Recovery Of Lead From Exhausted Lead-acid Battery Paste In Alkaline Solution Containing Xylitol

The demand for lead in human society is increasing,but the resources of lead concentrate are decreasing day by day.So lead recycling is important for the sustainable development of lead industry.Moreover,if the exhausted lead-acid battery is not recovered,it will be a great threat to the environment.As an important component of waste lead-acid batteries,lead paste has become a focus and difficulty in recycling for its complicated composition.The pyrometellurgy of secondary lead has some disadvantages,such as large energy consumption,relatively low direct recovery rate,emission of lead dust and SO2 which will pullut the the environment,while the hydrometallurgy process has aroused people's attention for the high yield of metal,less pollution,etc.The recycle system containing organic has become an important research direction because it is environmental friendly.In this paper,firstly,two different kinds of reducing agents?FeSO₄ and Na₂SO₃?were used for the reduction of PbO₂,and two different kinds of desulfurizing agents?Na OH and Na₂CO₃?were used for the desulfurization conversion of PbSO₄.Secondly,the leaching behavior of PbO₂,PbSO₄ and lead paste in alkaline solution containing xylitol was studied in detail.Finally,the electrodeposition process of leaching solution was studied premiminariliy.X-ray diffraction?XRD?,scanning electron microscopy?SEM?,energy spectrum?EDAX?were used to analyze the phase of insoluble matter in the process of reaction,elemental composition and morphology changes.Fourier transform infrared spectroscopy?FTIR?was used to identify the organic groups of resultant in the leaching solution.The main results of this paper are as follows.The reduction experiments of PbO₂ show that,the reduction effect of Na₂SO₃ is better than FeSO₄.The optimum conditions of FeSO₄ reduction are as follows: the excess coefficient of FeSO₄ is 1¹.1,the reaction time is 90¹20min,the reaction temperature is 90 ?,the molar ratio of H₂SO₄ to PbO₂ is 3:1,and the highest reduction rate of PbO₂ is only about 52.4%.The optimum conditions of Na₂SO₃ reduction are that,the excess coefficient of Na₂SO₃ is 6.0,the reaction time is 90¹20min,the reaction temperature is 90 ?,and the reduction rate of PbO₂ can reach 100%.The desulfurization experiments of PbSO₄ show that,the optimum condition of NaOH desulfurization is that: the reaction time is 60¹20min,the temperature is 90 ?,the excess coefficient of NaOH is about 1.4,and the desulfurization rate of PbSO₄ is only 88.88%.The best condition for Na₂CO₃ desulfurization is that: the reaction time is 60⁹0min,the temperature is 90 ?,the excess coefficient of Na₂CO₃ is 1.3,and the desulfurization rate of PbSO₄ is only 80.61%.The study on the leaching of PbO₂ in alkaline solution containing xylitol shows that,the-OH in xylitol can be oxidized into-COO-by PbO₂ in alkaline solution containing xylitol,-COO-and Pb exist in the form of metal organic compounds in solution.The concentration of xylitol and NaOH have significant effect on the leaching rate of PbO₂.The leaching rate of PbO₂ increases with the increase of xylitol concentration firstly and then decreases,and finally increases again.The change of xylitol concentration will lead to different leaching mechanisms.The optimum conditions of PbO₂ leaching in alkaline solution containing xylitol are as follows: the concentration of sodium hydroxide is 1.5²mol/L,the concentration of xylitol is 0.53⁰.79mol/L,the leaching temperature is 70 ?,the leaching time is from 30 to 60 min,and the leaching rate of PbO₂ is up to 99.18%.The study on the leaching of PbSO₄ in alkaline solution containing xylitol shows that,the concentration of xylitol and NaOH have prominent effect on the dissolution amount of lead sulfate in alkaline solution containing xylitol.The reaction time and temperature have little effect on leaching.When xylitol dissovled without Na OH in the solution,it does not react with lead sulfate.The dissolution of PbSO₄ is done under the action of xylitol and NaOH.The optimum conditions of PbSO₄ leaching in alkaline solution containing xylitol are as follows: the reaction time is 60⁹0min,the reaction temperature is 90 ?,the concentration of xylitol is 50⁸0g/L,the concentration of NaOH is 60⁸0g/L,the leaching rate of PbSO₄ is up to 100%.Through the study on the leaching of lead paste,it can be found that the optimum conditions are as follows: the reaction time is 30-60 min,the reaction temperature is 90?,the concentration of xylitol is 80¹20g/L,the concentration of NaOH is 60⁸0g/L.The leaching rate of lead paste can reach up to 92.66%.Leaching of lead paste can be achieved under this system in short time.Through the preliminary study,it can be found that: when the current density is 140A/m²,the temperature is 40 ?,the concentration of NaOH is 100g/L,the concentration of xylitol is 120g/L,the concentration of lead is 100g/L,the pole distance is 4cm,the flow rate is 15 m L/min,the current efficiency can reach up to 99.68%,the cathode energy consumption is 381.71 k Wh/t,the surface of the cathode lead is relatively smooth with less dendrite.