LEAD REMOVAL AND RECOVERY FROM BATTERY WASTEWATERS BY NATURAL ZEOLITE CLINOPTILOLITE

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Abstract
Technical feasibility of an ion exchange process for removal and recovery of lead present in battery manufacturing wastewaters is demonstrated. In absence of aluminium and ferric species, lead is quantitatively removed and recovered (≈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 exceeding 2,700 bed volumes (BV) (flowrate: Fexh10 BV/h) is obtained, when the initial Pb concentration is 4 mg/L, with the metal leakage steadily below the maximum allowable concentration (MACreg=5 BV/h) to minimize in situ precipitation of metals and preserve the zeolite from degradation. From spent regeneration eluate lead is recovered to the battery manufacturing operations. This latter operation is carried-out by precipitation in the form of hydroxycerussite (basic lead carbonate) or electrolysis as pure metal. In this way it is minimized the environmental impact after waste disposal (no hazardous waste formation) and, at the same time, it is recovered raw materials to the productive lines of origin (environmental protection and resource conservation). The exhausted mother liquors from lead precipitation operation is recycled to the subsequent zeolite regeneration step, after back-up of the initial regenerant concentration and solution pH.