Steering OH-triggered radicalization of surface phosphate functionality and its protonated analogues to accelerate mineralization of aqueous organic wastes

Abstract

Herein, iron oxide served as a host to support mono-dentate H3-XPO4X-guests (H3-XPO4 X -SUP; X = 1-3), whose relative compositions were varied by calcining a synthetic intermediate at 250-450 degrees C. This could produce H2PO4-SUP-rich P250, HPO4SUP-rich P350, and PO4 2 -SUP-rich P450 catalysts, all of which were subjected to characterizations, DFT 3 -calculations, and kinetic assessments of bisphenol A (BPA) mineralization runs for justifying six compelling findings specified below. The catalysts could proceed with the overall center dot OH -> H3-XPO4 SUP route consisting of center dot(X-1)-heterolytic H2O2 dissection and center dot OH -> H3-XPO4 SUP cycles, where the former was enabled by Lewis acidic (LA) center dot(X-1) -sites to generate center dot OH, whereas the latter was enabled using center dot OH as a radicalizer of H3-XPO4 X -SUP functionalities to exothermically generate H3-XPO4SUPanalogues. Of significance, the overall center dot OH -> H3-XPO4 center dot(X-1)-SUProute ener- center dot(X-1)-getically hinged on endothermic center dot OH desorption from LA sites. H2PO4-SUP was most adequate to reduce LA strength, desorbed center dot OH in the easiest manner, thereby rendering P250 to display the smallest energy barrier (EBARRIER) among P250-P450. Of additional significance, PO4 SUP bore the largest number of P+ -O- bonds available 3 -to center dot OH -> H3-XPO4SUPcycle, elevated collision frequency of center dot OH <-> H3-XPO4 center dot(X-1)-X -SUP or H3-XPO4 SUP <-> pollutant in the center dot(X-1) -most efficient fashion, thus making P450 exhibit the largest pre-factors (kAPP, 0) among P250-P450. In addition, EBARRIER outweighed kAPP, 0 in dictating BPA mineralization efficiencies for P250-P450, among which P250 with the largest H2PO4-SUP composition revealed the greatest BPA mineralization rate, while sustaining BPA mineral-ization multiple times via electron transfer pathway. Moreover, H3-XPO4 SUP outperformed conventional center dot OH center dot(X-1) -and SO4 SUP/NO3 center dot-center dot SUP analogues in mineralizing real wastewaters.