Oxidation of phthalate acid esters using hydrogen peroxide and polyoxometalate/graphene hybrids

Phthalate acid esters (PAEs) have been adsorbed and oxidatively degraded into small molecules including lactic acid (LA), formic acid (FA), H 2 O and CO 2 using polyoxometalates (POMs)/graphene hybrids. We demonstrated that super-lower concentrations of PAEs could be oxidized, which was due to their unique structure. POM molecules have been embedded onto graphene to form H 5 PMo 10 V 2 O 40 @surfactant(n)/Graphene(L wt%) (abbreviated as HPMoV@Surf(n)/GO(L wt%)) using surfactants with the carbon chain length n = 2, 4, 6 and 8 for the loading of HPMoV. The coexistence of the graphene and surfactant layer (on HPMoV@Surf(n)/GO(20 wt%)) adsorbed PAE molecules and transported them rapidly to HPMoV active sites. And n values determined the electron transfer ability between graphene and POMs that promoted PAEs oxidation. The loading of POMs on the surface of graphene permitted HPMoV@Surf(n)/GO(L wt%) act as interfacial catalyst which degraded various PAEs (i.e., diethyl phthalate (DEP), diallyl phthalate (DAP) and di (2-ethylhexyl) phthalate (DEHP)) while removed more than 70% of TOC and COD. The degradation of DEP achieved 93.0% with HPMoV@Surf(n)/GO(20 wt%) and H 2 O 2 , which followed first-order kinetics and the reaction activation energy ( Ea ) of 23.1 kJ/mol. Further, HPMoV@Surf(n)/GO(20 wt%) showed potential for the removal of PAEs in Wastewater Treatment Plant (WWTP), and the degradation efficiency for PAE (DEP) in secondary effluent achieved 55.0%. In addition, the loading method for POMs on graphene eliminated the leaching of POMs from graphene, and the degradation efficiency could still reach 88.1% after ten recycles. • A new approach method that oxidation of PAEs using hydrogen peroxide and polyoxometalate/ graphene hybrids. • The coexistence of the graphene and surfactant layer adsorbed PAE molecules to the HPMoV active sites. • The PAEs with long carbon chains were oxidized by interfacial POMs on the graphene surface without mass-transfer limitations. • As an interfacial catalyst degraded various PAEs while removed more than 70% of TOC and COD. • HPMoV@Surf(n)/GO(20 wt%) showed great potential for the removal of PAEs(DEP 55%)in WWTPs.