Enhanced Production and Recovery of Orthophosphate from Wastewater Containing Phosphonate 1-Hydroxyethane-1,1-diphosphonic Acid through Combined Packed-Bed Ozonation and Adsorption

Abstract

Phosphonates are widely used in industrial and household applications. Phosphorus (P) removal and recovery from phosphonates in wastewater require a (cost-)efficient process. This study developed a two-step approach for this challenge. In the first step, lava rock and expanded clay aggregates (ECA) were used to build two packed O3 bubble columns (LBC and EBC, respectively) and were compared with a nonpacked bubble column (BC). After 90 min of ozonation, the net production efficiency of orthophosphate (Ortho-P) from a commonly used phosphonate in the textile industry [1-hydroxyethane-1,1-diphosphonic acid (HEDP)] was higher in the LBC (66%), followed by the BC (59%) and EBC (44%). The lowest Ortho-P production efficiency in the EBC was because a high fraction of the produced Ortho-P was adsorbed on the surface of the ECA. However, when the adsorptive packing materials were reused during five consecutive ozonation cycles, the Ortho-P adsorption sites on the packing materials tended to be saturated. As such, the net production efficiency of Ortho-P in the LBC and EBC increased to 86 and 72%, respectively. In the second step, iron-coated sand granules were used to adsorb and recover the produced Ortho-P. Higher Ortho-P recovery efficiencies (66.4% for the LBC and 61.9% for the EBC) and Ortho-P sorption capacities (12.05 mg/g for the LBC and 8.13 mg/g for the EBC) were achieved in combination with packed-bed ozonation. This study provides insights into HEDP removal from wastewater and the recovery of Ortho-P as a valuable resource, which fits within the development of sustainable wastewater treatment processes.