Papers by Author: Hong Zheng

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Authors: Si Yuan Wu, Hong Zheng, Peter G. Weidler, Peng Cai
Abstract: With synthetic wastewater, a comparative study on co-sorption of Zn(II) and As(V) by Fe/Al-PILCs prepared at different calcination temperatures was investigated using a lab-scale batch experiment technique. The effects of relevant parameters, such as pH value of solution, adsorbent dosage and contact time were examined, respectively. The results show that sorption efficiencies of Zn(II) and As(V) by Fe/Al-PILC prepared at calcination temperatures of 300 °C are higher than those at 350 and 400 °C and the higher calcination temperature is, the lower sorption efficiencies of Zn(II) and As(V) are. Co-sorption isotherm data of Zn(II) and As(V) by Fe/Al-PILCs were fitted well to Langmuir isotherm and the maximum sorption capacities of Zn(II) and As(V) on Fe/Al-PILC (Q0) prepared at 300 °C are 13.95 and 15.87 mg/g, respectively, which are higher than those at calcination temperatures of 350 °C and 400 °C. The maximum sorption capacity of As(V) decreases more obviously with increasing calcination temperature than Zn(II) does. n>1 from Freundlich isotherm indicate that the sorption of Zn(II) and As(V) by Fe/Al-PILCs is favorable. E values from D-R model indicate that the type of sorption of Zn(II) and As(V) by Fe/Al-PILCs is physical. There is significant potential for Fe/Al-PILC prepared at calcination temperature of 300 °C as an adsorbent material for Zn(II) and As(V) removal from aqueous solutions.
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Authors: Peng Cai, Hong Zheng, Peng Liang, Shu Ping Liang
Abstract: Competitive adsorption experiment of fluoride and phosphate on MgAl-CO3 LDHs has been conducted. A series of batch experiments were performed to study the influence of various experimental parameters such as pH, adsorbent dosage and contact time on the adsorption of fluoride and phosphate on MgAl-CO3 LDHs. Three kinetic models have been evaluated in order to attempt to fit the experimental data, namely the pseudo-first order, the pseudo-second order and the Weber and Morris intraparticle diffusion model. The effects of the initial concentration and the addition order of fluoride and phosphate on their adsorption by MgAl-CO3 LDHs were also investigated. The results show that the optimal pH is 4 to 5, adsorbent dosage is 2 g/L and it takes about 2 hours to attain equilibrium. It was found that the pseudo-second order most closely describes the kinetics. The initial concentration and the addition order of fluoride and phosphate influence the adsorption of fluoride to a certain extent, but they have relatively small influence to the adsorption of phosphate on MgAl-CO3 LDHs.
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Authors: Su Yuan Wu, Hong Zheng, Peter G. Weidler, Peng Cai
Abstract: Co-sorption characteristics of Zn(II) and As(V) on the mixed Fe/Al-PILCs was investigated in a batch system at room temperature. The effects of relevant parameters, such as pH value of solution, adsorbent dosage, initial Zn(II) and As(V) concentrations and contact time were examined, respectively. The results show that co-sorption capacities and co-sorption rates of Zn(II) and As(V) by Fe/Al-PILC are higher and faster than those of single Zn(II) or single As(V) by Fe/Al-PILC. Co-sorption isotherm data of Zn(II) and As(V) by Fe-Al-PILC were fitted well to Langmuir isotherm and the maximum sorption capacities of Zn(II) and As(V) on mixed Fe-Al-PILCs (Q0) are 16.98 mg/g and 16.29 mg/g, respectively, which are higher than those in single system. n>1 from Freundlich isotherm indicate that the sorption of Zn(II) and As(V) by Fe-Al-PILC is favorable. E values from D-R model indicate that the type of sorption of Zn(II) and As(V) by Fe-Al-PILC is physical. The results indicate that there is significant potential for Fe/Al-PILCs as an adsorbent material for Zn(II) and As(V) removal from aqueous solutions.
