Rapid removal of cobalt ion from aqueous solutions by almond green hull

Almond green hull, an agriculture solid waste, was chemically treated and used for the adsorption of Co (II) from aqueous solutions. The efficiency of this new adsorbent was studied using batch adsorption technique under different experimental conditions such as sorbent amount, initial metal-ion concentration, contact time, adsorbent particle size, and chemical treatment. Optimum dose of sorbent for maximum metal-ion adsorption were 0.25 g for 51.5 mg l−1 and 0.4 g for 110 mg l−1 solutions, respectively. High removal efficiencies of Co (II) were occurred in the first 1 min of sorbent contact time. The adsorption of Co (II) on almond green hull was also observed to follow the pseudo second-order kinetics. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models. The Langmuir adsorption model fits the experimental data reasonably well compared to the Freundlich model. The maximum adsorption capacity of this new sorbent was found to be 45.5 mg g−1. The present study revealed that such a low cost material could be used as an efficient sorbent for the removal of cobalt from wastewater streams.