Please wait a minute...
[an error occurred while processing this directive]
Table of Content
28 April 2018, Volume 26 Issue 4
    Fluid Dynamics and Transport Phenomena
    CFD modeling of turbulent reacting flow in a semi-batch stirred-tank reactor
    Xiaoxia Duan, Xin Feng, Chao Yang, Zaisha Mao
    2018, 26(4):  675-683.  doi:10.1016/j.cjche.2017.05.014
    Abstract ( 1101 )   PDF (4301KB) ( 46 )  
    References | Related Articles | Metrics
    For the mixing-sensitive reactions, both chemical kinetics and mixing conditions of the reactants determine the distributions of products. The direct quadrature method of moments combining with the interaction by exchange with the mean micro-mixing model (DQMOM-IEM) has been validated for the chemical reacting flows in microreactors. Quite encouraging simulation results offer great promise, but the applicability of this method is needed to be explored furthermore, such as in stirred reactors. In this work, the two-environment DQMOM-IEM model was created with C language and used to customize Fluent through the user-defined functions. The mixing effects on the course of parallel competing chemical reactions carried out in a semi-batch single-phase stirred reactor were predicted. The simulation results show that the rising feed velocity enlarges the volume of reaction zone and maximize the yield of the by-product, which also indicates that the feed stream is more difficultly dispersed into the main stream and the zone surrounding feedpipe exit with high turbulent kinetic dissipation rate cannot be efficiently used.
    Synergistic and interference effects in coaxial mixers: Numerical analysis of the power consumption
    Juan Huang, Gance Dai
    2018, 26(4):  684-694.  doi:10.1016/j.cjche.2017.10.021
    Abstract ( 752 )   PDF (4747KB) ( 33 )  
    References | Related Articles | Metrics
    This paper is concerned with the design and application of coaxial mixers with the aid of analysis of interaction between each individual impeller. Two types of coaxial mixers pitched blade turbine (PBT)-helical ribbon (HR) and inner-outer HR operated in laminar regime were studied experimentally and numerically. The interaction implies synergistic and interference effects, which was revealed through the investigation of axial circulation rate, energy dissipation rate and power consumption. The influence factors including rotational speed ratio, rotating mode and impeller configuration were explored systematically. Quantitative analysis of power consumption involves three parameters:rate of variation in power consumption, interactive mode and ratio of power consumption. Analysis indicated that some important properties were embodied in the power curve. These properties are one-way and two-way interactions, critical speed ratio and dominant impeller. Finally, a new suggestion for power estimation was given.
    Separation Science and Engineering
    Atomic layer deposition of Al2O3 on porous polypropylene hollow fibers for enhanced membrane performances
    Xiaojuan Jia, Zexian Low, He Chen, Sen Xiong, Yong Wang
    2018, 26(4):  695-700.  doi:10.1016/j.cjche.2017.10.008
    Abstract ( 733 )   PDF (2470KB) ( 24 )  
    References | Related Articles | Metrics
    Porous polypropylene hollow fiber (PPHF) membranes are widely used in liquid purification. However, the hydrophobicity of polypropylene (PP) has limited its applications in water treatment. Herein, we demonstrate that, for the first time, atomic layer deposition (ALD) is an effective strategy to conveniently upgrade the filtration performances of PPHF membranes. The chemical and morphological changes of the deposited PPHF membranes are characterized by spectral, compositional, microscopic characterizations and protein adsorption measurements. Al2O3 is distributed along the cross section of the PP hollow fibers, with decreasing concentration from the outer surface to the inner surface. The pore size of the outer surface can be easily turned by altering the ALD cycles. Interestingly, the hollow fibers become much more ductile after deposition as their elongation at break is increased more than six times after deposition with 100 cycles. The deposited membranes show simultaneously enhanced water permeance and retention after deposition with moderate ALD cycle numbers. For instance, after 50 ALD cycles a 17% increase in water permeance and one-fold increase in BSA rejection are observed. Moreover, the PP membranes exhibit improved fouling-resistance after ALD deposition.
    Experimental investigation and cost assessment of the salt production by solar assisted evaporation of saturated brine
    Jing Zhao, Huaigang Cheng, Xiao Wang, Wenting Cheng, Fangqin Cheng
    2018, 26(4):  701-707.  doi:10.1016/j.cjche.2017.08.016
    Abstract ( 794 )   PDF (2703KB) ( 39 )  
    References | Related Articles | Metrics
    The technical feasibility and economy of solar heat collection-forced evaporation process are the keys to its practicality, especially its application in strong brine treatment. The operation cost of applying solar collection in salt manufacturing through depth evaporation of brine has been studied. For Na+, K+, Mg2+//Cl-, SO42--H2O salt-water system, most of the NaCl and all of the Carnallite were separated. The operation cost reached the optimum when the heat collection and evaporation were controlled at 75 and 55℃, respectively. When the solar radiation amount was 19557 kJ·m-2·d-1, the solar collector area for producing Carnallite was about 34.27 m2·(t salt)-1, and the operation cost was 13 USD·(t salt)-1. The energy consumption of salt manufacturing is at least 25% higher than that of natural evaporation. Regarding the economy, the solar assisted salt manufacturing process is recommended to be performed at a production scale of more than 20 tons per day.
