Surface-complexation-directed selective oxidation of phosphonates by decoration of copper anchoring sites

Organic phosphonates are recalcitrant contaminants in industrial and municipal wastewater. Their oxidative conversion to phosphate is promising for the in-depth removal and recovery of phosphorus. However, the treatment by conventional advanced oxidation processes (AOPs) usually demonstrates no precedence toward phosphonates, suffering from severe interference from co-existing substances and the overuse of costly oxidants. Herein we develop a copper-directed protocol for highly selective oxidation of phosphonates driven by simulated solar irradiation. Exploiting copper nanostructures decorated bismuth vanadate, hydroxyethylidene diphosphonic acid (HEDP), a representative phosphonate, converted to phosphate at > 93  % yield in two hours. Distinguished from Fe/UV or copper-free light-driven oxidation that is susceptible to common anions/organic matters, the protocol developed here offered excellent anti-interference performance, and was applicable for oxidative removal of HEDP in actual water matrices, maintaining 70–80 % yield of phosphate. Copper-promoted oxidation was also demonstrated for PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid), EDTMP (ethylenediamine tetra (methylene phosphonic acid)) and DTPMP (diethylenetriamine penta (methylene phosphonic acid)). Other than free radical mediated process, the copper enhanced phosphonate-catalyst interaction enables directional interfacial hole transfer to phosphonates, triggering their conversion to phosphate. The revealed selective oxidation pathway is envisioned to guide new protocol design for advanced treatment of phosphorus-containing wastewater.