Abstract
Application of Saudi activated clay (bentonite) to remove cadmium from wastewater was investigated. Natural local clay which was obtained from Khulays bentonite deposit was selected and activated using sulfuric acid to increase its adsorptive capacity. The removal characteristics of cadmium ions from wastewater were investigated under various operating variables such as contact time, initial metal concentration, clay dosage and solution pH. Batch scale equilibrium adsorption was carried out for a wide range of initial metals concentration. The results showed that the sorption of cadmium ions on Saudi activated clay was relatively fast and the equilibrium was achieved after only 20 min. The sorption data suggests that solution pH was the most important parameter in controlling cadmium sorption onto bentonite. They also showed that increasing the initial cadmium concentration decreased cadmium removal percentage due to the saturation of clay with cadmium ions. Furthermore, the adsorption of cadmium increased with increase in solution pH. The adsorption isotherm data were well fitted with both the linearized Langmuir and Freundlich models.