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

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.