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Table of Content
28 January 2020, Volume 28 Issue 1
    Fluid Dynamics and Transport Phenomena
    Numerical study on turbulent mixed convection in a vertical plane channel using hybrid RANS/LES and LES models
    Puxian Ding, Shuangfeng Wang, Kai Chen
    2020, 28(1):  1-8.  doi:10.1016/j.cjche.2019.04.007
    Abstract ( )   PDF (3032KB) ( )  
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    Two Delayed-Detached Eddy Simulation (DDES) models, and a Large-Eddy Simulation (LES) model are used to investigate the turbulent flows and mixed convection between a hot plate and a cold plate via the software FLUENT. The two DDES models include Production-limited DDES (PL-DDES) and Improved DDES (IDDES) models. The Wall-Adapting Local Eddy-Viscosity (WALE) model is the used LES model. The numerical computations are performed at Reynolds number Reb=4494 and different Richardson numbers Ri=0.025, 0.048, 0.1. The comparing data is from the Direct Numerical Simulation (DNS) at Reb=4494 and Ri=0.048. The comparison reveals that the two DDES models have better performance in predicting time-averaged parameters than the WALE model in the aiding flow. The best predicted time-averaged results are obtained by the PL-DDES model in the opposing flow. Furthermore, the results of different Ri obtained by the PL-DDES model agree well with the DNS data.
    Microscopic and macroscopic atomization characteristics of a pressure-swirl atomizer, injecting a viscous fuel oil
    Seyed Mohammad Ali Najafi, Pouria Mikaniki, Hojat Ghassemi
    2020, 28(1):  9-22.  doi:10.1016/j.cjche.2019.04.006
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    Combustion of heavy fuels is one of the main sources of greenhouse gases, particulate emissions, ashes, NOx and SOx. Gasification is an advanced and environmentally friendly process that generates combustible and clean gas products such as hydrogen. Some entrained flow gasifiers operate with Heavy Fuel Oil (HFO) feedstock. In this application, HFO atomization is very important in determining the performance and efficiency of the gasifiers. The atomization characteristics of HFO (Mazut) discharging from a pressure-swirl atomizer (PSA) are studied for different pressures difference (Δp) and temperatures in the atmospheric ambient. The investigated parameters include atomizer mass flow rate (), discharge coefficient (CD), spray cone angle (θ), breakup length (Lb), the unstable wavelength of undulations on the liquid sheet (λs), global and local SMD (sauter mean diameter) and size distribution of droplets. The characteristics of Mazut sheet breakup are deduced from the shadowgraph technique. The experiments on Mazut film breakup were compared with the predictions obtained from the liquid film breakup model. Validity of the theory for predicting maximum unstable wavelength was investigated for HFO (as a highly viscous liquid). A modification on the formulation of maximum unstable wavelength was presented for HFO. SMD decreases by getting far from the atomizer. The measurement for SMD and θ were compared with the available correlations. The comparisons of the available correlations with the measurements of SMD and θ show a good agreement for Ballester and Varde correlations, respectively. The results show that the experimental sizing data could be presented by Rosin-Rammler distributions very well at different pressure difference and temperatures.
    Numerical study on falling film flowing characteristics of R113 inside vertical tube under different structural conditions
    Weishu Wang, Yihan Liao, Youzhi Yan, Bingchao Zhao, Tao Wang, Shanshan Shangguan
    2020, 28(1):  23-32.  doi:10.1016/j.cjche.2019.07.021
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    To develop an appropriate falling film evaporation device for organic fluid cogeneration, a numerical study on the gas-liquid two-phase counter-current flow characteristics of R113 inside a vertical tube under different structural conditions was conducted using the Fluent software. The effects of the tube length, tube diameter, and annular gap on the falling film flow characteristics were determined, respectively. The results indicated that under a certain spray density, the falling film thickness in the region of the steady section was almost constant with different structural parameters for the tube diameter, tube length, and annular gap. In addition, a smaller tube diameter resulted in a steadier film flow. When the tube diameter decreased to a specific value, the film thickness showed a uniform distribution along the wall surface. This indicated that a best falling tube diameter exists. Meanwhile, the film fluctuation was enhanced with an increase in the tube length. When the tube length was greater than 1.2 m, the falling film splashed and could not completely wet the wall surface. The film fluctuation was enhanced by decreasing the annular gap, and the film could not be formed when the annular gap was smaller than 1.2 mm.
    An experimental study of immiscible liquid-liquid dispersions in a pump-mixer of mixer-settler
    Qiao Tang, Jiyizhe Zhang, Yuxin Wu, Yundong Wang, Zuohua Liu
    2020, 28(1):  33-45.  doi:10.1016/j.cjche.2019.07.022
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    Drop size distribution (DSD) or mean droplet size (d32) and liquid holdup are two key parameters in a liquid-liquid extraction process. Understanding and accurately predicting those parameters are of great importance in the optimal design of extraction columns as well as mixer-settlers. In this paper, the method of built-in endoscopic probe combined with pulse laser was adopted to measure the droplet size in liquid-liquid dispersions with a pump-impeller in a rectangular mixer. The dispersion law of droplets with holdup range 1% to 24% in batch process and larger flow ratio range 1/5 to 5/1 in continuous process was studied. Under the batch operation condition, the DSD abided by log-normal distribution. With the increase of impeller speed or decrease of dispersed phase holdup, the d32 decreased. In addition, a prediction model of d32 of kerosene/deionized system was established as d32/D=0.13(1+5.9φ)We-0.6. Under the continuous operation condition, the general model for droplet size prediction of kerosene/water system was presented as d32/D=C3(1+C4φ)We-0.6. For the surfactant system and extraction system, the prediction models met a general model as d32/D=nWe-0.6.
    Highly efficient[C8mim][Cl] ionic liquid accompanied with magnetite nanoparticles and different salts for interfacial tension reduction
    Sajjad Hashemi, Javad Saien
    2020, 28(1):  46-53.  doi:10.1016/j.cjche.2019.03.023
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    The 1-octyl-3-methylimidazolium chloride,[C8mim][Cl] ionic liquid (IL) was used as a novel surfactant in n-heptane/water system. The interfacial tensions (IFT) were measured and corresponding variations were investigated. An IFT reduction of 80.8% was appropriate under the IL CMC of about 0.1 mol·L-1 and stronger effects were achieved when magnetite nanoparticles and salts were present profoundly under alkaline pHs. The equilibrium IFT data were accurately simulated with the Frumkin adsorption model. Hereafter, the saturated surface concentration, equilibrium constant and interaction parameter were obtained and their variations were demonstrated. Further, emulsion stability and contact angle of oil/water interface over quartz surface were studied. The oil/water emulsion stability was hardly changed with nanoparticles; however, the stability of oil/water+IL emulsions was significantly improved. It was also revealed that the presence of sodium and calcium chloride electrolytes fortifies the IL impact, whereas sodium sulfate weakens. From dynamic IFT data and fitting with kinetic models, it was found that the IL migration toward interface follows the mixed diffusion-kinetic control model. Consequently, the IL diffusion coefficient and the appropriate activation energy were determined.
