continuous flow
    Tao Shen, Xin Ge, Hengjun Zhao, Zhixiong Xu, Shaofeng Tong, Shaodong Zhou, Chao Qian, Xinzhi Chen
    2020, 28(7):  1860-1865.  doi:10.1016/j.cjche.2020.02.024
    Abstract ( 213 )   PDF (615KB) ( 33 )  
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    Difluoromethane is typically produced vialiquid-phase fluorination as performed in a batch reactor. However, this process suffers from some problems, e.g., severe corrosion of the reactor, high safety risk, and the regeneration of the catalyst. In this paper, a flow process as performed in the tubular reactor was designed. The optimum conditions for continuous synthesis of difluoromethane were obtained as follows: the reaction temperature was 100 ℃, the molar ratio of dichloromethane to hydrogen fluoride was 1.6:1 and the reaction time was 300 s. The operation of the cyclic process was stable for 24 h with the conversion per pass of hydrogen fluoride up to 16.2%. The unreacted raw materials were easily reused. The deactivation of the common catalyst, antimony pentachloride, was investigated by catalyst concentration curve and XPS analysis. The approach proposed in this work is proven to be safe, efficient and low amount of catalyst.
    Efficient hydrolysis of cellulose to glucose catalyzed by lignin-derived mesoporous carbon solid acid in water
    Shuai Wang, Guobao Sima, Ying Cui, Longjun Chang, Linhuo Gan
    2020, 28(7):  1866-1874.  doi:10.1016/j.cjche.2020.03.012
    Abstract ( 89 )   PDF (2081KB) ( 40 )  
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    Two kinds of mesoporous carbon solid acids (LDMCE-SO3H and LDMCS-SO3H) were successfully prepared using masson pine alkali lignin as carbon source by evaporation-induced self-assembly (EISA) and salt-induced selfassembly (SISA) followed by sulfonation, respectively. In terms of preparation process, SISA (self-assembly in water and preparation time of 2 days) is greener and simpler than EISA (self-assembly in ethanol and preparation time of 7 days). The prepared LDMCE-SO3H and LDMCS-SO3H exhibit obvious differences in structural characteristics such as pore channel structure, specific surface area, mesopore volume and the density of -SO3H groups. Furthermore, the catalytic performances of LDMCE-SO3H and LDMCS-SO3H were investigated in the hydrolysis of microcrystalline cellulose in water, and the glucose yields of 48.99% and 54.42% were obtained under the corresponding optimal reaction conditions. More importantly, the glucose yields still reached 28.85% and 30.35% after five runs, and restored to 39.02% and 45.98% through catalysts regeneration, respectively, demonstrating that LDMCE-SO3H and LDMCS-SO3H have excellent recyclability and regenerability.
    Process Systems Engineering and Process Safety
    Identification of abnormal conditions in high-dimensional chemical process based on feature selection and deep learning
    Wende Tian, Zijian Liu, Lening Li, Shifa Zhang, Chuankun Li
    2020, 28(7):  1875-1883.  doi:10.1016/j.cjche.2020.05.003
    Abstract ( 86 )   PDF (1976KB) ( 39 )  
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    Identification of abnormal conditions is essential in the chemical process. With the rapid development of artificial intelligence technology, deep learning has attracted a lot of attention as a promising fault identification method in chemical process recently. In the high-dimensional data identification using deep neural networks, problems such as insufficient data and missing data, measurement noise, redundant variables, and high coupling of data are often encountered. To tackle these problems, a feature based deep belief networks (DBN) method is proposed in this paper. First, a generative adversarial network (GAN) is used to reconstruct the random and non-random missing data of chemical process. Second, the feature variables are selected by Spearman's rank correlation coefficient (SRCC) from high-dimensional data to eliminate the noise and redundant variables and, as a consequence, compress data dimension of chemical process. Finally, the feature filtered data is deeply abstracted, learned and tuned by DBN for multi-case fault identification. The application in the Tennessee Eastman (TE) process demonstrates the fast convergence and high accuracy of this proposal in identifying abnormal conditions for chemical process, compared with the traditional fault identification algorithms.
