Enhanced degradation of 2,4-dinitrotoluene by ozonation in the presence of manganese(II) and oxalic acid

Abstract

a b s t r a c tManganese catalytic ozonation of 2,4-dinitrotoluene (DNT) in the presence of oxalic acid was studied. The addition of manganese ion (Mn 2+ ) or oxalic acid alone in ozonation process did not enhance DNT degradation, but the addition of Mn 2+ coupled with oxalic acid accelerated degradation of DNT. The DNT degradation efficiency was influenced by carbonate in the catalytic ozonation process. Kinetics study showed that Mn 2+ catalytic ozonation significantly promoted the decomposition of ozone. Experimental results of electron spin resonance (ESR) demonstrated that addition of Mn 2+ and oxalic acid produced much hydroxyl radicals in catalytic ozonation system than that in single ozonation system. These results suggested that catalytic ozonation followed hydroxyl radical-type mechanism. Mn 2+ promoted decomposition of ozone to produce hydroxyl radical and it was oxidized into manganese oxide. Manganese oxide was reduced into Mn 2+ by oxalic acid, which is the key step of catalytic process. Based on above results, a cycle catalytic mechanism of Mn 2+ was proposed. Intermediates were determined by HPLC and GC-MS, and they mainly included aromatic organics and aliphatic carboxylic acids.

Visible-light sensitive cobalt-doped BiVO4 (Co-BiVO4) photocatalytic composites for the degradation of methylene blue dye in dilute aqueous solutions

“…The presence of carbonate/bicarbonate ions resulted in the lowest percentage of MB removal. It has been reported that that bicarbonate and carbonate ions are a radical scav- engers [45] that can trap hydroxyl radicals generated at the surface of the Co-BiVO 4 . As the concentration of reactive radicals decreased the percentage of photocatalytic decoloration was decreased.…”

Heterogeneous Catalytic Ozonation of Refinery Wastewater over Alumina-Supported Mn and Cu Oxides Catalyst

“…Therefore, hydroxyl groups on the Mn-Cu-O catalyst surface played an important role in HCOP system. The addition of NaH 2 PO 4 in the HCOP system allowed us to evaluate whether the hydroxyl groups on the catalyst were active sites for ozone decomposition into hydroxyl radicals Xiao et al 2008); (Zhao et al 2013. NaH 2 PO 4 can strongly bind with the surface hydroxyl group of the catalyst .…”

Combined heterogeneous and homogeneous photodegradation of a dye using immobilized TiO2 nanophotocatalyst and modified graphite electrode with carbon nanotubes

“…In recent years, various technologies have been developed for environmental pollutants removal [1]. In general, the treatment of dye-containing effluents is being undertaken by biological [2], adsorption [3], membrane [4], coagulation-flocculation [5], oxidation-ozonation [6] and advanced oxidation processes (AOPs) [7].…”