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Table of Content
28 January 2018, Volume 26 Issue 1
    Membrane materials in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures-A review
    Hong-Xia Liu, Naixin Wang, Cui Zhao, Shulan Ji, Jian-Rong Li
    2018, 26(1):  1-16.  doi:10.1016/j.cjche.2017.03.006
    Abstract ( )   PDF (2595KB) ( )  
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    The separation of aromatic/aliphatic hydrocarbon mixtures is a significant process in chemical industry, but challenged in some cases. Compared with conventional separation technologies, pervaporation is quite promising in terms of its economical, energy-saving, and eco-friendly advantages. However, this technique has not been used in industry for separating aromatic/aliphatic mixtures yet. One of the main reasons is that the separation performance of existed pervaporation membranes is unsatisfactory. Membrane material is an important factor that affects the separation performance. This review provides an overview on the advances in studying membrane materials for the pervaporation separation of aromatic/aliphatic mixtures over the past decade. Explored pristine polymers and their hybrid materials (as hybrid membranes) are summarized to highlight their nature and separation performance. We anticipate that this review could provide some guidance in the development of new materials for the aromatic/aliphatic pervaporation separation.
    Cultivation of microalgae for biodiesel production: A review on upstream and downstream processing
    Xin Bei Tan, Man Kee Lam, Yoshimitsu Uemura, Jun Wei Lim, Chung Yiin Wong, Keat Teong Lee
    2018, 26(1):  17-30.  doi:10.1016/j.cjche.2017.08.010
    Abstract ( )   PDF (1206KB) ( )  
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    Fluctuating market price of fossil fuel and overwhelming emission of greenhouse gases to the atmosphere have resulted in climate change and have been a global concern in this decade. Hence, biodiesel has become an alternative option to fossil diesel as it is renewable and environmentally friendly. Nevertheless, this alternative fuel that is usually derived from terrestrial oil crops will cause shortage in food supply and deforestation if mass production is realized. In recent years, cultivation of aquatic microorganism (particularly microalgae) to produce biodiesel is considered as a practical solution due to their high growth rate and ability to synthesize large quantity of lipid within their cell. However, the development of energy and cost-efficiency of microalgae cultivation system are the main issues in producing renewable microalgae biodiesel. Of late, wastewater or organic compost has been used as the cultivation medium as it can provide sufficient nutrients to sustain microalgae growth. Microalgae cultivation method and system are vitally important as these factors undoubtedly affect the final microalgae biomass and lipid yield. In this review, the cultivation system of microalgae, nutrients demanded for microalgae production, cell harvesting and drying, microalgae oil extraction, and utilization of microalgae biomass for biodiesel production are introduced and discussed. It is anticipated to convey clearer perspectives in upstream and downstream processes in microalgae-derived biodiesel production.
    Fluid Dynamics and Transport Phenomena
    Numerical study and acceleration of LBM-RANS simulation of turbulent flow
    Shuli Shu, Ning Yang
    2018, 26(1):  31-42.  doi:10.1016/j.cjche.2017.05.013
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    The coupled models of LBM (Lattice Boltzmann Method) and RANS (Reynolds-Averaged Navier-Stokes) are more practical for the transient simulation of mixing processes at large spatial and temporal scales such as crude oil mixing in large-diameter storage tanks. To keep the efficiency of parallel computation of LBM, the RANS model should also be explicitly solved; whereas to keep the numerical stability the implicit method should be better for RANS model. This article explores the numerical stability of explicit methods in 2D cases on one hand, and on the other hand how to accelerate the computation of the coupled model of LBM and an implicitly solved RANS model in 3D cases. To ensure the numerical stability and meanwhile avoid the use of empirical artificial limitations on turbulent quantities in 2D cases, we investigated the impacts of collision models in LBM (LBGK, MRT) and the numerical schemes for convection terms (WENO, TVD) and production terms (FDM, NEQM) in an explicitly solved standard k-ε model. The combination of MRT and TVD or MRT and NEQM can be screened out for the 2D simulation of backward-facing step flow even at Re=107. This scheme combination, however, may still not guarantee the numerical stability in 3D cases and hence much finer grids are required, which is not suitable for the simulation of industrial-scale processes. Then we proposed a new method to accelerate the coupled model of LBM with RANS (implicitly solved). When implemented on multiple GPUs, this new method can achieve 13.5-fold acceleration relative to the original coupled model and 40-fold acceleration compared to the traditional CFD simulation based on Finite Volume (FV) method accelerated by multiple CPUs. This study provides the basis for the transient flow simulation of larger spatial and temporal scales in industrial applications with LBM-RANS methods.
