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Table of Content
28 September 2014, Volume 22 Issue 9
    Gas-Liquid Mass Transfer Characteristics in a Gas-Liquid-Solid Bubble Column under Elevated Pressure and Temperature
    Haibo Jin, Suohe Yang, Guangxiang He, Delin Liu, Zemin Tong, Jianhua Zhu
    2014, 22(9):  955-961.  doi:10.1016/j.cjche.2014.06.019
    Abstract ( 3470 )   PDF (2017KB) ( 466 )  
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    The volumetricmass transfer coefficient kLa of gases (H2, CO, CO2) and mass transfer coefficient kL on liquid paraffin side were studied using the dynamic absorption method in slurry bubble column reactors under elevated temperature and elevated pressure. Meanwhile, gas-holdup and gas-liquid interfacial area a were obtained. The effects of temperature, pressure, superficial gas velocity and solid concentration on themass transfer coefficient were discussed. Experimental results show that the gas-liquid volumetric mass transfer coefficient kLa and interfacial area a increasedwith the increase of pressure, temperature, and superficial gas velocity, and decreased with the slurry concentration. The mass transfer coefficient kL increased with increasing superficial gas velocity and temperature and decreased with higher slurry concentration, while it changed slightly with pressure. According to analysis of experimental data, an empirical correlation is obtained to calculate the values of kLa for H2 (CO, CO2) in the gas-paraffin-quartz system in a bubble column under elevated temperature and elevated pressure.
    Heterogeneity of Adsorption Sites and Adsorption Kinetics of n-Hexane on Metal-Organic Framework MIL-101(Cr)
    Xuejiao Sun, Jinpeng Miao, Jing Xiao, Qibin Xia, Zhenxia Zhao
    2014, 22(9):  962-967.  doi:10.1016/j.cjche.2014.06.031
    Abstract ( 3818 )   PDF (551KB) ( 361 )  
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    The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-101(Cr) were studied by gravimetric method and temperature-programmed desorption (TPD) experiments. The MIL-101 crystals were synthesized by microwave irradiation method. The adsorption isotherms and kinetic curves of n-hexane on the MIL-101 were measured. Desorption activation energies of n-hexane fromthe MIL-101 were estimated by TPD experiments. The results showed that equilibrium amount of n-hexane adsorbed on the MIL-101 was up to 5.62 mmol·g-1 at 298 K and 1.6×104 Pa, much higher than that of some activated carbons, zeolites and so on. The isotherms of n-hexane on the MIL-101 could bewell fitted with Langmuir-Freundlich model. TPD spectra exhibit two types of adsorption sites on the MIL-101 with desorption activation energies of 39.41 and 86.69 kJ·mol-1. It reflects the surface energy heterogeneity on the MIL-101 frameworks for n-hexane adsorption. The diffusion coefficients of n-hexane are in the range of (1.35-2.35)×10-10 cm2·s-1 with adsorption activation energy of 16.33 kJ·mol-1.
    Novel Gas-assisted Three-liquid-phase Extraction System for Simultaneous Separation and Concentration of Anthraquinones in Herbal Extract
    Xingfu Yang, Xiangfeng Liang, Liangrong Yang, Feng Pan, Fuli Deng, Huizhou Liu
    2014, 22(9):  968-973.  doi:10.1016/j.cjche.2014.06.029
    Abstract ( 2960 )   PDF (3384KB) ( 351 )  
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    Gas-assisted three-liquid-phase extraction (GATE), which has the advantages of both three-liquid-phase extraction and solvent sublation, is a novel separation technique for separation and concentration of two organic compounds into different phases in one step. This highly effective and economically applicable method has been developed for separating emodin and rhein from herbal extract. In a GATE system composed of butyl acetate/ PEG4000/ammoniumsulfate aqueous solution, influence of various parameters including gas flow rate, flotation time, salt concentration, initial volumeof PEG and butyl acetatewas investigated. Within 50 min of 30 ml·min-1 nitrogen flow, removal ratio of emodin and rhein from aqueous phase could be over 99% and 97%, respectively. Mass fraction of emodin in the BA phase and rhein in the PEG phase could reach 97% and 95%, respectively. It is demonstrated that gas bubbling is effective for partitioning of emodin and rhein into butyl acetate and PEG phase respectively, and dispersed PEG and butyl acetate could be captured from the aqueous solution. Experimental results showthat GATE could be an effective and economical technology for concentration and separation of co-existed products in medicinal plants.
