[Removal of Cr(Ⅵ) via a Nickel Ferrite@Activated Carbon Composite Under Batch Experiments: Study of Characterization, Performance, and Mechanism].

A magnetic activated carbon adsorbent named NiFe2O4@AC was synthesized by modifying activated carbon with NiFe2O4 and used for the adsorption of Cr(Ⅵ) ions from waste water. The influencing factors, adsorption kinetics, and adsorption isotherms of Cr(Ⅵ) adsorption by the adsorbent were investigated. The results showed that the removal rate of Cr(Ⅵ) adsorption by NiFe2O4@AC reached 96.92%, and the adsorption amount reached 72.62 mg·g-1 at the adsorption conditions of temperature (298 K), pH 2, Cr(Ⅵ) initial concentration (150 mg·L-1), adsorbent dosage (0.1 g), and contact time (720 min). The experimental data were best described by the proposed secondary kinetics and Langmuir model, indicating that the adsorption process was a monolayer chemisorption process. The increase in temperature favored the adsorption of Cr(Ⅵ) on NiFe2O4@AC because the adsorption process was a spontaneous, heat-absorbing reaction. The adsorption mechanism of NiFe2O4@AC was mainly through complexation and electrostatic attraction to adsorb Cr(Ⅵ); meanwhile, the applied magnetic field could be separated from the solution, which has good application prospects.