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Authors: Yu Bing Pu, Jia Rui Wang, Hong Zheng, Peng Cai, Si Yuan Wu
Abstract: A series of MgAlFe-CO3 layered double hydroxides (LDHs) were successfully prepared by co-precipitation method. With synthetic wastewater, the effect of doped iron on fluoride sorption by calcined MgAlFe-CO3 layered double hydroxides (CLDH) under different pH and contact time conditions was investigated. The sorption isotherm data were fitted well to Langmuir isotherm at 25 °C. The maximum sorption capacity of fluoride on CLDH increases first and then decreases with the increase of Fe/Al molar ratio and attains maximum of 71.94 mg/g when Fe/Al molar ratio is 1:2, although doped iron is unfavorable to the regeneration of original layered structure for CLDH after fluoride adsorption. No aluminium in the solution after fluoride adsorption was detected when Fe/Al molar ratio is equal to or larger than 1:2. The results indicate that CLDH with proper Fe/Al molar ratio is a promising candidate as an adsorbent material for fluoride removal from aqueous solutions.
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Authors: Hong Zheng, Yang Wang, Peng Liang, Hong Bin Qi
Abstract: The ability of Cr-bentonite prepared using synthetic wastewater containing chromium was investigated for adsorptive removal of 4-aminophenol and 4-chlorophenol from aqueous solution in a batch system at 25 °C. The physic-chemical parameters including pH value of solution and contact time were studied. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models of sorption. The equilibrium sorption data for 4-aminophenol and 4-chlorophenol were well fitted to Langmuir adsorption isotherm and the monolayer sorption capacity was found to be 26.53 and 23.81 mg/g at 25 °C, respectively. The sorption energy calculated from Dubinin-Redushkevich (D-R) isotherm are 8.31 and 8.20 kJ/mol for the uptake of 4-aminophenol and 4-chlorophenol respectively which indicates that both the sorption processes are chemical in nature. The kinetic data were analyzed using pseudo-first order, pseudo-second order kinetic equation and intraparticle diffusion model. The experimental data fit very well the pseudo-second order kinetic model. Intraparticle diffusion affects 4-aminophenol and 4-chlorophenol uptake. Sorption studies carried out using industrial wastewater samples containing phenolic compounds show that there is significant potential for Cr-bentonite as an adsorbent material for phenollic compounds removal from aqueous solutions.
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Authors: Yi He Zhang, Qing Song Su, Li Yu, Li Bing Liao, Hong Zheng, Hai Tao Huang, Guo Ge Zhang, Ying Bang Yao, Cindy Lau, Helen Lai Wah Chan
Abstract: Phlogopite with layered silicate structure had been firstly chemically modified via an in situ intercalation method, and phlogopite-polymer nanocomposite films were prepared from 2,2'-bis (3,4-dicarboxyphenyl) hexafluropropane dianhydride (6FDA) and oxydimethyl aniline (ODA) in N,N-dimethylacetamide as a solvent by using in-situ polymerization process combined with ultrasonic dispersion and multi-step curing. The structure of phlogopite minerals and its polymer nanocomposites were characterized by X-ray diffraction (XRD) and infrared spectra (FTIR) respectively. The experimental results indicated that the phlogopites with layered nanostructure had lost their ordered structure and had been exfoliated or intercalated. Thereafter, they were dispersed randomly in the polyimide matrix. The dependence of dielectric properties and thermal stabilities of the nanocomposite films on the phlogopite content and frequency were studied.
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Authors: Yi He Zhang, Qing Song Su, Li Yu, Hong Zheng, Hai Tao Huang, Guo Ge Zhang, Ying Bang Yao, Helen Lai Wah Chan
Abstract: A sol-gel process was used to prepare polyimide-silica hybrid films from the polyimide precursors and TEOS in N,N- dimethyl acetamide, then the hybrid film was treated with hydrofluoric acid to remove the dispersed silica particles, leaving pores with diameters between 80nm to 1µm, depending on the size of silica particles. The structure and dielectric constant of the hybrid and porous films were characterized by FTIR,SEM. The porous films displayed relatively low dielectric constant compared to the hybrid polyimide-silica films.
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