    Interaction of two in-line bubbles of equal size rising in viscous liquid
    Zhen Tian, Xi Li, Youwei Cheng, Lijun Wang
    2020, 28(1):  54-62.  doi:10.1016/j.cjche.2019.06.003
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    The interaction of bubbles is the key to understand gas-liquid bubbling flow. Two-dimensional axis-symmetry computational fluid dynamics simulations on the interactive bubbles were performed with VOF method, which was validated by experimental work. It is testified that several different bubble interactive behaviors could be acquired under different conditions. Firstly, for large bubbles (d:4, 6, 8, 10 mm), the trailing bubble rising velocity and aspect ratio have negative correlations with liquid viscosity and surface tension. The influences of viscosity and surface tension on leading bubble are negligible. Secondly, for smaller bubbles (d:1, 2 mm), the results are complicated. The two bubbles tend to move together due to the attractive force by the wake and the potential repulsive force. Especially for high viscous or high surface tension liquid, the bubble pairs undergo several times acceleration and deceleration. In addition, bubble deformation plays an important role during bubble interaction which cannot be neglected.
    The investigation and optimization of drag reduction in turbulent flow of Newtonian fluid passing through horizontal pipelines using functionalized magnetic nanophotocatalysts and lecithin
    Nadia Esfandiari, Reza Zareinezhad, Zahra Habibi
    2020, 28(1):  63-75.  doi:10.1016/j.cjche.2019.04.015
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    The nanophotocatalysts were synthesized in four stages and evaluated by FTIR, FESEM and VSM analysis. The influence of nanofluids containing functionalized magnetic TiO2 nanophotocatalyst and dipalmitoylphosphatidylcholine lecithin in drag reduction of turbulent flow in four horizontal pipelines was studied. The effective parameters on drag reduction (nanoparticle concentration, surfactant concentration, pH and Re number) were investigated and optimized in each pipeline using response surface method. The drag reduction in 1/2" galvanized, 3/4" galvanized, 1/2" five-layer and 1/2" cuprous pipelines was found 99.1%, 92.5%, 87.6% and 85.2%, respectively. The model adequacy was measured using ANOVA. Based on the high determination coefficient, more than 95% of variance of experimental data in all pipelines was described by quadratic model.
    Separation Science and Engineering
    A rate-based method for dynamic analysis and optimal design of reactive extraction: n-Hexyl acetate esterification as an example
    Xutao Hu, Hao Qin, Biao Hu, Hongye Cheng, Lifang Chen, Zhiwen Qi
    2020, 28(1):  76-83.  doi:10.1016/j.cjche.2019.04.019
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    The dynamic analysis and optimal design of reactive extraction are challenging due to high nonlinearity of model equations and tough decision of judging criteria. In this work, a dynamic rate-based method is developed on gPROMS platform to get easy access to the solutions of reactive extraction with phase splitting. Based on rigorous criteria, dynamic analysis from initial state to final equilibrium (e.g., evolution of phase composition, mass transfer rate and reaction rate) and optimal design of operating conditions (e.g., extractant dosage and feed molar ratio) are achieved. To illustrate the method, the esterification of n-hexyl acetate is taken as an example. The approach proves to be reliable in the analysis and optimization of the exemplified system, which provides instructive reference for further process design and simulation of reactive extraction.
    Study on mass transfer of ethyl acetate in polymer adsorbent by experimental and theoretical breakthrough curves
    Lina Wang, Jiale Zheng, Lin Du, Songgeng Li, Wenli Song
    2020, 28(1):  84-89.  doi:10.1016/j.cjche.2019.03.006
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    A new polymeric adsorbent with highly hypercrosslinked structure was developed for the removal of VOCs from polluted air. The purpose of this work is to obtain the intraparticle mass transfer coefficient of the adsorbent particles. Adsorption experiments for obtaining breakthrough curves were carried out with a fixed bed system. A dynamic mathematical model for the fixed bed adsorption system was developed. By model fitting, the overall mass transfer coefficient was determined when the deviation error was minimum. Then, the intraparticle mass transfer coefficient of the adsorbent was determined when the external mass transfer resistance was eliminated at higher velocities. Furthermore, a linear relationship of the intraparticle mass transfer coefficient and equilibrium coefficient at lower inlet gas concentrations range was correlated. Moreover, an equation for predicting external mass transfer coefficient at low Reynolds number range at room temperature was obtained.
    Water-selective hybrid membranes with improved interfacial compatibility from mussel-inspired dopamine-modified alginate and covalent organic frameworks
    Hao Yang, Hong Wu, Fusheng Pan, Meidi Wang, Zhongyi Jiang, Qifan Cheng, Cheng Huang
    2020, 28(1):  90-97.  doi:10.1016/j.cjche.2019.03.007
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    Hybrid membranes combining the merits of both polymer matrices and fillers have drawn extensive attention. The rational design of polymer-filler interface in hybrid membranes is vitally important for reducing the occurrence of void defects. Herein, imine-type covalent organic frameworks (COFs) were selected as the fillers due to their totally organic nature and multi-functionalities. Mussel-inspired dopamine-modified sodium alginate (AlgDA) was synthesized as the polymer matrix. The dopamine modification significantly improves the AlgDA-COF compatibility, which enhances the COF content up to 50 wt% in the hybrid membranes. The improved interfacial compatibility enhances the membrane separation selectivity. Accordingly, when utilized for dehydration of ethanol/water mixed solution (water concentration of 10 wt%), the hybrid membrane reveals high water concentration of ~98.7 wt% in permeate, and stable permeation flux larger than 1500 g·m-2·h-1. This work might afford useful insights for fabricating hybrid membranes with high separation selectivity by optimizing the polymer-filler interface. Keywords:Alginate Dopamine Covalent organic framework Membrane
    Selective swelling of polysulfone/poly(ethylene glycol) block copolymer towards fouling-resistant ultrafiltration membranes
    Hao Yang, Jiemei Zhou, Zhaogen Wang, Xiansong Shi, Yong Wang
    2020, 28(1):  98-103.  doi:10.1016/j.cjche.2019.03.011
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    Fouling resistance of ultrafiltration (UF) membranes is critical for their long-term usages in terms of stable performance, so convenient approaches to prepare fouling-resistant membranes are always anticipated. Herein, we demonstrate the facile fabrication of antifouling polysulfone-block-poly(ethylene glycol) (PSF-b-PEG, SFEG) composite membranes. SFEG layer was coated onto macroporous supports and cavitated by immerging them in acetone/n-propanol following the mechanism of selective swelling induced pore generation. Thus-produced SFEG membranes possessed high permeance and excellent mechanical strength. Meanwhile, the structures and separation performances of the SFEG layers can be continuously tuned through simply changing swelling durations. More importantly, the hydrophilic PEG chains were spontaneously enriched onto the pore walls through swelling treatment, endowing intrinsic antifouling property to the SFEG membranes. Bovine serum albumin (BSA)/humic acid (HA) fouling tests proved the prominent fouling resistance of SFEG membranes, and the fouling resistance is expected to be long-standing because of the firm connection between PEG chains and PSF matrix by covalent bonding.