    Equilibrium of liquid-liquid extraction of 2-phenylbutyric acid enantiomers: Experiment and model
    Weifeng Xu, Guilin Dai, Kewen Tang, Panliang Zhang, Biquan Xiong, Yu Liu
    2018, 26(4):  708-714.  doi:10.1016/j.cjche.2017.09.002
    Abstract ( 776 )   PDF (2931KB) ( 27 )  
    References | Related Articles | Metrics
    The utilization of liquid-liquid extraction for the separation of 2-phenylbutyric acid (2-PBA) enantiomers was proposed. Factors affecting the extract process were investigated, including organic solvents, β-cyclodextrin derivatives, cyclodextrin concentration, pH and temperature. A model was proposed to describe the separation process based on the homogeneous phase reaction mechanism. Important parameters of this model were determined experimentally. The physical distribution coefficients for molecular and ionic 2-PBA were 0.129 and 7.455, respectively. The equilibrium constants of the complexation reactions were 89.36 and 36.78 L·mol-1 for (+)-and (-)-2-PBA, respectively. The model was verified by experiments and proved to be an excellent means to optimize the separation system. Through modeling prediction and experiment, the best conditions (e.g., pH value of 3.00, extractant concentration of 0.1 mol·L-1, temperature of 5.0℃) were acquired. Under this condition, the maximum enantioselectivity (2.096) was obtained.
    Preparation of PVC/PVP composite polymer membranes via phase inversion process for water treatment purposes
    Ahmed Bhran, Abeer Shoaib, Doaa Elsadeq, Ayman El-gendi, Heba Abdallah
    2018, 26(4):  715-722.  doi:10.1016/j.cjche.2017.09.003
    Abstract ( 1018 )   PDF (2190KB) ( 73 )  
    References | Related Articles | Metrics
    In this work, new composite membranes were successfully prepared via phase inversion technique using polyvinyl chloride (PVC) and polyvinylpyrrolidone (PVP) as polymers and tetrahydrofuran (THF) and N-methyl-2-pyrrolidone (NMP) as solvents. The prepared membranes have been characterized by scanning electron microscope (SEM), and fourier transforms infrared spectroscopy (FTIR). The scanning electron microscope results prove that the prepared membranes are smooth and their pores are distributed throughout the whole surface and bulk body of the membrane without any visible cracks. The stress-strain mechanical test showed an excellent mechanical behavior enhanced by the presence of PVP in the prepared membranes. The membranes performance results showed that the salt rejection reached 98% with a high flux. This, in turn, makes the prepared membranes can be applied for sea and brackish water treatment through membrane distillation technology.
    Design aspect of a novel L-shaped pulsed column for liquid-liquid extraction applications: Energy consumption and the characteristics velocity concept
    Pouria Amani, Elham Mohammadi, Sahar Akhgar
    2018, 26(4):  723-730.  doi:10.1016/j.cjche.2017.08.004
    Abstract ( 946 )   PDF (2111KB) ( 24 )  
    References | Related Articles | Metrics
    This article deals with the evaluation of the consumption of energy for a steady state solvent extraction in a novel L-shaped pulsed sieve-plate column, which is highly required for design and optimization of the periodic flow processes for industrial applications. In this regard, a comprehensive evaluation on the energy consumption in case of a pulsed flow for three different chemical systems is conducted and besides the influence of pulsation intensity, the effect of geometrical parameters including the plate spacing and the plate free area is investigated as well. Moreover, the concept of characteristic velocity models at flooding points is evaluated with respect to the variation of pressure drop along the column at different operational conditions.
    The adsorptive properties of UiO-66 towards organic dyes: A record adsorption capacity for the anionic dye Alizarin Red S.
    Marwa S. Embaby, Saber D. Elwany, Widiastuti Setyaningsih, Mohamed R. Saber
    2018, 26(4):  731-739.  doi:10.1016/j.cjche.2017.07.014
    Abstract ( 956 )   PDF (2717KB) ( 31 )  
    References | Related Articles | Metrics
    In order to decisively determine the adsorption selectivity of zirconium MOF (UiO-66) towards anionic versus cationic species, the adsorptive removal of the anionic dyes (Alizarin Red S. (ARS), Eosin (E), Fuchsin Acid (FA) and Methyl Orange (MO)) and the cationic dyes (Neutral Red (NR), Fuchsin Basic (FB), Methylene Blue (MB), and Safranine T (ST)) has been evaluated. The results clearly reveal a significant selectivity towards anionic dyes. Such an observation agrees with a plethora of reports of UiO-66 superior affinity towards other anionic species (Floride, PO43-, Diclofenac sodium, Methylchlorophenoxy-propionic acid, Phenols, CrO42-, SeO32-, and AsO4-). The adsorption process of ARS as an example has been optimized using the central composite design (CCD). The resultant statistical model indicates a crucial effect of both pH and sorbent mass. The optimum conditions were determined to be initial dye concentration 11.82 mg.L-1, adsorbent amount 0.0248 g, shaking time of 36 min and pH 2. The adsorption process proceeds via pseudo-second order kinetics (R2=0.999). The equilibrium data were fit to Langmuir and Tempkin models (R2=0.999 and 0.997 respectively). The results reveal an exceptional removal for the anionic dye (Alizarin Red S.) with a record adsorption capacity of 400 mg·g-1. The significantly high adsorption capacity of UiO-66 towards ARS adds further evidence to the recently reported exceptional performance of MOFs in pollutants removal from water.
