Study on the Milling-leaching Coupled Digestion of Panzhihua Ilmenite

The sulfate process of manufacturing TiO₂ pigments based on the Ti resources in Panxi area usually discharges 6 to 8 tons of dilute waste acid(20% concentration) per ton of products,which inevitably causes serious environmental problems.The dilute acid digestion of ilmenites can effectively reuse the waste acid to avoid discharge and reduce acid consumption for production.In this study,a milling-leaching reactor was designed to accommodate the coupled process of mechanical activation and dilute acid leaching.The optimum conditions of the reactor was determined as follows:70 r/min of stirring speed,10:1 of ball/ore ratio,1.5:1 of acid/ore ratio,60% of the initial concentration for sulfuric acid and 70℃ of reaction temperature.Under the conditions mentioned above,the Ti leaching ratio from the ilmenites can reach as high as 80%,the concentration of Ti solution was 130 g/L with an F value of about 3,and the stability of Ti solution was more than 350 mL.The obtained Ti solution satisfied the industrial standard for TiO₂ production by sulfate process.The milling-leaching coupled process,which uses the ball grinding to mechanically activate ilmenites,can effectively increase the leaching rate of ilmenite and enhance the mass transfer between solid and liquid phases in the reaction process.This dilute acid leaching process not only saves the acid consumption by completely recycling waste acid,but also reduces the acid fog pollution in leaching process.It offers a novel potential technology to circumvent the pollution problems in TiO₂ pigment production by sulfate process.