    CO2 absorption performance in a rotating disk reactor using DBU-glycerol as solvent
    Hualing Duan, Kun Zhu, Houfang Lu, Changjun Liu, Kejing Wu, Yingying Liu, Bin Liang
    2020, 28(1):  104-113.  doi:10.1016/j.cjche.2019.03.031
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    Gas-liquid mass transfer of rotating disk reactor was studied in CO2 absorption using 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)-glycerol solution as solvent. Effects of the rotating disk structure and various operation parameters on the CO2 absorption rate and CO2 removal efficiency were investigated. The rotating disk with optimal holes is conducive to mass transfer of CO2 and the formation of thin liquid film at the opening increases the gas-liquid contact area. With the increase of rotating speed, the liquid flow pattern on the rotating disk surface changes from thin film flow to separated streams and creates extra liquid lines attached to the rim of the disk, which leads to a very complicated change on the CO2 absorption rate and CO2 removal efficiency. The overall gas-phase mass transfer coefficient increases 138% as the rotating speed increasing from 250 to 1400 r·min-1. Increasing temperature from 298 to 338 K can enhance the CO2 absorption rate due to lowering the viscosity of the solvent. The rate-determined step for the absorption is focused on the gas side. The rotating disk reactor can effectively enhance the absorption of CO2 with viscous DBU-glycerol solvents.
    Gradient nanoporous phenolics as substrates for high-flux nanofiltration membranes by layer-by-layer assembly of polyelectrolytes
    Yazhi Yang, Qianqian Lan, Yong Wang
    2020, 28(1):  114-121.  doi:10.1016/j.cjche.2019.04.011
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    Thin film composite (TFC) membranes represent a highly promising platform for efficient nanofiltration (NF) processes. However, the improvement in permeance is impeded by the substrates with low permeances. Herein, highly permeable gradient phenolic membranes with tight selectivity are used as substrates to prepare TFC membranes with high permeances by the layer-by-layer assembly method. The negatively charged phenolic substrates are alternately assembled with polycation polyethylenimine (PEI) and polyanion poly(acrylic acid) (PAA) as a result of electrostatic interactions, forming thin and compact PEI/PAA layers tightly attached to the substrate surface. Benefiting from the high permeances and tight surface pores of the gradient nanoporous structures of the substrates, the produced PEI/PAA membranes exhibit a permeance up to 506 L·m-2·h-1·MPa-1, which is ~2-10 times higher than that of other membranes with similar rejections. The PEI/PAA membranes are capable of retaining >96.1% of negatively charged dyes following the mechanism of electrostatic repulsion. We demonstrate that the membranes can also separate positively and neutrally charged dyes from water via other mechanisms. This work opens a new avenue for the design and preparation of high-flux NF membranes, which is also applicable to enhance the permeance of other TFC membranes.
    Investigation on removing recalcitrant toxic organic polluters in coking wastewater by forward osmosis
    Zhiqiang Li, Lanying Jiang, Chongjian Tang
    2020, 28(1):  122-135.  doi:10.1016/j.cjche.2019.07.011
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    Investigation was made on the efficiency of two commercial membranes in removing via forward osmosis (FO) the low molecular weight organic compounds typical of coking wastewater. The membranes were supplied by Poten and HTI companies. The organics in the simulated coking water were indole and pyrridine. Under FO mode, the rejection to the organics by Poten membrane was around 50%, whereas that for HTI membrane was obviously higher, ranging from 65% to 74%. The response of the two membranes in terms of Water flux and reverse salt flux (RSF) towards changing feed/draw solution (DS) flow rates in FO mode showed similar tendency, but different degree. Generally, the flux in FO using HTI membranes was lower. For HTI membrane, FO operated with pressure retarded osmosis (PRO) mode was also performed and the overall rejection of the organics was slightly lower than that in FO mode. In the long term FO test within 15 days, both Poten and HTI membranes displayed flux reduction and rejection enhancement. But the variation with Poten membrane was much more obvious. Discussion was carried out about the reasons and the mechanisms behind the FO performance difference between two membranes and the variation in flux and rejection with operation conditions. Characterizations by SEM, FTIR, AFM, XRD and XPS were tried to support the proposed explanations.
    Catalysis, Kinetics and Reaction Engineering
    Hydrolysis of mechanically pre-treated cellulose catalyzed by solid acid SO42--TiO2 in water-ethanol solvent
    Xingyilong Zhang, Houfang Lu, Kejing Wu, Yingying Liu, Changjun Liu, Yingming Zhu, Bin Liang
    2020, 28(1):  136-142.  doi:10.1016/j.cjche.2019.02.027
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    An efficient catalyst SO42--TiO2 (ST) from industrial metatitanic acid has been successfully prepared to catalyze hydrolysis of ball-milling cellulose. The results show that the highest catalytic efficiency is obtained for ST calcined at 450℃ (ST-450) with the yield of 21.8% glucose, 13.0% 5-HMF and 4.2% furfural at 200℃ for 30 min. The ball milling of cellulose and solid acid catalyst significantly enhances the cellulose hydrolysis. The high Lewis to Brönsted acid sites ratio for ST-450 induced by bidentate ligands between SO42-and TiO2 benefits high organics yield, and high total acid sites contribute to the high cellulose conversion. The large pore volume of 0.29 cm3·g-1 and appropriate pore size of 7.35 nm of ST-450 also contribute to the high performance. High reaction temperature over 200℃ exhibits negative effect on glucose and 5-HMF yield due to undesired side reactions, while furfural product is stable in the reaction system. The bidentate ligands between SO42-and TiO2 are considered as active acid sites for cellulose hydrolysis in water-ethanol solvents.
