Effect Of Additives On Electrorefining Of Lead In Methanesulfonic Acid System

The Betts method is generally used in the electrorefining of crude lead.This process uses a fluorosilicic acid system as the electrolyte,which has the disadvantages of high volatility,easy decomposition,and high cost of fluorine-containing wastewater treatment.Methylsulfonic acid(MSA)has the advantages of low volatility,good stability,and easy disposal of production wastewater.It has great potential to use MSA system instead of fluorosilicic acid system for crude lead electrolytic refining.At present,the biggest challenge for the electrolytic refining of crude lead in the MSA system is the difficulty in controlling the morphology of cathode lead,and it is easy to grow dendrites.In response to this problem,this paper carried out research on the electrodeposition behavior and process application of additives on electrorefining of crude lead in MSA system.The research revealed the action mechanism of the additive on the lead deposition process,and established the related technology prototype.We carried out the industrialization pilot test for electrolytic refining of crude lead in the MSA system in a smelter,optimized the relevant process parameters,and verified the feasibility of the technology.The main conclusions of this paper are as follows:(1)The results of additives process screening research show that when Lugalvan BNO12,Lugalvan NES,and calcium lignosulfonate are added,flat and dense cathode lead with less dendrites can be obtained,and its main phase is elemental lead.(2)The results of additives electrochemical mechanism research show that with increasing concentration of Lugalvan BNO12,Lugalvan NES and calcium lignosulfonate,the nucleation overpotential NOP and the diffusion coefficient D increases,the nucleation density N and and the rate of crystal growth K’decreases,and the latter change tends to be stable,but the strong adsorption and instantaneous nucleation mode during lead deposition remain unchanged.(3)The results of additives application scheme research show that the optimal concentration of Lugalvan BNO12 is 2～3 g/L,Lugalvan NES is 3～5 g/L,and calcium lignosulfonate is 0.5～1 g/L.When the additive is used in combination,the flattening and densifying effect of the cathode lead is better,the dosage of the additive is reduced,and the crystal grains grow preferentially on the(220)crystal plane.The results of pilot test show that the use of combination of calcium lignosulfonate and Lugalvan BNO12 in the process of crude lead electrolytic refining in MSA system can obtain a flat and less dendrites cathode lead,the purity of lead reaches 99.99%,exceeding the 99.970%standard of"Lead Ingots"(GB/T 469-2013),the anode slime has a good adhesion effect and is easy to scrape.At a current density of 180 A/m~2,the cathode current efficiency exceeds 98%,and the energy consumption ranges from 77.81 to 94.03 k Wh/t Pb.There are 48 figures,30 tables and 100 references in this dissertation.