Degradation of Organophosphorus Pollutants into Inorganic Phosphates by Co(II)/NaBO3 System and Its Phosphorus Recycling

Abstract

With the increase of demand of phosphorus resources and its natural shortage, circulating utilization of organophosphorus contaminants into phosphatic fertilizer could provide a sustainable way to achieve the phosphorus cycle. Herein, a homogeneous catalytic system of Co(II)/sodium peroxyborate (NaBO₃·4H₂O, SPB) was developed for the degradation of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and glyphosate (PMG) into inorganic phosphate (o-PO₄^3-). The Co(II)/SPB system maintained excellent catalytic performance for HEDP degradation under a broad initial pH range (2.91-11.01) due to its self-regulating pH phenomenon. Trapping experiments, quantitative experiments, and supplementary techniques suggested that the HEDP degradation was mainly affected by the combined action of free radical species (^•OH and O₂^•-) and nonradical species (Co(III) and ¹O₂). More importantly, the Co(II)/SPB system also exhibited excellent catalytic performance in the treatment of actual glyphosate wastewater with 11.0% decrease in total organic carbon (TOC), 55.4% decrease in chemical oxygen demand (COD) after 60 h, and the o-PO₄^3- formation of 66.5 μM, which had been further transformed into struvite (phosphate fertilizer) with an 84.75% yield. In addition, germination experiments demonstrated that the biotoxicity of glyphosate to wheat seed was greatly reduced after treatment by the Co(II)/SPB system.