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A novel magnetic polymeric adsorbent, namely, magnetic hydrogel, was used to investigate its reusability and applicability in Cr(VI)-bearing wastewater treatment using magnetic separation. Different concentrations and amounts of NaCl solution and a stepwise approach were used for the regeneration experiment. A stepwise adsorption process followed by stepwise 3.0 M NaCl regeneration with a 40:1 wastewater-to-recovery volume ratio was found to be the most applicable working condition. The Cr concentration in the recovery solution was increased 25–30 times to 500–600 mg/L. The Cr(VI) removal and recovery performance of magnetic hydrogel was maintained for 20 cycles. An industrial wastewater treatment prototype, including a magnetic separation unit, was developed. The magnetic separation unit was designed to provide a magnetic field at the bottom with a zigzag pathway feature for maximizing the chance of capturing magnetic hydrogel. The separation efficiency for the magnetic hydrogel was above 97% throughout the 20 cycles of treatment.
Tang et al. (Tue,) studied this question.