    A robust predictive tool for estimating CO2 solubility in potassium based amino acid salt solutions
    Ebrahim Soroush, Shohreh Shahsavari, Mohammad Mesbah, Mashallah Rezakazemi, Zhi'en Zhang
    2018, 26(4):  740-746.  doi:10.1016/j.cjche.2017.10.002
    Abstract ( 762 )   PDF (1899KB) ( 26 )  
    References | Related Articles | Metrics
    The acid gas absorption in four potassium based amino acid salt solutions was predicted using artificial neural network (ANN). Two hundred fifty-five experimental data points for CO2 absorption in the four potassium based amino acid salt solutions containing potassium lysinate, potassium prolinate, potassium glycinate, and potassium taurate were used in this modeling. Amine salt solution's type, temperature, equilibrium partial pressure of acid gas, the molar concentration of the solution, molecular weight, and the boiling point were considered as inputs to ANN to prognosticate the capacity of amino acid salt solution to absorb acid gas. Regression analysis was employed to assess the performance of the network. Levenberg-Marquardt back-propagation algorithm was used to train the optimal ANN with 5:12:1 architecture. The model findings indicated that the proposed ANN has the capability to predict precisely the absorption of acid gases in various amino acid salt solutions with Mean Square Error (MSE) value of 0.0011, the Average Absolute Relative Deviation (AARD) percent of 5.54%, and the correlation coefficient (R2) of 0.9828.
    Catalysis, Kinetics and Reaction Engineering
    Cobalt catalysts for Fischer-Tropsch synthesis: The effect of support, precipitant and pH value
    Zhenhua Li, Mengyao Si, Li Xin, Renjie Liu, Runxue Liu, Jing Lü
    2018, 26(4):  747-752.  doi:10.1016/j.cjche.2017.11.001
    Abstract ( 880 )   PDF (4074KB) ( 47 )  
    References | Related Articles | Metrics
    In this report, Co-based catalysts supported on ZnO, Al2O3 and ZrO2 as well as the ZrO2 derived from different precipitants and different pH values were prepared by co-precipitation method. Their catalytic Fischer-Tropsch synthesis (FTS) performance was investigated in a fixed-bed reactor. The results revealed that Co catalyst supported on ZrO2 exhibited better FTS catalytic performance than that supported on ZnO or Al2O3. For the Co/ZrO2 catalyst, different precipitants showed the following an activity order of NaOH > Na2CO3 > NH4OH, and the best pH value is 13. The catalysts were characterized by N2 adsorption-desorption, XRF, XRD, H2-TPR, H2-TPD and TEM. It was found that the main factor affecting the CO conversion of the catalyst was the amounts of low-temperature active adsorption sites. Moreover, the selectivity of C5+ hydrocarbons had a positive relationship with the peak temperature of the weak hydrogen adsorption sites. The higher the peak temperature, the higher the C5+ selectivity is.
    Porous g-C3N4 with enhanced adsorption and visible-light photocatalytic performance for removing aqueous dyes and tetracycline hydrochloride
    Junlei Zhang, Zhen Ma
    2018, 26(4):  753-760.  doi:10.1016/j.cjche.2017.10.010
    Abstract ( 1028 )   PDF (2521KB) ( 38 )  
    References | Related Articles | Metrics
    Porous g-C3N4 samples were obtained by simply calcining bulk g-C3N4 in static air in a muffle oven. The photocatalytic performance of these samples was evaluated through the removal of aqueous organic dyes (methylene blue and methyl orange) and tetracycline hydrochloride under visible-light irradiation (λ > 420 nm). Compared to bulk g-C3N4, porous g-C3N4 exhibited much better capability for removing these contaminants, especially under visible-light irradiation, due to the enlarged specific surface area and more efficient separation of photogenerated charge carries. In particular, porous g-C3N4 obtained by calcining bulk g-C3N4 in air at 525℃ showed the highest visible-light-driven catalytic activity among these samples. Superoxide radical anions (·O2-) were found to be the primary active species responsible for photodegradation.
    Effect of preparation methods on the structure and catalytic performance of Fe-Zn/K catalysts for CO2 hydrogenation to light olefins
    Xu Wang, Jianli Zhang, Jingyu Chen, Qingxiang Ma, Subing Fan, Tiansheng Zhao
    2018, 26(4):  761-767.  doi:10.1016/j.cjche.2017.10.013
    Abstract ( 782 )   PDF (2316KB) ( 31 )  
    References | Related Articles | Metrics
    Potassium promoted iron-zinc catalysts prepared by co-precipitation method (C-Fe-Zn/K), solvothermal method (S-Fe-Zn/K) and hydrothermal method (H-Fe-Zn/K) could selectively convert CO2 to light olefins, respectively. The physicochemical properties of the obtained catalysts were determined by SEM, N2 physisorption, XRD, H2-TPR, CO2-TPD and XPS measurements. The results demonstrated that preparation methods had great influences on the morphology, phase structures, reduction and adsorption behavior, and hence the catalytic performance of the catalysts. The samples prepared by hydrothermal and co-precipitation method generated small uniform particles and led to lower specific surface area. In contrast, microspheres with larger specific surface area were formed by self-assembly of nanosheets using solvothermal method. ZnFe2O4 was the only detectable phase in the fresh C-2Fe-1Zn/K, S-3Fe-1Zn/K and S-2Fe-1Zn/K samples. ZnFe2O4 and ZnO co-existed with increasing Zn content in S-1Fe-1Zn/K sample, while ZnO and Fe2O3 could be observed over H-2Fe-1Zn/K sample. All the used samples contained Fe3O4, ZnO and Fe5C2. The peak intensity of ZnO was strong in the AR-H-2Fe-1Zn/K sample while it was the lowest in the AR-C-2Fe-1Zn/K sample after reaction. The formation of ZnFe2O4 increased the interaction between iron and zinc for C-2Fe-1Zn/K and S-Fe-Zn/K samples, causing easier reduction of Fe2O3 to Fe3O4. The surface basicity of the sample prepared by co-precipitation method was much more than that of the other two methods. During CO2 hydrogenation, all the catalysts showed good activity and olefin selectivity. The CO selectivity was increased with increasing Zn content over S-Fe-Zn/K samples. H-2Fe-1Zn/K catalyst preferred to the production of C5+ hydrocarbons. CO2 conversion of 54.76% and C2=-C4= contents of 57.38% were obtained on C-2Fe-1Zn/K sample, respectively.
