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Table of Content
28 November 2015, Volume 23 Issue 11
    A dual-scale turbulence model for gas-liquid bubbly flows
    Xiaoping Guan, Zhaoqi Li, Lijun Wang, Xi Li, Youwei Cheng
    2015, 23(11):  1737-1745.  doi:10.1016/j.cjche.2015.09.003
    Abstract ( 2199 )   PDF (3945KB) ( 91 )  
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    A dual-scale turbulence model is applied to simulate cocurrent upward gas-liquid bubbly flows and validated with available experimental data. In the model, liquid phase turbulence is split into shear-induced and bubbleinduced turbulence. Single-phase standard k-ε model is used to compute shear-induced turbulence and another transport equation is added to model bubble-induced turbulence. In the latter transport equation, energy loss due to interface drag is the production term, and the characteristic length of bubble-induced turbulence, simply the bubble diameter in this work, is introduced to model the dissipation term. The simulated results agree well with experimental data of the test cases and it is demonstrated that the proposed dual-scale turbulence model outperforms other models. Analysis of the predicted turbulence shows that themain part of turbulent kinetic energy is the bubble-induced one while the shear-induced turbulent viscosity predominates within turbulent viscosity, especially at the pipe center. The underlying reason is the apparently different scales for the two kinds of turbulence production mechanisms: the shear-induced turbulence is on the scale of the whole pipe while the bubble-induced turbulence is on the scale of bubble diameter. Therefore, the model reflects the multi-scale phenomenon involved in gas-liquid bubbly flows.
    Gas-liquid hydrodynamics in a vessel stirred by dual dislocated-blade Rushton impellers
    Fengling Yang, Shenjie Zhou, Xiaohui An
    2015, 23(11):  1746-1754.  doi:10.1016/j.cjche.2015.09.002
    Abstract ( 2418 )   PDF (3992KB) ( 89 )  
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    Towards the objective of improving the gas dispersion performance, the dislocated-blade Rushton impeller was applied to the gas-liquid mixing in a baffled stirred vessel. The flow field, gas hold-up, dissolved oxygen, power consumption before and after gassing were studied using the computational fluid dynamics (CFD) technique. Dispersion of gas in the liquid was modelled using the Eulerian-Eulerian approach along with the dispersed k-ε turbulent model. Rotation of the impeller was simulated with the multiple reference frame method. A modified drag coefficient which includes the effect of turbulence was used to account for the momentum exchange. The predictions were compared with their counterparts of the standard Rushton impeller and were validated with the experimental results. It is concluded that the dislocated-blade Rushton impeller is superior to the standard Rushton impeller in the gas-liquid mixing operation, and the findings obtained here lay the basis of its application in process industries.
    Convective mass transfer enhancement in a membrane channel by delta winglets and their comparison with rectangular winglets
    Jingchun Min, Bingqiang Zhang
    2015, 23(11):  1755-1762.  doi:10.1016/j.cjche.2015.09.006
    Abstract ( 1689 )   PDF (3591KB) ( 52 )  
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    Numerical calculations were conducted to simulate the flow and mass transfer in narrow membrane channels equipped with delta winglets, which are often used as longitudinal vortex generators to enhance heat transfer in heat exchanger applications. The channel consists of an impermeable solid wall and a membrane. The delta winglets are attached to the solidwall surface to enhance the mass transfer near themembrane surface and suppress the concentration polarization. Thewinglet performancewas evaluated in terms of concentration polarization factor versus consumed pumping power. Calculations were implemented for NaCl solution flow in a membrane channel having a height of 2.0 mmfor Reynolds numbers ranging from 400 to 1000. The delta winglets were optimized under equal pumping power condition, and the results of optimization suggest winglet height of 5/6 of the channel height, aspect ratio of 2.0, attack angle of 30°, and awinglet interval equal to the channel height. The optimal deltawingletswere comparedwith the optimal rectangular wingletswe found previously, and it is shown that the rectangular winglets yield a somewhat better performance than the delta winglets.
