Adsorption and Removal of Cr, Cu, Pb, and Zn from Aqueous Solution by Magnetic Nano-Chitosan.

Magnetic nano-chitosan (MNC) was prepared and characterized. The kinetics, thermodynamics, and influencing factors of the adsorption of Cr, Cu, Pb, and Zn, as well as their competitive adsorption onto MNC in aqueous solution, were studied. The results showed that the adsorption kinetics and thermodynamics of Cr, Cu, Pb, and Zn were well described by the pseudo-second-order kinetic model and Langmuir isothermal adsorption model, indicating that the adsorption was mainly chemical adsorption and endothermic. Increasing the dosage of MNC, the equilibrium adsorption capacity (q) of Cr, Cu, Pb, and Zn decreased; their removal rate (η) increased. With the increase in the solution's pH, the q and η of Cr first increased and then decreased; the q and η of Cu, Pb, and Zn increased. With the increase in the metal ion initial concentration, the q increased; the η of Cr, Cu, and Zn decreased, while the η of Pb increased first and then decreased. Temperature had a weak influence on the q of Cr and Pb, while it had a strong influence on Cu and Zn, the q and η were greater when the temperature was higher, and the adsorption was spontaneous and endothermic. The q and η of Cu, Pb, and Zn decreased in the presence of co-existing ions. The influences among metal ions existed in a binary and ternary ion system. The current study's results provide a theoretical support for the simultaneous treatment of harmful metal ions in wastewater by MNC.