Adsorption of phosphate from aqueous solutions and sewage using zirconium loaded okara (ZLO): Fixed-bed column study

• Dynamic adsorption of P from water and wastewater by Zr(IV)-loaded okara was tested.
• Effects of column design parameters on the adsorption performance were investigated.
• The dynamic adsorption capacity of Zr(IV)-loaded okara for P was reasonably high.
• The spent column was effectively regenerated with 0.2 M NaOH followed by 0.1 M HCl.
• Zr(IV)-loaded okara column was efficient in eliminating P from municipal sewage.

This study explores the potential of removing phosphorus from aqueous solutions and sewage by Zr(IV)-loaded okara (ZLO) in the fixed-bed column. Soybean residue (okara) was impregnated with 0.25 M Zr(IV) solution to prepare active binding sites for phosphate. The effect of several factors, including flow rate, bed height, initial phosphorus concentration, pH and adsorbent particle size on the performance of ZLO was examined. The maximum dynamic adsorption capacity of ZLO for phosphorus was estimated to be 16.43 mg/g. Breakthrough curve modeling indicated that Adams–Bohart model and Thomas model fitted the experimental data better than Yoon–Nelson model. After treatment with ZLO packed bed column, the effluent could meet the discharge standard for phosphorus in Australia. Successful desorption and regeneration were achieved with 0.2 NaOH and 0.1 HCl, respectively. The results prove that ZLO can be used as a promising phosphorus adsorbent in the dynamic adsorption system.