    GPU-based discrete element simulation on flow stability of flat-bottomed hopper
    Li Peng, Zheng Zou, Libo Zhang, Qingshan Zhu, Hongzhong Li
    2018, 26(1):  43-52.  doi:10.1016/j.cjche.2017.07.021
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    In this study, the flow stability of the flat-bottomed hopper was investigated via GPU-based discrete element method (DEM) simulation. With the material height inside the hopper reducing, the fluctuation of the flow rate indicates an unstable discharge. The flow regions of the unstable discharge were compared with that of the stable discharge, a key transformation zone, where the voidage showed the largest difference between unstable and stable discharge, was revealed. To identify the relevance of the key transformation zone and the hopper flow stability, the voidage variation of the key transformation zone with material height reducing was studied. A sharp increase in the voidage in the key transformation zone was considered to be the standard for judging the unstable hopper flow, and the ‘Top-Bottom effect’ of the hopper was defined, which indicated the hopper flow was unstable when the hopper only had the top area and the bottom area, because the voidage of particles in the top area and the bottom area were both variables.
    Separation Science and Engineering
    Tuning sol size to optimize organosilica membranes for gas separation
    Huating Song, Yibin Wei, Chenying Wang, Shuaifei Zhao, Hong Qi
    2018, 26(1):  53-59.  doi:10.1016/j.cjche.2017.04.010
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    A series of organosilica sols are prepared by the polymeric sol-gel method using 1, 2-bis(triethoxysilyl)ethane (BTESE) as the precursor. Particle size distributions of the BTESE-derived sols are systematically investigated by carefully adjusting the synthesis parameters (i.e., water ratios, acid ratios and solvent ratios) in the sol process. In certain conditions, increasing the water ratio or the acid ratio tends to cause larger sol sizes and bimodal particle size distributions. However, higher solvent ratios lead to smaller sol sizes and unimodal particle size distributions. The organosilica membranes prepared from the optimized sols show excellent H2 permeances (up to 4.2×10-7 mol·m-2·s-1·Pa-1) and gas permselectitivies (H2/CO2 is 9.5, H2/N2 is 50 and H2/CH4 is 68). This study offers significant insights into the relationship between the sol synthesis parameters, sol sizes and membrane performance.
    Oil-water pre-separation with a novel axial hydrocyclone
    Meili Liu, Jiaqing Chen, Xiaolei Cai, Yanhe Han, Si Xiong
    2018, 26(1):  60-66.  doi:10.1016/j.cjche.2017.06.021
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    A novel hydrocyclone with guide vanes, named as axial hydrocyclone (AHC), is designed to tackle the problem of oil-water separation faced by most mature oilfields. Optimal design of the AHC is carried out by using numerical methods. The effects of guide vanes, cone angle, tapered angle and overflow pipe on the oil-water separation are discussed in this paper. The results show that a double swirling flow is generated in the tapered section where oil-water separation occurs. Both the cylindrical and the tapered section have important influences on AHC performance. On the basis of single factor results, response surface methodology is employed to optimize the AHC design. The experimental results indicate that the novel AHC has an excellent performance for the oil-water separation.
    Study on extraction kinetics of α-cyclopentylmandelic acid enantiomers with hydroxyethyl-β-cyclodextrin as chiral selector
    Panliang Zhang, Pan Jiang, Weifeng Xu, Yu Liu, Biquan Xiong, Yunren Qiu, Kewen Tang
    2018, 26(1):  67-72.  doi:10.1016/j.cjche.2017.04.001
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    In this work, the kinetic study on reactive extraction of α-cyclopentylmandelic acid (α-CPMA) enantiomers was performed in a Lewis cell using hydroxyethyl-β-cyclodextrin (HE-β-CD) as chiral selector. The enantioselective complexation equilibrium between HE-β-CD and α-CPMA enantiomers was studied by phase solubility method. The important process parameters affecting the initial extraction rate were separately studied and the reaction rate equations were deduced. The optimal conditions for kinetic study were as follows:stirring speed of 75 r·min-1, interfacial area of 12.56 cm2, pH of 2.5, initial HE-β-CD concentration of 0.05 mol ·L-1, initial α-CPMA concentration of 5 mmol·L-1, and temperature of 278 K. The reaction has been found to be first order in α-CPMA and second order in HE-β-CD with the forward rate constants of 2.056×10-3 m6·mol-2·s-1 and 1.459×10-3 m6·mol-2·s-1 for (S)-α-CPMA and (R)-α-CPMA, respectively. The complexation equilibrium constants were evaluated as 61 L·mol-1 and 117 L·mol-1 for (S)-α-CPMA and (R)-α-CPMA, and the intrinsic enantioselectivity is estimated as 1.92.
