Removal of manganese from drinking water using natural and modified clinoptilolite

Four types of natural zeolites can be found in large quantities in various parts of the world and are relatively cheap to mine. Clinoptilolite has been used in this investigation for the removal of Mn⁺⁺ ions from water. Forms of the zeolite modified with Na⁺, NH₄⁺, K⁺, Mg⁺⁺, Fe⁺⁺, Fe³⁺, Ca⁺⁺, Li⁺ as well as naturally occurring clinoptilolite were used in this investigation. Selectivity tests were performed to find the most effective form for the purpose. Isotherms for the potassium form and the natural zeolite were obtained. The kinetics of the ion exchange were also studied and the rate-limiting mechanism was found to be film diffusion. Nevertheless with stirring the exchange is fairly rapid. The results obtained showed that clinoptilolite treated with lithium or sodium was the most effective form for manganese removal and the calcium form was the worst exchanger.