Lead removal and recovery from battery wastewaters by natural zeolite clinoptilolite

Technical feasibility of an ion exchange process for removal and recovery o f lead present in battery manufacturing wastewaters is demonstrated. In abs ence of aluminium and ferric species, lead is quantitatively removed and re covered (approximate to 90%) from the neutralised wastewaters after elution on the natural zeolite clinoptilolite. Control of pH to 5.5-6 is necessary to minimise degradation of the exchanger material. Throughput volumes exce eding 2,700 bed volumes (BV) (flowrate: F-exh= 10 BV/h) is obtained, when t he initial Pb concentration is 4 mg/L, with the metal leakage steadily belo w the maximum allowable concentration (MAC<0.2 mgPb/L) set by the EU for di scharge in rivers, lakes, coastal seawater. Regeneration of the zeolite is carried out by controlled elution of limited amounts of 1M NaCl, pH 4.5 (40 BV, F-reg=5 BV/h) to minimize in situ precipitation of metals and preserve the zeolite from degradation. From spent regeneration eluate lead is recove red to the battery manufacturing operations. This latter operation is carri ed-out by precipitation in the form of hydroxycerussite (basic lead carbona te) or electrolysis as pure metal. In this way it is minimized the environm ental impact after waste disposal (no hazardous waste formation) and, at th e same time, it is recovered raw materials to the productive lines of origi n (environmental protection and resource conservation). The exhausted mothe r liquors from lead precipitation operation is recycled to the subsequent z eolite regeneration step, after back-up of the initial regenerant concentra tion and solution pH.