    Distinguished discriminatory separation of CO2 from its methane-containing gas mixture via PEBAX mixed matrix membrane
    Pouria Abbasszadeh Gamali, Abbass Kazemi, Reza Zadmard, Morteza Jalali Anjareghi, Azadeh Rezakhani, Reza Rahighi, Mohammad Madani
    2018, 26(1):  73-80.  doi:10.1016/j.cjche.2017.04.002
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    Highly selective separation of CO2 from its methane-containing binary gas mixture can be achieved by using Poly(ether-block-amide) (PEBAX) mixed matrix membranes (MMMs). According to FESEM and AFM analyses, silica-based nanoparticles were homogenously integrated within the polymer matrix, facilitating penetration of CO2 through the membrane while acting as barrier for methane gas. The membrane containing 4.6 wt% fumed silica (FS) (PEBAX/4.6 wt% FS) exhibits astonishing selectivity results where binary gas mixture of CO2/CH4 was used as feed gas. As detected by gas chromatography, in the permeate side, data showed a significant increase of CO2 permeance, while CH4 transport through the mixed matrix membrane was not detectable. Moreover, PEBAX/4.6 wt% FS greatly exceeds the Robeson limit. According to data reported on CO2/CH4 gas pair separation in the literature, the results achieved in this work are beyond those data reported in the literature, particularly when PEBAX/4.6 wt% FS membrane was utilized.
    Hierarchical pore structure of activated carbon fabricated by CO2/microwave for volatile organic compounds adsorption
    Wenjuan Qiu, Kang Dou, Ying Zhou, Haifeng Huang, Yinfei Chen, Hanfeng Lu
    2018, 26(1):  81-88.  doi:10.1016/j.cjche.2017.04.006
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    An activated carbon pore-expanding technique was achieved through innovative reactivation by CO2/microwave. The original and modified activated carbons were characterized by nitrogen adsorption-desorption, scanning electron microscopy, transmission electron microcopy, and Fourier transform infrared spectroscopy. The mesopore volume increased from 0.122 cm3·g-1 to 0.270 cm3·g-1, and a hierarchical pore structure was formed. A gradual decrease in the phenolic hydroxyl and carboxyl groups on the surface of activated carbon enhanced the surface inertia of granular activated carbon (GAC). The toluene desorption rate of the modified sample increased by 8.81% compared with that of the original GAC. Adsorption isotherm fittings revealed that the Langmuir model was applicable for the original and modified activated carbons. The isosteric adsorption heat of toluene on the activated carbon decreased by approximately 50%, which endowed the modified sample with excellent stability in application. The modified samples showed an enhanced desorption performance of toluene, thereby opening a way to extend the cycle life and improve the economic performance of carbon adsorbent in practical engineering applications.
    Effect of potassium permanganate dosing position on the performance of coagulation/ultrafiltration combined process
    He Zhao, Liang Wang, Hongwei Zhang, Xiaona Wu, Bin Zhao, Fei Han
    2018, 26(1):  89-95.  doi:10.1016/j.cjche.2017.03.037
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    The effects of potassium permanganate (KMnO4) dosing position on the natural organic matter (NOM) removal as well as membrane fouling were investigated in the coagulation/ultrafiltration combined process. KMnO4 oxidation altered the NOM characteristics in terms of hydrophobicity and molecular weight, and destroyed humic substances originated from terraneous organisms in raw water. The optimal KMnO4 dosage was 0.5 mg·L-1 in the peroxidation enhanced coagulation process with respect to the dissolved organic carbon (DOC) removal. When KMnO4 was dosed into both upstream and downstream of coagulation, namely in the proposed twoposition dosing mode, coagulation and KMnO4 oxidation worked individually on the apparent DOC removal. However, compared to the KMnO4 addition prior to or after coagulation, the two-position dosing mode dramatically alleviated membrane fouling and reduced fouling irreversibility. This was attributed to the change of NOM characteristics as a result of KMnO4 addition prior to coagulation and the presence of MnO2 on membrane surface as a result of KMnO4 addition prior to ultrafiltration. This work may provide useful information for the application of KMnO4 oxidation in the coagulation/ultrafiltration combined system.
