Study On The Process Of Extracting Gallium From Yellow Phosphorous Dust Ash By Vacuum Carbothermal Reduction

The development of science and technology makes gallium widely used in semiconductor materials,chemical industry,alloys and other fields.Currently,about99%of gallium is recovered from the by-products of the aluminum smelting industry in the world.Lead-zinc ore is the second largest source of gallium.In addition,fly ash and vanadium-titanium magnetite also contain a certain amount of gallium.In order to meet the demand for gallium in various countries in the world today,people have begun to focus on the development of new gallium resources.Yellow phosphorous dust is an important secondary resource.It contains about 0.05%gallium and has a considerable recycling value.Yellow phosphorus occupies a relatively important position in China's national economic industry.Every 1 t of yellow phosphorus produced will produce 200 kg of dust ash.Therefore,how to efficiently recycle gallium in yellow phosphorus dust ash and avoid its harm to the environment is a major issue in current research,but there are few reports on the recovery,enrichment and detection methods of gallium in yellow phosphorus dust ash.In view of this,this paper launched a study on the process conditions of gallium recovery and enrichment in yellow phosphorus dust.The pretreatment-vacuum metallurgy combined process is used to treat yellow phosphorus dust.First,the phase composition,element content and morphology of the raw materials were analyzed by means of XRD,XRF,ICP,SEM,etc.Based on this,theoretical analysis was carried out,which showed that the pre-removal of phosphorus in Na₂CO₃roasting by water immersion and vacuum carbon thermal reduction were feasible.And carried out experimental exploration of its process,focusing on the recovery of gallium and phosphorus.The results show:?1?Characterize the dust by XRF,XRD,SEM/EDS and thermogravimetric analysis,and found that the chemical composition of yellow phosphorus dust is complex,the highest content element is phosphorus,accounting for 18.65%,and the gallium content is 0.04%,Its phase composition is mainly KH₂PO₄,Ca₃?PO₄?₂and SiO₂;the main phases of water slag XRD obtained by water immersion after roasting Na₂CO₃are silicate,Mg S,KCl and SiO₂,these substances and valuable components Gallium is tightly bound,so it is difficult to recover gallium from the leaching residue.?2?Thermodynamic research results show that Ga₂O₃in yellow phosphorus dust can be reduced to Ga,Ga₂O,Ga O by carbon under standard conditions,where the starting temperature for conversion to Ga is 1273K;under the condition that the system pressure is 10Pa,The temperature at which the reaction of Ga₂O₃and carbon occurs is657K lower than the standard state?10⁵Pa?,and the order of reduction of each oxide from easy to difficult is as follows:Pb O>Fe₂O₃>Zn O>Ga₂O₃>SiO₂>Al₂O₃>Mg O>Ca O?3?Through exploratory experiments,it was found that simple water immersion,dilute acid leaching pretreatment,NaOH roasting water immersion and in the standard state,the carbothermal reduction experiment results are not good.The removal effect of water-soluble substances such as Na and K in the yellow phosphorus dust is not obvious,and the phosphorus cannot be effectively removed;Na₂CO₃roasting and water immersion can obtain a better phosphorus removal effect.Under the conditions of roasting temperature 900?,holding time 120 min,and ratio?dust ash/Na₂CO₃?is1:1,the phosphorus removal rate can reach 84.55%,and the gallium loss rate can be controlled within 5%.?4?Vacuum carbon thermal reduction experimental research was carried out on the yellow phosphorus dust after pretreatment with Na₂CO₃roasting and water immersion,and the effects of reduction temperature,holding time and activated carbon addition on the volatilization rate of gallium and phosphorus were investigated.The preferred process for recovering gallium and phosphorus is:system pressure 10?30Pa,reduction temperature 1373 K,holding time 60 min,active carbon addition 55%,gallium volatilization rate reaches 73.89%,phosphorus volatilization rate reaches34.57%,the process parameters to be further optimized.