Recovery Of Lead From Fluorescent Lamp Glass By Mechanochemical Process

Fluorescent lamp is widely used in lighting industry because of its high luminous efficiency and long life.With the widespread use of fluorescent lamp,the end-of-life pressure of fluorescent lamp glass will be generated more and more.Fluorescent lamp glass,as a typical lead glass,will lead to serious environmental pollution and human health hazard if without proper treatment and disposal.Therefore,in this research,mechanochemical sulfidation method is applied to convert the lead in fluorescent lamp glass into lead sulfide.And then the sample after mechanochemical treatment was oxidized by hydrogen peroxide to become lead sulfide and realize its recovery through leaching with sodium chloride.The single factor experiments was carried out to explore the key influence factors,then set up the corresponding response surface model.Through the solid phase reaction kinetics model to explore the reaction mechanism,the changes of reaction process along with the milling speed and ball-material ratio.Chemical reaction in the process of leaching process is revealed by leaching dynamics research.Through the analysis of the economic value,the industrialization application was preliminary evaluated.The specific conclusions are as follows:?1?The main influencing factors of mechanochemical sulfidation of lead in fluorescent lamp glass are milling time,milling speed,ball-to-material ratio and amount of vulcanizing agent.The sulfidation rate of lead in glass was increased with the increase of milling time and milling speed.And it was increased with the increase of the ball-material ratio at first then decreased.When the ball-material ratio was 50 g/g,the sulfidation rate is maximum of82.48%.Meanwhile,the sulfidation rate was decreased with the increase of the amount of vulcanizing agent.When n_Pb²⁺:n_S^2-=1:1.2,the sulfidation rate was 63.11%.The best process parameters were milling time for 2 h,milling speed at 750 rpm,ball-to-material ratio 50 g/g,n_Pb²⁺:n_S^2-=1:1.2,and the sulfidation rate 96.18%.?2?By further studying of the relationship between milling time,milling speed and ball to material ratio,the response surface model between mechanochemical sulfidation reaction rate constant and milling speed and ball to material ratio was established by using the Delogu dynamic model.The response surface model was K=0.865-0.0023V-0.1125S+0.000278VS.This model was used to predict reaction rate constants in other cases,and compared with the actual measured values obtained through experiments.It was found that the model is suitable for the process,the accuracy of the prediction value is high,and it has good use value.?3?The reaction mechanism of mechanochemical sulfidation on lead of fluorescent lamp glass was analyzed by macroscopic solid-state reaction kinetics model.It was found that the reaction mechanism of mechanochemical sulfidation on lead of fluorescent lamp glass was closely related to the milling speed.When milling speed at 450 rpm,the chemical reaction process is close to the nucleation reaction model.And it is close to the first and half-order chemical reaction model and second-order chemical reaction model at 550rpm and 650rpm respectively.In particular,when milling speed at 750rpm,the reaction process is close to the first and half-order reaction model also.?4?Lead leaching experiments from a mechanochemical sulfidation sample were carried out using hydrogen peroxide as an oxidizing agent and a sodium chloride solution as a leaching agent.As a result,it was found that the sulfurized sample after pretreatment with sodium hydroxide solution is more favorable for the oxidation of hydrogen peroxide.The main influencing factors on lead leaching from sodium chloride solution were leaching time,leaching temperature,liquid-solid ratio and sodium chloride concentration.When the leaching time 120 min,leaching temperature 100°C,the liquid-solid ratio 1:50,and the sodium concentration 25%,the leaching rate of lead was 79.72%.?5?The leaching kinetic of lead leaching from sodium chloride showed that the activation energy of the leaching reaction and the reaction order gradually decreased with the increase of the milling speed.The activation energy decreased from 85.88 KJ/mol at 350 rpm to 31.34KJ/mol at 750 rpm.The reaction order decreased from 7.44 to 2.66 at the same conditions.In addition,it is found that the leaching reaction process was changed from chemical reaction control process to chemical reaction and product layer diffusion mixing control process.?6?Through the analysis of the economic benefits and environmental benefits of the process of lead recovering from fluorescent lamp glass by mechanochemical sulfidation.It is found that the 200,000 tons fluorescent tube will generate a return of 14.4 million yuan.At the same time,it will reduce 1.836 million tons of lead mineral resource,the consumption of72,000 tons of raw coal,the emission of 2.660 million tons of sewage,10,000 tons of sulfur dioxide,and 6.006 million tons of waste residues.