    Adsorption characteristics of a novel ceramsite for heavy metal removal from stormwater runoff
    Jianlong Wang, Yuanling Zhao, Pingping Zhang, Liqiong Yang, Huai'ao Xu, Guangpeng Xi
    2018, 26(1):  96-103.  doi:10.1016/j.cjche.2017.04.011
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    Urban sediments have rapidly increased in recent years around the world, and their effective management has become an important problem. To remove heavy metals from stormwater runoff and use sediments as a resource, a novel ceramsite was developed using sewer pipe sediments (SPS), river bed sediments (RBS), urban water supply treatment sludge (WSTS), and wastewater treatment plant excess sludge (WWTS). The optimal composition was determined based on the Brunauer-Emmett-Teller specific surface area and an orthogonal test design. The adsorption characteristics of the novel ceramsite for dissolved heavy metals (Cu2+ and Cd2+) were investigated through adsorption isotherms and kinetic experiments at (25±1)℃. Both Cu2+ and Cd2+ were effectively removed by the novel ceramsite, and their equilibrium adsorption was 4.96 mg·g-1 and 3.84 mg·g-1, respectively. Langmuir isotherms and a pseudo-first-order kinetic equation described the adsorption process better than other techniques. Characterization analysis of the ceramsite composition before and after heavy metal adsorption showed that the Cu2+ and Cd2+ contents in the ceramsite increased after adsorption. The results revealed that adsorption is both a physical and chemical process, and that ceramsite can be used as a bioretention medium to remove heavy metals from stormwater runoff while simultaneously converting problematic urban sediments into a resource.
    Effective and simple recovery of 1,3-propanediol from a fermented medium by liquid-liquid extraction system with ethanol and K3PO4
    Daiana Wischral, Hongxin Fu, Fernando L. Pellegrini Pessoa, Nei Pereira Jr, Shang-Tian Yang
    2018, 26(1):  104-108.  doi:10.1016/j.cjche.2017.06.005
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    1,3-Propanediol, traditionally obtained from fossils, has numerous industrial applications, including use in the production of high performance polymers. The microbial production of 1,3-propanediol presents several opportunities, and the final purity grade determines its price and commercial viability. The development of novel separation technology could improve the economic viability of the bioproduction of 1,3-propanediol. Thus, we investigated salting-out extraction as a novel process for 1,3-propanediol recovery from fermentation broth. Initially, a screening for the best salt/solvent combination was conducted and then optimized using the response surface methodology. The solvents studied were methanol, ethanol, isopropanol and acetone, and the salts examined were K2HPO4, Na2CO3, K2CO3, (NH4)2SO4, NaHPO4, K3PO4 and C6H5NaO7. The optimal extraction system consisted of 34 wt% K3PO4, 28 wt% ethanol, and 38 wt% fermentation broth containing 23.0 g·L-1 1,3-propanediol, which gave the highest partition coefficient of 33 and recovery yield of 97%. The results demonstrated that salting-out extraction was a promising method for 1,3-propanediol recovery from fermentation broth.
    Catalysis, Kinetics and Reaction Engineering
    Rh2O3/monoclinic CePO4 composite catalysts for N2O decomposition and CO oxidation
    Huan Liu, Zhen Ma
    2018, 26(1):  109-115.  doi:10.1016/j.cjche.2017.02.007
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    CePO4 (in particular, monoclinic CePO4) has been rarely used to make supported catalysts. Herein, monoclinic CePO4 nanoparticles were prepared by calcining hexagonal CePO4 nanorods (prepared by precipitation) in air at 900℃. Monoclinic CePO4 nanowires were prepared by calcining hexagonal CePO4 nanowires (prepared by hydrothermal synthesis at 150℃) in air at 900℃. Both monoclinic CePO4 materials were used to support Rh2O3 by impregnation using Rh(NO3)3 as a precursor (followed by calcination). The catalytic performance of Rh2O3/monoclinic CePO4 composite materials in N2O decomposition and CO oxidation was investigated. It was found that Rh2O3 supported on monoclinic CePO4 nanowires was much more active than Rh2O3 supported on monoclinic CePO4 nanoparticles. The stability of catalysts as a function of reaction time on stream was studied in both reactions. The influence of co-fed CO2, O2, and H2O on the catalytic activity in N2O decomposition was also studied. These catalysts were characterized by employing N2 adsorption-desorption, ICP-OES, XRD, TEM, XPS, H2-TPR, O2-TPD, and CO2-TPD. The correlation between physicochemical properties and catalytic properties was discussed.
