| Titanium dioxide played an important role in chemical raw materials,playing an important role in the fields of coatings,paper,plastics and ceramics etc.The production methods of titanium dioxide are chlorination method and sulfuric acid method.Most enterprises of our country were still using the traditional sulfuric acid method.According to the statistics,0.2?0.3 t acid hydrolysis slag would be produced by producing per 1 t of titanium dioxide in the factory,the content of TiO2 in 15?30%.The content of Fe was as many as Ti.Because the waste was difficult to handle,it usually was washed and filter-pressed then wasted or landfilled,which not only wasted Ti and Fe resources,but also polluted the environment.If the Ti and Fe could be recycled by a appropriate method,it would be of great significance.Based on this,the leaching process of Ti and Fe of acid leaching residues was studied in this paper.The main research contents are as follows:(1)The causes of acid leaching residue were studied by water washing,conventional acid leaching and intensified leaching test.The results showed that the leaching rate of Ti was less than 1%by leaching the acid residue with clean water.The leaching rate of Ti and Fe was 42.94%and 41.14%by conventional leaching with sulfuric acid.The leaching rate of Ti and Fe was increased to 60.41%and 59.72%by leaching with sulfuric acid and adding ammonium fluoride.The attachment and encapsulation of CaSO4 on the surface of FeTiO3 formed during the acid hydrolysis of ilmenite concentrate and promotion of SiO2 content after acid hydrolysis,which were the two main reasons causing acid residue difficult to be leached.(2)The leaching scheme of Ti and Fe in acid hydrolysis residue was investigated by air roasting,nitrogen roasting and air alkali roasting.The results showed that the leaching rate of Ti and Fe was reduced to 24.86%and 34.59%after air roasting and acid leaching.The leaching rate of Ti and Fe was increased to 68.52%and 71.41%by acid leaching after nitrogen roasting.The leaching rate of Ti and Fe was increased to 68.16%and 68.22%by air alkali roasting and acid leaching.The existing method was improved,and the new process of nitrogen alkali roasting,washing and acid leaching was obtained.(3)The roasting process,washing process and impurity removal of the washing water were studied.The results showed that the optimum roasting conditions were the quality ratio of alkali/ore of 1,the roasting temperature of 500 ?,and the roasting time of 60 min.The optimum washing conditions were washing time of 20 min,liquid solid ratio of 5,stirring speed of 300 r/min,without heating.In the washed water,the highest recyclable rate of NaOH was 55.53%.The residual Na2SiO3 could be removed by adding CaO.At the solid-liquid ratio of 0.016,reaction time of 20 min,stirring speed of 300 r/min,room temperature,the highest recyclable rate of NaOH can be increased to 71.84%.(4)The acid leaching process and acid leaching kinetics of the new process were studied.The results showed that the optimum leaching conditions were reaction time of 60 min,liquid-solid ratio of 3,stirring speed of 700 r/min,sulfuric acid concentration of 11 mol/L,leaching temperature of 95 ? and acid sludge size of 0.147 mm.At these condution,the leaching rate of Ti and Fe reached 90.35%and 89.33%.The acid leaching kinetics could be described by shrinking core model.And the reaction was controlled by internal diffusion.The macroscopic dynamic equation could be obtained by processing experimental data:In the formula,x is the leaching rate of Ti,the unit of 1;C is the concentration of sulfuric acid,the unit of mol/L;d0 is the initial particle diameter of the slag,the unit of mm;t is the leaching time,the unit of s. |
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