随着我国不锈钢粗钢产量逐年增大，对不锈钢进行酸洗而产生的酸洗废酸也在逐年增多。不锈钢酸洗排放的废硫酸溶液中含大量游离酸，根据本课题组开发的酸再生循环工艺，在有效回收废酸中有价金属离子的同时，使酸洗废酸中游离酸浓度增大得到再生硫酸。针对不锈钢酸洗废液中再生硫酸浓度较高、中和处理试剂消耗高、废渣产生量大的问题，研究了溶剂萃取法回收不锈钢酸洗废液中硫酸的工艺。研究发现，有机体系40%(体积分数)三(2-乙基己基)胺(TEHA)+50%异构十三醇+10% Exxsol D110为最优化组成，硫酸萃取率随TEHA浓度增加而升高，随温度升高萃取率降低，表明萃取反应为放热反应，计算所得萃取反应的ΔH=?7.5708 kJ/mol。根据萃取和反萃分配曲线分别绘制了McCabe-Thiele图，在30℃、相比A/O=1:2条件下，经过3级(理论)萃取，硫酸的萃取率可达79.8%以上；采用水作反萃剂，在30℃、相比A/O=1:1条件下，经过3级(理论)反萃，硫酸的反萃率可达85.5%。萃取、反萃动力学快，分相迅速，可满足工业连续生产要求。

As the output of the stainless steel is increasing year by year, the waste acid produced by pickling the stainless steel is also increasing year by year. The waste sulfuric acid solution discharged by pickling the stainless steel contains a large amount of free acid. According to the acid recycling process developed by our research group, the free acid concentration in the waste acid can increase to obtain the regenerated sulfuric acid while quite effectively recovering these valuable metal ions in the waste acid. In this work, the technology of recovering sulfuric acid from the stainless steel pickling waste solution by the solvent extraction was studied, aiming at the problems of high concentration of regenerated sulfuric acid in the stainless steel pickling waste solution, high consumption of neutralization treatment reagent, large amount of waste residue, and so on. It was found that the organic system of 40% (volume fraction, the same below) tris-2-ethylhexylamine (TEHA)+50% isomeric tridecyl alcohol+10% Exxsol D110 was the optimal composition. The extraction rate of sulfuric acid increased with the increased concentration of TEHA. With the temperature increasing of the extraction, the extraction rate of sulfuric acid decreased, indicating that the extraction reaction was exothermic reaction and the enthalpy (ΔH) of the extraction reaction was calculated as ?7.5708 kJ/mol. McCabe-Thiele diagrams were drawn according to the distribution curves of the extraction and the stripping. Under the condition of 30℃ and A/O=1:2, the extraction rate of sulfuric acid could reach 79.8% by 3 stages (theoretical). Using the deionized water as the stripping agent, the stripping rate of sulfuric acid could reach 85.5% after 3 (theoretical) stages at 30℃ and A/O=1:1. The kinetics of the extraction and stripping was very fast and the phase separation was rapid at the same time, which can perfectly meet the requirements of industrial continuous production.