废金属切削液中含有大量的COD，严重破坏水生态环境，需处理达标后才可排放。建立了破乳-混凝-氧化-吸附法处理废切削液的方法。取1 L废水加浓硫酸破乳，破乳后取上层清液100 mL，调节pH为7时加入聚合硫酸铁（PFS）0.18 g、阳离子型聚丙烯酰胺（PAM）5 mg，混凝效果达到最佳；混凝后取100 mL上层清液加入FeSO₄·7H₂O 7 g，20 min后加入30%的H₂O₂，调节pH为3，氧化后再将pH调为碱性，使Fe²⁺以Fe（OH）₂形式沉淀下来，氧化效果最佳；氧化后再用颗粒状活性炭吸附，COD去除率为92.2%，效果较佳，可为处理废金属切削液提供参考。

Spent metal cutting fluid contains a large amount of COD, which may seriously damage the water ecological environment.A method containing demulsification, coagulation, oxidation and adsorption is established to treat with spent metal cutting fluid.One liter of spent fluid is demulsified with concentrated sulfuric acid.After demulsification, 100 mL of the supernatant is taken out, into which 1.8 g of polyferrous sulfate and 5 mg of cationic polyacrylamide are added after its pH value is adjusted to 7, the best coagulation effect is obtained.After coagulation, 100 mL of the supernatant is taken out and is added with 7 g of FeSO₄·7H₂O at first, and added with 30% H₂O₂ 20 min later.Then, the pH value of the supernatant is adjusted to 3, and further to alkaline after oxidation, so that Fe²⁺ can be precipitated in the form of Fe(OH)₂.The best oxidation effect is gotten finally.After oxidation, granular activated carbon is used for adsorption treatment to the supernatant, and COD removal rate can reach 92.2%, which can provide a reference for the treatment of waste metal cutting fluid.