Abstract
Given the toxicity and economy of lead, it is important to achieve good recovery in the recycling of waste lead storage batteries. Lead sulfate (PbSO4), which plays an important part in reactions of the lead storage battery, is formed in accordance with Faraday's law during discharge. PbSO4, is the main component in a waste battery paste and account for up to 50% of the paste by weight. PbSO4 can be isolated from the waste battery paste as raw material by the nitrate acid leaching-ammoniacal ammonium sulfate leaching-refining and solid-liquid separation process. First, the paste was treated by nitrate acid leaching to convert PbO to lead nitrate (Pb(NO3)2), then leach residue containing lead sulfate and lead dioxide was leached with ammoniacal ammonium sulfate, based upon the solubility of PbSO4 in aqueous ammoniacal ammonium sulfate solution. After solid-liquid separation the solution is then purified, PbSO4 was obtained by removal of free ammonia and heating. The paired electro-synthesis of PbO2 and Pb as lead storage battery active materials using PbSO4 as a precursor was investigated. Optimal synthesis conditions were determined by investigating the effect of the particle diameter and distribution of the precursor, current density, temperature, and operating time. Experimental results show that lead can be recovered effectively as PbSO4, and as a precursor, can be readily converted to PbO2 and Pb for directly making lead-battery pastes by controlling the electrochemical process and the particle diameter and distribution of the precursor in microscale powders. Results in this work are used to underpin the development of a new process that can be used for recovering lead from lead battery pastes. The route is suitable for large scale operations which in turn entail large scale movement of battery waste materials. The new process can avoid both smelting, desulphurisation and electro-winning. PbSO4, as a precursor, can be readily converted to PbO2 and Pb for directly making lead storage battery pastes for achieving lead recovery simultaneously. Key words : paired electro-synthesis, lead storage battery, lead sulfate, lead monoxide, lead dioxide
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