Preparation of Manganese Inprinted Cysteine-chitosan Resin and Its Selective Adsorption of Mn²⁺ in Dilute Solution

Mn²⁺ inprinted adsorbent grafted by cysteine (Cys-Mn-CCTS) was synthesized via combination of carboxyl groups of cysteine with crosslinked chitosan microspheres (Mn-CCTS) by combining sol-gel method with reverse phase suspension method involving kerosene as dispersant, manganese nitrate as inprinted molecular and epoxy chloropropane as cross-linking agent. Their structures were analyzed utilizing the techniques of SEM and FTIR. Static adsorption experiments for Mn²⁺ with low concentration indicate that the adsorption performance of Cys-Mn-CCTS is obviously improved. The removal rates of Mn²⁺ with initial concentrations of 5 mg/L and 10 mg/L are respectively raised from 22.56% and 16.26% to 82.87% and 82.56% at 303 K by Cys-Mn-CCTS. pH values from 4 to 9 have a negligible effect on the adsorption performance of Cys-Mn-CCTS, which reaches the best at pH 5 with the adsorption capacity of 7.02 mg/g and the removal rate of 96.29%. The adsorption kinetics follows the Lagergren pseudo-second-order rate model, and the removal rate of Mn²⁺ reaches 91.9% after 2 h. However, the adsorption capacity and removal rate of Mn²⁺ are 2.16 mg/g and 29.6% respectively even when the total concentration of interfering metal ions of Ca²⁺ and Mg²⁺ is up to 200 mg/L in dilute solution. Therefore, the Cys-Mn-CCTS to some extend can be considered to have selective adsorption for Mn²⁺ in dilute solution.