Competitive adsorption characteristics of Co2+, Ni2+, and Cr3+ by IRN-77 cation exchange resin in synthesized wastewater.

Adsorption properties of Co2+, Ni2+, and Cr3+ on an Amberlite IRN-77 cation exchange resin were investigated in batch systems. Levels of adsorption rapidly approached an equilibrium state within 1 h. The adsorption characteristics of each metal onto the resin were accurately represented by Langmuir isotherms. Co2+ and Ni2+, which have an equivalent electrovalence, displayed similar levels of adsorption onto the resin when they coexisted in the solution. However, when Cr3+ was added to the solution it competitively replaced Co2+ and Ni2+ ions that had been previously adsorbed onto the resin, resulting in the desorption of these metals into the solution. The result was likely due to a higher adsorption affinity of Cr3+ relative to Co2+ and Ni2+. This implies that interactively competitive adsorption of multi-cations onto the resin should be thoroughly considered when contemplating the efficient operation of an ion exchange process in the treatment of industrial wastewater.