    Light olefin production by catalytic co-cracking of Fischer-Tropsch distillate with methanol and the reaction kinetics investigation
    Hui Zou, Teng Pan, Yanwen Shi, Youwei Cheng, Lijun Wang, Yu Zhang, Xi Li
    2020, 28(1):  143-151.  doi:10.1016/j.cjche.2019.04.010
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    Catalytic co-cracking of Fischer-Tropsch (FT) light distillate and methanol combines highly endothermic olefin cracking reaction with exothermic methanol conversion over ZSM-5 catalyst to produce light olefins through a nearly thermoneutral process. The kinetic behavior of co-cracking reactions was investigated by different feed conditions:methanol feed only, olefin feed only and co-feed of methanol with olefins or F-T distillate. The results showed that methanol converted to C2-C6 olefins in first-order parallel reaction at low space time, methylation and oligomerization-cracking prevailed for the co-feed of methanol and C2-C5 olefins, while for C6-C8 olefins, monomolecular cracking was the dominant reaction whether fed alone or co-fed with methanol. For FT distillate and methanol co-feed, alkanes were almost un-reactive, C3-C5 olefins were obtained as main products, accounting for 71 wt% for all products. A comprehensive co-cracking reaction scheme was proposed and the model parameters were estimated by the nonlinear least square method. It was verified by experimental data that the kinetic model was reliable to predict major product distribution for co-cracking of FT distillate with methanol and could be used for further reactor development and process design.
    Isomerization of n-pentane catalyzed by amide-AlCl3-based ionic liquid analogs with various additives
    Pengcheng Hu, Jingwei Zheng, Wei Jiang, Lijuan Zhong, Shufeng Zhou
    2020, 28(1):  152-157.  doi:10.1016/j.cjche.2019.04.018
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    The isomerization of n-pentane to generate high-quality blending components for clean gasoline was catalyzed by several amide-AlCl3-based ionic liquid (IL) analogs with various amides as donor molecules. The catalytic performance of these IL analogs was evaluated in a magnetic agitated autoclave operated in batch mode. IL analog based n-methylacetamide (NMA)-AlCl3 with the amide/AlCl3 molar ratio of 0.65 showed excellent performance toward n-pentane isomerization because 0.65NMA-1.0AlCl3 had a low viscosity and bidentate coordination structure. The influences of reaction time, reaction temperature, and stirring speed on the catalytic performance were also investigated. Optimal reaction conditions comprised the reaction time of 1 h, the reaction temperature of 40℃, and the stirring speed of 1500 r·min-1. Under optimal condition, the n-C5 conversion, research octane number (RON) increment, total liquids yield, and isoparaffin yield in isomerized oil were 56.80%, 13.51, 89.90 wt%, and 44.32 wt%, respectively. A new mathematical model was constructed to predict the relationships among RON increment, RON increment/n-C5 conversion ratio, and n-C5 conversion. The new model indicated that an appropriate conversion per pass of n-C5 did not exceed 50%-55%. Various cycloparaffin additives were used to improve the catalytic performance of 0.65NMA-1.0AlCl3. The n-C5 conversion increased from 56.80% to 67.32%. The RON increment, total liquids yield, and isoparaffin yield reached 17.83, 97.36 wt%, and 63.74 wt%, respectively.
    Solventless ketalization of glycerol to solketal with acetone over the ionic liquid[P(C4H9)3C14H29][TsO]
    Yu Ji, Tengda Zhang, Xia Gui, Haijian Shi, Zhi Yun
    2020, 28(1):  158-164.  doi:10.1016/j.cjche.2019.07.019
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    The ketalization of glycerol with acetone was conducted over an ionic liquid[P(C4H9)3C14H29][TsO] (TTPT) in a batch reactor. A scheme to obtain the purified product using TTPT as a homogeneous catalyst is proposed and a maximum solketal yield of 86% is achieved at acetone/glycerol molar ratio of 6/1, reaction time of 0.5 h, reaction temperature of 303 K, catalyst amount of 5 wt% of glycerol. TTPT was recycled and reused for ten times without obvious losses in terms of quantity and activity. Furthermore, effects of various experimental parameters (stirring speed, catalyst loadings, temperature and reactant composition) on the reaction kinetics are investigated. In terms of kinetics modeling, Kγ is fitted by reactant composition at the temperature range 298 K-323 K, which was a concise strategy that showed good precision in the kinetics fitting. The activation energy for this ketalization reaction was evaluated to be 28.2 kJ·mol-1. In addition, the kinetics of the reaction at a temperature exceeding the boiling point of acetone were also studied. We believe that all the results are important for further development of a technology for the continuous synthesis of solketal.
    Process Systems Engineering and Process Safety
    Performance enhancement of water bath heater at natural gas city gate station using twisted tubes
    P. Soleimani, M. Khoshvaght-Aliabadi, H. Rashidi, H. Bahmanpour
    2020, 28(1):  165-179.  doi:10.1016/j.cjche.2019.03.018
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    Natural gas is transported from producing regions to consumption regions by using transmission pipelines at high pressures. At consumption regions, the pressure of natural gas is reduced in city gate stations (CGSs). Before the pressure reduction process, the temperature of natural gas is increased usually by using a water bath heater, which burns natural gas as fuel, to protect against freezing of natural gas. These types of heat exchangers have a low efficiency and consume a lot of fuel to generate the required heat. In the current study, the twisted configuration of the heating coil is proposed and investigated to enhance the heat transfer through a water bath heater with a nominal capacity of 1000 m3·h-1. Firstly, the implementation procedure is validated with data collected from the CGS of Qaleh-Jiq (located in Golestan province of Iran). A very good agreement is achieved between the obtained results and the real data. Then, three different twist ratios are considered to examine the twisting effects. The proposed technique is evaluated in the terms of velocity, temperature, and pressure variations, and the results are compared with the conventional case, i.e. straight configuration. It is found that both the heat transfer rate and the pressure drop augment as the twist ratio is raised. Finally, it is concluded that the twisted tubes can reduce the length of the gas coil by about 12.5% for the model with low twist ratio, 18.75% for the model with medium twist ratio, and 25% for the model with high twist ratio as compared to the straight configuration.
