Use of alginate-clinoptilolite beads for heavy metal removal in continuous flow reactors

Environmental pollution is a serious problem in today's world. Heavy metals are one of the important pollutants threatening water resources. Particularly industrial activities are responsible for heavy metal pollution. Since these metals are known with their toxicity and bioaccumulation tendency, wastewater containing heavy metals are required to be treated. Adsorption is an alternative methods which is highly selective, easy to operate and cheap in heavy metal removal. Variety of adsorbents is applied for adsorption and alginate and its combinations have been still under investigations. Alginate is a biopolymer and an environmentally compatible compound. In this study, alginate is combined with clinoptilolite to form alginate - clinoptilolite (A - C) beads and then tested for the treatment of synthetic mixed heavy metal solution (Pb2+, Cu2+, Cd2+) using a continuously operated adsorption column. Firstly, A - C beads characterized in terms of surface properties and size distribution. After that, the effect of flow rates (2 - 7.5 ml/min), heavy metal concentrations (10 - 50 mg/l) and adsorbent mass (10 - 20 g) on adsorption capacities of the metals were investigated. Results showed that Pb2+ ion is the most preferred ion for adsorption by A - C beads and then Cu2+ and Cd2+ followed. Among the flow rates, effective heavy metals removal was obtained at 2 ml/min being 98 % for Pb2+. Increasing heavy metal concentration up to 50 mg/l improved Pb2+ maximum adsorption capacity to 238.5 mg Pb2+/g A - C beads whereas adsorption capacities of Cu2+ and Cd2+ were affected negatively. Using twice more adsorbent especially increased Cu2+ and Cd2+ removals. For efficient treatment of heavy metal mixtures either low flow rates or high amount of adsorbents usage may be recommended.