Preparation Of Ultrafine Lead Oxide From Spent Lead Acid Battery Paste By Leaching Process With Aqueous Citric Acid Followed By Calcination At Low Temperature

In traditional pyrometallurgical process of recycling of spent lead acid battery pastes, SO₂and lead volatile particulates are generated as secondary pollutants. In addition, thetraditional preparation process of lead oxide is high-energy consuming. Moreover, thestarting materials for ultrafine lead oxide preparation are much costly, although it is a trendto make high performance lead acid battery by using ultrafine lead oxide. In this study,ultrafine lead oxide was prepared via a low temperature calcination process, by using leadcitrate as a precursor. And lead citrate was synthesized from the starting materials of spentlead acid battery paste in citric acid system. This work was focoused on the decompositionexperiment and characterization of lead oxide. The content of this thesis contains follwingthree parts.1. Synthesis of three types of lead citrate from leaching of spent lead acid batterypasteIn leaching system of C6H8O7H₂O-Na3C₆H₅O₇·2H₂O, the final synthesized lead citratewas sheet-shape crystal of Pb（C₆H₆O₇）·H₂O under the optimum leaching conditions. Twotypes of lead citrate were obtained in leaching system of CH3COOH-Na3C₆H₅O₇·2H₂O, i.e.column-shape crystal of Pb₃（C₆H₅O₇）₂.3H₂O and flaky crystal of Pb₃（C₆H₅O₇）₂.4.4H₂O.2. The mechanism study on preparation of ultrafine lead oxide from decompositionof lead citrate precursorsThe decomposition mechanism of the three types lead citrate in both N2gas and air werestuied in a tubular furnace. Both lead citrate and oxide products were characterized by meansof TG-DTA, FT-IR, XRD, and SEM. The results showed that when the three types leadcitrate was calcined in flowing N2gas, β-PbO in the orthorhombic phase was the mainproduct containing small amount of Pb and amorphous carbon. On combusting the citrate instatic air, two stages were took place in the calcination. First stage was decomposition ofcitrate which was alike of pyrolysis of citrate in N2, accompanying by a little of oxidationreaction when temperature was below350oC.; second stage was combustion of amorphouscarbon when the temperature was higher than350oC.In air, lead citrate decomposed fast. And the products were both a mixture of orthorhombic β-PbO, tetragonal-PbO and Pb, with β-PbO as the major product. theparticle size of ultrafine lead oxide is in range of100⁵00nm. The property of thenanostructural lead oxide was investigated by electrochemical technique, such as cyclicvoltammetry （CV）. The CV measurements presented the electrochemical redox potentials,with reversibility and cycle stability.3. The preliminary study of fluidized bed for preparation of ultrafine lead oxide bydecompositon of lead citrateAccording physical property of lead citrate powder, a cold fluidezed bed experimentalequiment was designed. And preliminary study on the fluidized performance of lead citratehas been investigated. The results showed that when air （6oC,65%humidity） flow velocitywas2.7m3/h, column-shape crystal of Pb₃（C₆H₅O₇）₂.3H₂O could be fluidized well indilute-phase fluidezed bed, and circulating fluidized bed was a viable option to prepare leadoxide by calcination of lead citrate.In this study, it has been proved the feasibility that preparation of ultrafine lead oxide fromspent lead acid battery paste by leaching process with citrate followed by calcination at lowtemperature. The results in this thesis provided a technic support for green recyling of spentlead acid battery paste.