    3D printed millireactors for process intensification
    Harrson S. Santana, Alan C. Rodrigues, Mariana G. M. Lopes, Felipe N. Russo, Jo?o L. Silva Jr, Osvaldir P. Taranto
    2020, 28(1):  180-190.  doi:10.1016/j.cjche.2018.12.013
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    The scope of the present research aims at demonstrating the 3D printing use in the manufacturing of microchannels for chemical process applications. A comparison among digital model processing applications for 3D print (slicers) and a print layer thickness analysis were performed. The 3D print fidelity was verified in several devices, including the microchannels' printing with and without micromixer zones. In order to highlight the 3D print potential in Chemical Engineering, the biodiesel synthesis was also carried out in a millireactor manufactured by 3D printing. The millireactor operated under laminar flow regime with a total flow rate of 75.25 ml·min-1 (increment of about 130 times over traditional microdevices used for biodiesel production). The printed millireactor provided a maximum yield of Ethyl Esters of 73.51% at 40℃, ethanol:oil molar ratio of 7 and catalyst concentration of 1.25 wt% and residence time about 10 s. As a result of flow rate increment attained in the millireactor, the number of required units for scaling-up the chemical processes is reduced. Using the approach described in the present research, anyone could produce their own millireactor for chemical process in a simple way with the aid of a 3D printer.
    Chemical Engineering Thermodynamics
    Investigation of liquid-liquid equilibrium of the ternary system (water+1,6-diaminohexane+2-methyl-1-propanol or 3-methyl-1-butanol) at different temperatures
    Yonghui Dou, Huanxin Li, Xiaoqiang Gao, Guoji Liu, Li Xu
    2020, 28(1):  191-197.  doi:10.1016/j.cjche.2019.06.009
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    In this study, the LLE data of ternary system (water+1,6-diaminohexane+2-methyl-1-propanol) and (water+1,6-diaminohexane+3-methyl-1-butanol) were measured at 293.15, 303.15 and 313.15 K under atmospheric pressure. Reliability of the experimental tie-line data was checked by empirical Hand, Othmer-Tobias and Bachman equations. Distribution coefficient (D) and selectivity (S) were calculated in order to investigate capability of the studied organic solvents for 1,6-diaminohexane extraction. The high values of separation factors demonstrated that 2-methyl-1-propanol and 3-methyl-1-butanol were applicable for this purpose. The experimental data were correlated by nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models. The percent-root-mean-square deviation (RMSD) values for NRTL and UNIQUAC models were less than 0.15, which indicated that the experimental data have been sufficiently correlated.
    Solubility and thermodynamics of lamotrigine in ternary mixtures of ionic liquids ([OMIm][Br]+[HMIm][Br]+water) at different temperatures
    Mohammad Barzegar-Jalali, Abolghasem Jouyban, Fleming Martinez, Hemayat Shekaari, Seyyedeh Narjes Mirheydari
    2020, 28(1):  198-207.  doi:10.1016/j.cjche.2019.02.026
    Abstract ( )   PDF (1289KB) ( )  
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    Experimental mole fraction solubility of lamotrigine (LTG) in ternary aqueous mixtures of two ionic liquids (ILs), 1-hexyl and 1-octyl-3-methylimidazolium bromide,[HMIm][Br] and [OMIm][Br] were reported at several temperatures T=(293.15 to 313.15) K. The van't Hoff and (Jouyban-Acree-van't Hoff, E-Jouyban-Acree-van't Hoff, e-NRTL, UNIQUAC and Wilson) models were used to correlate the solubility data. The comparison of the models with temperature and solvent composition dependencies shows that the Wilson model has the minimum ARD which are relatively close to those obtained from Jouyban-Acree-van't Hoff and E-Jouyban-Acree-van't Hoff models and maximum ARD belonged to the UNIQUAC model. The order of ARDs for these models is:Wilson < Jouyban-Acree-van't Hoff, E-Jouyban-Acree-van't Hoff < e-NRTL < UNIQUAC. Moreover, the apparent thermodynamic functions, Gibbs free energy, enthalpy and entropy of dissolution and mixing were calculated based on the van't Hoff and Gibbs free energy equations. The strong LTG-ILs interactions and enthalpic contribution of the dissolution process resulted from the calculated thermodynamic functions.
    Leaching calcium from phosphogypsum desulfurization slag by using ammonium chloride solution: Thermodynamics and kinetics study
    Yanjun Zhong, Ting Shi, Qiuge Chen, Xiushan Yang, Dehua Xu, Zhiye Zhang, Xinlong Wang, Benhe Zhon
    2020, 28(1):  208-215.  doi:10.1016/j.cjche.2019.08.006
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    Phosphogypsum (PG) desulfurization slag is a calcium-rich residue from reductive decomposition of PG using sulfur as the reductant. We proposed a technology of preparation light calcium carbonate with PG desulfurization slag, which mainly contains two steps:leaching and carbonizing. In this work, we concentrated on the former, in which ammonium chloride aqueous solution was utilized as leaching agent to extract calcium from the slag, and conducted thermodynamics and kinetics study on it. FactSage software was employed to do thermodynamic and phase equilibrium diagram calculations. The influence of leaching conditions including agitation speed, initial concentration of leaching solution, reaction temperature, and liquid/solid ratio on the calcium leaching rate was discussed in detail by means of experiment optimal design. A kinetic model developed from the shrinking core model was given to describe the leaching process. The apparent kinetic activation energy (Ea) of the leaching reaction was calculated to be 10.58 kJ·mol-1.
