Cadmium removal from aqueous solutions by pumice and nano-pumice

Use of low-cost minerals to eliminate mining and industrial pollutants is the main goal of this study. We investigated the ability of pumice and nano-pumice to remove cadmium from a synthetic aqueous solution. Batch experiments were performed to investigate adsorption characteristic; therefore, the effective factors influencing the adsorption process including solution pH, contact time and initial concentration have been considered. Equilibrium data were attempted by Langmuir and Freundlich isotherm models to realize the interaction between adsorbent and adsorbate. The results show that cadmium adsorption on Pumice follows the Langmuir isotherm model with a R-2 of 0.9996 and shows a homogeneous and mono-layer adsorption. Whereas, cadmium adsorption on nano-Pumice follows a Freundlich model (R-2=0.9939) and exhibits a multi-layer adsorption. The maximum mono-layer capacity (q (max) ) of cadmium for pumice and nano-pumice was calculated 26 and 200mg/g, respectively. Two different kinetics models including pseudo first-order and pseudo second-order were studied to evaluate the rate and mechanism of cadmium adsorption by pumice and nano-pumice. The kinetics data indicate that a pseudo second-order model provides the best correlation of the experimental data.