    Ethylbenzene disproportionation and p-xylene selectivity enhancement in xylene isomerization using high crystallinity desilicated H-ZSM-5
    Marjan Farshadi, Cavus Falamaki
    2018, 26(1):  116-126.  doi:10.1016/j.cjche.2017.03.023
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    Desilication accompanied with minimum loss of crystallinity effect of a high alumina ZSM-5 zeolite on the isomerization reaction of ethylbenzene/xylene mixtures has been considered. Desilication was assessed through XRF, XRD, FTIR, TEM, nitrogen adsorption/desorption, NH3-TPD, 29Si and 27Al MAS NMR analytical techniques. Desilication was accompanied with the creation of super acid sites. There exists a limit (Si/Al molar ratio of 9.67) for keeping high crystallinity and obtaining improved catalytic performance. Desilication promotes ethylbenzene conversion by disproportionation and trans-alkylation reactions while the same reactions are limited for the xylene isomers. The p-xylene approach to equilibrium improves by more than 7% at 400℃ and a WHSV of 2 h-1 for the optimum sample with respect to the parent zeolite. At the same conditions, the optimum sample exhibits the maximum ethylbenzene conversion of 89%, i.e. more than 40% w.r.t. of the parent zeolite. However, the xylene yield decreases only 3%.
    Regulation of isobutane/1-butene adsorption behaviors on the acidic ionic liquids-functionalized MCM-22 zeolite
    Keting Jin, Tao Zhang, Shaojun Yuan, Shengwei Tang
    2018, 26(1):  127-136.  doi:10.1016/j.cjche.2017.05.023
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    The adsorption ratio of isobutane/1-butene on the catalyst surface is one of the most important factors for the C4 alkylation process. Regulation of isobutane/1-butene adsorption ratio on the zeolite-supported acid catalyst is a big challenge for catalyst preparation. To regulate the isobutane/1-butene adsorption ratio, four types of ionic liquid (i.e., IL) with different alkyl chain lengths and different acid group numbers were synthesized and were subsequently immobilized onto the MCM-22 zeolite. The as-synthesized IL-immobilized MCM-22 (i.e., MCM-22-IL) was characterized by FTIR, TGA, BET, XPS and XRD, and their adsorption capacities and adsorption molar ratios of isobutane to 1-butene (I/O) were investigated to correlate with surface features of MCM-22-IL. Results showed that the immobilization of ILs led to a decrease of specific surface area and pore volume. But the surface density of acid groups was increased and the adsorption molar ratio of isobutane/1-butene (I/O) was significantly improved by the immobilization of ionic liquids. The adsorption molar ratio of I/O is substantially improved from 0.75 to above 0.9 at 300 kPa upon immobilizing ILs. Although the alkyl chain length of ILs was found to have little effect on the adsorption molar ratio of I/O, the increase of acid group numbers led to a dramatic decrease in the adsorption I/O ratio. The results illustrated that immobilizing ionic liquids is an effective way to modify the textural, chemical and morphological properties of MCM-22. Accordingly, the immobilization of ionic liquids provides a novel and a feasible way to regulate the adsorption I/O ratio on an adsorbent or a solid catalyst.
    Process Systems Engineering and Process Safety
    Modeling and identification for soft sensor systems based on the separation of multi-dynamic and static characteristics
    Pengfei Cao, Xionglin Luo, Xiaohong Song
    2018, 26(1):  137-143.  doi:10.1016/j.cjche.2017.06.013
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    Data-driven soft sensor is an effective solution to provide rapid and reliable estimations for key quality variables online. The secondary variables affect the primary variable in considerably different speed, and soft sensor systems exhibit multi-dynamic characteristics. Thus, the first contribution is improving the model in the previous study with multi-time-constant. The characteristics-separation-based model will be identified in substep way, and the stochastic Newton recursive (SNR) algorithm is adopted. Considering the dual-rate characteristics of soft sensor systems, the proposed model cannot be identified directly. Thus, two auxiliary models are first proposed to offer the intersample estimations at each update period, based on which the improved algorithm (DAM-SNR) is derived. These two auxiliary models function in switching mechanism which has been illustrated in detail. This algorithm serves for the identification of the proposed model together with the SNR algorithm, and the identification procedure is then presented. Finally, the laboratorial case confirms the effectiveness of the proposed soft sensor model and the algorithms.
