Removal of heavy metal ions by lignocellulosic-formaldehyde ion exchange resin produed from water hyacinth

Abstract

The water hyacinth was treated with acidic formaldehyde solution at concentration of 2, 5, 10, 20, 30 and 37% (v/v), respectively. It was found that the 5% formaldehyde treated water hyacinth (5% FTWH) was the most effective one for removing heavy metal ions in batch experiments. In column experiments, total capacities of 5% FTWH were found to be 1.0962, 0.6983 and 1.0375 meq/g for Cu², Ni²⁺ and Zn²⁺ ions, respectively. Furthermore, the values of copper ion exchange were always higher than those of nickel and zinc ions. After breakthrough curves, the heavy metal ions were completely eluted with 0.5 N HCI about 1 bed volume. After subsequent washing the packed column with deionized water for re-use, the acid regeneration had no apparent effect on their capacity for at least five times. The Pearson's correlation coefficient for Cu², Ni²⁺ and Zn²⁺ were -0.85, -1.00 and – 0.78 respectively. This indicates that decreasing the metal ion concentrations of the solutions led to an increase in the dynamic capacities. For treatment of Zn-electroplating wastewater, a 5% FTWH packed column could be used satisfactorily to remove the heavy metal ions. According to the results, 5% FTWH could be effectively used as an alternative to the non-biodegradable ion exchange resin for removing some heavy metal ions from electroplating wastewaters.