removal of zn2+ and cr6+from waste water samples, using natural iranian (aftar) zeolites

this paper concerns the removal of zn 2+ and cr 6+ ions from waste water using a naturally occurring zeolite from semnan region in iran. a continuous fixed-column study was carried out by using zeolite as a low-cost adsorbent for the removal of zn 2+ and cr 6+ ions from aqueous solution under the effect of various process parameters such as, grain size and time. the efficiency of removal is higher for zn than cr ions. the zn 2+ and cr 6+ ions uptake by zeolite increased with initial ions concentration and column height, but decreased as the flow rate increased. the adsorption capacity reached a maximum at grain size of 0.71mm.