    Influence of the Surface and Structural Characteristics of Activated Carbons on Adsorptive Removal of Halo-Olefinic Impurities from 1,1,1,3,3-Pentafluoropropane
    Bo Zhang, Chuang Zhang, MingquanWei
    2014, 22(9):  974-979.  doi:10.1016/j.cjche.2014.06.020
    Abstract ( 3461 )   PDF (525KB) ( 400 )  
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    Halo-olefinic impurities in 1,1,1,3,3-pentafluoropropane (HFC-245fa) product used as blowing agents, etc. could damage the human body and must be removed. Activated carbon was treated by HCl, HNO3 and NaOH, respectively. The adsorptive performance of unmodified and modified activated carbons for the removal of a low content of 1-chloro-3,3,3-trifluoro-1-propene (HCFC-1233zd), 1,3,3,3-tetrafluoro-1-propene (HFC-1234ze), 1-chloro-1,3,3,3-tetrafluoro-1-propene (HFC-1224zb) and 2-chloro-1,3,3,3-tetrafluoro-1-propene (HFC-1224xe) halo-olefins in the 1,1,1,3,3-pentafluoropropane (HFC-245fa) product was investigated. These halo-olefinic impurities could be substantially removed from the HFC-245fa product via the adsorption over activated carbon when the adsorption temperature was under 333 K, which can be attributed to the π-π dispersion interactions between the halo-olefins and carbon graphite layer. The basic surface groups of activated carbon could catalyze the decomposition of HFC-245fa to formHFC-1234ze. However, the significant increase in the amount of surface acidic groups of activated carbon led to a distinct decrease of adsorption capacity due to the reduction in themicropore volume of adsorbent and a decrease in the strength of the π-π dispersive interactions between haloolefin molecules and carbon basal. The breakthrough time of halo-olefinic impurities on activated carbon increased with the increase of molecular mass and the decrease of molecular symmetry.
    Separation of Primary Alcohols and Saturated Alkanes from Fisher-Tropsch Synthesis Products
    Suqiao Li, Zhongli Tang, Fujun Zhou, Wenbin Li, Xigang Yuan
    2014, 22(9):  980-983.  doi:10.1016/j.cjche.2014.06.025
    Abstract ( 3254 )   PDF (294KB) ( 182 )  
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    Amethod for separating primary alcohols and saturated alkanes fromthe products of Fisher-Tropsch synthesis is developed. The separation scheme consists of three steps: (1) the raw material is pre-separated by fractional distillation into four fractions according to normal boiling points; (2) appropriate extractants are selected to separate the primary alcohols from the saturated alkanes in each fraction; (3) the extractants are recovered by azeotropic distillation and the primary alcohols in the extract phase are purified. Based on the proposedmethod, the total recovery rates of the primary alcohols and the saturated alkanes are 86.23% and 84.62% respectively.
    Porous Spherical Cellulose Carrier Modified with Polyethyleneimine and Its Adsorption for Cr(Ⅲ) and Fe(Ⅲ) from Aqueous Solutions
    Zhijian He, Hang Song, Yannan Cui, Weixia Zhu, Kaifeng Du, Shun Yao
    2014, 22(9):  984-990.  doi:10.1016/j.cjche.2014.07.001
    Abstract ( 3554 )   PDF (1253KB) ( 259 )  
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    An efficient porous spherical polyethyleneimine-cellulose (PEI-cell) absorbent was synthesized and characterized. The main influencing factors and adsorption mechanism for two typical metal ions, Cr3+ and Fe3+, were investigated. The adsorption performance primarily depends on the initial concentration of metal ions, pH value and temperature, and the chelation action between N atoms of PEI-cell and metal ions plays an important role. Under dynamic adsorption conditions, the saturation adsorption of polyethyleneimine-cellulose is 83.98 mg·g-1 for Cr(Ⅲ) and 377.19 mg·g-1 for Fe(Ⅲ), higher than reported data and that of unmodified cellulose. The adsorption can be well described with second-order kinetic equation and Freundlich adsorption model, and ΔH, ΔG and ΔS of the adsorption are all negative. With 5% HCl as eluent, the elution ratio of Cr(Ⅲ) and Fe(Ⅲ) achieved 99.88% and 97.74% at 313 K, respectively. After the porous PEI-cell was reused 6 times, it still presented satisfactory adsorption performance. Above results show the advantages such as easily-acquired raw material, high efficiency, stable recycling performance and biodegradability.
