Wet Oxidation and Catalytic Wet Oxidation

Abstract

This review article explores three major aspects of the wet oxidation (WO) and catalytic wet oxidation (CWO) processes (with the major focus being on WO and CWO, using air or oxygen as an oxidant). These aspects are (a) the fundamental chemistry of WO/CWO; (b) important aspects of catalysts, with regard to the CWO process; and (c) engineering aspects of the WO/CWO process. The applications of WO and CWO technology to treat industrial wastewater clearly illustrate the potential of these processes for treating wastewater from a wide number of industries. WO/CWO is a fertile area of research with significant scope for further research and innovation, particularly in the areas of catalyst development, the understanding of catalytic mechanisms, and the fundamental chemistry that occurs during WO/CWO. Selected examples of findings to date are discussed in this review.

Heterogeneous catalytic oxidation of phenol by in situ generated hydrogen peroxide applying novel catalytic membrane reactors

“…Also, various emphases have been made concerning H 2 O 2 dosage, pH, temperature, type of heterogeneous catalyst (e.g., nanoparticles, different metals including noble ones supported on different types of supports etc. [10]) to increase the oxidation efficiency. Nevertheless, AOPs based on hydrogen peroxide as oxidant are applied in a few specific cases due to the cost of the H 2 O 2 .…”

Chemical and toxicological evaluation of an emerging pollutant (enrofloxacin) by catalytic wet air oxidation and ozonation in aqueous solution

“…Generally, the use of high operation temperature would be helpful to the increase of chemical reaction rate due to the promotion of the speed of oxygen mass transfer and the decrease of the viscosity of the reaction solution as well (Kolaczkowski et al, 1999;Bhargava et al, 2006). The effect of reaction temperature ranging from 110°C to 180°C was investigated (data not shown).…”

Wet Air Oxidation of Benzene

“…The free radical mechanism has been proposed by many researchers [13,16,32,39,45,51,54,67]; however, only a few of them supported that by direct experimental evidence [6]. In the absence of initiators, free radicals are formed by the reaction of oxygen with the weakest C-H bonds of the oxidized organic compound as follows:…”

“…The co-oxidation is one of these methods. In this method the free radicals that are produced from an easily oxidizable compound are used to initiate the oxidation of more refractory compounds [6]. In his study of WO of sodium malonate in highly alkaline solution, Tardio [61] used this method to determine the presence of free radical intermediates.…”

“…This can 11 be attributed to the effect pH has on the chemical structure of the phenol, Le. the phenolate ion is highly reactive [6,36]. The change ofpH during the oxidation period has a noticeable effect on both the phenol decomposition and COD removal [39].…”