    Cobalt-free gadolinium-doped perovskite Gdx1-xFeO3-δ as high-performance materials for oxygen separation
    Yanjie Wang, Qing Liao, Yan Chen, Libin Zhuang, Haihui Wang
    2015, 23(11):  1763-1767.  doi:10.1016/j.cjche.2015.08.023
    Abstract ( 2142 )   PDF (1698KB) ( 69 )  
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    Cobalt-free oxides Gdx1-xFeO3-δ (0.01 ≤ x ≤ 0.1)were achieved by a solid state reactionmethod. It is found that Gdx1-xFeO3-δ (0.025 ≤ x ≤ 0.1) exhibits the cubic perovskite structure. Among Gdx1-xFeO3-δ (0.025 ≤ x ≤ 0.1), the Gd0.025Ba0.975FeO3-δ (GBF2.5) membrane shows the outstanding phase structure stability and the highest oxygen permeation,which can reach 1.44ml·cm-2·min-1 at 950 ℃ under air/He oxygen partial pressure gradient. The GBF2.5 membranewas successfully operated formore than 100 h at 800 ℃ and the oxygen permeation flux through the membrane is 0.62 ml·cm-2·min-1. After 100 h oxygen permeation experiment at 800 ℃, X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDXS) demonstrate that the GBF2.5 exhibits phase structure stability even at intermediate temperature.
    Synthesis and adsorption property of zeolite FAU/LTA from lithium slag with utilization of mother liquid
    Guo Lin, Qiang Zhuang, Qun Cui, Haiyan Wang, Huqing Yao
    2015, 23(11):  1768-1773.  doi:10.1016/j.cjche.2015.10.001
    Abstract ( 2461 )   PDF (1493KB) ( 241 )  
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    Co-crystalline zeolite FAU/LTA-0 was synthesized by hydrothermal method from lithiumslag. To make themost of excess silicon and alkali sources inmother liquid derived fromFAU/LTA-0, zeolite FAU/LTA-1bwas synthesized in the samemethodwith the use ofmother liquid by adding a certain amount of aluminumsource. Influences of different adding ways of aluminum source and recycling dosages of mother liquid on synthesis of zeolites FAU/ LTA with mother liquid were investigated. The phase, microstructure and thermostability of FAU/LTA-0 and FAU/LTA-1b were characterized by XRD, SEM and TG-DTA. The calcium and magnesium cation exchange capacities (CECs) of the zeolites were determined. The results have shown that co-crystalline zeolite can be synthesized with the use of mother liquid by adding aluminum source after 2 h of reaction. Compared with FAU/LTA-0, the crystal twinning structure of FAU/LTA-1b became weaker, the grain size was smaller, and the thermostability was better. With a lower dosage of mother liquid, the content of P-type impurity in product decreased significantly, and the content of LTA phase increased. The reuse rate of mother liquid can reach 48%. The CECs of FAU/LTA-1b-150 can reach 343 mg CaCO3·g-1 and 180 mg MgCO3·g-1, showing more excellent adsorption capacities than FAU/LTA-0 and commercial zeolite 4A. The full recycling use of mother liquid to synthesize zeolite FAU/LTA which can be applied for detergent not only improves resource utilization but also reduces production cost.
    Simulation and analysis of multi-stage centrifugal fractional extraction process of 4-nitrobenzene glycine enantiomers
    Ping Wen, Kewen Tang, Jicheng Zhou, Panliang Zhang
    2015, 23(11):  1774-1781.  doi:10.1016/j.cjche.2015.08.015
    Abstract ( 2456 )   PDF (2170KB) ( 66 )  
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    Based on the interfacial ligand exchangemodel and the law of conservation ofmass, themulti-stage enantioselective liquid-liquid extraction model has been established to analyze and discuss on multi-stage centrifugal fractional extraction process of 4-nitrobenzene glycine (PGL) enantiomers. The influence of phase ratio, extractant concentration, and PF6- concentration on the concentrations of enantiomers in the extract and raffinate was investigated by experiment and simulation. A good agreement between model and experiment was obtained. On this basis, the influence ofmany parameters such as location of stage, concentration levels, extractant excess, and number of stages on the symmetric separation performance was simulated. The optimal location of feed stage is the middle of fractional extraction equipment. The feed flow must satisfy a restricted relationship on flow ratios and the liquid throughout of centrifugal device. For desired purity specification, the required flow ratios decrease with extractant concentration and increase with PF6- concentration.When the number of stages is 18 stages at extractant excess of 1.0 or 14 stages at extractant excess of 2.0, the eeeq (equal enantiomeric excess) can reach to 99%.
