| 英文摘要 |
Lead acid batteries are commonly used in the automobiles. The Environmental Protection Administration (EPA) has estimated that about 50,000 tonnes of lead acid battery waste were created every year. Recycling processof lead-acid batteries causes a lot of interest in the issues of the environmental protection.
A treatment method is disclosed. The treatment method can recycle lead from air pollution control residues (APCR). In the treatment method, at first, APCR is well mixed with waste sodium hydroxide to release lead ion from APCR. Then, an electrolysis device including at least one cathode and at least one anode is provided for the leachate. Thereafter, an electrolyzing step is performed to use the electrolysis device to electrolyze the leachate so as to reduce the lead ions on the cathode for metal recovery.
A hydro-electrometallurgical process to treat with fly ash by leachant and leachate electrolyte on lead recovery was proposed. This study was undertaken to determine the physical and chemical characterization, leaching and electrolysis characteristics of the fly ash, generated by an actual plant and to investigate various leaching agent yield and leachate electrolysis on lead recovery.
The fly ash from spent of discarded lead-acid batteries contains mostly lead compound, the main content of A1 sample lead was 66.3%, the particle size distribution of A1 sample 90% was ＜24.8 μm . X-ray powder diffractograms of the fly ash were identification of PbO2.PbO and PbSO4. It can be solubilized with leaching agent, the result being solubility lead that can ultimately be exposed to electrolysis.
In order to investigate how [OH−] influences fly ash of leachability , NaOH was used as alkali leaching agent and how [H+] influences fly ash of leachability, HNO3 and CH3COOH were used as leaching agent. The percent of lead leaching yield % in leachate was found between 3.5~69% of fly ash. The parameters considered were the leaching agent concentration, the S/L ratio, and the leaching time under the working circumstances, the optimum conditions was 1.875 M NaOH, S/L ratios of 12, at 8 hour and temperatures 27±3℃, The lead leaching yield % in leachate was found 69% of fly ash. To explore the changes of leachate electrolytic on lead recovery, the anode material and current density and specific energy consumption were also considered during the reaction.
The experiments of cathodic Pb and anodic PbO2 electrodeposition, the weight percentage of cathodic Pb and anodic PbO2 for Pb were the range of 22.4~32.1% and 66.0~77.6% during 120 min electrolysis, respectively. We aimed at developing a process using both reactions simultaneously for treating aqueous of Pb2+ from lead–acid battery recycling plants of fly ash. It was new method to treat of fly ash and considered with economic and environmental issue.
1. Component analysis of Fly ash by SEM-EDS
The main elements of fly ash are lead (Pb), sulfur (S), oxygen (O), and the lead weight percentage of fly ash is between 63-78 wt%. Fly ash have a high recovery value because of its high lead (Pb) content. From fly ash leaching and electrolysis experiment, we can know that producing of 1 kilograms of lead cost less than 2 dollars at lead concentrations (20 g / L) conditions. This method is better than pyrometallurgy, which is using in factories. The producing of 1 kilograms of lead cost 3.8 dollars by pyrometallurgy. At the end, the method can produce the purity 99.9% of lead on the electrolytic cathode, the purity of lead fits the quality requirements of crude lead.
2. The study of fly ash leaching with waste H2SO4
1. We can increase the pH of waste H2SO4 and the concentrations of lead by increasing the solid-liquid ratio. Because of increasing the pH of waste H2SO4, we can reduce the cost from waste acid-base neutralization.
2. The optimum operating conditions is 1 (kg/L).
3. The intial pH of waste H2SO4 will affect the leaching concentrations of lead and the magnitude of changes of pH.
4. The sludges of leaching experiment is PbSO4 by XRD analysis. It can be produced to many chemical products,such as yellow lead, mineral orange, lead nitrate, lead acetate, basic lead carbonate by a series of reactions. The process is low cost and have high value of products.
3. The study of slags leaching and electrolyze lead
The target is reclamation of the lead in slags and the surplus to become innoxious. Accordind to our experiment data, slags contain 20~60 wt% of lead. So 200~600 kg of lead can be reclaim from every ton of slags. It is equivalen to 12~36 thousand NT dollars. If the surplus can be innoxious, we can save 12 thousand NT dollars from every ton of slags. The factory A produces 10 ton of slags every months. We can that there will 180~420 thousand NT dollars of benefit every month.
Developing the technique of leaching and electrolysis can reclaim lead from fly ash and slags. The recovery of fly ash and slags is more than 80% and 50%. Compare with pyrometallurgy, this technique has the advantage of low cost of devise in the beginning.
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