    Using hot-vapor bypass for pressure control in distillation columns
    Stefano Ciannella, Arthur Siqueira Damasceno, Ícaro Cazé Nunes, Gilvan Wanderley de Farias Neto, Wagner Brandão Ramos, Romildo Pereira Brito
    2018, 26(1):  144-151.  doi:10.1016/j.cjche.2017.07.023
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    Distillation column control is widely explored in literature due to its complexity and importance in chemical and petrochemical industries. In this process, pressure represents one of the most important variables to be controlled. However, there are few studies about how pressure affects the dynamic behavior of distillation columns and most research on distillation column control involve direct manipulation of cooling fluid through the condenser. Nevertheless, such an approach demands constant changes in cooling fluid flowrates that are commonly by the order of tons per hour, which can be difficult to work or even unfeasible in a real plant. Furthermore, this strategy is usually avoided, as it can cause fouling and corrosion acceleration. The hot-vapor bypass strategy fits well as a solution for these issues, eliminating the need to dynamically manipulate cooling fluid flowrates in the condensation unit. This work presents the modeling and simulation of a conventional distillation column for the separation of water and ethanol, in which a comparative study between a conventional pressure control and a control using hot-vapor bypass was performed. The main results were obtained through dynamic simulations which considered various disturbances in the feed stream, and demonstrated superior performance by the hot-vapor bypass system over the usual scheme proposed in literature, while evaluating the Integral Absolute Error (IAE) norm as the control performance index.
    Chemical Engineering Thermodynamics
    Experimental investigation and development of new correlation for influences of temperature and concentration on dynamic viscosity of MWCNT-SiO2 (20-80)/20W50 hybrid nano-lubricant
    Kazem Motahari, Mohammad Abdollahi Moghaddam, Mojtaba Moradian
    2018, 26(1):  152-158.  doi:10.1016/j.cjche.2017.06.011
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    In current research, MWCNT-SiO2/oil hybrid nano-lubricant viscosity is experimentally examined. By dispersing 0.05%, 0.1%, 0.2%, 0.4%, 0.8% and 1% volume of MWCNTs and SiO2 nanoparticle into the engine oil SAE 20W50, the temperature and solid volume fraction consequences were studied. At 40 to 100℃ temperature, the viscosities were assessed. The results indicated Newtonian behavior for the hybrid nano-lubricant. Moreover, solid volume fraction augmentation and temperature enhanced the viscosity enhancement of hybrid nano-lubricant. At highest solid volume fraction and temperature, nano-lubricant viscosity was 171% greater compared to pure 20W50. Existed models lack the ability to predict the hybrid nano-lubricant viscosity. Thus, a new correlation regarding solid volume fraction and temperature was suggested with R-squared of 0.9943.
    Interaction of cetyltrimethylammonium bromide with drug in aqueous/electrolyte solution: A combined conductometric and molecular dynamics method study
    Md. Anamul Hoque, Md. Masud Alam, Mohammad Robel Molla, Shahed Rana, Malik Abdul Rub, Mohammad A. Halim, Mohammed Abdullah Khan, Farida Akhtar
    2018, 26(1):  159-167.  doi:10.1016/j.cjche.2017.06.016
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    Interaction between beta-lactum antibiotic drug ciprofloxacin hydrochloride (CFH) and cationic surfactant cetyltrimethylammonium bromide (CTAB) was performed conductometrically in aqueous as well as in the occurrence of different salts (NaCl, KCl as well as NH4Cl) over the temperature range of 298.15-323.15 K at the regular interval of 5 K. CFH drug has been suggested for the treatment of bacterial infections such as urinary tract infections and acute sinusitis. A clear critical micelle concentration (CMC) was obtained for pure CTAB as well as (CFH + CTAB) mixed systems. The decrease in CMC values of CTAB caused by the addition of CFH reveals the existence of the interaction between the components and therefore it is the indication of micelle formation at lower concentration of CTAB and their CMC values further decrease in attendance of salts. A nonlinear behavior in the CMC versus T plot was observed in all the cases. The ΔGm0 values are found to be negative in present study systems demonstrated the stability of the solution. The values of ΔHm0 and ΔSm0 reveal the existence of hydrophobic and electrostatic interactions between CFH and CTAB. The thermodynamic properties of transfer for the micellization were also evaluated and discussed in detail. Molecular dynamic simulation disclosed that environment of water and salts have impact on the hydrophobic interaction between CFH and CTAB. In water and salts, CTAB adopts spherical micelle in which charged hydrophilic groups are interacted with waters whereas hydrophobic tails form the core of the micelle. This hydrophobic core region is highly conserved and protected. In addition, micelle formation is more favorable in aqueous NaCl solution than other solutions.
