Supercritical Water Oxidation (SCWO) for Wastewater Treatment

Abstract

Water behaves as an acidic and alkaline precursor for acidic or basic reactions, since the formation of both H 3 O C and OH -ions takes place in accordance with the self-dissociation of water at near-critical and above supercritical (T c D 374 ı C, P c D 22.1 MPa) conditions. Therefore, supercritical water is considered both as a solvent for organic materials and as a reactant at processes such as the oxidative treatment of wastewaters, the gasification of aqueous organic solutions and the production of fine metal oxide particles. Supercritical water oxidation is a very efficient method for wastewater treatment, which is based on oxidation of organic compounds in aqueous media above critical temperature and pressure conditions of pure water.In this chapter, general information on supercritical water oxidation processes is given, effects of operational parameters such as temperature, pressure, reaction time, waste and oxidant concentration on waste treatment are discussed, and applied scientific methods and practical solutions to possible operational problems such as corrosion, salt deposition and carbonization are compiled in detail. Treatment of industrial wastewaters such as olive mill, textile dyehouse, cheese whey and commercial pesticide with high environmental hazard potential are subjected and evaluated in order to understand the effects of reactor temperature, organics and oxidant concentrations, residence time and reactor pressure. Hydrothermal degradation and oxidation kinetics of wastewater are stracked in terms of total organic carbon (TOC) and analyzed, followed by discussion of supercritical water oxidation rate models.

Investigation of Jatropha Oil Transesterification into Methyl Esters under Supercritical Methanol Environment using Advanced Heterogeneous Catalysts

“…The volume of activation (ΔV≠) within the reactor can be obtained by the partial derivatives with respect to pressure, where (ΔV≠) as shown in Equation (2) below represents a residual function between the partial volumes of the reactants and the transition state. Thus, the correlation between pressure and rate constant can be deduced [44] $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr \left( {{{\partial \left( {\ln k} \right)} \over {\partial P}}} \right)_T = - {{\Delta V^\# } \over {RT}}\hfill\cr}}$$$ …”

Functional Materials for Waste-to-Energy Processes in Supercritical Water

“…Oxygen is the most used oxidant agent in SCWO [90,92,[97][98][99][100][101], which is supplied to the system at various concentrations. Another oxidant used is H 2 O 2 [13,15,34,54,55,59,93,94,[102][103][104][105][106][107][108] which during the preheating decomposes and yield molecular oxygen [98,108].…”