Removal of Copper Ions from Aqueous Solution by a Hydrotalcite-Like Absorbent FeMnMg-LDH
2020
Zhou, Hongguang | Tan, Youlin | Gao, Wei | Zhang, Yue | Yang, Yanmei
FeMnMg-LDH with hydrotalcite-like structure was synthesized via a coprecipitation method and applied to copper ion removal from aqueous solution. FT-IR, SEM, PXRD, TEM, and XPS were applied to characterization analysis. Factors like temperature, pH, contact time, initial concentration, and coexisting cations were systematically studied. FeMnMg-LDH has an excellent performance on copper adsorption, with a maximum capacity of 204.07 mg/g at 25 °C, which is much higher than that of most other similar LDHs. The effects of coexisting cations on the removal efficiency of copper ions are various and following the order of Zn²⁺ > Pb²⁺ > Mg²⁺ > Ca²⁺, which may be due to the solubility of their hydroxides. The result of adsorption thermodynamics indicates that the adsorption process is endothermic and spontaneous. The adsorption kinetics are in accord with the pseudo-second-order kinetic model, and particles that appear in the SEM figures are both suggesting that chemical complex formed during the adsorption process. Meanwhile, the result of DKR model fitting indicates that the isomorphic substitution mechanism is involved in the adsorption process. Thus, the main adsorption mechanisms of FeMnMg-LDH in the removal of Cu²⁺ from aqueous solution in this study are isomorphic substitution and surface-induced precipitation. Graphical abstract
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