Fast degradation of phthalate acid esters by polyoxometalate nanocatalysts through adsorption, esterolysis and oxidation

Abstract A novel route was created to facilitate the degradation of diethyl phthalate (DEP) upon micellar polyoxometalate (POM) catalysts and H 2 O 2 . The best catalytic activity was obtained using [C 16 H 33 N(CH 3 ) 3 ]H 4 PMo 10 V 2 O 40 ( N -hexadecyl -N,N,N- trimethylammonium tetrahydrogen decamolybdo-divanadophosphate, abbreviated as (CTA)H 4 PMoV) with 90.2% degradation efficiency within 30 min, while the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiency were about 77.7% and 74.3% within 40 min. The highest efficiency was attributed to the concentration of DEP by amphiphilic POM catalyst, coupling with its strong Bronsted acidity and higher redox potential to catalyze esterolysis and oxidation of DEP. This allowed the phthalate acid esters (PAEs) with long carbon chains in super low concentration of 0.03 μM to be efficiently decomposed. The above synergistic effects explored DEP being degraded into ethanol, lactic acid and CO 2 , which were non-toxic to the water surroundings. And the reaction activation energy (Ea) of 12.49 kJ/mol was obtained upon the degradation of DEP with (CTA)H 4 PMoV followed first-order kinetics. Meanwhile, (CTA)H 4 PMoV acted as a heterogeneous catalyst, which showed long duration and higher stability with only 3.7% loss amount during ten recycles.