    Faujasite zeolite decorated with cobalt ferrite nanoparticles for improving removal and reuse in Pb2+ ions adsorption
    Elaine C. Paris, João O. D. Malafatti, Henrique C. Musetti, Alexandra Manzoli, Alessandra Zenatti, Márcia T. Escote
    2020, 28(7):  1884-1890.  doi:10.1016/j.cjche.2020.04.019
    Abstract ( 115 )   PDF (2748KB) ( 152 )  
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    Water pollution caused by heavy metals ions has been gaining attention in recent years, increasing the interest in the development of methodologies for their efficient removal focusing on the adsorption process for these purposes. The current challenge faced by adsorption processes is the adequate adsorbent immobilization for removal and reuse. Thus, the present work aimed at producing a faujasite zeolite nanocomposite decorated with cobalt ferrite nanoparticles for Pb2+ ions adsorption in an aqueous medium improving magnetic removal and reuse. As a result, a high surface area (434.4 m2·g-1) for the nanocomposite and an 18.93 emu·g-1 saturation magnetization value were obtained, indicating magnetic removal in a promising material for adsorption process. The nanocomposite regeneration capacity evaluated by magnetic recovery after 24 h suspension presented a high Pb2+ ion adsorptive capacity (98.4%) in the first cycle. Around 98% of the Pb2+ ions were adsorbed in the second cycle. In this way, the synthesized faujasite:cobalt ferrite nanocomposite reveals itself as a promising alternative in adsorption processes, aiming at a synergic effect of FAU zeolite high adsorptive activity and the cobalt ferrite nanoparticles magnetic activity, allowing for adsorbent recovery from the aqueous medium via magnetic force and successive adsorptive cycles.
    Vapor recompressed dividing-wall distillation columns: Structure and performance
    Lijing Zang, Kejin Huang, Yang Yuan, Xing Qian, Liang Zhang, Haisheng Chen, Shaofeng Wang
    2020, 28(7):  1891-1897.  doi:10.1016/j.cjche.2020.05.005
    Abstract ( 97 )   PDF (1464KB) ( 28 )  
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    Due to the topological structure of double columns and multiple separating sections in dividing-wall distillation columns (DWDCs), the development of vapor recompressed dividing-wall distillation columns (DWDC-VRHPs) represents a challenging issue with great complexities and tediousness. For the separations of light-component dominated and wide boiling-point ternary mixtures, because the purification of the light-component from the intermediate-and heavy-components incurs the primary energy dissipation, the application of vapor recompressed heat pumps (VRHP) should be aimed to reduce the irreversibility and this leads to the generation of the optimum topological structures of the DWDC-VRHPs, i.e., a DWDC plus a two-stage VRHP. The first-stage VRHP is to preheat feed, not only taking the advantages of the small temperature elevation available but also favoring the mass transfer between the vapor and liquid phases through feed splitting. The second-stage VRHP is to reduce further separation irreversibility. The philosophy can be applied to any DWDCs no matter where the dividing wall locates. Two case studies on the separations of ternary mixtures of benzene, toluene, and o-xylene and n-pentane, n-hexane, and n-heptane demonstrate the economic optimality of the proposed DWDC-VRHPs and reveal the inherent interplay between internal and external process integration.
    Chemical Engineering Thermodynamics
    Strain-controlled graphdiyne membrane for CO2/CH4 separation: Firstprinciple and molecular dynamic simulation
    Xin Zheng, Shuai Ban, Bei Liu, Guangjin Chen
    2020, 28(7):  1898-1903.  doi:10.1016/j.cjche.2020.05.024
    Abstract ( 130 )   PDF (2606KB) ( 44 )  
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    Tensile strain of porous membrane materials can broaden their capacity in gas separation. In this work, using van der Waals corrected density functional theory (DFT) and molecular dynamics (MD) simulations, the performance and mechanism of CO2/CH4 separation through strain-oriented graphdiyne (GDY) monolayer were studied by applying lateral strain. It is demonstrated that the CO2 permeance peaks at 1.29×106 gas permeation units (GPU) accompanied with CO2/CH4 selectivity of 5.27×103 under ultimate strain, both of which are far beyond the Robeson's limit. Furthermore, the GDY membrane exhibited a decreasing gas diffusion energy barrier and increasing permeance with the increase of applied tensile strain. CO2 molecule tends to reoriented itself vertically to permeate the membrane. Finally, the CO2 permeability decreases with the increase of the temperature from 300 K to 500 K due to conserving of rotational freedom, suggesting an abnormal permeance of CO2 in relation to temperature. Our theoretical results suggest that the stretchable GDY monolayer holds great promise to be an excellent candidate for CO2/CH4 separation, owing to its extremely high selectivity and permeability of CO2.
