Abstract:

The magnetic separation technology was combined with chemical flocculation and solvent extraction method to synthetically provide a new way of treating chromium-containing wastewater by the application of magnetic flocculation and high gradient magnetic separation (HGMS) for magnetic-fluids extraction.Namely magnetic flocculation method was used to treat high concentration chromium-containing electroplating wastewater once, and the optimal magnetic flocculation conditions were obtained by orthogonal test method:pH 8, the dosage of magnetic Fe₃O₄ particles 4 g, mixing speed 80 r·min^-1, the main flocculant PAFC dosage 6 ml, under which can reduce the chromium concentration in the wastewater from 4325.13 mg·L^-1 to 29.8·mg·L^-1. After magnetic flocculation treatment, the method of high gradient magnetic-fluids extraction was used in secondary processing, the wastewater was pumped and continuously flowed through two series of high gradient magnetic-fluids extraction devices within seven hours, and the highest extraction rate could achieve 99.4%, average extraction rate could achieve 98.97%, under optimal conditions. Furthermore, chromium concentration could be reduced to 0.31 mg·L^-1, which met the national emission standard. Under alkaline conditions, the stripping rate of magnetic fluid was more than 90%, and the regenerated magnetic fluid extraction agent can be reused.

Key words: magnetic flocculation, HGMS magnetic-fluid extraction, integration treatment, chromium-containing wastewater

摘要：

将磁分离技术和化学絮凝法、溶剂萃取法相结合，提出磁絮凝法和高梯度磁流体萃取法集成处理高浓度含Cr电镀废水的新工艺。采用磁絮凝法对高浓度含Cr电镀废水进行一次处理，通过正交实验方法获得了最佳磁絮凝条件：pH 8，磁性Fe₃O₄颗粒用量4 g，搅拌速度80 r·min^-1，主絮凝剂PAFC用量6 ml，可使废水中Cr浓度由4325.13 mg·L^-1降为29.8 mg·L^-1；采用高梯度磁流体萃取法对磁絮凝后废水进行二次处理，将该废水流经两个串联的高梯度磁流体萃取装置，持续动态萃取7 h，在最佳萃取条件下，最高萃取率为99.40%，平均萃取率98.97%，总萃余液Cr浓度由29.8 mg·L^-1降为0.31 mg·L^-1，低于国家排放标准；碱性条件下磁流体萃取剂反萃率大于90%，再生磁流体萃取剂可重复使用。

关键词: 磁絮凝, 高梯度磁流体萃取, 集成处理, 含铬废水