    Preparation and Application of the Sol-Gel Combustion Synthesis-Made CaO/CaZrO3 Sorbent for Cyclic CO2 Capture Through the Severe Calcination Condition
    Baowen Wang, Xiaoyong Song, ZonghuaWang, Chuguang Zheng
    2014, 22(9):  991-999.  doi:10.1016/j.cjche.2014.06.034
    Abstract ( 3714 )   PDF (1607KB) ( 137 )  
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    Calciumlooping method has been considered as one of the efficient options to capture CO2 in the combustion flue gas. CaO-based sorbent is the basis for application of calcium looping and should be subjected to the severe calcination condition so as to obtain the concentrated CO2 stream. In this research, CaO/CaZrO3 sorbents were synthesized using the sol-gel combustion synthesis (SGCS) method with urea as fuel. The cyclic reaction performance of the synthesized sorbents was evaluated on a lab-scaled reactor system through calcination at 950℃ in a pure CO2 atmosphere and carbonation at 650℃ in the 15% (by volume) CO2. The mass ratio of CaO to CaZrO3 as 8:2 (designated as Ca8Zr2) was screened as the best option among all the synthesized CaO sorbents for its high CO2 capture capacity and carbonation conversion at the initial cycle. And then a gradual decay in the CO2 capture capacity was observed at the following 10 successive cycles, but hereafter stabilized throughout the later cycles. Furthermore, structural evolution of the carbonated Ca8Zr2 over the looping cycles was investigated. With increasing looping cycles, the pore peak and mean grain size of the carbonated Ca8Zr2 sorbent shifted to the bigger direction but both the surface area (SA) ratio Φ and surface fractal dimension Ds decreased. Finally, morphological transformation of the carbonated Ca8Zr2 was observed. Agglomeration and edge rounding of the newly formed CaCO3 grainswere found as aggravated at the cyclic carbonation stage. As a result, carbonation of Ca8Zr2 with CO2was observed only confined to the external active CaO by the fast formation of the CaCO3 shell outside, which occluded the further carbonation of the unreacted CaO inside. Therefore, enough attention should be paid to the carbonation stage and more effective activation measures should be explored to ensure the unreacted active CaO fully carbonated over the extended looping cycles.
    Phase Transfer Catalysis: Oxidation of 2-Methyl-1-butanol
    T. Sankarshana, E. Yadagiri, J. S. N. Murthy
    2014, 22(9):  1000-1004.  doi:10.1016/j.cjche.2014.06.023
    Abstract ( 2846 )   PDF (359KB) ( 116 )  
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    In liquid-liquid systems, the substrates in the liquids are inaccessible to each other for the reaction. By adding a small quantity of phase transfer catalyst, the reaction can bemade accessible and accelerated. The present study involves the phase transfer catalyzed oxidation of 2-methyl-1-butanol by quaternary ammoniumpermanganate (tricaprylyl methyl ammonium permanganate). The attempt was to compare the kinetics under homogeneous and heterogeneous conditions. Experiments were conducted in a batch reactor to determine the kinetics under homogeneous conditions. A baffled borosilicate agitated reactor was used to find the enhancement factor and the kinetics under heterogeneous conditions. The rate constants determined under both homogeneous and heterogeneous conditions agreed very well. The oxidation was found to be first order with respect to each of the reactants, quaternary ammonium permanganate and the alcohol, resulting in an overall second order rate expression. Aliquat336 (tricaprylylmethylammonium chloride) was found to be the best compared with the other catalysts tested (triethylbenzylammoniumchloride, tetrabutylammonium bromide, tetrabutylammonium iodide and tetrabutylammonium hydrogen sulfate) and it gave an enhancement factor of 9.8.
