Application of magnetic hydrogel for anionic pollutants removal from wastewater with adsorbent regeneration and reuse

A novel magnetic hydrogel coupling with a wastewater treatment prototype is proposed in this study for the removal of various types of anionic pollutants from wastewater. Within 5 min of kinetic studies, 97.5, 99.9, 100.0, 81.7, and 98.9% of Cr(VI), amaranth, methyl orange, nitrate, and phosphate were removed from wastewater, whereas these adsorbed anions were desorbed to varying extents using NaCl for 15 min. The maximum adsorption capacities of Cr(VI), amaranth, methyl orange, nitrate, and phosphate were 205 mg/g, 830 mg/g, 1,390 mg/g, 188 mg/g, and 227 mg/g, respectively. An industrial wastewater treatment prototype was developed featuring a magnetic separation unit for the recovery of spent magnetic hydrogel. A separation efficiency over 98% can be maintained throughout 60 adsorption-desorption cycles of Cr(VI) wastewater treatment. The estimated wastewater treatment cost in consideration of chemical usage only is USD 0.58/m³. The chemical cost of the treatment is comparatively less expensive than chemical reduction and precipitation methods.