Study On Removal Of Iron From The Waste Sulfuric Acid Generated During The Production Of TiO₂with Sulfuric Acid

Titanium waste sulfuric acid generated during the production of TiO2with sulfuric acid can be used in the production of wet-process phosphoric acid so as to make the best of the sulfuric acid in the waste sulfuric acid. It can not only reduce the cost of the production of TiO2by sulfuric acid, but also reduce the cost of raw materials of wet-process phosphoric acid, which doubtlessly has great significance to the environmental protection and the improvement of economy. However, there is4%～6%iron in the waste sulfuric acid which has negative effect on the quality of phosphate products such as available phosphorus degradation, caking and poor color. Therefore, the iron content must be strictly controlled when the waste sulfuric acid was used in the production of wet-process phosphoric acid, which restricts the utilization of waste sulfuric acid, In order to increase the usage of white waste acid, iron in waste acid should be removed.The solubility of ferrous sulfate, ferric sulfate in sulfuric acid solution was measured by using the balance method in this paper. According to the solubility of Fe2+and Fe3+in sulfuric acid solution, a new method of removal iron from waste sulfuric acid by crystallization was studied. Firstly the waste sulfuric acid was concentrated to increase the concentration of sulfuric acid in the waste acid, so that the ferrous sulfate could crystal from the waste acid; Then through oxidation reaction to make ferrous sulfate changed to ferric sulfate which would precipitate from the solution by crystallization. The effects of parameters of crystallization were studied and the better operation conditions of crystallization were determined. Under the optimal conditions, the residual iron content in the waste sulfuric acid was lower than0.2%.Based on the experimental research, the process route of removal iron from waste acid was designed. And industrial tests were carried out in waste acid workshop of Sichuan Lomon Titanium Industry Co., Ltd. Results showed that by using this new method, the overall iron removal rate can reach95%, the residual iron content in waste acid drop to an average of0.18%.