    Biotechnology and Bioengineering
    Protein retention in dextran-grafted cation exchange chromatography: The influence of pHs, counterions and polymer structure
    Run Liu, Qinghong Shi
    2020, 28(7):  1904-1910.  doi:10.1016/j.cjche.2020.01.006
    Abstract ( 136 )   PDF (1881KB) ( 33 )  
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    Polymer-grafted ion exchange adsorbents were of great interest for the development of high-performance protein chromatography in biopharmaceutical and related fields. In this work, protein retention was systematically investigated in ion exchange chromatography packed respectively with dextran-grafted cation exchange adsorbents containing sulphopropyl (SP) ligand, SP Sepharose XL and Capto S, and non-grafted cation exchange adsorbent, SP Sepharose FF, using five proteins. With an increase of buffer pHs, retention factors of proteins decreased among all the adsorbents, demonstrating the dominant role of electrostatic interaction for protein binding on cation exchange adsorbents. The evidences further revealed that the scattered positive charges on the surface of protein molecules, rather than net charge of protein molecule, determined protein retention on cation exchange adsorbent. Likely, counterions including NH4+, K+, Na+ and Mg2+ exhibited distinct influence on protein retention. It was well ascribed to solvent-mediated indirect ion-macromolecule interactions and direct ion-macromolecule interactions. Compared with SP Sepharose FF, polymer structure in dextran-grafted cation exchange adsorbents ultimately brought about different ligand distributions and smaller pore sizes, thereby regulating protein retention in cation exchange chromatography. By comparing the retention of myoglobin and β-lactoglobulinB in SP Sepharose XL and Capto S, we reasonably speculated that the enhancement of nonelectrostatic interaction caused by reducing the space arm length was a major reason for an increasing retention factor of myoglobin in Capto S. The results in this research help us understand adsorption mechanism of protein in polymer-grafted adsorbents and give scientific guidance for the development of chromatographic materials.
    Energy, Resources and Environmental Technology
    Acid precipitation coupled membrane-dispersion advanced oxidation process (MAOP) to treat crystallization mother liquor of pulp wastewater
    Rongzong Li, Zhaoyang Li, Qian Jiang, Zhaoxiang Zhong, Ming Zhou, Weihong Xing
    2020, 28(7):  1911-1917.  doi:10.1016/j.cjche.2019.08.001
    Abstract ( 125 )   PDF (2361KB) ( 72 )  
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    Treatment to crystallization mother liquor containing high concentration of organic and inorganic substances is a challenge in zero liquid discharge of industrial wastewater. Acid precipitation coupled membrane-dispersion advanced oxidation process (MAOP) was proposed for organics degradation before salt crystallization by evaporation. With acid-MAOP treatment CODCr in mother liquor of pulping wastewater was eliminated by 55.2% from ultrahigh initial concentration up to 12,500 mg·L-1. The decolorization rate was 96.5%. Recovered salt was mainly NaCl (83.3 wt%) having whiteness 50 brighter than industrial baysalt of whiteness 45. The oxidation conditions were optimized as CO3 = 0.11 g·L-1 and CH2O2 = 2.0 g·L-1 with dispersing rate 0.53 ml·min-1 for 100 min reaction toward acidified liquor of pH = 2. Acidification has notably improved evaporation efficiency during crystallization. Addition of H2O2 made through membrane dispersion has eliminated hydroxyl radical “quench effect” and enhanced the degradation capacity, in particular, the breakage of carbon-chloride bonds (of both aliphatic and aromatic). As a result, the proposed coupling method has improved organic pollutant reduction so as the purity of salt from the wastewater mixture which can facilitate water and salt recycling in industry.
