Adsorption of Anionic and Cationic Metals by Non-Ionic Polymeric Resins

摘要

Experiments were conducted to determine the effect of pH on the adsorption of cadmium and zinc cations and anionic chromate ion on six synthetic polymer resin absorbents. In general, the removal of Zn(II) and Cd(II) increased with increasing pH while the adsorption of chromate ion increased with decreasing pH. Of the six resins examined, Amberlite XAD-7 was the most effective for cations while Ambersorb XE-348 was the most effective for the metal anion. The adsorption of chromate was significantly more sensitive to the adsorbate concentration than the adsorbent dose. Adsorption maxima shifted to a lower pH as the resin dose was decreased. Chromate adsorption was best described by an equation in the form of the BET isotherm. Both the Langmuir and Freundlich equations were successful in fitting the cation adsorption data. Comparison of the Langmuir parameters obtained for the adsorption of Zn(II) and Cd(II) by Amberlite XAD-7 with those of other adsorption systems suggests that the non-ionic polymeric resins are relatively ineffective adsorbents for simple unhydrolyzed cations. Further study is required with chromate ion although the results suggest that its adsorption by carbonaceous resins may be economically feasible.