Using Acid-Activated Azad Kashmir Clays to Remove Cadmium and Lead Ions from Wastewater

The adsorption of cadmium and lead ions on purified and acid-activated Azad Kashmir clays were investigated in a batch system. Solutions of lead and cadmium having concentrations typically found in industrial wastewater were used to develop a cheap and reliable adsorbent using local clay for removal of heavy metals from wastewater. The raw clay sample was purified and activated by sulphuric acid before being used for adsorption study. It was characterized by X-ray diffraction and chemical analysis according to the International Standards of Testing (ASTM C 323-56, 2016). The effects of factors like pH, adsorbent quantity, concentration of adsorbate and temperature were studied for both metals. The Langmuir and Freundlich models were used for analysis of adsorption equilibrium. Thermodynamic parameters were calculated. Azad Kashmir clay removed lead and cadmium with maximum adsorption capacity of 3.93 mg metal/g and 7.81 mg metal/g of clay (30 degrees C; pH 7.3). These values were calculated by applying Langmuir and Freundlich adsorption isotherms to the actual experimental results obtained in this study. The thermodynamic data indicated that the adsorption reaction for cadmium is spontaneous and exothermal while it is endothermic for lead. The Freundlich model provided best fit for sorption isotherms for both cadmium and lead.