    Density, refractive index and liquid-liquid equilibrium data of polyethylene glycol 3000 + potassium formate + water at different pH values
    Fatemeh Ahmadi, Mohsen Pirdashti, Abbas Ali Rostami
    2018, 26(1):  168-174.  doi:10.1016/j.cjche.2017.07.003
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    New liquid-liquid equilibrium data for polyethylene glycol (PEG) 3000 + CHO2K + H2O systems were measured at 298.15 K and pH values of 7.95, 8.40 and 9.98. It was found that an increase in pH caused the binodal curve to be displaced downward and the two-phase region to expand. Accordingly, the binodal curve was adjusted to the Pirdashti equation and the tie-line compositions were correlated using the Othmer-Tobias, Bancroft and Hand equations. The study measured the refractive index and densities of several homogeneous binary and ternary solutions. The solutions were used for calibration within a range of 0% to 30% of the mass of the PEG and potassium formate. The density and refractive index data show a linear variation with the mass fraction of the polymer and the salt. The effect of pH on the binodal, tie-line lengths (TLL) and slope of the tie-line (STL) in the systems was examined. It was found that an increase in pH increased the TLL and decreased the STL. It was observed that the density of the aqueous two-phase system was influenced by the TLL. The difference in density between phases (Δρ) increased as the TLL and pH increased. It was found that the TLL and Δρ showed a linear relationship. The effective excluded volume (EEV) of the PEG was obtained and it was found that EEV also increased as the pH increased.
    Biotechnology and Bioengineering
    Lipid enhancement in microalgae by temporal phase separation: Use of indigenous sources of nutrients
    Nidhin Sreekumar, Ajit Haridas, G. S. Godwin, N. Selvaraju
    2018, 26(1):  175-182.  doi:10.1016/j.cjche.2017.03.004
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    Microalgae have been recommended as superior candidate for fuel production because of their advantages of higher photosynthetic efficiency, biomass & lipid productivity, and faster growth rate as compared to other energy crops. To meet up all these criteria, we have developed a continuous outdoor micro-algal raceway pond reactor (RPR) and a lab scale indoor tubular photo bioreactor (PBR) for biofuel production. An attempt to utilise indigenous sources of nutrients to improve the economics also revealed that micro-algal culturing can also be used as a mode of nutrient removal and water treatment. The photosynthetic rate and lipid production were enhanced by arresting daytime cell division and promoting night-time cell division. A 50% lipid improvement was observed for the particular algal consortia. Microscopic studies revealed that temporal phase separation could be achieved by adjusting nutrient distribution pattern. To monitor temporal phase separation, it is required to know DNA multiplication model. Quantification of gDNA in RPR confirmed that cell division happens during the night which positively affects the photosynthetic efficiency and lipid productivity of microalgae.
    Determination of 4-nonylphenol and 4-tert-octylphenol compounds in various types of wastewater and their removal rates in different treatment processes in nine wastewater treatment plants of Iran
    Bijan Bina, Farzaneh Mohammadi, Mohammad Mehdi Amin, Hamid Reza Pourzamani, Zeynab Yavari
    2018, 26(1):  183-190.  doi:10.1016/j.cjche.2017.04.009
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    Alkylphenols (APs), considered as xenoestrogenic compounds, mainly exist as 4-nonylphenol (4-NP) and 4-tertoctylphenol (4-t-OP) in environments. The high stability and accumulation of APs in aquatic systems have caused endocrine disruption. In this study we measured APs in the wastewater influent and effluent samples, from the urban, rural, livestock, commercial and hospital wastewater treatment plants (WWTPs) in Iran. Dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-mass spectrometry (GC-MS) was used for the extraction and determination of 4-NP and 4-t-OP. In these treatment plants, various processes such as activated sludge, aerated lagoon, moving bed biofilm reactor and activated sludge along with wetland were applied. The highest concentration of 4-NP and 4-t-OP was observed in commercial and livestock sewages. The activated sludge along with wetland and then the MBBR process showed the highest removal rates of pollutants. The rates of biodegradability and accumulation in sludge were determined and also the specific adsorption coefficient Kd and the organic carbon-water partition coefficient kOC of the sludge for APs were calculated.