    A new long-side-chain sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/polybenzimidazole (PBI) amphoteric membrane for vanadium redox flow battery
    Bowen Jiang, Lei Hu, Xiaoming Yan, Jiahui Sun, Li Gao, Yan Dai, Xuehua Ruan, Gaohong He
    2020, 28(7):  1918-1924.  doi:10.1016/j.cjche.2020.03.010
    Abstract ( 126 )   PDF (1585KB) ( 25 )  
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    A new amphoteric membrane was prepared by blending long-side-chain sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (S-L-PPO) and polybenzimidazole (PBI) for vanadium redox flow battery (VRFB) application. An acid-base pair structure formed between the imidazole of PBI and sulfonic acid of S-L-PPO resulted in lowered swelling ratio. It favors to reduce the vanadium permeation. While, the increased sulfonic acid concentration ensured that proton conductivity was still at a high level. As a result, a better balance between the vanadium ion permeation (6.1×10-9 cm2·s-1) and proton conductivity (50.8 mS·cm-1) in the S-L-PPO/PBI-10% membrane was achieved. The VRFB performance with S-L-PPO/PBI-10% membrane exhibited an EE of 82.7%, which was higher than those of pristine S-L-PPO (81.8%) and Nafion 212 (78.0%) at 120 mA·cm-2. In addition, the S-LPPO/PBI-10% membrane had a much longer self-discharge duration time (142 h) than that of Nafion 212 (23 h).
    Overwhelming low ammonia escape and low temperature denitration efficiency via MnOx-decorated two-dimensional MgAl layered double oxides
    Junqi Tian, Yanqin Li, Xia Zhou, Yongbin Yao, Denghao Wang, Jianming Dan, Bin Dai, Qiang Wang, Feng Yu
    2020, 28(7):  1925-1934.  doi:10.1016/j.cjche.2020.01.004
    Abstract ( 98 )   PDF (5406KB) ( 23 )  
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    Low temperature catalysts are attracting increasing attention in the selective catalytic reduction (SCR) of NO with NH3. MnOx-decorated MgAl layered double oxide (Mn/MgAl-LDO) was synthesized via a facile fast pour assisted co-precipitation (FP-CP) process. Compared to the Mn/MgAl-LDO obtained via slow drop assisted coprecipitation (SD-CP) method, the Mn/MgAl-LDO (FP-CP) has excellent activity. The Mn/MgAl-LDO (FP-CP) catalyst was shown to possess a high NO conversion rate of 76%-100% from 25 to 150 ℃, which is much better than the control Mn/MgAl-LDO (SD-CP) (29.4%-75.8%). In addition, the Mn/MgAl-LDO (FP-CP) offered an enhanced NO conversion rate of 97% and a N2 selectivity of 97.3% at 100 ℃; the NO conversion rate was 100% and the N2 selectivity was 90% at 150 ℃ with a GHSV of 60,000 h-1. The Mn/MgAl-LDO (FP-CP) catalyst exhibited a smaller fragment nano-sheet structure (sheet thickness of 7.23 nm). An apparent lattice disorder was observed in the HRTEM image confirming the presence of many defects. The H2-TPR curves show that the Mn/MgAl-LDO (FPCP) catalyst has abundant reducing substances. Furthermore, the enhanced surface acidity makes the NH3 concentration of the Mn/MgAl-LDO (FP-CP) catalyst lower than 100 ml·m-3 after the reaction from 25 to 400 ℃. This can effectively reduce the ammonia escape rate in the SCR reaction. Thus, the Mn/MgAl-LDO (FP-CP) catalyst has potential applications in stationary industrial installations for environmentally friendly ultra-low temperature SCR.
