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| Removal of methylene blue in aqueous solution by citric acid-modified rice straw loaded with Fe3O4 composite |
| Received:August 02, 2018 |
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| KeyWord:citric acid;modified rice straw;magnetic Fe3O4;methylene blue;functional groups;adsorption |
| Author Name | Affiliation | E-mail | | LI Lin-xuan | School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China | | | LIAO Yun-kai | School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China | | | FAN Shi-suo | School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China | fanshisuo@ahau.edu.cn |
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| Abstract: |
| For this study, two adsorption materials, citric-acid-modified rice straw (CA-RS) and citric-acid modified rice straw loaded with Fe3O4 (CA-RS-Fe) were prepared via the chemical precipitation method. The adsorption materials were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) techniques. Their adsorption ability for methylene blue (MB) removal in an aqueous solution was investigated. Influencing factors, including solid-to-liquid ratios, temperature, solution pH, and concentrations, were evaluated. Results showed that at the optimal solid-to-liquid ratio of 1.0 g·L-1, more than 95% of MB was removed by CA-RS with a pH ranging from 3.0~11.0. Adsorption kinetics of MB by the CA-RS and CA-RS-Fe methods could be well-described by the pseudo-second-order kinetics model. Furthermore, the Langmuir isotherm equation could describe the adsorption of MB on CA-RS and CA-RS-Fe. The characterization results of FTIR and XPS, before and after adsorption, reveal that functional groups, especially carboxyl group in the CA-RS, played important roles in MB removal. The interaction mechanisms between MB and CA-RS involved electrostatic attraction, hydrogen bonding, and π-π interaction. Introduction of Fe3O4 reduced the amount of carboxyl groups and decreased the adsorption of MB. However, rapid and simple solid-liquid separation was achieved, owing to the existence of Fe3O4. This indicates that CA-RS could be a good adsorbent for MB dye-removal from wastewater, and the loading of Fe3O4 in CA-RS can be beneficial for solid-liquid separation. |
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