由于氰化物对硫铁矿有一定的抑制作用，直接采用浮选法回收氰化尾渣中硫铁矿的效果不理想。因此，必须先对氰化尾渣进行预处理，使被抑制矿物恢复浮选活性。采用添加还原剂和浓硫酸协同预处理方法使被抑制矿物恢复活性，并分别考察加药顺序、焦亚硫酸钠用量和pH值等因素对硫精矿回收率和尾矿品位的影响。浮选试验采用一粗、一精、二扫流程，考察了pH值调节剂、铵盐和复合抑制剂等对硫精矿回收率和尾矿品位的影响。最终确定预处理最佳工艺条件：先添加2 kg/t的Na₂S₂O₅药剂预处理1 h，然后加入浓硫酸将矿浆pH值调至2~3并维持2 h，再用NaOH将pH值调至6~7。浮选最佳条件：丁胺黑药用量为500 g/t，复合抑制剂用量为300~500 g/t，通过试验取得硫精矿品位为40%~42%，尾矿中S元素品位为6%~8%的良好结果。

Since cyanide has a certain inhibitory effect on pyrite，the effect of directly using flotation to recover pyrite in cyanide tailings is not satisfactory.Therefore，the inhibited mineral flotation activity must be recovered by pretreatment of the cyanide tailings.In the gold industry，the cyanide tailings S separation process uses acid addition cyanide removal method，metal ion precipitation cyanide method and addition of redox and cyanide removal agent cyanide method or a combination method to restore the inhibited pyrite.Research papers specifically for the flotation of pyrite in cyanide tailings are rarely seen in domestic industry research.There are many problems in the pretreatment and flotation，such as the mechanism is not clear，the dosage of the drug is extensive，the production cost is high，and the index is unstable.In this study，the synergistic pretreatment method of adding reducing agent and concentrated sulfuric acid was used to restore the inhibited mineral activity，and the effects of dosing order，sodium pyrosulfite dosage and pH value on the recovery rate of sulfur concentrate and tailing grade were investigated.Pretreatment tests show that:Adding sodium pyrosulfite first and then adding concentrated sulfuric acid is better than the reverse; When the sodium pyrosulfite in an amount of 2 000 g/t and pH=2~3 can achieve the best results.The flotation tests adopt the process of one roughing，one refining and two scavenging，and the effects of pH adjusters，ammonium salts and composite inhibitors on the recovery rate of sulfur concentrate and tailing grade were investigated.The flotation test found that using CaO as a pH adjuster has an inhibitory effect on the flotation activity of pyrite，and the addition of an ammonium salt can restore this activity，but there is still a problem of foam sticking.Although the use of composite inhibitors can improve the concentrate grade and reduce the impurity content of Pb and Zn in the concentrate，the Pb and Zn in the concentrate are too fine to be entrained by the foam，so the Pb and Zn grades of the S concentrate cannot be further reduced by the flotation method alone.The test finalizes the optimum process conditions for the pretreatment：The first step was added 2 000 kg/t Na₂S₂O₅ regent for pretreatment for 1 h，concentrated sulfuric acid was then added to the slurry,and the pH value was adjusted to 2~3 and maintained 2 h，NaOH and then adjusted to pH=6~7.The optimum flotation conditions are as follows：the dosage of dibutyl dithiophosphate is 500 g/t，the dosage of composite inhibitor is 300~500 g/t， and the good results of sulfur concentrate grade of 40 \mathrm{\%} ~42 \mathrm{\%} and S element grade of tailings of 6 \mathrm{\%} ~8 \mathrm{\%} are obtained through experiments.