An economic removal of Cu2+ and Cr3+ on the new adsorbents: Pumice and polyacrylonitrile/pumice composite

In this article, the adsorption of Cu^2+ and Cr^3+ onto pumice (Pmc) and polyacrylonitrile/pumice (PAn/Pmc) composite has been investigated by using a batch method at room temperature and their adsorption properties were compared. To highlight their application, selected information on pH, initial metal concentration and adsorption capacity of the adsorbents is presented. Depending on the characteristics of the individual adsorbents viz. surface modification, initial concentration of adsorbates, and pH, their adsorption capacities were found to vary. The time required for the removal of metal ions (100–500 mg/g) from aqueous solutions was about 6 h. The experimental data have been analyzed using the Langmuir and Freundlich isotherm models. The results of adsorption were fitted to the Langmuir models and coefficients indicated favorable adsorption of Cu^2+ and Cr^3+ on the adsorbents. Adsorption of Cu^2+ and Cr^3+ in the solutions was in following order: (PAn/(Pmc) composite > Pmc). The adsorption capacity of the adsorbents Pmc and (PAn/Pmc) were determined from the isotherms equations and were found to be 0.055 and 0.065 mmol/g for Cu^2+ and 0.031 and 0.268 mmol/g for Cr^3+, respectively. More than 80% of studied cations were removed by Pmc and 87% (PAn/Pmc), respectively, from aqueous solutions in single step. Effective removal of metal ions was demonstrated at pH values of 8.0. The mechanism for cations removal by the Pmc and (PAn/Pmc) composite includes complexation and sorption. The process is very efficient especially in case of low concentrations of pollutants in aqueous solutions, where common methods are either economically unfavorable or technically complicated.