A Study On The Recycling Technique Of Secondary Lead Slag

The secondary lead slag is a kind of waste that urgently needs to be properly treated in the lead recycling industry chain.Traditional lead slag making bricks and other routes have potential environmental hazards due to the possible leaching of lead in the environment,and lead has not been recycled.At present,the recycling method of lead slag remains in the recovery process of primary lead slag in wet acid medium,and pays little attention to the difference between the composition ratio of primary lead slag and secondary lead slag.According to literature reports,few researchers have determined the recovery method based on sufficient phase analysis of lead slag.This subject takes the secondary lead slag provided by Hubei Jinzhan Technology Co.,Ltd.of Camel Group as the research object.Through XRD,SEM-EDS,XPS and other characterization methods,combined with chemical phase analysis methods,the lead slag is analyzed in detail.Based on the purpose of obtaining refined lead,a new process for resource utilization of recycled lead slag is proposed.The influences of related process parameters on the process of ball milling,magnetic separation,acid leaching conversion of H₂O₂-H₂SO₄,methylsulfonic acid leaching have been studied in the following steps.The results of ball milling-magnetic separation experiments show that:ball filling rate,ball-to-material mass ratio,ball milling speed,ball milling time all have an impact on the ball milling effect.Within the experimental range,the ball mill speed has the greatest influence on the slag crushing effect.When the speed is 200 r/min and 300 r/min,the slag is obviously granular after ball milling.After ball milling at 400 r/min and 500 r/min,the slag is seriously sludged.A large amount of fluoride scum will be generated in the scum,and lead-containing particles with extremely small diameters are wrapped in the scum,which makes it difficult for the lead-containing particles to react with the leaching solution,so the lead leaching rate reduces.Based on this,the optimal ball milling conditions are determined as follows:ball filling rate is 60%,ball-to-material mass ratio is 5:1,ball milling time is 30min,ball milling speed is 300 r/min.Under this ball milling condition,the yield of the magnetic separation product is 23.80%,and the iron grade of the magnetic separation product is 37.64%,which does not reach the standard of GB/T 36704-2018 that the TFe content of magnetite concentrate is greater than 60%,and cannot be used as a raw material for pig iron.But the result of the solid waste leaching toxicity test is lower than the standard value.It is a general industrial solid waste,which has realized the reduction of hazardous solid waste,with a reduction degree of 23.80%.During the acid leaching conversion of H₂SO₄/H₂O₂,the Fenton reaction between H₂O₂and Fe²⁺in the lead slag produces hydroxyl radicals and new Fe³⁺.There are three strong oxidizing substances in the system:H₂O₂,hydroxyl radicals and Fe³⁺,which greatly promotes vulcanization.In the experimental range,the best conditions are as follows:the concentration of sulfuric acid is 1.0 mol/L,the ratio of liquid to solid is 20:1,the amount of H₂O₂ is 3.00 m L,and the reaction time is 40 min,the mechanical stirring speed is 500 r/min and the temperature is 20°C.After the conversion,the content of easily soluble oxidized lead,sulfide lead,and insoluble lead in the slag are 91.43%,0.54%,8.03%respectively,and the conversion rate of sulfide lead ups to 94.96%,the conversion rate of insoluble lead is37.41%.The process of carbonation converts Pb SO₄ into Pb CO₃.Because the generated Pb CO₃ will wrap on the surface of Pb SO₄ and hinder the further conversion of Pb SO₄,Pb SO₄ cannot be completely converted into Pb CO₃,and the lead leaching rate of the subsequent acid leaching process is slightly reduced.During the process of methane sulfonic acid leaching of lead,the liquid-solid ratio,methane sulfonic acid concentration,reaction time,and mechanical stirring speed all affect the lead leaching rate.Within the scope of the experiment,the best process conditions are:the concentration of methane sulfonic acid is0.5 mol/L,liquid-solid ratio of 15:1,reaction time of 20 min,mechanical stirring speed of500 r/min,temperature of 20°C.Under these conditions,the lead leaching rate is 90.58%.The enriched lead methanesulfonate leachate is subjected to diaphragm electrolysis,and high-purity refined lead is deposited on the cathode.The lead leaching concentration of the original slag exceeds the concentration limit(5mg/L).The magnetic products and the final tailings are all below the limit,which are general industrial solid waste.The original slag is transformed from hazardous solid waste to general industrial solid waste,realizing the reduction,resource utilization and harmless treatment of slag.