Cadmium removal from wastewater using nano-clay/TiO2 composite: kinetics, equilibrium and thermodynamic study

Abstract

In this research, commercial nano-clay (NC) was modified with TiO2 functional groups and characterized via XRD and FTIR methods. The modified nano-clay was applied as an adsorbent for the removal of cadmium from wastewater solutions. The effects of the operating parameters including initial pH, cadmium concentration and adsorbent concentration were analyzed by the Taguchi method. The optimum conditions for cadmium removal by the nanoclay/TiO2 composite were an initial feed pH of 6, an initial concentration of 30 mg/L, and an adsorbent concentration of 4.5 g/L. Under these conditions, nearly 90% of the cadmium ions were removed by modified nano-clay after one hour. The equilibrium results showed that the Freundlich model could well fit the experimental data, and this indicated the multilayer adsorption process. The adsorption capacity of the nano-clay for cadmium improved from 8.92 mg/g to 16.20 mg/g by modification with TiO2. The kinetic data were analyzed using the pseudo-first order, pseudo-second-order, and intraparticle kinetics models. Thermodynamic studies indicated the exothermic and spontaneously nature of the adsorption process.