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Chemical Oxidation Services
Oxidation processes can be used to transform organic contaminants into less toxic and less mobile forms, with complete reactions producing carbon dioxide and water. They are referred to as `redox reactions`, as the oxidising agent gains electrons (reduced valence state-reduction) while the contaminant loses electrons (increased valence state-oxidation). This electron exchange breaks carbon bonds creating new smaller compounds. Oxidants can also be used for iron and chromium precipitation and the destruction of cyanides and sulphides.
The most commonly used oxidising agents are hydrogen peroxide (H2O2), sodium persulphate (S2O8) and potassium permanganate (KMnO4). Many redox reactions require chemical additions, such as pH alterations, or the presence of catalysts (Fentons Reagent combines iron with hydrogen peroxide) to economically facilitate the required reaction. Therefore, for successful applications of oxidation techniques, an understanding of chemical kinetics and the thermodynamic potential of the reactions is essential.
A number of parameters can effect the redox reactions, such as soil organic matter, pH, existing redox conditions, nature and extent of contamination, and carbonate/bicarbonate concentrations. Therefore, as an important part of the design process, HBR undertake laboratory treatability studies to establish optimum conditions the reactions to take place and the existing oxidant demand of the soils and groundwater.
HBR apply the process either in-situ, by introducing oxidants into the subsurface with gravity wells or injection methods or ex-situ by soil mixing or groundwater circulation systems. For ex-situ soil applications, HBR`s mixing plants incorporate feed systems, which are suitably resistant to the corrosive nature of oxidizing agents and capable of the control and collection of off-gasses produced during reactions.
Contaminants that can be typically treated include:
- petroleum, diesel, MTBE, BTEX
- chlorinated solvents
- pesticides and herbicides
- carbon disulphide
- polychlorinated byphenyls (PCB`s)
- cyanides and sulphides