The adsorption behavior of walnut shells in the presence of colloidal gold for thallium(I) ions from aqueous solution was investigated. The thallium content in the samples before and after contact with walnut shells was determined by differential pulse anodic stripping voltammetry. The adsorption capacity was studied in relation to the function of equilibrium time, the amount of adsorbent, the concentration of thallium, and pH. For the sake of comparison, the sorptive properties of walnut shells were compared to soapnut powder.
The obtained results clearly indicate that both walnut shells and soap nuts are effective sorbents for thallium(I) ions (removal efficiency over 90%). The best results of sorption were achieved at pH = 7.5 after contact time of 30 min. The addition of colloidal gold stabilised by lignosulfonate as the co-adsorber enhances the sorption ability of walnut shells to over 99%.