Removal of zinc (Zn~(2+)) through biopolymer-enhanced ultrafiltration

摘要

This work presents for the first time the coupling of a biodegradable polymer, sodium lignosulfonate (SLS), with ultrafiltration to remove Zn~(2+) ions from model solution as well as zinc plating bath solution. SLS was first characterized using Fourier transform infrared spectroscopy to determine the functional groups of the biopolymer. Elemental analyses were performed to determine the polymer's C, H, and S content. The effect of polymer:Zn~(2+) molar ratio, initial solution pH, and stirring time on Zn~(2+) removal was investigated. The results showed that the pH of the initial solution significantly affected the removal of Zn~(2+), and the maximum removal was achieved in the pH range of 3-7. Increasing the molar ratio of lignosulfonate to zinc from 5 to 30 improved the removal of Zn~(2+) from 72 to 90. Furthermore, the ion exchange reaction between functional groups of lignosulfonate and Zn~(2+) reached equilibrium within 30 min. The presence of mon-ovalent ions, Na~+ and K~+, did not affect the removal rate; however, divalent cations, Ca~(2+), and Mg~(2+) reduced the removal rate of Zn~(2+) from 90 to 80. In a later stage of the work, Zn~(2+) was removed from zinc plating bath water sample by biopolymer-enhanced ultrafiltration. The optimum conditions were applied to the actual water sample, and 80 of Zn2+ was removed from the solution.