    A local and global statistics pattern analysis method and its application to process fault identification
    Hanyuan Zhang, Xuemin Tian, Xiaogang Deng, Lianfang Cai
    2015, 23(11):  1782-1792.  doi:10.1016/j.cjche.2015.09.004
    Abstract ( 1901 )   PDF (1096KB) ( 133 )  
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    Traditional principal component analysis (PCA) is a second-ordermethod and lacks the ability to provide higherorder representations for data variables. Recently, a statistics pattern analysis (SPA) framework has been incorporated into PCAmodel tomake full use of various statistics of data variables effectively. However, thesemethods omit the local information, which is also important for process monitoring and fault diagnosis. In this paper, a local and global statistics pattern analysis (LGSPA) method, which integrates SPA framework and locality preserving projections within the PCA, is proposed to utilize various statistics and preserve both local and global information in the observed data. For the purpose of fault detection, two monitoring indices are constructed based on the LGSPA model. In order to identify fault variables, an improved reconstruction based contribution (IRBC) plot based on LGSPA model is proposed to locate fault variables. The RBC of various statistics of original process variables to the monitoring indices is calculated with the proposed RBC method. Based on the calculated RBC of process variables' statistics, a new contribution of process variables is built to locate fault variables. The simulation results on a simple six-variable system and a continuous stirred tank reactor system demonstrate that the proposed fault diagnosis method can effectively detect fault and distinguish the fault variables from normal variables.
    A novel two-stage Lagrangian decomposition approach for refinery production scheduling with operational transitions in mode switching
    Lei Shi, Yongheng Jiang, Ling Wang, Dexian Huang
    2015, 23(11):  1793-1800.  doi:10.1016/j.cjche.2015.08.017
    Abstract ( 1914 )   PDF (460KB) ( 64 )  
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    To address large scale industrial processes, a novel Lagrangian scheme is proposed to decompose a refinery scheduling problemwith operational transitions inmode switching into a production subproblemand a blending and delivery subproblem. To accelerate the convergence of Lagrange multipliers, some auxiliary constraints are added in the blending and delivery subproblem. A speed-up scheme is presented to increase the efficiency for solving the production subproblem. An initialization scheme of Lagrange multipliers and a heuristic algorithm to find feasible solutions are designed. Computational results on three cases with different lengths of time horizons and different numbers of orders show that the proposed Lagrangian scheme is effective and efficient.
    Nonlinear state estimation for fermentation process using cubature Kalman filter to incorporate delayed measurements
    Liqiang Zhao, Jianlin Wang, Tao Yu, Kunyun Chen, Tangjiang Liu
    2015, 23(11):  1801-1810.  doi:10.1016/j.cjche.2015.09.005
    Abstract ( 2685 )   PDF (2196KB) ( 87 )  
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    State estimation of biological process variables directly influences the performance of on-linemonitoring and optimal control for fermentation process. A novel nonlinear state estimation method for fermentation process is proposed using cubature Kalman filter (CKF) to incorporate delayed measurements. The square-root version of CKF (SCKF) algorithm is given and the system with delayed measurements is described. On this basis, the sample-state augmentation method for the SCKF algorithmis provided and the implementation of the proposed algorithmis constructed. Then a nonlinear state spacemodel for fermentation process is established and the SCKF algorithmincorporating delayedmeasurements based on fermentation processmodel is presented to implement the nonlinear state estimation. Finally, the proposed nonlinear state estimation methodology is applied to the state estimation for penicillin and industrial yeast fermentation processes. The simulation results show that the on-line state estimation for fermentation process can be achieved by the proposedmethod with higher estimation accuracy and better stability.
    Measurement and correlation of physical properties of aqueous solutions of tetrabutylammonium hydroxide, piperazine and their aqueous blends
    Rizwan Safdar, Abdul Aziz Omar, Lukman B. Ismail, Arhama Bari, Bhajan Lal
    2015, 23(11):  1811-1818.  doi:10.1016/j.cjche.2015.08.006
    Abstract ( 2385 )   PDF (676KB) ( 82 )  
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    The density, viscosity and refractive index of aqueous solutions of tetrabutylammoniumhydroxide (TBAOH), piperazine (PZ) and their aqueous blends are determined at several temperatures (303.15 to 333.15 K). All these measured physicochemical properties decreases with an increase in temperature. The density data is used to calculate the coefficient of thermal expansion and excess molar volume of all aqueous binary and ternary solutions. The coefficient of thermal expansion increases with increase in temperatures and concentrations. The negativity of excess molar volume for all the aqueous solution decreasedwith increase in temperature. Each physical property is correlated with temperature by least square method and the corresponding coefficients for each property are presented. The prediction values fromcorrelations for the physical properties are in good agreement with the experimental values.
