Catalytic aerobic oxidation of P(I)/P(III) into P(V) over PdNi10 as a low-cost alternative catalyst rivaling Pd

Abstract

Chemical oxidation is essential in treating P(I)/P(III)-bearing wastewater, while conventional oxidation processes suffer from low selectivity and high cost induced by oxidant reagents. Herein, a low-cost catalyst PdNi10 was developed to rival the noble metal Pd, which had been known as the only catalyst enabling chemical-free oxidation of P(I)/P(III) into P(V) by ambient O2. The PdNi10 fabricated via optimized method even outperformed Pd in catalytic activity at identical dosage (0.10 g L−1), achieving efficient conversion of 1.00 mM of P(I) into P(V) (>94% in 30 min) with wide applicable pH range from 3.0 to 9.0. The aerobic oxidation of P(I) and P(III) over PdNi10 was confirmed via scavenging experiments to be both dominated by non-radical pathways with apparent activation energies of 44.5 and 21.3 kJ mol−1, respectively. Interestingly, the individual roles of Ni components of PdNi10 in the catalytic oxidation were found negligible. The H2O-methanol binary solvent experiment suggested that H2O mediated the catalytic reaction and the interfacial OH groups as a result of H2O dissociation served as the main reactive oxidant species for P(I)/P(III) oxidation. Furthermore, synergistic mechanism was proposed for the Ni and Pd sites with favorable roles in the essential reaction steps of dehydrogenation and hydroxylation, respectively. This study is believed to advance the treatment strategy of P(I)/P(III)-rich wastewater and to shed new light on the development of low-cost catalysts enabling chemical-free aerobic oxidation processes under facile condition.