Recovering Gallium From Fly Ash By Solvent Extraction And Mechanism Research

With the promotion of development plan for LED industry by government and rapid development of the semiconductor industry and solar cell industry.There will have a substantial increase of the consumption with gallium in our country.However,there is no independent mineral deposit containing gallium in nature and it is generally found by a very small amount in aluminum ore,zinc ore,iron ore,coal and other rocks Increasing market demands and the limited natural resources may trigger global competition for gallium resources.Therefore,the development of gallium recovery technology from secondary resources-fly ash has attraced a lot of attraction recently.Several separation techniques have been proposed for the recovery of gallium,including ion exchange,precipitation,solvent extraction and so on.Solvent extraction is one of the most widely applied technologies for metal recovery due to its advantages including less time consuming,high selectivity and low operational cost.Synergetic extraction is widely used in the separation of metals due to its advantages in improving extraction capacity and separation ability.Therefore,this paper focuses on acid organophosphorous extractant,mixed extractant and ionic liquid extractant,systematically researched the promotion and mechanism of separation and recovery of gallium by solvent extraction.The main research contents and conclusions are as follows:(1)The effects of aqueous acidity and extractant concentration on the extraction of gallium and the equilibrium pH of the raffinate were studied by using acidic organophosphorous extractants(D2EHPA,PC88A,Cyanex 272).And the extraction mechanism was determined.Finally,the stripping extraction effect of gallium with different stripping solutions was studied.The results show:Extraction capacity of acid extractant:D2EHPA>PC88A>Cyanex 272.As the initial pH of the aqueous phase increased,more and more gallium was extracted into the organic phase and leading to a higher equilibrium pH.3 M hydrochloric acid solution was the best stripping solutions.And the stripping extraction capacity of the three extractants:D2EHPA<PC88A<Cyanex 272.Finally,the extraction mechanism equation of acid extractant is deduced as follows:Ga(OH)+2,org+(HA)2)2,org=Ga(OH)2A·HAorg+ H+aq·(2)The extraction effect of the binary extractant of acid organophosphorous extractant(D2EHPA,PC88A,Cyanex 272)and neutral extractant(TBP,N503)/alkaline extractant(Alamine336)on gallium was investigated.Therefore,the effects of the concentration of acidic extractant,neutral extractant and alkaline extractant on the extraction of gallium in binary mixed system were studied.And compared with the extraction of gallium using acid extractant alone,investigate whether it has a synergistic effect.Finally,the synergistic extraction mechanism was determined.The results show that:In the mixture system of D2EHPA/PC88A/Cyanex 272 and TBP/N503/Alamine336,only the binary mixed extractant Cyanex 272 and Alamine336 showed significant synergistic effects.The maximum synergy factor R=3.11.In addition,its equilibrium pH was higher than that of gallium extracted with acid extractant alone.Finally,the reaction mechanism equation of synergetic extraction was determined:Ga(OH)2+ + H2A2 + 2R3N = Ga(OH)A2 + 2R3NH+.(3)Bif-ILEs are prepared by acid-base neutralization([A336][D2EHPA],[A336][PC88A],[A336][Cyanex 272]).And Bif-ILEs were used to study the recovery and separation of gallium.The results show that:The extraction ability of the three Bif-ILEs for gallium follows:[A336][D2EHPA]>[A336][PC88A]>[A336][Cyanex 272].When the Bif-ILEs concentration was raised to 0.15 M,the gallium was completely extracted,significant internal synergies were observed(R=108.27).When the acidity of the aqueous phase is higher than pH=1,the extraction of gallium by Bif-ILEs increases with the concentration of hydrochloric acid in the aqueous phase.When the acidity of the aqueous phase is lower than pH=1,the extraction rate of gallium by Bif-ILEs increases with the decrease of the concentration of hydrochloric acid in the aqueous phase.It was found by FT-IR that the acidic organic phosphorus extractant forms Bif-ILEs with cationic functional group.During the extraction process,P=0 of Bif-ILEs has a strong interaction with gallium.In addition,the extraction mechanism equations of[A336][D2EHPA],[A336][PC88A],[A336][Cyanex 272]are derived as followsGa(OH)2++Cl-+ 4[A336][D2EHPA]= Ga(OH),Cl·4[A336][D2EHPA]Ga(OH)2++Cl-+ 4[A336][PC88A]=Ga(OH)2Cl·4[A336][PC88A]Ga(OH)2++Cl-+2[A336][Cyanex 272]=Ga(OH)2Cl·2[A336][Cyanex 272]Finally,Bif-ILEs not only has a high gallium extraction,but also can achieve the separation of gallium and aluminum in the initial aqueous phase pH=2.