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.