Adsorption of gallium in alkali extraction of aluminum from high alumina fly ash

The high alumina fly ash is mainly generated in central and western Inner Mongolia Autonomous region and the northern Shanxi province,in which the content of alumina is up to 50%.The associated content of gallium can reach 60 mg/kg,which is an important secondary resource containing aluminum and gallium.In order to elevate the value of resource utilization and realize the high efficiency extraction of low concentration gallium solution during the process of alumina extraction,the gallium containing alkali liquid system of high alumina fly ash Pre-desilication-Bayer-Sub-molten salt method was investigated in the aluminum process.The static adsorption law of gallium ions in gallium containing model solution was studied,and the effects of different adsorption time,adsorption temperature,initial concentration of gallium and alkali concentration on the adsorption of gallium ions by chelated resin were systematically investigated.The dynamic adsorption and elution tests of gallium alkalic liquid with low concentration were verified by using adsorption column.The results of static adsorption show that the high efficiency of gallium ions containing gallium in low concentration can be achieved by using LSC-600 chelating resin.The equilibrium adsorption capacity of gallium ions with an initial concentration of less than 400 mg/L resin is less affected by the adsorption temperature.In the system of a gallium ion concentration higher than 400 mg/L,the equilibrium adsorption capacity of the resin decreases with the temperature of adsorption.The equilibrium adsorption capacity of gallium ions is the largest when the adsorption temperature is 50 ℃.With the increase of the concentration of Na OH,the adsorption capacity of gallium ions by chelating resin increases in the first period and then decreases in the last period.The equilibrium adsorption capacity of gallium ions by chelating resin increases with the initial concentration of gallium ions.The initial concentration of gallium ions is higher than 1 200 mg/L.The adsorption capacity of the resin is saturated.When the adsorption temperature is 50 ℃,the initial concentration of gallium ions is 1 200 mg/L,and the maximum adsorption capacity of the resin is 36 mg/g when the base concentration is 5 mol/L.The kinetic fitting results show that the adsorption kinetics of gallium ions by alkali resin conforms to the quasi-secondary kinetic equation and accords with the chemical adsorption process.The adsorption isotherm fitting results show that the adsorption of gallium ions by LSC-600 chelating resin conforms to the Langmuir isothermal equation,which indicats that the chelation adsorption process of gallium ions belongs to single-layer adsorption. The dynamic adsorption and eluting results of the resin show that the liquid flow rate is increased with the decrease of the volume of adsorption bed when the resin reaches the adsorption equilibrium.When the initial concentration of gallium ions,adsorption temperature and adsorption flow rate are 50 mg/L,50 ℃ and 2.5 BV/h,respectively,the resin has the best adsorption effect on alkali solution containing the low concentration gallium ion,and the maximum adsorption capacity is 3.13 mg/g.The concentration of gallium ions in the eluting solution increases and then decreases with the increase of bed layer number.The maximum concentration of gallium is 1 936 mg/L when eluting solution is 0.7 BV.The concentration of gallium in the solution of the high concentration( 0.3-1.5 BV) is 1 248 mg/L,and the concentration ratio is up to 25.