    Nitrogen-doped carbon stabilized LiFe0.5Mn0.5PO4/rGO cathode materials for high-power Li-ion batteries
    Haifeng Yu, Zhaofeng Yang, Huawei Zhu, Hao Jiang, Chunzhong Li
    2020, 28(7):  1935-1940.  doi:10.1016/j.cjche.2020.01.008
    Abstract ( 91 )   PDF (3694KB) ( 28 )  
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    Exploring high ion/electron conductive olivine-type transition metal phosphates is of vital significance to broaden their applicability in rapid-charging devices. Herein, we report an interface engineered LiFe0.5Mn0.5PO4/rGO@C cathode material by the synergistic effects of rGO and polydopamine-derivedN-doped carbon. The well-distributed LiFe0.5Mn0.5PO4 nanoparticles are tightly anchored on rGO nanosheet benefited by the coating of N-doped carbon layer. The design of such an architecture can effectively suppress the agglomeration of nanoparticles with a shortened Li+ transfer path. Meantime, the high-speed conducting network has been constructed by rGO and N-doped carbon, which exhibits the face-to-face contact with LiFe0.5Mn0.5PO4 nanoparticles, guaranteeing the rapid electron transfer. These profits endow the LiFe0.5Mn0.5PO4/rGO@C hybrids with a fast charge-discharge ability, e.g. a high reversible capacity of 105 mAh·g-1 at 10 C, much higher than that of the LiFe0.5Mn0.5PO4@C nanoparticles (46 mA·h·g-1). Furthermore, a 90.8% capacity retention can be obtained even after cycling 500 times at 2 C. This work gives a new avenue to fabricate transition metal phosphate with superior electrochemical performance for high-powerLi-ion batteries.
    Inhibition of different types of inert dust on aluminum powder explosion
    Linlin Dai, Lin Hao, Wei Kang, Wei Xu, Ning Shi, Hongyuan Wei
    2020, 28(7):  1941-1949.  doi:10.1016/j.cjche.2020.02.021
    Abstract ( 94 )   PDF (2325KB) ( 121 )  
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    Aluminum powder explosion accidents occurred frequently, but the mechanism of aluminum powder explosion is unclear. Therefore, the inhibitive effect of aluminum powder explosion plays a key role. To evaluate the inhibition capacity of different kinds of carbonates and phosphates: NaH2PO4, (NH4)2HPO4, NH4H2PO4, KHCO3 and NaHCO3 on aluminum deflagrations, a standard 20-L spherical chamber was used to determine the explosion severity, characterized by the maximum explosion pressure (Pmax). New parameters have been proposed: the minimum significant inert concentration (MSIC) and the minimum complete inert concentration (MCIC), which characterized the effect of inert. Experimental results showed that from the minimum significant inert concentration (MSIC) and the minimum complete inert concentration (MCIC), phosphate can have a significant inhibiting effect. 40% NaH2PO4 can totally inert the aluminum explosion, and 50% (NH4)2HPO4 or 50% NH4H2PO4 can also suppress the explosion. Through simulation, phosphate mainly acts via a chemical inhibition pathway, which inhibits the reaction of aluminum powder and oxygen by catalyzing the recombination of H atoms and O atoms. Carbonate performs inhibition in chemically, producing CO2, diluting the oxygen around the aluminum powder. Studies indicated that the explosion pressure of the mixture decreases as the concentration of inert dust increases. However, when the concentration of carbonates was low, SEEP (suppressant enhanced explosion parameter) phenomenon was found. This research work has a potential industrial application in high hazard aluminum working condition, which can help decrease the explosion pressure and reduce the accident loss.
    Materials and Product Engineering
    Mechanism of size effects of a filler on the wear behavior of ultrahigh molecular weight polyethylene
    Huan Zhang, Shicheng Zhao, Zhong Xin, Chunlin Ye, Zhi Li, Jincheng Xia, Jiaorong Li
    2020, 28(7):  1950-1963.  doi:10.1016/j.cjche.2020.03.001
    Abstract ( 108 )   PDF (7164KB) ( 12 )  
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    Although the size effects of a filler are closely related to the complex multi-level structures of their polymer composites; unfortunately, such relationships remain poorly understood. In this study, we investigated the effects of various sizes (40-600 nm) of silicon carbide (SiC) fillers on the wear behavior of ultrahigh molecular weight polyethylene (UHMWPE) in the presence of the silane coupling agent KH-560. All of these SiC fillers improved the wear resistance of UHMWPE significantly, with a medium size (150 nm) being optimal. To examine the reasons for this behavior, we analyzed the multi-level structures of the samples in terms of their matrix structures (crystalline; amorphous; interphase), matrix-filler interactions (physical adsorption; chemical crosslinking; hybrid network) and the external effects of SiC fillers (bearing loads; transferring frictional heat). The high rigidity and thermal conductivity of SiC fillers and, more importantly, the intrinsic characteristics of the matrix structures (larger crystal grains; higher interphase; stronger amorphous entangled networks) were the key parameters affecting the enhancement in the wear-resistance of the UHMWPE. Herein, we also provide interpretations of the corresponding physical effects. Our results should improve our understanding of the structure-property relationships and, thus, should guide the formula design of UHMWPE composites.
