VO-WO/TiO Catalyst for Efficient Synergistic Control of NO and Chlorinated Organics: Insights into the Arsenic Effect.

Municipal solid waste incineration and the iron and steel smelting industry can simultaneously discharge NO and chlorinated organics, particularly polychlorinated dibenzo--dioxins and polychlorinated dibenzofurans (PCDD/Fs). Synergistic control of these pollutants has been considered among the most cost-effective methods. This work combined experimental and computational methods to investigate the reaction characteristics of a catalytically synergistic approach and gives the first insight into the effect of arsenic (As) on the multipollutant conversion efficiency, synergistic reaction mechanism, and toxic byproduct distribution over a commercial VO-WO/TiO catalyst. The loaded AsO species were shown to distinctly decrease the formation energy of an oxygen vacancy at the V-O-V site, which likely contributed to the extensive formation of more toxic polychlorinated byproducts in the synergistic reaction. The AsO species strongly attacked neighboring V═O sites forming the As-O-V bands. Such an interaction deactivated the deNO reaction, but led to excessive NO being oxidized into NO that greatly promoted the V-V redox cycle and in turn facilitated chlorobenzene (CB) oxidation. Subsequent density functional theory (DFT) calculation further reveals that both the AsO and AsO loadings can facilitate HO adsorption on the VO-WO/TiO catalyst, leading to competitive adsorption between HO and CB, and thereby deactivate the CB oxidation with water stream.