Removal of low concentration Cr(VI) from aqueous solution by magnetic-fluids fixed bed using the high gradient magnetic separation

[Display omitted] ► The original magnetic-fluids fixed bed using HGMS has been explained. ► The feasibility was studied by extraction experiments of Cr(VI). ► The optimum extraction conditions were investigated. ► The method obtained a high extraction capacity with a continuous process. The focus of this paper was a novel model of Cr(VI) extraction process. The original so-called “magnetic-fluids fixed bed” (MFFB), which bridged the solvent extraction and the fixed-bed extraction by the theory of the high gradient magnetic separation (HGMS), has been explained. The MFFB integrated the advantages of the two above mentioned classical extraction methods and overcame their drawbacks. The feasibility of this method was studied by extraction experiments of Cr(VI) from aqueous solution. The influences of the design of ferromagnetic steel wires in magnetic separation column, the pH value of feed solution, TBP concentration in magnetic fluids, and flow rate of aqueous solution in column were investigated. Under the optimum conditions, the proposed method obtained high extraction efficiency with continuous process.