    Interaction of ciprofloxacin hydrochloride with sodium dodecyl sulfate in aqueous/electrolytes solution at different temperatures and compositions
    Sk. Md. Ali Ahsan, Md. Ruhul Amin, Shamim Mahbub, Mohammad Robel Molla, Shahina Aktar, Malik Abdul Rub, Md. Anamul Hoque, Muhammad Nadeem Arshad, Mohammed Abdullah Khan
    2020, 28(1):  216-223.  doi:10.1016/j.cjche.2019.03.019
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    Interactions of ciprofloxacin hydrochloride (CPFH) with sodium dodecyl sulfate (SDS) were investigated by conductivity measurement in H2O/electrolyte solutions (NaCl, Na2SO4 & Na3PO4) over 298.15-318.15 K temperature range (with 5 K interval) considering the human body temperature. In all cases, two critical micelle concentrations (c*) were observed which are increased in the presence of drug and decreased in the presence of salts enunciating the presence of interaction amongst the studied components. For (CPFH+SDS) system in the presence of salt, the c* values at 303.15 K and I=0.50 mmol·kg-1 followed the order:CNaCl > CNa2SO4 > CNa3PO4. The G1,m0 and ΔG2,m0 values are found to be negative for all systems that show that the micellization process is thermodynamically spontaneous. For (CPFH+SDS) system in water, the ΔHm0 & ΔSm0values reveal that the micellization processes is both entropy dominated in almost all cases. In the occurrence of electrolytes, ΔHm0 and ΔSm0 values indicate that micellization processes are both entropy & enthalpy restricted at upper temperature but it becomes totally entropy dependent at higher temperature. The higher positive ΔSm0 values indicate the enhanced hydrophobic interaction in presence of salts. The enthalpy-entropy compensation was determined from the linear relationship between ΔHm0 and ΔSm0 values in every state. Different transfer energies as well as compensation temperature and intrinsic enthalpy were also evaluated and the behaviors were comparable to other biological system.
    Effect of salts and their interaction with ingenious surfactants on the interfacial tension of crude oil/ionic solution
    Mostafa Lashkarbolooki, Roohollah Parvizi, Shahab Ayatollahi, Ebrahim Ghaseminejad Raeeni
    2020, 28(1):  224-235.  doi:10.1016/j.cjche.2019.04.008
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    Understanding the roles of asphaltene and resin as natural surfactants existed in crude oil can enlighten contradicting reported results regarding interfacial tension (IFT) of crude oil/aqueous solution as a function of salinity and ion type. In this way, this study is aimed to investigate the effect of these natural surface active agents on IFT of with special focus on SO42- anion and Mg2+ cation. Two different synthetic oil solutions of 8 wt% of the extracted asphaltene and resin dissolved in toluene are prepared, and then IFT values are measured. After that, the obtained results are compared with the IFT of intact crude oil in contact with the same saline solutions examined in the previous stage. The obtained results showed a synergistic effect of Na2SO4+MgCl2 solution unlike the MgSO4+MgCl2 and CaSO4+MgCl2 solutions on IFT reduction of resin at MgCl2 concentration of 15000 mg·kg-1. In summary, it is found that the affinity of asphaltene molecules towards the interface of oleic phase/ionic solution leads to higher IFT variation.
    A study on periodic boundary condition in direct numerical simulation for gas-solid flow
    Shiwen Liu, Xiaowen Liu, Feiguo Chen, Limin Wang, Wei Ge
    2020, 28(1):  236-241.  doi:10.1016/j.cjche.2019.04.025
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    Direct numerical simulation (DNS) of gas-solid flow at high resolution has been carried out by coupling the lattice Boltzmann method (LBM) for gas flow and the discrete element method (DEM) for solid particles. However, the body force periodic boundary condition (FPBC) commonly used to cut down the huge computational cost of such simulation has faced accuracy concerns. In this study, a novel two-region periodic boundary condition (TPBC) is presented to remedy this problem, with the flow driven in the region with body force and freely evolving in the other region. With simulation cases for simple circulating fluidized bed risers, the validity and advantages of TPBC are demonstrated with more reasonable heterogeneity of the particle distribution as compared to the corresponding case with FPBC.
    Biotechnology and Bioengineering
    Zwitterionic polymer-coated porous poly(vinyl acetate-divinyl benzene) microsphere: A new support for enhanced performance of immobilized lipase
    Yifeng Li, Chunyu Zhang, Yan Sun
    2020, 28(1):  242-248.  doi:10.1016/j.cjche.2019.03.002
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    Enzyme immobilization has attracted great attention for improving the performance of enzymes in industrial applications. This work was designed to create a new support for Candida rugosa lipase (CRL) immobilization. A porous poly(vinyl acetate-divinyl benzene) microsphere coated by a zwitterionic polymer, poly(maleic anhydride-alt-1-octadecene) and N,N-dimethylethylenediamine derivative, was developed for CRL immobilization via hydrophobic binding. The catalytic activity, reaction kinetics, stabilities and reusability of the immobilized CRL were investigated. It demonstrated the success of the zwitterionic polymer coating and subsequent CRL immobilization on the porous microsphere. The immobilized lipase (p2-MS-CRL) reached 27.6 mg·g-1 dry carrier and displayed a specific activity 1.5 times higher than free CRL. The increase of Vmax and decrease of Km were also observed, indicating the improvement of catalytic activity and enzyme-substrate affinity of the immobilized lipase. Besides, p2-MS-CRL exhibited significantly enhanced thermal stability and pH tolerance. The improved performance was considered due to the interfacial activation regulated by the hydrophobic interaction and stabilization effect arisen by the zwitterionic polymer coating. This study has thus proved the advantages of the zwitterionic polymer-coated porous carrier for lipase immobilization and its potential for further development in various enzyme immobilizations.
    Transformation of phthalic acid diesters in an anaerobic/anoxic/oxic leachate treatment process
    Qun Wang, Lanhui Jiang, Chengran Fang, Hongzhi Mao, Haifeng Zhuang
    2020, 28(1):  249-253.  doi:10.1016/j.cjche.2019.07.005
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    Transformations of di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) have been investigated in anaerobic/anoxic/oxic (A/A/O) leachate treatment processes. Although the DBP removal processes are different when the DBP initial concentration is different, the overall system DBP removal efficiencies are high (>94%). DEHP is much more difficult to remove than DBP. The removal efficiency of DEHP is approximately 75%-78%. The results of mass balance calculations indicate that approximately 33.7%-50.7% of the DBP is degraded by the activated sludge, 48.9%-64.9% accumulates in the system, and 0.4%-1.4% is contained in the final effluent. Approximately 15.0%-19.0% of the DEHP is degraded by activated microcosms, 75.8%-79.0% accumulates in the system, and 5.2%-6.0% is contained in the final effluent. Biodegradation and adsorption to the activated sludge are the main mechanisms for DBP removal and adsorption to the activated sludge is the main mechanism for DEHP removal. The different removal mechanisms of the two PAEs may be related to their different molecular structures. However, PAEs are not really removed when they adsorb onto the sludge. Therefore, methods for decreasing PAEs adsorption and increasing the biodegradation efficiencies of the leachate treatment processes should be further investigated.