    Hydrolysis Kinetics of 2-Pyridinecarboxamide, 3-Pyridinecarboxamide and 4-Pyridinecarboxamide in High-Temperature Water
    Jie Fu, Haoming Ren, Ju Zhu, Xiuyang Lu
    2014, 22(9):  1005-1008.  doi:10.1016/j.cjche.2014.06.024
    Abstract ( 2787 )   PDF (3216KB) ( 83 )  
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    A kinetic study is reported here on hydrolysis of three pyridinecarboxamides in high-temperature water in the temperature range of 190-250℃ at 8 MPa. 2-Pyridinecarboxamide, 3-pyridinecarboxamide and 4-pyridinecarboxamide hydrolyze to corresponding picolinic acids. 2-Picolinic acid is further decarboxylated to pyridine. Experiments at different temperatures show that the first-order rate constants display an Arrhenius behavior with activation energies of (110.9 ± 2.3), (70.4 ± 2.1) and (61.4 ± 1.8) kJ·mol-1 for 2-pyridinecarboxamide, 3-pyridinecarboxamide and 4-pyridinecarboxamide, respectively. These kinetic parameters for pyridinecarboxamide hydrolysis are more reliable and accurate than those from the consecutive hydrolysis of cyanopyridines.
    Solubilization of Phenanthrene and Fluorene in Equimolar Binary Mixtures of Gemini/Conventional Surfactants
    Huma Siddiqui, Mohammad Kamil, Manorama Panda, Kabir-ud-Din
    2014, 22(9):  1009-1015.  doi:10.1016/j.cjche.2014.06.028
    Abstract ( 2933 )   PDF (1750KB) ( 105 )  
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    This study deals with the enhanced solubilization of polycyclic aromatic hydrocarbons (PAHs) such as phenanthrene (PHE) and fluorene (FLR) in a pure cationic gemini (G6) and three conventional surfactants [polyethylene glycol dodecyl ether (Brij35), cetyltrimethyl ammonium bromide (CTAB) and sodium lauryl sulfate (SDS)] as well as in their equimolar binary combinations (G6-Brij35, G6-CTAB and G6-SDS). Their solubilization efficiency toward PHE and FLR has been quantified in terms of the molar solubilization ratio (MSR) and themicelle-water partition coefficient (Km). The ideality/nonideality of the mixed micelles is discussed with the help of Clint, Rubingh and Rosen's approaches. These theories determine the deviation of experimental critical micelle concentration (CMC) values fromideal criticalmicelle concentration, whichwas measured by evaluating the interaction parameters (βm and βσ). Negative values of βm were observed in all the equimolar binary systems, which show synergismin the mixedmicelles.Whereas at air/liquid interface synergismwas observed in the systems G6-CTAB and G6-Brij35; G6-SDS exhibited an antagonistic effect. The order of MSR and Km was G6-CTAB N G6-Brij35 N G6-SDS for phenanthrene as well as for fluorene.
    Sn-1,3-specific Interesterification of Soybean Oil with Medium-chain Triacylglycerol Catalyzed by Lipozyme TL IM
    Hongli Yang, YingMu, Hongtao Chen, Chunyang Su, Tiankui Yang, Zhilong Xiu
    2014, 22(9):  1016-1020.  doi:10.1016/j.cjche.2014.06.027
    Abstract ( 3139 )   PDF (2116KB) ( 179 )  
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    The structured lipids are produced through sn-1,3-specific interesterification of soybean oil with medium-chain triacylglycerol (MCT) in continuous reactions catalyzed by Thermomyces lanuginose lipase (Lipozyme TL IM). Cheap Lipozyme TL IM presents similar interesterification degree (ID), sn-1,3-specificity and residual activity as expensive Rhizomucor miehei in batch reactions. In packed-bed interesterification of soybean oil with MCT catalyzed by LipozymeTL IM, the residence time has a significant effect on ID,while temperature has a small effect at 45-70℃. The sn-1,3-specificity of Lipozyme TL IM is not satisfactory when reaction temperature is higher than 60℃. The optimal residence time and temperature are 30-40 min and 55℃, respectively. Among the solvents, including acetone, isopropanol, tert-butanol, and isobutanol, used to recover the activity of the used Lipozyme TL IM, acetone is the most suitable one than the other solvents.