    Influence of Zr, Ce, and La on Co3O4 catalyst for CO2 methanation at low temperature
    Yuwen Zhou, Yuexiu Jiang, Zuzeng Qin, Qinruo Xie, Hongbing Ji
    2018, 26(4):  768-774.  doi:10.1016/j.cjche.2017.10.014
    Abstract ( 892 )   PDF (2163KB) ( 44 )  
    References | Related Articles | Metrics
    The Co3O4 and Zr-, Ce-, and La-Co3O4catalysts were prepared, characterized, and applied to produce CH4 from CO2 catalytic hydrogenation in low temperature as 140-220℃. The results indicated that the addition of Zr, Ce, or La to the Co3O4 decreased the crystallite sizes of Co and the outer-shell electron density of Co3+, and increased the specific surface area, which would provide more active sites for the CO2 methanation. Especially, the addition of Zr also changed the reducing state of Co3O4 via an obvious change in the interaction between Co3O4 and ZrO2. Furthermore, Zr doped into the Co3O4 increased the basic intensity of the weak and medium basic sites, as well as the amount of Lewis acid sites, and Brønsted acid sites were also found on the Zr-Co3O4 surface. The introduction of Zr, Ce, or La favored the production of CH4, and the Zr-Co3O4 catalyst exhibited the highest CO2 conversion (58.2%) and CH4 selectivity (100%) at 200℃, and 0.5 MPa with a gaseous hourly space velocity of 18,000 ml·gcat-1·h-1, and the catalytic activity of CO2 methanation for the Zr-, Ce-, and La-Co3O4 exhibited more stable than Co3O4 in a 20-h reaction.
    Process Systems Engineering and Process Safety
    Online complex nonlinear industrial process operating optimality assessment using modified robust total kernel partial M-regression
    Fei Chu, Wei Dai, Jian Shen, Xiaoping Ma, Fuli Wang
    2018, 26(4):  775-785.  doi:10.1016/j.cjche.2017.06.019
    Abstract ( 778 )   PDF (765KB) ( 29 )  
    References | Related Articles | Metrics
    Although industrial processes often perform perfectly under design conditions, they may deviate from the optimal operating point owing to parameters drift, environmental disturbances, etc. Thus, it is necessary to develop efficacious strategies or procedure to assess the process performance online. In this paper, we explore the issue of operating optimality assessment for complex industrial processes based on performance-similarity considering nonlinearities and outliers simultaneously, and a general enforced online performance assessment framework is proposed. In the offline part, a new and modified total robust kernel projection to latent structures algorithm, T-KPRM, is proposed and used to evaluate the complex nonlinear industrial process, which can effectively extract the optimal-index-related process variation information from process data and establish assessment models for each performance grades overcoming the effects of outlier. In the online part, the online assessment results can be obtained by calculating the similarity between the online data from a sliding window and each of the performance grades. Furthermore, in order to improve the accuracy of online assessment, we propose an online assessment strategy taking account of the effects of noise and process uncertainties. The Euclidean distance between the sliding data window and the optimal evaluation level is employed to measure the contribution rates of variables, which indicate the possible reason for the non-optimal operating performance. The proposed framework is tested on a real industrial case:dense medium coal preparation process, and the results shows the efficiency of the proposed method comparing to the existing method.
    A novel process integrating vacuum distillation with atmospheric chlorination reaction for flexible production of tetrachloroethane and pentachloroethane
    Xian Chen, Yunpeng Li, Ge Xu, Jihai Tang, Zhuxiu Zhang, Ming Chen, Zhaoyang Fei, Mifen Cui, Xu Qiao
    2018, 26(4):  786-794.  doi:10.1016/j.cjche.2017.10.023
    Abstract ( 756 )   PDF (944KB) ( 16 )  
    References | Related Articles | Metrics
    In this paper, we developed a novel process integrating vacuum distillation with atmospheric chlorination reaction (VD-ACR) to realize the flexible production of tetrachloroethane (TeCA) and pentachloroethane (PCA) from 1,2-dichloroethane (DCA). During the simulation, the distillation column and reactors were operated for separation and chlorination respectively under variable pressures and temperatures. It is interesting to note that VD-ACR processes producing pure TeCA or PCA can exhibit the similar configuration parameters after optimization, which enables the flexible production of TeCA and PCA with different molar ratios via changing operating parameters. The molar ratio of TeCA/PCA can be fine-tuned within the range of 0.9:0.1-0.1:0.9 through adjusting the amount of chlorine pumped into side reactors, giving rise to the increase of the heat duty of reboiler by five times. A pilot-scale experiment was then operated based-upon this VD-ACR process and the result matched well with the simulation. Therefore, the VD-ACR model presented in this study will be beneficial for the industrial-scale flexible production of TeCA and PCA from DCA.
