Assessment of ability of three chemical oxidants to remove hydrocarbons from soils polluted by Bonny Light crude oil.

Abstract

Three prominent hydrocarbon groups found in crude oil- Polycyclic Aromatic Hydrocarbon (PAH);Benzene,Toluene,Ethylbenzene and Xylene(BTEX) and Total Petroleum hydrocarbon(TPH) were used to study the ability of three chemical oxidants-Fenton’s reagent, Potassium permanganate, and Potassium persulfate to degrade hydrocarbons in crude oil inundated soils. This was done by spiking soil samples with Bonny light crude oil and subsequently treating the mixture with the different chemical oxidants at acidic, neutral and basic pH media for each of the oxidants. Oil extracts from the treated and untreated soil samples were later analyzed for the three hydrocarbon groups using a gas chromatograph (GC). Treatment with Fenton’s reagent proved very efficient in the removal of the hydrocarbons especially at the acidic pH with some components of TPH experiencing complete disappearance. Also the four ringed-PAHs were depleted more than the three ringed- ones at the indicated pHs. For the treatment with potassium persulfate, while the oxidant was good in the removal of BTEX at the different pHs, it was found to be very inefficient for the removal of PAHs. Generally, Four and five ringed–PAHs were degraded more than the three and two ringed-PAHs, an indication that degradation of PAHs by oxidants may be a function of hydrocarbon structure. Treatment with potassium permanganate was found to be pH dependent with most of the depletions occurring at acidic pH. Even though potassium permanganate was not as good as the other oxidants in the removal of aliphatic hydrocarbons(TPH), it was found to be effective in the removal of aromatic hydrocarbon(BTEX and PAH). Also the four ringed-PAHs such as pyrene, benzoanthracene, and chrysene were seriously attacked at all pHs. BTEX was also attacked more at acidic pH with above 90% removal at the acidic pH.