Adsorption of cadmium(II) ions from aqueous solution using different adsorbents

Abstract

A comparative study on the adsorption of cadmium from aqueous solutions on a few low cost and locally available untreated and chemically treated adsorbents is carried out. Mustard husk, carbon aerogel and treated GAC are found to be most effective adsorbents in addition to treated GAC for the removal of cadmium from the aqueous solution solution at varying process parameters such as. pH (2-12) adsorbent dose (0.5-1.2 g/100 mL), contact time (24-72 h) and initial cadmium concentration (1-5 mg/L). Treated GAC, carbon aerogel, and mustard husk show 100, 87 and 72 per cent adsorptive removal of cadmium, respectively, under optimized conditions of pH 4 and dosage 1 g/100 mL for 2 mg/L cadmium aqueous solutions in 48 h. The adsorption parameters are determined using both Langmuir and Freundlich isotherm models. Surface complexation and ion exchange are the major removal mechanisms involved. The adsorption isotherm studies indicate that the adsorption process is a monolayer coverage of cadmium on surface of treated GAC and fits into the Langmuir model. The adsorptive behaviour of cadmium on untreated mustard husk and carbon aerogel satisfies not only the Langmuir assumptions but also the Freundlich assumptions, i.e., multilayer formation on the surface of the adsorbent with an exponential distribution of site energy. The results of the experimental studies as well as the model parameters are presented.