    Ghezeljeh nanoclay as a newnatural adsorbent for the removal of copper and mercury ions: Equilibrium, kinetics and thermodynamics studies
    Majid Soleimani, Zahra Hassanzadeh Siahpoosh
    2015, 23(11):  1819-1833.  doi:10.1016/j.cjche.2015.08.024
    Abstract ( 2224 )   PDF (3574KB) ( 152 )  
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    Heavy metal determination was carried out by applying the solid phase extraction (SPE) method in batchmode followed by atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) fromaqueous solutions using Ghezeljehmontmorillonite nanoclay as a newnatural adsorbent. The Ghezeljeh clay is characterized by using Fourier Transform Infrared (FT-IR) Spectroscopy, Scanning Electron Microscopy-Energy Dispersive Spectrometry (SEM-EDS) and X-ray Diffractometry (XRD) and X-ray Fluorescence (XRF). The results of XRD and FT-IR of nanoclay confirm that montmorillonite is the dominant mineral phase. Based on SEM images of Ghezeljeh clay, it can be seen that the distance between the plates is Nano. The effects of varying parameters such as initial concentration of metal ions, pH and type of buffer solutions, amount of adsorbent, contact time, and temperature on the adsorption process were examined. The effect of various interfering ions was studied. The adsorption data correlated with Freundlich, Langmuir, Dubinin-Radushkevich (D-R), and Temkin isotherms. The Langmuir and Freundlich isotherms showed the best fit to the equilibrium data for Hg(II), but the equilibrium nature of Cu(II) adsorption has been described by the Langmuir isotherm. The kinetic data were describedwith pseudo-first-order, pseudo-second-order and double-exponential models. The adsorption process follows a pseudo-second-order reaction scheme. Calculation of ΔG0, ΔH0 and ΔS0 showed that the nature of Hg(II) ion sorption onto the Ghezeljeh nanoclay was endothermic and was favored at higher temperature, and the nature of Cu(II) ion sorption was exothermic and was favored at lower temperature.
    Improvement of the riboflavin production by engineering the precursor biosynthesis pathways in Escherichia coli
    Zhibo Xu, Zhenquan Lin, Zhiwen Wang, Tao Chen
    2015, 23(11):  1834-1839.  doi:10.1016/j.cjche.2015.08.013
    Abstract ( 2236 )   PDF (625KB) ( 58 )  
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    3,4-Dihydroxy-2-butanone 4-phosphate (DHBP) and GTP are the precursors for riboflavin biosynthesis. In this research, improving the precursor supply for riboflavin production was attempted by overexpressing ribB and engineering purine pathway in a riboflavin-producing Escherichia coli strain. Initially, ribB gene was overexpressed to increase the flux from ribulose 5-phosphate (Ru-5-P) to DHBP. Then ndk and gmk genes were overexpressed to enhance GTP supply. Subsequently, a R419Lmutationwas introduced into purA to reduce the flux from IMP to AMP. Finally, co-overexpression of mutant purF and prs genes further increased riboflavin production. The final strain RF18S produced 387.6 mg riboflavin·L-1 with a yield of 44.8 mg riboflavin per gram glucose in shake-flask fermentations. The final titer and yield were 72.2% and 55.6% higher than those of RF01S, respectively. It was concluded that simultaneously engineering the DHBP synthase and GTP biosynthetic pathway by rational metabolic engineering can efficiently boost riboflavin production in E. coli.
    Design of reactive distillation processes for the production of butyl acrylate: Impact of bio-based raw materials
    Alexander Niesbach, Natalia Fink, Philip Lutze, Andrzej Górak
    2015, 23(11):  1840-1850.  doi:10.1016/j.cjche.2015.08.019
    Abstract ( 2310 )   PDF (1232KB) ( 253 )  
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    The chemical industry is nowadays predominantly using fossil rawmaterials, but the alternative use of bio-based resources is investigated to account for the foreseeable scarcity of fossil feedstocks. Amain challenge of using biobased feedstocks is the complexity of the impurity profile. For an economic production of bio-based chemicals, the use of intensified processes is inevitable and approaches are needed for the various process intensification techniques to identify their applicability to be used for the production of bio-based components. In the presented study, an approach is shown for the reactive distillation (RD) technology to identify the most critical bio-based impurities and their impact on the reactive distillation process. The investigated case-study is the production of n-butyl acrylate from acrylic acid and n-butanol. Among all initially identified impurities, the key impurities, having the biggest impact on the product purity in the reactive distillation process, are found. These impurities are then studied in more detail and an operating window depending on the impurity concentration is identified for the reactive distillation column. Furthermore, an integrated design of upstreamand downstreamprocesses is facilitated, as the presented results can be used in the development of the fermentation processes for the production of the bio-based reactants by decreasing the concentration of the critical impurities.
