Catalytic Ozonation Of Recalcitrant Organic Chemicals In Water Using Vanadium Oxides Loaded ZSM-5 Zeolites

The discharge of wastewater having recalcitrant organic chemicals?ROCs?can have significant and adverse environmental effects.High efficiency catalytic ozonation process?COP?is among the most promising and simple treatments,that utilize a range of different catalysts for ROCs treatment.The present study investigates the application of a cost-efficient COP treatment for the removal of ROCs from the wastewater.Novel catalytic materials using vanadium?V?oxides deposited onto the surface of Na ZSM-5zeolites?V/ZSM?were found to have high efficiency.The constructed?1.0wt%of V loading and 450°C of calcination?exhibited the highest activity among the developed catalyst compositions.The highly-dispersed V oxides(V⁴⁺and V⁵⁺)and Si-OH-Al framework structures were determined to promote the surface reaction and generation of hydroxyl radicals?·OHs?.The removal mechanisms for ROCs are illustrated by:1)ROCs are mineralized or degraded to intermediates by direct ozonation and then partially adsorbed by V1/ZSM₄₅₀;2)Dissolved ozone adsorbs on the Si-OH-Al active sites and then decomposed to·OHs;3)Dissolved ozone adsorbs on the V-OHs active sites,where ozone oxidizes V⁴⁺-OHs to V⁵⁺-OHs,along with·OHs generation;4)Adsorbed chemicals and intermediates are oxidized or activated and reduce V⁵⁺-OHs to V⁴⁺-OHs;5)The oxidized or activated species are subsequently desorbed from the catalyst surface and further oxidized by·OHs and molecular ozone on the catalyst surface and in solution.Theincreased the mineralization rate of nitrobenzene and benzoic acid by 50%and 41%in comparison to single ozonation.·OHs and molecular ozone interacts with nitrobenzene or benzoic acid via electrophilic or nucleophilic addition produce phenols.The phenols are oxidized to alcohols,aldehydes,ketones and carboxylic acids mainly by electrophilic addition and then mineralized to CO₂ and H₂O.This study demonstrates the enhanced potential of V/ZSM catalysts used with COP for the treatment of petrochemical wastewaters.