Study On Technology Of Preparing Titanium-rich Materials From Low Grade Titanium Slag

At present,ilmenite is used as the main raw material in production of titanium dioxide by sulfuric method in China,large amouts of wastes were discharged and thus lead to serious environmental problems.In this paper,low grade titanium slag was used as raw material to prepare Ti-rich materials by multistage recycle process of alkaline leaching-dilute acid washing-acid leaching.FactSage software was used to calculate the standard Gibbs free energy change,standard enthalpy change and standard equilibrium constant of the main reactions in the leaching process.The related ternary E-pH diagrams were drawn.Effects of parameters,include concentration,temperature,time and liquid-solid ratio on titanium contents in titanium-rich material were studied.The following research results were obtained:(1)The main phases in low grade titanium slag are:anosovite and anorthite.(2)It is concluded that the reaction of the leaching process was feasible through the thermodynamic calculation of the standard Gibbs free energy change,standard enthalpy change and standard equilibrium constant of the main reaction of the process.(3)It has been found that the pH of alkaline leaching should be higher than 14 and the pH of dilute acid washing should be lower than 1 and increasing temperature can reduce the pH of alkali leaching and decreasing temperature can increase the pH of acid leaching through the system analysis of the ternary potential-pH diagrams for Al-Ti-H₂O,Ca-Ti-H₂O,Fe-Ti-H₂O,Mg-Ti-H₂O,V-Ti-H₂O,Mn-Ti-H₂O,Mg-V-H₂O and Ca-V-H₂O systems.(4)The experimental conditions for the better multistage recycle process of alkaline leaching-dilute acid washing-acid leaching were determined by leaching experiments.The optimal alkaline leaching conditions were:NaOH concentration 10%(mass fraction),L/S 4,temperature 95?,time 60 min.The better dilute acid washing conditions were HCI concentration 2%(mass fraction),L/S 6,temperature 45? and time 60 min.After the leaching in the third stage,the TiO₂ grade was increased to 80.49%.The optimal acid leaching conditions were HCl concentration 12%(mass fraction),L/S 6,temperature 85? and time 60 min.After acid leaching,the grade of TiO₂ is increased to 85.8%.When acid and alkali leaching solution were recycled twice,358 mL of H₂O,0.36 mol of NaOH and 0.06 mol of HCl can be saved.