    Study on reactions of gaseous P2O5 with Ca3(PO4)2 and SiO2 during a rotary kiln process for phosphoric acid production
    Qiang Liu, Weizao Liu, Li Lü, Ruhu Li, Bin Liang, Hairong Yue, Shengwei Tang, Chun Li
    2018, 26(4):  795-805.  doi:10.1016/j.cjche.2017.11.016
    Abstract ( 718 )   PDF (5879KB) ( 42 )  
    References | Related Articles | Metrics
    In a rotary kiln process for phosphoric acid production, the reaction between gaseous phosphorus pentoxide (P2O5) and phosphate ore and silica contained in feed balls (the so-called P2O5 "absorption") not only reduces phosphorous recovery but also generates a large amount of low melting-point side products. The products may give rise to formation of kiln ring, which interferes with kiln operation performance. In this study, the reactions of gaseous P2O5 with solid calcium phosphate (Ca3(PO4)2), silica (SiO2) and their mixture, respectively, were investigated via combined chemical analysis and various characterizations comprised of X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis and differential scanning calorimeter (TG&DSC), and scanning electron microscopy and energy dispersive spectrometer (SEM&EDS). Attentions were focused on apparent morphology, phase transformation and thermal stability of the products of the P2O5 "absorption" at different temperatures. The results show that the temperature significantly affected the "absorption". The reaction between pure Ca3(PO4)2 and P2O5 occurred at 500℃. Calcium metaphosphate (Ca(PO3)2) was the primary product at the temperatures ≤ 900℃ with its melting point ≤ 900℃ while calcium pyrophosphate (Ca2P2O7) was obtained over 1000℃, which has a melting point ≤ 1200℃. The "absorption" by pure SiO2 started at 800℃ and the most significant reaction occurred at 1000℃ with formation of silicon pyrophosphate (SiP2O7) product of melting point ≤ 1000℃. Using mixed Ca3(PO4)2 and SiO2 as raw material, the "absorption" by Ca3(PO4)2 was enhanced due to existence of silica. At 600-700℃, silica was inert to P2O5 and thus formed a porous structure in the raw material, which accelerated diffusion of gaseous P2O5 inside the mixture. At higher temperatures, the combined "absorption" by calcium phosphate and reaction between silicon dioxide and the "absorption" product calcium pyrophosphate, reinforced the "absorption" by the mixture. Besides, it was found that both Ca(PO3)2 and SiP2O7 were unstable at high temperatures and would decompose to Ca2P2O7 and SiO2, respectively, at over 1000℃ and 1100℃ with the release of gaseous P2O5 at the same time.
    Chemical Engineering Thermodynamics
    Measurement and correlation of solid-liquid phase equilibria for binary and ternary systems consisting of N-vinylpyrrolidone, 2-pyrrolidone and water
    Ao Su, Sifang Li
    2018, 26(4):  806-811.  doi:10.1016/j.cjche.2017.09.012
    Abstract ( 815 )   PDF (674KB) ( 72 )  
    References | Related Articles | Metrics
    The solid-liquid equilibria (SLE) for binary and ternary systems consisting of N-Vinylpyrrolidone (NVP), 2-Pyrrolidone (2-P) and water are measured. The phase diagrams of NVP (1) + 2-P (2), NVP (1) + water (2), NVP (1) + 2-P (2) + 1 wt% water (3) and NVP (1) + 2-P (2) + 2 wt% water (3) are identified as simple eutectic type with the eutectic points at 263.75 K (x1E=0.5427), 251.65 K (x1E=0.3722), 260.25 K (x1E=0.5031) and 256.55 K (x1E=0.4684), respectively. The phase diagram of 2-P (1) + water (2) has two eutectic points (x1E=0.1236, TE=259.15 K and x1E=0.7831, TE=286.15 K) and one congruent melting point (x1C=0.4997, TC=303.55 K) because of the generation of a congruently melting addition compound:2-P·H2O. The ideal solubility and the UNIFAC models were applied to predict the SLE, while the Wilson and NRTL models were employed in correlating the experimental data. The best correlation of the SLE data has been obtained by the Wilson model for the binary system of NVP + 2-P. The UNIFAC model gives more satisfactory predictions than the ideal solubility model.
    Biotechnology and Bioengineering
    Novel kinetic model for the simulation analysis of the butanol productivity of Clostridium acetobutylicum ATCC 824 under different reactor configurations
    Hugo I. Velázquez-Sánchez, Ricardo Aguilar-López
    2018, 26(4):  812-821.  doi:10.1016/j.cjche.2017.07.018
    Abstract ( 693 )   PDF (3438KB) ( 35 )  
    References | Related Articles | Metrics
    Acetone-butanol-ethanol (ABE) fermentation process can be exploited for the generation of butanol as biofuel, however it does need to overcome its low volumetric solvent productivity before it can commercially compete with fossil fuel technologies. In this regard, mathematical modelling and simulation analysis are tools that can serve as the base for process engineering development of biological systems. In this work, a novel phenomenological kinetic model of Clostridium acetobutylicum ATCC 824 was considered as a benchmark system to evaluate the behaviour of an ABE fermentation under different process configurations using both free and immobilized cells:single stage batch operation, fed-batch, single stage Continuous Stirred Tank Reactor (CSTR) and multistage CSTRs with and without biomass recirculation. The proposed model achieved a linear correlation index r2=0.9952 and r2=0.9710 over experimental data for free and immobilized cells respectively. The predicted maximum butanol concentration and productivity obtained were 13.08 g·L-1 and 1.9620 g·L-1·h-1 respectively, which represents an increase of 1.01% and 990% versus the currently developed industrial scale process reported currently into the literature. These results provide a reliable platform for the design and optimization of the ABE fermentation system and showcase the adequate predictive nature of the proposed model.