    Energy, Resources and Environmental Technology
    Platanus orientalis leaves based hierarchical porous carbon microspheres as high efficiency adsorbents for organic dyes removal
    Xuezhen Jiang, Panpan Sun, Lin Xu, Yingru Xue, Heng Zhang, Wancheng Zhu
    2020, 28(1):  254-265.  doi:10.1016/j.cjche.2019.03.030
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    Water contamination caused by hazardous organic dyes has drawn considerable attention, among all of the techniques released, adsorption has been widely used, which however to a large degree is dependent on the development of high efficiency adsorbents. Waste biomass based porous carbon is becoming the new star class of adsorbents, and thus contribute more to the sustainable development of the society. In this work, for the first time to the best of our knowledge, abundant waste fallen Platanus orientalis leaves are employed as the raw material for hierarchical activated porous carbon (APC) microspheres via a mild hydrothermal carbonization (210℃, 12.0 h) followed by one-step calcination (750℃, 1.0 h). The APC microspheres exhibit a specific surface area of 1355.53 m2·g-1 and abundant functional groups such as O—H and C=O. Furthermore, the APC microspheres are used as the adsorbents for removal of RhB and MO, with the maximum adsorption capabilities of 557.06 mg·g-1 and 327.49 mg·g-1, respectively, higher than those of the most porous carbon originated from biomass. The adsorption rates rapidly approach to 98.2% (RhB) and 95.4% (MO) within 10 min. The adsorption data can be well fitted by Langmuir isotherm model and the pseudo-second-order kinetic model, meanwhile the intra-particle diffusion and Boyd models simultaneously indicate that the diffusion within the pores is the main rate-limiting step. Besides, the APC microspheres also demonstrate good recyclability, and may also be applied to other areas such as heterogeneous catalysis and energy storage.
    Oxidation of petroleum-based byproducts diformyltricyclodecanes (DFTD) with O2 under catalyst-free and ultra-low temperature
    Libo Zhang, Bowen Xing, Bailian Deng, Tianfu Wang, Hui Ming
    2020, 28(1):  266-270.  doi:10.1016/j.cjche.2019.04.012
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    Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes (DFTD) to dicarboxyltriclodecanesacids (DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as oxidant. In the perspective of industry process, oxygen pressure and contents, solvent and raw material initial concentrations were screened to evaluate their influence on DCTDA generation. Results indicate that DFTD oxidation can occur rather easily under no-catalyst and ultra-low temperature conditions with O2 as oxidant. Oxygen content and pressure had positive effect on DCTDA production, γ-valerolactone (GVL) behaved best on DFTD generation in dynamics, while methanol could be used as a protective solvent to preserve DFTD. Besides, the existence of water in solvent was not beneficial to DCTDA production because of poor DFTD compatibility with water. The mechanisms of O2 and solvent influence on DCTDA generation were discussed. Meanwhile, the oxidation route of DFTD-Intermediate-DCTDA was proposed. The present work exhibits the valued potential of DFTD, which will have a positive effect on high added value of petroleum based by-products.
    Chlorine-free emission disposal of spent acid etchant in a three-compartment ceramic membrane reactor
    Fanglu Yuan, Lele Cui, Peipei Ding, Wenheng Jing
    2020, 28(1):  271-278.  doi:10.1016/j.cjche.2019.04.026
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    Electrochemical technologies for the on-site treatment of spent acid etchant have received great attention due their ease of operation and economic benefits. On the other hand, a large amount of Cl2 is generated during the electrolysis process, which leads to potential environmental risks. In the present work, a novel threecompartment ceramic membrane flow reactor, including a cathode chamber, an anode chamber, and a gas absorption chamber was developed. The three chambers were divided by an Al2O3 ceramic membrane and a breathable hydrophobic anode diffusion electrode (ADE). The Cl2 evolution onset potential of the ADE was increased to 1.19 V from 1.05 V of the graphite felt, effectively inhibiting the chlorine evolution reaction (CER). The anode-generated Cl2 diffused into the gas absorption chamber through the ADE and was eventually consumed by the H2O2 adsorbent. Cu could be recovered without emitting chlorine due to the special structure of reactor. The current efficiency of copper precipitation and cathode reduction from Cu2+ to Cu+ reached 97.7% at a working current of 150 mA. These results indicated that the novel membrane reactor had high potential for application in the copper recovery industry.
    Simulated biomass tar removal mechanism by a Quench Coupled with ADsorption Technology (QCADT)
    Xiaosong Zhang, Jiawei Pan, Liang Wang, Hongqi Sun, Yuezhao Zhu, Haijun Chen
    2020, 28(1):  279-285.  doi:10.1016/j.cjche.2019.06.007
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    Tar removal is a bottleneck in the smooth commercialization of biomass gasification technology. Based on introducing adsorption process into Quench Coupled with ABsorption Technology (QCABT) previously proposed by the author's group, Quench Coupled with ADsorption Technology (QCADT) has been developed to narrow this gap. Additionally, benzene and naphthalene, which are more similar to the real tar for containing aromatic ring structures, were adopted as light and heavy simulated tar, respectively. Also their removal behavior by QCADT was investigated. The results show that the removal mechanism of QCADT is similar to that of QCABT, except for the higher overall tar removal rate due to adsorption effect. Adsorbents with both micro- and narrow mesopores exhibit a better benzene removal performance, while narrow mesopores play dominant roles in naphthalene removal. Penetration adsorption loading of benzene and naphthalene on AC-1 can reach 0.38 g·g-1 and 0.34 g·g-1, respectively. The sawdust hardly has any tar removal effect. Combined micro- and meso-pores, will benefit both deep tar removal and large adsorption rate, providing a high tar removal efficiency.
    The relationships among sCOD, VFAs, microbial community, and biogas production during anaerobic digestion of rice straw pretreated with ammonia
    Xiaoyu Zuo, Hairong Yuan, Akiber Chufo Wachemo, Xitong Wang, Liang Zhang, Juan Li, Hongliang Wen, Jiaxi Wang, Xiujin Li
    2020, 28(1):  286-292.  doi:10.1016/j.cjche.2019.07.015
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    This study investigated the effects of soluble chemical oxygen demand (sCOD), volatile fatty acids (VFAs), and microbial community on biogas production in the process of rice straw (RS) anaerobic digestion (AD). The results showed that the sCOD concentrations and VFA production appeared the same trend, which was inversely related with that of daily biogas production. The cumulative methane yield of RS was 194.9 ml·(g VS)-1·-1. The modified Gompertz model is the best fit for measured methane yields of RS in the three kinetic models of first-order kinetic, Cone and modified Gompertz. Firmicutes, Bacteroidetes, and Euryarchaeota were the dominant microbial phyla throughout AD process. At the genus level, the microorganisms mainly composed of Clostridium, Vadin, Terrisporobacter, Methanosaeta, Methanobacterium, and Methanosarcina. Proteiniphilum showed strong relationship with sCOD and VFA production. Clostridium and Terrisporobacter displayed relationship with biogas production. Therefore, in order to improve the stability of the AD system, the parameter changes of VFAs, sCOD, and biogas yield were monitored in the RS AD process. The study can provide theoretical basis for improving the efficiency of RS AD.
