| The titanium pigment is white pigments with wide utilization, which is applied in various fields of social economy. With continuous improvement and development of titanium pigment preparation technology, production with excellent pigment properties, optical properties has become the developed trend of titanium dioxide industry. Therefore, the present prevalence of domestic enterprises is not high quality, difficult to quality products and world competition. With the increasingly severe environmental requirements and the development of titanium dioxide production of chloride, sulfuric acid production of titanium dioxide will face significant challenges, mainly in how to address the use of ferrous sulfate and acid wastewater treatment and utilization.In order to make use of the high titanium slag for the production of titanium dioxide by the sulfuric acid method, the raw material of 90 wt.% TiO2 was modified in our study. After modification of the high titanium slag, the acid leaching rate was significantly increased to 96.23 wt.%. There was no ferrous sulfate by-products generated in the leaching process which dealing with the difficuty of ferrous sulfate treatment in the production of titanium dioxide and the difficulty of titanium- ferrous separationin in titanium slag smelting by the sulfuric acid method. Otherwise, the produced calcium sulfate can be processed into gypsum for the construction industry.CaO and NaNO3 were used as modificate additive and the effects of the additive ratio and calcination temperature on composition phase were studied. The response surface methodology (RSM) based on central composite design (CCD) was used to optimize the three important variable- leaching temperature, leaching time and liquid to solid ratio for the laeching rate of TiO2. Testing program was designed by Design Expert7.1 software and 20 experimental points (including 6 center) for response surface analysis test were carried out. Based on the CCD, a quadratic model was developed to correlate the reaction cariables to the leaching rate and the optimum conditions were obtained.One factor test was carried out and the optimal modificate condition was found:high titanium slag and CaO, NaNO3 in the ratio of 10:8:3, roasting temperature of 1200-1300℃and roasting time of 120min. In the modified calcined, the titanium dioxide in high-titanium slag reacted with CaO then transerfered into CaTiO3. As the temperature and the ratio of additives increaced, the content of CaTiO3 increased. RSM optimization of modified high-titanium slag leaching parameters are:temperature of 60℃, leaching time of 90min, liquid to solid ratio of 4.5:1 and the leaching rate of the predictive value of 94.42% and the experimental value was 94.20%. It indicated that the model is significant. Under this optimized conditions, different modified samples of A-1～A-12 for leaching experiments were carried out, the highest leaching rate was obtained from the sample A-6 which was 96.23%. The model shows that is significant, Which indicated that the leaching temperature x1, x2, said leaching time, x3 liquid to solid ratio, y that the leaching rate. In addition, through modification of the leaching kinetics of high titanium slag after the experiment, the dynamic equations can be proved consistent, are shrinking core model. Experience through the Arrhenius equation, and a range of different temperatures lnk-1/T diagram, obtained the activation energy is 46.76 kJ·mol-1, leaching kinetics equation is: Therefore, determined that the leaching process is chemical reaction control.The proposed modification process of the feasibility of high titanium slag was proved by the modified residue acid solution leaching results which enrichs the production of raw materials for sulfuric acid, solve the environmental quality problem brought by sulfuric acid process that agrees well with the national sustainable development strategy. |
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