Cadmium removal from industrial sewage by using Bentonite and Kaolinite absorbent gravels

Abstract

Many types of water pollutants have been identified and categorized. Heavy metals is one of the most important and hazardous ones. Among all heavy metals, cadmium has a significant effect on all living organisms. Cadmium can be dissolved in water and be absorbed by Plants and then concentrates and moves up the food chain. Which causes toxication in Plants and causing Cancer and numerous other illnesses in humans and other living beings. Using surface absorption is proved to be a suitable method for removing heavy metals from industrial sewages. In this study, Bentonite and Kaolinite were used as surface absorption agents and White Cement was used as a binding agent to keep particles in a firm gravel shape. When poured into the current of sewage, surface absorbing gravels can remove Cadmium ions from sewage. Performance affecting factors such as optimum mass ratio between absorbent agent and binder agent, an optimum mass ratio between Bentonite and Kaolinite, gravels diameter, primary concentration of Cadmium, contact duration and sewage pH was separately examined and optimized by measuring post contact concentration of Cadmium of the samples. Results showed that gravels with absorbent: binder ratio of 3:1, absorbent mass made out of 80% bentonite and 20% kaolinite, when broken to a diameter of 4.75mm < D <6.35mm can refine sewage with 250ppm primary concentration of Cadmium and pH of 7.5 up to 99.97% in 5 hours contact duration.