    Improving supercritical water gasification of sludge by oil palm empty fruit bunch addition: Promotion of syngas production and heavy metal stabilization
    Zhouchao Weng, Ekkachai Kanchanatip, Dwi Hantoko, Mi Yan, Hongcai Su, Sicheng Zhang, Guobin Wang
    2020, 28(1):  293-298.  doi:10.1016/j.cjche.2019.08.004
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    The co-gasification of sewage sludge and palm oil empty fruit bunch (EFB) in supercritical water (SCW) was conducted at 400℃ with a pressure of over 25 MPa. This study aimed to investigate the influence of EFB addition on the syngas production and its composition. The heavy metal distribution and the leaching potential of the solid residue were also assessed. The results showed that syngas yield significantly increased with the addition of EFB into the feedstock. The cold gas efficiency (CGE) and carbon efficiency (CE) of co-gasification were higher than those of individual gasification. The actual syngas production from co-gasification of sludge and EFB was 45% higher than the theoretical total volume. The results indicated that the addition of EFB to sludge had the synergetic promotion effect on syngas production from sludge and EFB in supercritical water. This enhancement might be due to the dissolution of alkali metals from EFB and the adjustment of organic ratio. In addition, higher percentage of heavy metals were deposited and stabilized in the solid residue after SCWG. The leaching concentration of heavy metals from the solid residues was decreased to a level below the standard limit which enables it to be safely disposed of in landfill. In conclusion, the EFB addition has been proved to promote syngas production, as well as, stabilize the heavy metal in solid residues during co-SCWG.
    Activation mechanisms on potassium hydroxide enhanced microstructures development of coke powder
    Xiaojing Chen, Huirong Zhang, Yanxia Guo, Yan Cao, Fangqin Cheng
    2020, 28(1):  299-306.  doi:10.1016/j.cjche.2019.07.023
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    Coke powder is expected to be an excellent raw material to produce activated carbon because of its high carbon content. Potassium hydroxide (KOH), as an effective activation agent, was reported to be effective in activating coke powder. However, the microstructures development in the coke powder and its mechanisms when KOH was applied were still unclear. In this study, effects of KOH on the microstructure activation of coke powder were investigated using the surface area and pore structure analyzer, scanning electron microscope (SEM) and thermogravimetry-differential scanning calorimetry-mass spectrometry (TG-DSC-MS), etc. Results revealed that the addition KOH at its lower ratio (mass ratios of KOH and coke powder in a range of 0.5 and 1) decreased the specific surface area and average lateral sizes, but sharply increased of the specific surface area to 132 m2·g-1 and 355 m2·g-1 and decreased of the space size of aromatic crystallites upon the further increase of the KOH addition amounts (ratios of KOH and coke powder in a range of 3 and 7), generating a number of new micropores and mesopores. The mechanisms study implied surface reactions between KOH and aliphatic hydrocarbon side chain and other carbon functional groups of the coke powder to destruct aromatic crystallites in one dimension and broaden pores at lower KOH addition. In the activation process, KOH was decomposed to be more active components, which can be rapidly destruct the aromatic layers in spatial scope to form developed porous carbon structures within coke powder at higher KOH addition.
    Materials and Product Engineering
    Surface and structure characteristics of commercial K-Feldspar powders: Effects of temperature and leaching media
    Hamed Salimkhani, Tohid Joodi, Aidin Bordbar-Khiabani, Ali Motei Dizaji, Behnam Abdolalipour, Ali Azizi
    2020, 28(1):  307-317.  doi:10.1016/j.cjche.2018.11.016
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    This study presents morphological and structural variations of K-Feldspar mineral after acid treatment. Both organic and inorganic acids such as C2H2O4, HCl, HNO3 and H2SO4 were employed for this purpose. Another aim of this study was to find an optimum experimental condition for iron (Fe) removal with a minimum damage on the structure of K-Feldspar in which high whiteness index is obtained. The effect of different parameters such as concentration, pH and temperature on the final structure of this mineral was investigated. To find out the chemical composition of powder, XRF was utilized. FTIR, XRD and SEM were employed to study the structure of mineral. Spectrophotometry was chosen to analyze whiteness index of powder after acid treatment. It was found that O—Al—O bond at 647 cm-1 for H2SO4 and HNO3 treated sample disappeared. However, HCl and C2H2O4 were ineffective at this band. In addition, the results revealed an increase in K-Feldspar content, a decrease in Fe content, an increase in whiteness index and no significant structural change for C2H2O4 leached sample. Whiteness index of 91% was obtained for C2H2O4 leached sample with the pH of 2.5 to 3 at temperature of 50℃ and during 1 h.
    Enhanced degradation of reactive dyes using a novel carbon ceramic electrode based on copper nanoparticles and multiwall carbon nanotubes
    Fatemeh Jafari, Navid Nasirizadeh, Mohammad Mirjalili
    2020, 28(1):  318-327.  doi:10.1016/j.cjche.2019.05.001
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    A novel carbon ceramic electrode consisting of CuNPs and MWCNT was developed to treat reactive orange 84 (RO84) wastewater using ultrasound-assisted electrochemical degradation. The proposed electrode generated more hydroxyl radicals than non-nanoparticle electrodes did. In addition, a new electrochemical sensor was applied to determine residue RO84 in an aqueous medium during discoloration. This sensor is based on a glassy carbon electrode modified with gold nanourchins and graphene oxide and can detect RO84 concentration in the range of 1.0-1200 μmol·L-1 with the detection limit of 0.03 μmol·L-1. The degradation effects of the modified electrode on RO84 were evaluated systematically with different initial pH values, time durations, and amounts of CuNPs and MWCNT. The results suggested that the removal efficiency of RO84 was approximately 83% after 120 min of electrolysis in a phosphate buffer with pH 8.0 using a carbon ceramic electrode made with 4.0 wt% CuNPs and 4.0 wt% MWCNT. The possible mechanism of RO84 degradation was monitored by gas chromatography-mass spectrometry, and degradation pathways were proposed.