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| Study on the adsorption performance and mechanism of calcined magnetically modified oyster shells on cadmium in water/soil solution |
| Received:January 31, 2023 |
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| KeyWord:modified;oyster shells;biomass;magnetic adsorbent;cadmium |
| Author Name | Affiliation | E-mail | | GUO Kexin | School of Environment and Energy, South China University of Technology, Guangzhou 510006, China | | | WANG Heng | School of Environment and Energy, South China University of Technology, Guangzhou 510006, China | | | YI Xiaoyun | School of Environment and Energy, South China University of Technology, Guangzhou 510006, China | xyyi@scut.edu.cn | | DANG Zhi | School of Environment and Energy, South China University of Technology, Guangzhou 510006, China | |
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| Abstract: |
| The aim of this study was to obtain magnetic materials that are easy to recycle and have strong adsorption properties for heavy metals. Oyster shells were used as raw materials and iron phosphate and ferrous carbonate were used as iron sources. Magnetic materials were prepared using the co-precipitation method, and calcined and modified to obtain calcined iron phosphate oyster shells（CPO）and calcined ferrous carbonate oyster shells（CCO）. The adsorption characteristics of Cd（Ⅱ）were explored using different initial pH values, adsorption isotherms, and kinetics, and the mechanism of adsorption of Cd（Ⅱ）were analyzed using by SEM-EDS, XRD, FTIR, and XPS. The experimental studies were carried out in Cd-contaminated soil to explore the removal effect of materials on total Cd and various forms of Cd in soil solution. The results showed that the optimal pH value of Cd（Ⅱ）adsorption between the two materials was between 4-6. The maximum theoretical adsorption capacity of Cd（Ⅱ）by CPO and CCO in water reached 214.20 mg·g-1 and 116.04 mg·g-1 at 35 ℃. The adsorption process conformed to the Langmuir model, indicating that it is a single-layer adsorption. The adsorption equilibrium of CPO and CCO was reached at 100 min, and the adsorption process was in line with the quasi-second-order kinetics, indicating chemical adsorption. The characterization results showed that the adsorption mechanism of Cd（Ⅱ）by CPO and CCO was mainly chemisorption, including electrostatic interaction, the complexation of carboxyl and hydroxyl groups and Cd（Ⅱ）on the surface of the material, and the precipitation of phosphate, carbonate, and Cd（Ⅱ）. The removal rates of total Cd were 28.67% and 22.05%, and the recovery rates were 92.39% and 89.72% in the soil experiments. In conclusion, the calcined iron phosphate and calcined ferrous carbonate oyster shells prepared in this study had a large adsorption capacity of Cd（Ⅱ）and a high recovery rate, which had good application potential. |
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