    Oxygen Gasification of Municipal Solid Waste in a Fixed-bed Gasifier
    Miaomiao Niu, Yaji Huang, Baosheng Jin, Xinye Wang
    2014, 22(9):  1021-1026.  doi:10.1016/j.cjche.2014.06.026
    Abstract ( 3054 )   PDF (663KB) ( 146 )  
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    Four wastematerials, paper,wood, textile and kitchen garbage, inmunicipal solidwastewere gasified separately with oxygen in a fixed bed reactor. The yields of products char, tar and gas, the composition of gas components H2, CO,CO2 and CH4, and the lower heating value (LHV)were examined at temperatures between 700 and 900℃ and equivalence ratio (ER) between 0.14 and 0.32. Characteristics of gas evolution during gasification were investigated. Results show that a higher temperature improves the formation of H2 and CO while lowers the yield of CO2 and CH4. The LHV of syngas increases with temperature and varies in the range of 6-10 MJ·m-3, reaching the maximum at 800℃ or above. As ER increases, both combustible gas component and LHV of syngas decrease while the yield of CO2 rises linearly. The appropriate ER for obtaining high quality gas is in the range of 0.18-0.23. Temperature and ER have significant effects on the product distribution. Higher temperature and ER are favorable for higher gas yield and lower yield of char and tar in the gasification of textile and kitchen garbage. At 800℃, the gas evolution may be divided into two regions. In the first region, the flow rate of gas increases and then decreases rapidly, while in the second region the flow rate decreases monotonically to lower level.
    Kinetics Analysis on Mixing Calcination Process of Fly Ash and Ammonium Sulfate
    Peng Wang, Laishi Li, DezhouWei
    2014, 22(9):  1027-1032.  doi:10.1016/j.cjche.2014.06.033
    Abstract ( 3280 )   PDF (1120KB) ( 140 )  
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    The further development of the extraction of alumina that is produced in the calcination process of ammonium sulfate mixed with fly ash was limited because of the lack of systematic theoretical study. In order to aggrandize the research of the calcination process, the kinetics and reaction mechanism of the calcinationswere studied. The result suggests that there are two stages in the calcination process, and the alumina extraction rate increases swiftly in the initial stage, but slows down increasing in the later stage. The apparent activation energy of the initial and later stages equals to 13.31 and 35.65 kJ·mol-1, respectively. In the initial stage, ammonium sulfate reacts directly with mullite in the fly ash to form ammonium aluminum sulfate, while in the later stage, aluminum sulfate is formed by the reaction between ammonium aluminum sulfate and ammonium sulfate.
    Thermodynamic Analysis of Methane-fueled Solid Oxide Fuel Cells Considering CO Electrochemical Oxidation
    Qiong Sun, Keqing Zheng, Meng Ni
    2014, 22(9):  1033-1037.  doi:10.1016/j.cjche.2014.06.018
    Abstract ( 2552 )   PDF (543KB) ( 374 )  
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    Thermodynamic analyses in the literature have shown that solid oxide fuel cells (SOFCs)with proton conducting electrolyte (H-SOFC) exhibited higher performance than SOFCwith oxygen ion conducting electrolyte (O-SOFC). However, these studies only consider H2 electrochemical oxidation and totally neglect the contribution of CO electrochemical oxidation in O-SOFC. In this short communication, a thermodynamic model is developed to compare the theoretically maximum efficiencies of H-SOFC and O-SOFC, considering the electrochemical oxidation of CO in O-SOFC anode. It is found that O-SOFC exhibits a higher maximum efficiency than H-SOFC due to the contribution from CO electrochemical oxidation, which is contrary to the common understanding of electrolyte effect on SOFC performance. The effects of operating temperature and fuel utilization factor on the theoretical efficiency of SOFC are also analyzed and discussed.