    Evaluation of the effects of AlkylPhenolic compounds on kinetic coefficients and biomass activity in MBBR by means of respirometric techniques
    Bijan Bina, Farzaneh Mohammadi, Mohammad Mehdi Amin, Hamid Reza Pourzamani, Zeynab Yavari
    2018, 26(4):  822-829.  doi:10.1016/j.cjche.2017.07.024
    Abstract ( 670 )   PDF (1554KB) ( 29 )  
    References | Related Articles | Metrics
    The presence of AlkylPhenols (APs) in aquatic systems is considered as one of the environmental concerns in recent decades which are generally used as surfactants. APs are endocrine disruptors and estrogen-mimicking, causing harmful effects such as feminization and carcinogenesis on aquatic environment and human health. The most commercially important APs are 4-NonylPhenol (4-NP) and 4-tert-OctylPhenol (4-t-OP). Moving bed biofilm reactor (MBBR), which combined attached and suspended growth advantages, is an advanced biological treatment process for municipal and industrial wastewaters that has drawn considerable attention from many researchers to remove toxic pollutants from wastewater. The aim of this research was to evaluate Bacterial activities and kinetic coefficients in the presence of APs. This study was carried out using laboratory-scale MBBR fed with synthetic wastewater containing 4-NP and 4-t-OP. The reactor was operated at different loads of chemical oxygen demand (COD) and APs and different hydraulic retention time (HRT). The respirometric technique was applied to investigate the effect of APs on heterotrophic and autotrophic activity and kinetic coefficients in biomass obtained from MBBR. Respirometric technique demonstrates a reliable tool in order to assess the biofilm kinetic coefficients and biomass viability to insert in the mathematical models. The calculated kinetic parameters were in the range of conventional and extended aeration activated sludge processes. The results demonstrate that APs have significant inhibitory effects on activity and growth rate of heterotrophic and autotrophic bacteria, heterotrophs have been less affected by the presence of 4-NP and 4-t-OP, and these compounds had greater inhibitory effects on autotrophic bacteria.
    Energy, Resources and Environmental Technology
    Doping effects on the electro-degradation of phenol on doped titanium suboxide anodes
    Xuan Yang, Jiuji Guo, Zhaowu Zhu, Hui Zhang, Tao Qi
    2018, 26(4):  830-837.  doi:10.1016/j.cjche.2017.12.007
    Abstract ( 767 )   PDF (1300KB) ( 25 )  
    References | Related Articles | Metrics
    Titanium suboxide is an excellent electrode material for many oxidization reactions. In this article, the electrodes of pure Ti4O7, doped Ti4O7 and the mixed-crystal of Ti4O7 and Ti5O9 were prepared to evaluate their activities and doping effects in the electro-degradation of phenol. It was revealed by the HPLC analysis results that the degradation intermediates and routes were significantly affected by the doping element. On the pure Ti4O7 anode, a series of classic intermediates were obtained from benzoquinone and hydroquinone to various carboxylic acids. These intermediates were degraded gradually to the final organic intermediate of oxalate in all experiments. At last, oxalate was oxidized to CO2 and H2O. Distinctively, the Y-doped Ti4O7 anode directly broke phenol to α-ketoglutaric acid without the intermediates of benzoquinone and hydroquinone. The strong oxidization ability of the Y-doped Ti4O7 anode might be responsible for the highest COD removal ratio. In contrast, the Ga-doped Ti4O7 anode showed the worst degradation activity in this article. Three intermediates of benzoquinone, hydroquinone and maleic acid were found during the degradation. Benefiting from the weak ability, oxalate was efficiently accumulated with a very high yield of 74.6%. The results demonstrated promising applications from electrochemical preparation to wastewater degradation by adjusting the doping reagent of Ti4O7 electrodes.
