Due to the potential of kaolin as an adsorbent for removal of heavy metals from solution, the competitive adsorption of Lead (Pb) and Copper (Cu) by kaolin was investigated to provide further understanding on the binding behaviors and capacities of these two metals onto kaolin. The Langmuir and Freundlich isotherms were applied to further explain the competition between the metals. Three different solutions were used, each at concentrations 10, 20, 30, 45, 60 and 75mg/L: single-metal solution of Pb (Pb-Only), single-metal solution of Cu (Cu-Only), and solution of both metals at the same concentrations (Binary solution). The kaolin adsorbed Pb about twice more than Cu, both for the binary solution and for the single-metal solutions. This correlated well with predictions of maximum adsorption capacity (Q) for kaolin, where Q for Pb was about twice as much as that for Cu, both in the binary solution and in the single-metal solution. Competition from Cu in binary solution reduced Pb adsorption by 9%, while Cu rather increased by 4.1%, relative to their respective adsorptions in Pb-Only and Cu-Only, respectively. However, during competitive adsorption in the binary solution, the relative proportions of adsorbed Pb increased by 11.4% as the initial metals concentration increased from 10 – 75mg/L, while that of Cu reduced by the same proportion. This was explainable by their respective separation factors (RL), which indicated higher favorability of kaolin for Pb than for Cu. Furthermore, bonding energy (KL) of Pb unto kaolin during competition was about 2.5 times that of Cu, and was likely able to cause Pb to displace Cu from kaolin surface. This study reveals greater adsorption capacity of kaolin for Pb than for Cu, and could provide the basis for future projects/studies that would employ kaolin in Pb and Cu removal.
Competitive adsorption of Cu2+ in Cu2+, Co2+ and Ni2+ mixed multi–metal solution onto graphene oxide (GO)–based hybrid membranes