    Influences of operating conditions on biocatalytic activity and reusability of Novozym 435 for esterification of free fatty acids with short-chain alcohols: A case study of palm fatty acid distillate
    Sawittree Mulalee, Pongrumpa Srisuwan, Muenduen Phisalaphong
    2015, 23(11):  1851-1856.  doi:10.1016/j.cjche.2015.08.016
    Abstract ( 1909 )   PDF (2008KB) ( 143 )  
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    In the present study, the effects of operating conditions on biocatalytic activity and stability of Novozym 435 for repeated-batch biodiesel production from free fatty acid (FFA) were investigated. Thermal deactivation caused by increased operating temperature from 45 to 50 ℃ could seriously affect the reusability of Novozym 435. The deactivation of Novozym 435 during the esterification of oleic acid with ethanol tended to be stronger than that in the system with methanol. Under the optimal conditions, considering both biocatalytic activity and stability of the enzyme, Novozym 435 could be reused for 13 cycles for biodiesel productions from oleic acid and absolute alcohols (methanol and ethanol) with FFA conversions of at least 90%. The presence of 4%-5% water in ethanol significantly affected the reusability of Novozym435. Changes in the surface morphology of Novozym435 during the esterification with various conditions were observed. Itwas revealed that the reduction in catalytic activity was related to the swelling degree of the catalyst surface. Additionally, biodiesel production fromlowcost renewable feedstocks, such as palmfatty acid distillate (PFAD) and 95% ethanolwas examined. The esterification of PFAD with 95% ethanol catalyzed by Novozym 435 in 10-repeated batch operation showed the similar results in FFA conversion as compared to those using oleic acid. Novozym 435 remained active and could maintain 97.6% of its initial conversion after being used for 10 batches.
    Production of biodiesel from palm fatty acid distillate using sulfonated-glucose solid acid catalyst: Characterization and optimization
    Ibrahim M. Lokman, Umer Rashid, Yun Hin Taufiq-Yap
    2015, 23(11):  1857-1864.  doi:10.1016/j.cjche.2015.07.028
    Abstract ( 2421 )   PDF (779KB) ( 85 )  
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    A palm fatty acid distillate (PFAD) has been used for biodiesel production. An efficient sulfonated-glucose acid catalyst (SGAC) was prepared by sulfonation to catalyze the esterification reaction. The effect of three variables i.e. methanol-to-PFAD molar ratio, catalyst amount and reaction time, on the yield of PFAD esters was studied by the response surface methodology (RSM). The optimum reaction conditions were: 12.2:1 methanol-to-PFAD molar ratio, 2.9% catalyst concentration and 134 min of time as predicted by the RSM. The reaction under the optimum conditions resulted in 94.5% of the free fatty acid (FFA) conversion with 92.4% of the FAME yield. The properties of the PFAD esters were determined according to biodiesel standards.
    A direct electrochemical route from oxides to TiMn2 hydrogen storage alloy
    Jing Zhu, Lei Dai, Yao Yu, Jilin Cao, Ling Wang
    2015, 23(11):  1865-1870.  doi:10.1016/j.cjche.2015.08.033
    Abstract ( 2240 )   PDF (2597KB) ( 112 )  
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    This study is for investigating the direct electro-deoxidation ofmixed TiO2-MnO2 powder to prepare TiMn2 alloy in molten calciumchloride. The influences of process parameters, such as sintering temperature, cell voltage, and electrolysis time, on the electrolysis processwere examined to investigate themechanismof alloy formation. The composition and morphology of the products were analyzed by XRD and SEM, respectively. The electrochemical property of TiMn2 alloywas investigated by cyclic voltammetrymeasurements. The results showthat pure TiMn2 can be prepared by direct electrochemical reduction of mixed TiO2/MnO2 pellets at a voltage of 3.1 V in molten calcium chloride of 900 ℃ for 7 h. The electro-deoxidation proceeds from the reduction of manganese oxides to Mn,which is reduced by TiO2 or CaTiO3 to formTiMn2 alloy. The cyclic voltammetrymeasurements using powder microelectrode show that the prepared TiMn2 alloy has good electrochemical hydrogen storage property.
