Removal of Cd (Ⅱ) by polystyrene-base chelating resins: adsorption properties and experiences of industrial wastewater treatment

摘要

This study involved the adsorption removal of Cd (Ⅱ) by "green" chelating PS-DETA resins and its application in a column mode for industrial wastewater treatment. An initial factorial design of experiments showed that factors such as pH of the solution, agitation speed, and contact time were important. Competing adsorption of Cd (Ⅱ) and Zn (Ⅱ) onto the PS-DETA resins in binary system showed that the adsorption affinity may be in the following order: Cd (Ⅱ)(＞＞) Zn (Ⅱ). The adsorption kinetics for Cd (Ⅱ) was found to follow pseudo-second-order reaction. Isotherm studies conducted at 5-500 mg/g of initial Cd (Ⅱ) concentrations provided the maximum adsorption capacities of 92.1 mg/g for the PS-DETA resins. The Langmuir isotherm model was found to describe adsorption well indicating the monolayer adsorption process. It was evident from results of the desorption studies that desorption efficiency larger than 99.6% could be obtained for Zn (Ⅱ) and Cd (Ⅱ) with 0.1 M HCl or HNO_3. Data from a column study using PS-DETA resins for Cd (Ⅱ) and Zn (Ⅱ) from industrial wastewater showed that after approximately 760 BV, removal of Cd (Ⅱ) achieved 50%. Hence, it was concluded that it was effective to remove Cd (Ⅱ) from industrial waste-water with the column operation although the adsorption capacity of the PS-DETA resins for Cd (Ⅱ) and Zn (Ⅱ) was found to be less than the adsorption capacity obtained in the batch study.