    Adsorption equilibrium and the effect of honeycomb heat exchanging device on charge/discharge characteristic of methane on MIL-101(Cr) and activated carbon
    Guobin Zhao, Qingrong Zheng, Xuan Zhang, Weidong Zhang
    2020, 28(7):  1964-1972.  doi:10.1016/j.cjche.2020.04.021
    Abstract ( 89 )   PDF (2804KB) ( 20 )  
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    Experiments were conducted for developing suitable ANG adsorbents for vehicular applications. MIL-101 and activated carbon samples were respectively prepared by hydrothermal and chemical activation methods. Two samples were undergone structure analysis on adsorption data of nitrogen at 77.15 K, and adsorption data of methane were then volumetrically measured within temperature-pressure range 293.15 K-313.15 K and 0-8 MPa. A conformable vessel in volume 2.5 L was employed for charge/discharge tests under the flow rate 10-30 L·min-1. It shows that limit isostreic heat of methane adsorption is respectively about 25.15 kJ·mol-1 and 22.94 kJ·mol-1 on the activated carbon and the MIL-101, and isosteric heat within the experimental condition is 14-19.5 kJ·mol-1; employing a smaller charge/discharge flow rate can weaken the temperature fluctuation of the adsorbent bed and increase the charge/discharge amount; employing honeycomb heat exchanging device enhance the thermal conductivity of the adsorbent bed by consuming a negligible part of volume of the vessel. It suggests that a smaller flow rate for charge/discharge should be employed, and MOFs together with the honeycomb heat exchanging device are promising for practical applications.
    Preparation and characterization of neodymium hydroxide powder via the hydration method
    Hongxi Li, Chenggong Xu, Qishan Yang
    2020, 28(7):  1973-1980.  doi:10.1016/j.cjche.2020.04.018
    Abstract ( 92 )   PDF (3233KB) ( 38 )  
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    The preparation of Nd(OH)3 powder by the direct hydration method using Nd2O3 as a raw material was studied, and the effects of stirring mode, H2O and Nd2O3 molar ratio, stirring rate, and reaction time on temperature change and conversion rate in a hydration system were analyzed. The reasonable process conditions for the direct hydration of Nd(OH)3 by Nd2O3 were then determined. Process, morphology, and structure were considered in the preparation of neodymium hydroxide powder, and its composition was investigated by X-ray powder diffraction, scanning electron microscopy, laser particle size analysis, thermogravimetric differential thermal analysis, and chemical analysis. It has been proved that the process is simple and feasible, in line with the concept of modern green chemistry, and the products also meet the market requirements.
    Synergistic effect of MXene on the flame retardancy and thermal degradation of intumescent flame retardant biodegradable poly (lactic acid) composites
    Haowei Huang, Dexuan Dong, Weijie Li, Xinya Zhang, Li Zhang, Ying Chen, Xinxin Sheng, Xiang Lu
    2020, 28(7):  1981-1993.  doi:10.1016/j.cjche.2020.04.014
    Abstract ( 135 )   PDF (9763KB) ( 16 )  
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    The effect of Ti3C2 MXene nanosheets on the intumescent flame retardant (IFR) poly (lactic acid) (PLA) composites was investigated among a series of PLA/IFR/MXene, which were prepared by melt blending 0-2.0 wt% MXene, 10.0 wt%-12.0 wt% IFR and PLA together. The results of limiting oxygen index (LOI) and vertical burning (UL-94) discover that the combination of 0.5 wt% MXene and 11.5 wt% IFR synergistically improves the fire safety of PLA to reach UL-94 V-0 rating with LOI value of 33.0%. The PLA/IFR/MXene composites perform an obvious reduction in peak of heat release rate (HRR) in cone calorimeter tests (CCTs). Furthermore, the carbon residues after CCTs were characterized by scanning electron microscope (SEM), laser Raman spectroscopy (LRS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It is demonstrated that both the titanium composition of the MXene structure and the characteristics of the two-dimensional material enhance the PLA/IFR/ MXene composite materials' ability to produce a dense barrier layer to resist burnout during thermal degradation.