    Simple processing technology of leaching water using CO2 microbubbles
    Kenzi Suzuki, Chunshan Li, Suojiang Zhang
    2015, 23(11):  1871-1874.  doi:10.1016/j.cjche.2015.08.034
    Abstract ( 2006 )   PDF (1388KB) ( 44 )  
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    The effectiveness of CO2 microsize bubbles for removal of Ca2+ ions in the leaching water discharged from the final landfill site was evaluated using imitation water. For the important parameter in the Ca2+ ion removal, it was found that the treatment in alkaline region above pH = 10 was optimum. The possibility of using CO2 microbubbles was examined by substitution of chemical Na2CO3, which is used in large quantities today. In addition, the excellence of CO2 microbubbles was demonstrated by comparing with CO2 millimeter size bubbles.
    Removal of elemental mercury by modified bamboo carbon
    Zengqiang Tan, Guoping Niu, Xiaowen Chen
    2015, 23(11):  1875-1880.  doi:10.1016/j.cjche.2015.09.001
    Abstract ( 2107 )   PDF (508KB) ( 84 )  
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    Themercury removal performance ofmodified bamboo charcoal (BC) was investigatedwith a bench-scale fixedbed reactor. A simple impregnation method was used tomodify the BC with ZnCl2 and FeCl3 separately. BET and XPS were used to determine the pore structure and surface chemistry of the sorbents. The role of Fe3+ in the removal of elemental mercury bymodified sorbents was discussed. The experimental results suggest that themodified BCs have excellent adsorption potential for elemental mercury at a relatively higher temperature, 140 ℃. The BET surface area and average pore size ofmodified sorbents do not shownoticeable priority compared to unmodified BC. XPS spectra indicate that Fe atoms mainly exist in the form of Fe3+ for the FeCl3-impregnated BC. Better performance of FeCl3-impregnated BC at different temperatures (20, 140 and 180 ℃) suggests the enhancement of non-chloride functional groups (Fe3+). Inhibition effect of SOx and NO for Hg0 removal by BC samples is present in the study.
    Analysis of fouling characteristic in enhanced tubes using multiple heat and mass transfer analogies
    Zepeng Wang, Guanqiu Li, Jingliang Xu, JinjiaWei, Jun Zeng, Decang Lou, Wei Li
    2015, 23(11):  1881-1887.  doi:10.1016/j.cjche.2015.07.011
    Abstract ( 2160 )   PDF (2105KB) ( 73 )  
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    This paper provides a comprehensive analysis on cooling tower fouling data taken from seven 15.54 mm I.D. helically ribbed, copper tubes and a plain tube at Re = 16000. There are two key processes during fouling formation: fouling deposition and fouling removal, which can be determined by mass transfer and fluid friction respectively. The mass transfer coefficient can be calculated through three analogies: Prandtl analogy, Von-Karman analogy, and Chilton-Colburn analogy. Based on our analyses, Von-Karman analogy is the optimized analogy, which can well predict the formation of cooling tower fouling. Series of semi-theoretical fouling correlations as a function of the product of area indexes and efficiency indexes were developed, which can be applicable to different internally ribbed geometries. The correlations can be directly used to assess the fouling potential of enhanced tubes in actual cooling tower water situations.
    Long-term nitritation performance of ammonium-rich landfill leachate
    Hongwei Sun, Xintao LÜ, Yongzhen Peng, Shuying Wang, Juan Ma
    2015, 23(11):  1888-1893.  doi:10.1016/j.cjche.2015.08.014
    Abstract ( 2278 )   PDF (1337KB) ( 85 )  
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    This study presents a biological system combined upflow anaerobic sludge bed (UASB) with sequencing batch reactor (SBR) to treat ammonium-rich landfill leachate. The start-up and operation of the nitritation at low temperatures were investigated. The synergetic interaction of free ammonia (FA) inhibition on nitriteoxidizing bacteria (NOB) and process control was used to achieve nitritation in the SBR. It is demonstrated that nitritation was successfully started up in the SBR at low temperatures (14.0 ℃-18.2 ℃) by using FA inhibition coupled with process control, and then was maintained for 482 days at normal/low temperature. Although ammonia-oxidizing bacteria (AOB) and NOB co-existed within bacterial clusters in the SBR sludge, AOB were confirmed to be dominant nitrifying population species by scanning electron microscopic (SEM) observation and fluorescence in situ hybridization (FISH) analysis. This confirmation not only emphasized that cultivating the appropriate bacteria is essential for achieving stable nitritation performance, but it also revealed that NOB activity was strongly inhibited by FA rather than being eliminated altogether from the system.
