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| The adsorption of Cd2+ and Zn2+ in aqueous solutions by dairy manure and walnut shell biochar |
| Received:May 31, 2018 |
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| KeyWord:dairy manure biochar;walnut shell biochar;Cd2+;Zn2+;adsorption |
| Author Name | Affiliation | E-mail | | LIU Jian-nan | School of Environmental Science and Engineering, Shanghai Jiao tong University, Shanghai 200240, China | | | FENG Ji-meng | School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China | | | LI Dan | School of Environmental Science and Engineering, Shanghai Jiao tong University, Shanghai 200240, China | | | WANG Xin-ze | School of Environmental Science and Engineering, Shanghai Jiao tong University, Shanghai 200240, China | | | SHAN Ai-dang | School of Materials Science and Engineering, Shanghai Jiao tong University, Shanghai 200240, China | adshan@sjtu.edu.cn |
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| Abstract: |
| In order to remove Cd2+ and Zn2+ from aqueous solutions efficiently, using dairy manure and walnut shells as raw materials, biochar was prepared at different pyrolysis temperatures. The adsorption equilibrium method and dynamic adsorption method were used to study the kinetic characteristics of biochar and the adsorption effect of biochar on Cd2+ and Zn2+ in aqueous solutions. The adsorption mechanism was investigated by detecting biochar before and after adsorption using X-ray diffraction and Fourier transform infrared spectroscopy. The results showed that biomass materials and pyrolysis temperature were two major factors affecting the adsorption effect of biochar. The adsorption effect of dairy manure biochar was greater than that of walnut shell biochar, and the adsorption effect of biochar prepared at 700℃ was greater than that of biochar prepared at 300℃. Langmuir isotherms were more suitable for describing the Cd2+ and Zn2+ adsorption mechanisms of biochar. Dairy manure biochar prepared at 700℃ (DM 700) was the most effective adsorption material for Cd2+ and Zn2+, with maximum adsorption capacities of 117.5 mg·g-1 and 59.4 mg·g-1, respectively. The adsorption kinetics of DM700 fit better with pseudo-second order kinetics and included the rapid stage and slow stage. Ion exchange and the complex reaction between hydroxyl and carboxyl groups in biochar with Cd2+ and Zn2+ were the main adsorption mechanisms. CdCO3 and Zn3 (PO4)2 precipitates were formed after Cd2+ and Zn2+ were adsorbed. Therefore, DM 700 has great potential as an adsorbent for Cd2+ and Zn2+.This study provides a theoretical basis and application reference for biochar removal of heavy metals from water and soil. |
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