Assessment of zeolite and compost-zeolite mixture as permeable reactive materials for the removal of lead from a model acidic groundwater

Column experiments were performed to assess the effectiveness of zeolite and compost-zeolite mixture in removing dissolved lead (Pb2+) from acidic water of pH 2.4. The acid neutralizing ability and hydraulic performance of the materials were also studied. Fitting the advection-dispersion equation (ADE) and mathematical models (i.e. the Dose-Response, Adams-Bohart, and Yoon-Nelson models) to the Pb2+ experimental breakthrough curves (BTCs) was also performed. The compost-zeolite mixture proved to be better than zeolite alone both: in removing Pb2+ and in buffering the acidic pH. The maximum adsorption capacity, q(o) obtained for zeolite was 0.097 mg/g and 0.151 mg/g for the compost-zeolite mixture, respectively. Lead removal was attributed to ion exchange and adsorption. Observed Pb2+ BTCs demonstrated sorption-related nonequilibrium effects in the columns. The hydraulic conductivity of zeolite decreased by 2% and by 28.8% in the case of compost-zeolite mixture at the end of the experiment. The entire experimental BTC of Pb2+ was well described by the Dose-Response model while the Adams-Bohart model was better in describing only the initial part of the lead BTCs.