    The green hydrolysis technology of hemicellulose in corncob by the repeated use of hydrolysate
    Lei Guo, Yangdong Hu, Lianying Wu, Chen Liang, Weitao Zhang
    2018, 26(1):  191-195.  doi:10.1016/j.cjche.2017.07.012
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    To achieve green hydrolysis technology of hemicellulose through repeated using hydrolysate, the hydrolysis of hemicellulose in corncob was studied. The influence of repeated use of corncob hydrolysate on concentrations of D-xylose and L-arabinose was investigated. The loss rates of D-xylose in the prepared D-xylose solutions both with and without corncob, and repeated using corncob hydrolysate under identical acidity condition were discussed. The result shows that D-xylose concentration and L-arabinose concentration are all gradually increasing with the growing time of repeated use of corncob hydrolysate. After the fifth repetition, the concentrations of D-xylose and L-arabinose are 196.7 g·L-1 and 22.0 g·L-1, respectively. Substance inhibiting the degradation of D-xylose is generated during repeated use of corncob hydrolysate, and the production is further proved by the change of D-xylose concentration and the loss rate of D-xylose over heating time.
    Materials and Product Engineering
    Comparative experimental study on reactive crystallization of Ni(OH)2 in an airlift-loop reactor and a stirred reactor
    Tianrong Cao, Weipeng Zhang, Jingcai Cheng, Chao Yang
    2018, 26(1):  196-206.  doi:10.1016/j.cjche.2017.03.007
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    The objective of this work is to study the reactive crystallization in an airlift-loop reactor (ALR) using the precipitation of Ni(OH)2 as a model reaction. The growth of Ni(OH)2 particles in an ALR and a stirred tank was quantified by scanning electronic microscope (SEM), X-ray diffraction (XRD), laser particle analyzer, tap densitometer and optical microscope, and the growth process of Ni(OH)2 particles is analyzed. It is found that the Ni(OH)2 particles prepared in an ALR have a better sphericity than those in a stirred tank and the growth of Ni(OH)2 particle tap density mainly depends on the size of crystallites:the bigger the size of crystallites, the bigger the tap density is. Based on these, the growth process of Ni(OH)2 particles in ALR is elaborated. Crystallites precipitated from solution aggregate to form large particles with much void. These constituting crystallites continue to grow up, that takes up the void inside particles and makes the tap density increase.
    Bi-/multi-modal pore formation of PLGA/hydroxyapatite composite scaffolds by heterogeneous nucleation in supercritical CO2 foaming
    Xin Xin, Yixin Guan, Shanjing Yao
    2018, 26(1):  207-212.  doi:10.1016/j.cjche.2017.04.005
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    Scaffolds with multimodal pore structure are essential to cells differentiation and proliferation in bone tissue engineering. Bi-/multi-modal porous PLGA/hydroxyapatite composite scaffolds were prepared by supercritical CO2 foaming in which hydroxyapatite acted as heterogeneous nucleation agent. Bimodal porous scaffolds were prepared under certain conditions, i.e. hydroxyapatite addition of 5%, depressurization rate of 0.3 MPa·min-1, soaking temperature of 55℃, and pressure of 9 MPa. And scaffolds presented specific structure of small pores (122 μm±66 μm) in the cellular walls of large pores (552 μm±127 μm). Furthermore, multimodal porous PLGA scaffolds with micro-pores (37 μm±11 μm) were obtained at low soaking pressure of 7.5 MPa. The interconnected porosity of scaffolds ranged from (52.53±2.69)% to (83.08±2.42)% by adjusting depressurization rate, while compression modulus satisfied the requirement of bone tissue engineering. Solvent-free CO2 foaming method is promising to fabricate bi-/multi-modal porous scaffolds in one step, and bioactive particles for osteogenesis could serve as nucleation agents.
    Preparation of water-soluble magnetic nanoparticles with controllable silica coating
    Yaping Zhang, Bin Zhen, Hansheng Li, Yaqing Feng
    2018, 26(1):  213-217.  doi:10.1016/j.cjche.2017.05.017
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    This work provides a general method for preparing monodisperse, water-soluble and paramagnetic magnetic nanoparticles which are easy to be modified. Firstly, magnetic silica with core-shell structure was prepared according to a previous work. Then, the magnetic silica was treated with alkali solution to afford magnetic nanoparticles. With the increase of calcination temperature for the preparation of magnetic silica, the crystallinity and the magnetic responsibility of magnetic silica strengthened, meanwhile, the corresponding magnetic nanoparticles kept monodisperse without any aggregation. The magnetic nanoparticles are comprised of cobalt ferrite and a silica coating. The silica coating on the cobalt ferrite facilitates the magnetic nanoparticles well-dissolved and monodisperse in water, and easily modified.