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| Adsorption mechanism and optimization of the adsorption conditions of modified serpentine for Pb2+ removal |
| Received:January 24, 2022 |
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| KeyWord:high temperature modified serpentine;lead;adsorption mechanism;desorption;Box-Behnken response surface methodology |
| Author Name | Affiliation | E-mail | | XU Pengchao | School of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | KE Chuanhao | School of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | WU Yan | School of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | | | LIU Zhi | Shenyang Institute of Environmental Sciences, Shenyang 110016, China | | | DU Liyu | School of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China | duliyu2006@syau.edu.cn | | YANG Yuhong | College of Biotechnology, Shenyang Agricultural University, Shenyang 110866, China | |
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| Abstract: |
| To enhance the removal effect of serpentine on Pb2+ pollutants and achieve efficient removal of Pb2+ from wastewater, this study modified natural serpentine minerals at high temperature and investigated the adsorption and desorption mechanism of modified serpentine to Pb2+. In addition, the effects of the amount of serpentine, initial pH of solution, particle size, and absorption time of serpentine on adsorption amount and Pb2+ removal rate were investigated. The experimental conditions for Pb2+ adsorption by modified serpentine were optimized using the Box-Behnken response surface method. The results showed that the adsorption performance of modified serpentine was significantly improved. The theoretical maximum saturation capacity was high, and both adsorption processes were more consistent with the Freundlich isothermal adsorption and the Quasi-secondary kinetic models. The adsorption processes were carried out by spontaneous heat absorption. The adsorption mechanism of Pb2+ adsorption by modified serpentine was mainly based on the combination of Mg2+, generated from the cleavage of serpentine, with dissolved CO2 in solution to form MgCO3, and the solvation substitution of MgCO3 with Pb2+ in solution to generate PbCO3 precipitate. Pb2+ binds to the high-energy bonds formed on the surface of modified serpentine and absorbed in the form of Pb(NO3)2·Si-O and PbO ·O-Si-O complexes. The modified serpentine was adsorbed on the surface as Pb(NO3)2·Si-O and PbO·O-Si-O complexes. The desorption amount and removal rate of Pb2+ in solution were low. The adsorption of modified serpentine on Pb2+ was relatively stable, and Pb2+ was not easily desorbed out. The best adsorption conditions of modified serpentine for Pb2+ in solution were 1:200(m:V)solid-liquid ratio, pH=5.5, 140 mesh particle size, and 36 h adsorption time; the adsorption amount and Pb2+ removal rate were 15.26 mg·g-1 and 79.89%, respectively. The present study shows that the adsorption performance of modified serpentine to Pb2+ is significantly improved, with high adsorption capacity, more stable adsorption, and less desorption, indicating that serpentine has potential application value for the removal of Pb2+ from wastewater. |
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