Hydrolysis Process Of Titanium In Sulfuric-Chloric Acid Solutions

Titanium dioxide(TiO2)is the best white pigment with widely applications and bright prospects in many industries.Among the rich titanium mineral resources existed in China,most of them are hosted in vanadium-titanium magnetite.Therefore,the novel metallurgical process using Sodium Oxide molten salt was proposed by our research group for comprehensive utilization of Ti,V and Fe from them.However,after extraction of Fe and V resources,large amount of Ti component was still remained in the titanium slag with perovskite structure(CaTiO3),leading to difficulties to realize high value utilization of this titanium slags.In order to decompose this perovskite titanium slags efficiently,therefore,a promising approache of Sulfuric-Chloric Mixture Acid(SCMA)method has been proposed for preparation of anatase-type metatitanic acid particles.This SCMA method mainly contained the decomposition of titanium slag by low concentration of mixture acid,followed by the thermal hydrolysis of low titanyl SCMA solutions.Among the process,the hydrolysis process played an important role to decide the properties and qualities of the TiO2 products.But the controlling of this hydrolysis process and corresponding mechanisms in this SCMA system should be future studied.Then,the SCMA method was applied to perovskite-containing titanium slag to realize the efficient reuse of titanium components and the recovery of waste acid.This laid a theoretical and practical foundation of the further application of the SCMA method to prepare titanium dioxide products.Therefore,the main contents and achievements of this paper were as follows:(1)The systematic regulations of the hydrolysis process of the SCMA titanium solution were investigated.(1)Increasing the reaction temperature and the concentration of titanium solution increased the hydrolysis ratio,reduced the agglomerated particle size and increased the grain size of metatitanic acid.Especially,the promoting effect of hydrolysis temperature was relatively obvious.When the hydrolysis temperature was up to 150-160?,the hydrolysis rate was above 95%and the aggregated particle size of metatitanic acid reached about 2(?)The molar ratio of Cl-:SO42-had little effect on the hydrolysis rate,but a significant influence on the particle size and morphology of the metatitanic acid.When the molar ratio of Cl-:SO42-was 1:1,the hydrolyzed particle size was about 2 ?m with the metatitanic acid in a uniform spherical shape.But when the molar ratio of Cl-:SO42-was more than 2:1,the hydrolyzed particle size was larger to 8 ?m with agglomeration.(?)The Al3+had a negative effect on the hydrolysis ratio at a lower hydrolysis temperature(130?).But the Al3+admixture was beneficial to promote the formation of lamellar structure of metatitanic acid,which had a slight influence on the grain size.The effect of Na+was not obvious on the whole hydrolysis process.(IV)After PEG 1000 dispersant addition,the hydrolysis ratio under normal pressure increased and the distribution of metatitanic acid particles was facilitated.If the molar ratio of Cl-was low,the PEG addition also helped reducing the particle size of metatitanic acid with a uniform spherical distribution.(2)The titanium hydrolysis mechanisms of SCMA system were deduced.By comparing the Raman spectra obtained from experiments and theoretical calculations(DFT),the possible titanium cluster structures in the titanium SCMA solutions were determined.Besides,the Arrhenius formulas and the Boltzmann distribution models were used to fit the relationship between the hydrolysis parameters and the grain size,thus the grain size was predicted successfully.And based on the microstructure and the corresponding energy change of the intermediates,the hydrolysis mechanisms were speculated in this SCMA system.(3)Based on the hydrolysis results and the corresponding mechanisms,the SCMA method was furthermore introduced to decompose perovskite titanium slags to prepare qualified metatitanic acid.The thermodynamics and kinetics of the mixed acid decomposition of titanium slags were systematically studied.After 4 cycles of experiments,the leaching ratio could reach 80%.By thermal hydrolysis,the hydrolysis ratio reached 90%and the metatitanic acid showed a uniform particle size distribution with the size of 2-3 ?m.Moreover,the method had good economic and environmental advantages compared with the traditional sulfate process.This SCMA method realized recycle of waste acid and reuse of titanium components,thereby achieving cleaner production.(4)The effects of doping and calcination of metatitanic acid on the properties of titanium dioxide pigments were studied.The results showed that the proper doping,the calcination temperature and the holding time were conducive to improving pigment performances.After treatment with K2SO4 and H3PO4,the best samples obtained under different temperature of 850?890? could approach the pigment performance of AO 101 TiO2 product on the market.Besides,the metatitanic acid hydrolyzed by the addition of Al3+and Na+were calcinated.The Al3+and Na+ could prevent the calcined products from sintering during the calcination process.