Industrial wastewater treatment for toxic heavy metals using natural materials as adsorbants

Abstract

The presence of toxic heavy elements such as arsenic, cadmium and mercury in industrial wastewater and waterways is a serious pollution problem. The treatment of such contaminated water by conventional techniques, which often includes an ion-exchange or similar step, is expensive. This paper examines the use of natural materials such as hair, and certain plants, which are inexpensive, for the absorption and hence the clean up of heavy elements from polluted water. Our results show that these natural materials concentrate the heavy elements, in certain cases, to the extent of up to 500 fold or even better. The contact time required is of the order of several hours. The capacities of absorption vary from about 1 g/kg to about 5 g/kg for mercury, and are lower for arsenic and cadmium. The results show that with hair, nearly 10,000 liters of mercury contaminated water, a typical daily output from a 100 ton chlor-alkali plant, can be treated with about 1/2 kg of hair valued at about 25 cents. This makes the process extremely cost-effective compared to the conventional processes now in use.