    Comprehensive Alcohol-/Ion-Responsive Properties of Poly(N-Isopropylacrylamide-co-Benzo-18-Crown-6-Acrylamide) Copolymers
    Xiaojie Ju, Shuowei Pi, Rui Xie, Xiaojing Guo, Jieyi Liu, Yalan Yu, Lu Jiang, Xiaohua Lu, Qianming Chen, Liangyin Chu
    2014, 22(9):  1038-1045.  doi:10.1016/j.cjche.2014.06.021
    Abstract ( 2976 )   PDF (1736KB) ( 304 )  
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    In this paper, we report on the comprehensive alcohol-/ion-responsive properties of a smart copolymer poly(Nisopropylacrylamide-co-benzo-18-crown-6-acrylamide) (P(NIPAM-co-BCAm)). The orthogonal design method is adopted for experimental design. The experimental results show that alcohol can trigger the shrinking and Ba2+ can induce the swelling of the P(NIPAM-co-BCAm) copolymer. According to the phase transition temperature (LCST) change results of the copolymer, the influence of variables on the LCST changes weakens in the following order: alcohol concentration N alcohol species N metal ion species N BCAm concentration N ion concentration. The larger the alcohol concentration and the larger the molecular size of alcohols, the lower the LCST value; on the contrary, the more the BCAm content in the copolymer or the larger the BCAm/ion complex stability constant (lgK) or the larger the ion concentration is, the higher the LCST value. For a P(NIPAM-co-BCAm) copolymerwith a fixed BCAmcontent, a binary function of ion concentration and lgK of BCAm/ion is developed to precisely predict the LCST values of the copolymer in different metal ion solutions. The results provide valuable information for fabricating artificial biomimetic G-protein-gated inwardly rectifying potassium (GIRK) channels that are activated by alcohol and inhibited by Ba2+.
    In-situ IR Monitoring the Synthesis of Amphiphilic Copolymery P(HEMA-co-tBMA) via ARGET ATRP
    Wenjing Lin, Youqiang Yang, Ruihao Chen, Xiufang Wen, Yu Qian, Chengzhi Cai, Lijuan Zhang
    2014, 22(9):  1046-1054.  doi:10.1016/j.cjche.2014.06.030
    Abstract ( 3014 )   PDF (3803KB) ( 209 )  
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    The amphiphilic copolymer poly(hydroxyethyl methacrylate-co-tert-butyl methacrylate) [P(HEMA-co-tBMA)] was synthesized by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP), with the synthesis process monitored by in-situ infrared spectroscopy (IR). The molecular weight, chemical structure and characteristics of the copolymer were determined by 1H NMR, gas chromatography and gel permeation chromatography. The influences of various parameters on the living polymerization were explored. The molecularweight of the copolymer with narrowmolecularweight distribution (Mw/Mn b 1.50) increases approximately linearly with the monomer conversion, indicating a good control of polymerization. In the reaction temperature range from 50℃ to 90℃, the monomer conversion is higher at 60℃. The tBMA conversion rate decreases gradually with the increase of tBMA content, while the HEMA conversion is hardly affected by HEMA content. Weak polar solvent is more favorable to the polymerization compared to polar solvent. The molar ratio of reducing agent to catalyst has significant effect on the polymerization and increasing the amount of reducing agent will accelerate the reaction rate but causes wider molecular weight distribution. It is indicated that in-situ IR monitoring contributes to a more in-depth understanding of the mechanism of methacrylate monomer copolymerization.
    Preparation of a Novel Coal Gangue-Polyacrylamide Hybrid Flocculant and Its Flocculation Performance
    Xiangao Quan, Huiyun Wang
    2014, 22(9):  1055-1060.  doi:10.1016/j.cjche.2014.06.032
    Abstract ( 3482 )   PDF (2270KB) ( 67 )  
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    A novel flocculant based on hybrid coal gangue-polyacrylamide (HCGPAM) has been prepared by using modified coal gangue and polyacrylamide. Factors related to the preparation such as reaction time, temperature, concentration of the polymer monomer and ratio of initiators are investigated. The product is characterized by infrared spectra (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), aswell as viscometry. The flocculating tests on oilfield drilling wastewater show that the removal efficiency is 85.5% and the light transmittance is 53.6%. The results indicate that the coal gangue could be used for the preparation of inorganic-organic hybrid flocculant and the removal efficiency is much higher than that of commercial polyacrylamide (PAM) or PAM/ coal gangue blend.