Separation of Cd(ii) and Ni(ii) in a binary mixture through competitive adsorption and acid leaching

Abstract

Different heavy metals present simultaneously in aqueous solutions should be separated to promote environmental protection. In this study, the biosorbent, succinylated maize straw, was used to separate and recover Cd(II) and Ni(II) ions from a binary mixture. The effects of various factors, such as contact time, pH, multi-metal isotherms, and adsorbent dose on the simultaneous removal of the two metal ions were investigated; a separation factor was introduced to evaluate this separation behavior. A separation process was proposed on the basis of the competitive adsorption results to separate metal ions from the binary system. This technique was then successfully employed to separate Cd(II) and Ni(II) ions from the simulated leach liquor of spent Ni–Cd batteries. Approximately 90% of the adsorbed Cd(II) ions were recovered, and the resulting solution contained <0.7 wt% of Cd(II) and >99 wt% of Ni(II).