    Mechanistic study on the cellulose dissolution in ionic liquids by density functional theory
    Yingying Yao, Yao Li, Xiaomin Liu, Xiaochun Zhang, Jianji Wang, Xiaoqian Yao, Suojiang Zhang
    2015, 23(11):  1894-1906.  doi:10.1016/j.cjche.2015.07.018
    Abstract ( 2557 )   PDF (7919KB) ( 64 )  
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    Ionic liquids (ILs) have attractedmany attentions in the dissolution of cellulose due to their unique physicochemical properties as green solvents. However, themechanism of dissolution is still under debate. In this work, computational investigation for themechanisms of dissolution of cellulose in [Bmim]Cl, [Emim]Cl and [Emim]OAc ILs was performed, and itwas focused on the process of breakage of cellulose chain and ring opening using cellobiose as a model molecule. The detailed mechanism and reaction energy barriers were computed for various possible pathways by density functional theoretical method. The key findingwas that ILs catalyze the dissolution process by synergistic effect of anion and cation, which led to the cleavage of cellulose chain and formation of derivatives of cellulose. The investigation on ring opening process of cellobiose suggested that carbene formed in ILs played an important role in the side reaction of cellulose, and it facilitated the formation of a covalent bond between cellulose and imidazolium core. These computation results may provide new perspective to understand and apply ILs for pretreatment of cellulose.
    Facile synthesis of porous Pd nanoflowerswith excellent catalytic activity towards CO oxidation
    Tareque Odoom-Wubah, Mingming Du, Williams Brown Osei, Daohua Sun, Jiale Huang, Qingbiao Li
    2015, 23(11):  1907-1915.  doi:10.1016/j.cjche.2015.08.009
    Abstract ( 2597 )   PDF (18203KB) ( 28 )  
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    Microorganism-mediated, hexadecyltrimethylammonium chloride (CTAC)-directed (MCD) method was employed in this work to synthesize Pd nanoflowers (PdNFs). Proper Pichia pastoris cells (PPCs) dosage, ascorbic acid (AA), Pd(NO3)2 and CTAC concentrations were essential for the growth of the PdNFs. The size of the assynthesized PdNFs could be tuned by adjusting the amount of Pd(NO3)2 solution and dosage of PPCs used. Characterization techniques such as X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to verify the nature of the PdNFs. Finally the PdNF/PPC nanocomposites were immobilized onto TiO2 supports to obtain bio-PdNF/TiO2 catalysts which showed excellent catalytic activity for CO oxidation, obtaining 100% conversion at 100 ℃ and remaining stable over a period of 52 h of reaction time.
    N-methyl-2-(2-nitrobenzylidene) hydrazine carbothioamide—A new corrosion inhibitor for mild steel in 1 mol·L-1 hydrochloric acid
    K. Krishnaveni, K. Sampath, J. Ravichandran, C. Jayabalakrishnan
    2015, 23(11):  1916-1922.  doi:10.1016/j.cjche.2015.08.004
    Abstract ( 2032 )   PDF (1178KB) ( 43 )  
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    The corrosion inhibition of mild steel in 1 mol·L-1 hydrochloric acid by N-methyl-2-(2-nitrobenzylidene) hydrazine carbothioamide (MNBHC)was studied usingweight loss and electrochemical studies. Results obtained indicate that the inhibitor is effective in hydrochloric acid medium and the efficiency decreases with increase in temperature. Added halide additives improve the efficiency of the inhibitor. The AC impedance studies reveal that the process of inhibition is through charge transfer. Polarization studies indicate the mixed nature of the inhibitor. Fromthe thermodynamic, spectral and surface analyses the nature of adsorption has been found out. The adsorption of the inhibitor on mild steel follows the Langmuir isotherm.