    Decomposition behavior of CaSO4 during potassium extraction from a potash feldspar-CaSO4 binary system by calcination
    Li Lü, Chun Li, Guoquan Zhang, Xiaowei Hu, Bin Liang
    2018, 26(4):  838-844.  doi:10.1016/j.cjche.2017.10.001
    Abstract ( 666 )   PDF (3095KB) ( 27 )  
    References | Related Articles | Metrics
    The extraction of potassium from a tablet mixture of K-feldspar ore and CaSO4 by roasting was studied with a focus on the effects of the decomposition behavior of CaSO4 on the potassium extraction process. The roasted slags were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, and thermogravimetric (TG) analysis. The XRD analysis revealed that hydrosoluble mischcrystal K2Ca2(SO4)3 was obtained by ion exchange of Ca2+ in CaSO4 and K+ in KAlSi3O8. Meanwhile, the intermediate product, SiO2, separated from KAlSi3O8 and reacted with CaSO4 to decompose CaSO4. The SEM results showed that some blowholes emerged on the surface of the CaSO4 particles when they reacted with SiO2 at 1200℃, which indicates that SO2 and O2 gases were released from CaSO4. The TG curves displayed that pure CaSO4 could not be decomposed below 1200℃, while the mixture of K-feldspar ore and CaSO4 began to lose weight at 1000℃. The extraction rate of potassium and decomposition rate of CaSO4 were 62% and 44%, respectively, at a mass ratio of CaSO4 to K-feldspar ore of 3:1, temperature of 1200℃, tablet-forming pressure of 6 MPa, and roasting time of 2 h. The decomposition of CaSO4 reduced the potassium extraction rate; therefore, the required amount of CaSO4 was more than the theoretical amount. However, excess CaSO4 was also undesirable for the potassium extraction reaction because a massive amount of SO2 and O2 gas were derived from the decomposition of CaSO4, which provided poor contact between the reactants. The SO2 released from CaSO4 decomposition can be effectively recycled.
    The extraction of potassium from K-feldspar ore by low temperature molten salt method
    Zhao Wang, Quanyou Zhang, Ying Yao, Yongzhong Jia, Bingjun Xie
    2018, 26(4):  845-851.  doi:10.1016/j.cjche.2017.09.006
    Abstract ( 776 )   PDF (1685KB) ( 33 )  
    References | Related Articles | Metrics
    The low temperature molten salt method was used to extract potassium from K-feldspar ore, and some related factors including mass ratio between NaNO3, NaOH, H2O and K-feldspar ore, particle size of K-feldspar ore, reaction temperature and time were investigated, respectively. In addition, the optimum condition for this method was determined by a series of condition experiments. What was more, the K-feldspar ore and the leach residue after reaction based on the above optimum condition were analyzed by XRD, SEM and EDS, separately. The results of which indicated that the mechanism of extraction of potassium for this method was according to the ion exchange reaction between sodium ion and potassium ion, and the extraction ratio of potassium had an obvious improvement than that of traditional methods, which could reach up to 96.25%. Therefore, this method can be a feasible solution to extract potassium from K-feldspar ore for its low energy consumption and high efficiency.
    Transesterification of sunflower oil in microchannels with circular obstructions
    Harrson S. Santana, João L. Silva Jr, Deborah S. Tortola, Osvaldir P. Taranto
    2018, 26(4):  852-863.  doi:10.1016/j.cjche.2017.08.018
    Abstract ( 816 )   PDF (8915KB) ( 12 )  
    References | Related Articles | Metrics
    The present paper studied numerical and experimentally the transesterification reaction between sunflower oil and ethanol with NaOH catalyst in microchannels with circular obstructions. The micromixer design influence on fluid mixing and oil conversion was investigated for a range of operating conditions:Reynolds number (Re=0.1-100), Temperature (25-75℃), ethanol/oil molar ratio (6-12), and catalyst concentration (0.75 wt%-1.25 wt%), using three microchannel configurations (Length=35 mm; Width=1500 μm; Height=200 μm):T-shape-channel without obstructions; MCO-channel with 3 obstructions ensemble-equally disposed over longitudinal length; MWO-channel with 7 obstructions ensemble. The MCO micromixer was based on literature work, and the MWO is a totally new micromixer design. Experimental tests were conducted in similar conditions in microreactors using these micromixers (Length=411 mm) made of polydimethylsiloxane. The MCO configuration presented the highest performance (mixing index of 0.80 at Re=100), oil conversion of 81.13% at 75℃, molar ratio of 9 and catalyst concentration of 1%. Experimental results showed high conversions for MCO and MWO configurations (99.99%) at 50℃, molar ratio of 9 and catalyst concentration of 1%, with a residence time of 12 s.
    17α-Ethinylestradiol removal from water by magnetic ion exchange resin
    Liang Wang, Lu Liu, Zhaohui Zhang, Bin Zhao, Junjing Li, Bingjie Dong, Nian Liu
    2018, 26(4):  864-869.  doi:10.1016/j.cjche.2017.08.006
    Abstract ( 943 )   PDF (658KB) ( 31 )  
    References | Related Articles | Metrics
    Magnetic ion exchange (MIEX) resins have received considerable attention in drinking water treatment due to their fast and efficient removal of dissolved organic carbon (DOC). Two types of mechanisms, i.e., ion exchange, reversible and irreversible adsorption, may occur during pollutants removal by MIEX. This work examined the removal mechanism of 17α-Ethinylestradiol (EE2) by MIEX. As one of typical estrogen micro-pollutants, EE2 existed as neutral molecule in natural water, and its charge density was close to zero[(0.00000219 ±0.00000015) meq·(μg EE2)-1] based on the potentiometric titration method. However, the removal of EE2 by MIEX was much higher than that of other micro-pollutants previously reported. Multi-cycle adsorptionregeneration experiments and ion exchange stoichiometry analysis were conducted to elucidate the removal mechanism of EE2 by MIEX resin. The results suggested that the main removal mechanism of EE2 by MIEX was ion exchange instead of reversible micro-pore adsorption. The experimental analysis based on Donnan theory indicated that the internal micro-environment of resin beads was alkaline, in the alkaline environment EE2 would be ionized into negatively charged groups. As a result, ion exchange reaction occurred inside the pore of MIEX resin, and the removal process of EE2 by MIEX was dominated by the ion exchange reaction.
