Catalytic and Noncatalytic Wet Oxidation

Abstract

The wet oxidation of organic compounds composed only of C, H, and O, dyes, amides, and water-soluble polymers is discussed to clarify the basic nature of this process. The reactivity of the organic compounds composed of C, H, and O, dyes, and some amides was correlated well with their carbon content in the molecule (C/MW) or carbon content in their skeletal structure (C/MW‘). This C/MW index can be applied to roughly estimate the behavior of wastewaters containing various organic compounds. Polymers are easily decomposed by the wet oxidation because they can undergo intramolecular hydrogen abstraction in the chain-propagation step. The biodegradability of polymers and amides was improved by wet oxidation treatment, indicating an asset of this process. The function of homogeneous copper salts and the effect of hydrogen peroxide are discussed. The action of Co/Bi composite oxide designed for the treatment of refractory carboxylic acids, Mn/Ce composite oxide for ammonia and other organic compounds, and Ru/CeO2 catalyst for the decomposition of PEG, formaldehyde, etc., is explained. The high potential of Ru and CeO2 as active catalyst components is emphasized.

Carbon materials and catalytic wet air oxidation of organic pollutants in wastewater

“…WAO performance can be improved by the addition of homogeneous [5,6] or heterogeneous [4] catalysts at subcritical conditions or at severe 'supercritical' operating conditions [7,8]. Alternatively, low temperature oxidation processes replace oxygen by stronger oxidants such as O 3 [9,10] or H 2 O 2 [9,11,12] in combination with an energy input to form reactive OH-radicals [13,14].…”

“…Alternatively, low temperature oxidation processes replace oxygen by stronger oxidants such as O 3 [9,10] or H 2 O 2 [9,11,12] in combination with an energy input to form reactive OH-radicals [13,14]. Several reviews on catalytic and non-catalytic WAO [4,5,[15][16][17][18][19], supercritical water oxidation (SCWO) [7,8,[20][21][22] and advanced oxidation processes (AOP) [23][24][25] are now available in literature.…”

“…For wastewater containing low to medium organic concentration, batch and continuous CWAO yielded satisfactory results in laboratory studies [4,5,[15][16][17][18][19]. Relatively mild operating conditions of temperature and pressure lead to substantially lower investment and operation cost.…”

Wet air oxidation of nitrobenzene enhanced by phenol

“…However, to overcome the problem of recovery/removal of the toxic catalysts from the final effluent, heterogeneous catalysts such as transition metal oxides, c-alumina supported with CuO, copper, manganese, and lanthanum oxides on a 0045-6535/$ -see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi: 10.1016/j.chemosphere.2004.11.004 zinc aluminate spinel, and multicomponent oxides CuO AE ZnO, Ru/Ce, Mn/Ce and Co/Bi have been developed (Imamura, 1999).…”

Wet Air Oxidation of Benzene

“…The wet air oxidation of acetic acid was studied by Merchant [46] and it was found that only 7% COD reduction was achieved at 275°C in 5 hours. The WAO of both formic acid and acetic acid were studied by Imamura [24] at 220°C and partial oxygen pressure of 3 MPa in 2 hours. 99% TOC reduction and 100%…”