    From pollutant to solution of wastewater pollution: Synthesis of activated carbon from textile sludge for dye adsorption
    Syieluing Wong, Nurul Atiqah Najlaa Yac'cob, Norzita Ngadi, Onn Hassan, Ibrahim M. Inuwa
    2018, 26(4):  870-878.  doi:10.1016/j.cjche.2017.07.015
    Abstract ( 862 )   PDF (1602KB) ( 111 )  
    References | Related Articles | Metrics
    Adsorption is an important process in wastewater treatment, and conversion of waste materials to adsorbent offers a solution to high material cost related to the use of commercial activated carbon. This study investigated the adsorption behaviour of Reactive Black 5 (RB5) and methylene blue (MB) onto activated carbon produced from textile sludge (TSAC). The activated carbon was synthesized through chemical activation of precursor followed with carbonization at 650℃ under nitrogen flow. Effects of time (0-200 min), pH (2-10), temperature (25-60℃), initial dye concentration (0-200 mg·L-1), and adsorbent dosage (0.01-0.15 g) on dye removal efficiency were investigated. Preliminary screening revealed that TSAC synthesized via H2SO4 activation showed higher adsorption behaviour than TSAC activated by KCl and ZnCl2. The adsorption capacity of TSAC was found to be 11.98 mg·g-1 (RB5) and 13.27 mg·g-1 (MB), and is dependent on adsorption time and initial dye concentration. The adsorption data for both dyes were well fitted to Freundlich isotherm model which explains the heterogeneous nature of TSAC surface. The dye adsorption obeyed pseudo-second order kinetic model, thus chemisorption was the controlling step. This study reveals potential of textile sludge in removal of dyes from aqueous solution, and further studies are required to establish the applicability of the synthesized adsorbent for the treatment of waste water containing toxic dyes from textile industry.
    Oilfield produced water treatment in internal-loop airlift reactor using electrocoagulation/flotation technique
    Saad H. Ammar, Ahmed S. Akbar
    2018, 26(4):  879-885.  doi:10.1016/j.cjche.2017.07.020
    Abstract ( 712 )   PDF (2254KB) ( 25 )  
    References | Related Articles | Metrics
    Oilfield produced water is large quantities of salty water trapped in underground formations and subsisted under high temperatures and pressures that are brought to the surface along with oil during production. Produced water (PW) contains a lot of pollutants such as hydrocarbons and metals, this water must be treated before disposal. Therefore, different techniques are being used to treat produced water. Electrocoagulation is an efficient treatment technique involving the dissolution of anodes and formation of electro-coagulants, while the simultaneous generation of H2 bubbles at the cathode leads to the pollutant removal by flotation. Electrocoagulation (EC) method is one of the most promising and widely used processes to treat oilfield produced water. In the present work, a conventional internal-loop (draught tube) airlift reactor was utilized as electrocoagulation/flotation cell for PW treatment by inserting two aluminum electrodes in the riser section of the airlift reactor. The EC airlift reactor was operated in a batch mode for the liquid phase. Different experimental parameters were studied on the oil and turbidity removal efficiencies such as current density, initial pH, electrocoagulation time, and air injection. The experimental results showed that mixing of the oil droplets in the PW was accomplished using only the liquid recirculation resulted by H2 microbubbles generated by EC process which enhanced the oil removal. The experimental results further showed that the EC time required achieving ≥ 90% oil removal efficiency decreases from 46 to 15 min when operating current density increases from 6.8 to 45.5 mA·cm-2. This reactor type was found to be highly efficient and less energy consuming compared to conventional existing electrochemical cells which used mechanical agitation.
    An innovative design of septic tank for wastewater treatment and its performance evaluation: An applicable model for developing countries
    Sajjad Haydar, Mehwish Anis, Gul E Hina, Javed Anwar Aziz, Mudasar Arbi
    2018, 26(4):  886-891.  doi:10.1016/j.cjche.2017.10.015
    Abstract ( 923 )   PDF (404KB) ( 45 )  
    References | Related Articles | Metrics
    A study was carried out to evaluate the treatment efficiency of modified model of septic tank (ST) for the treatment of domestic wastewater. The objective was to explore the possibility of increasing the removal efficiency, at household level, thereby reducing cost and treatment burden on city level treatment plants. For this purpose, a bench scale model of ST was prepared and operated continuously for 78 days at different detention times i. e., 48, 24 and 12 h and at two reactor temperatures viz. 15℃ and 25℃. Domestic wastewater was fed to the bench scale ST without pre-settling. Research was conducted under two different arrangements. Firstly, by installing baffles in the bench scale ST (called Run-1 setup), and secondly by installing perforated plates between the baffles (called Run-2 setup). Results demonstrated that Run-2 setup is better than Run-1 setup. Temperature significantly affects the efficiency. Detention time of 24 h was found feasible. Run-2 setup demonstrated a percentage BOD removal of 45% with effluent BOD of 113 mg·L-1 at 15℃ and 85% removal with effluent BOD of 31 mg·L-1 at 25℃. It is concluded that if a modified design of ST using Run-2 setup is provided at household level, the effluent coming out of the house will meet the National Environmental Quality Standards (NEQS) when reactor temperature is close to 25℃. Development authorities are suggested to change their by-laws and make modified ST mandatory for all households. This may significantly reduce the cost and footprint of city level wastewater treatment plants being planned.