Treatment of heavy, long-chain petroleum-hydrocarbon impacted soils using chemical oxidation

Chemical oxidation is a promising approach for in situ or ex situ treatment of heavy, long-chain (C₁₂ - C₄₀) petroleum-hydrocarbon impacted soils. Aqueous chemical oxidation treatments (sodium percarbonate, hydrogen peroxide, sodium persulfate, chlorine dioxide, sodium permanganate, and ozone) using two oxidant concentrations were tested in batch tests on soils containing C₁₂ - C₄₀ total petroleum hydrocarbon (TPH) concentrations of 1.6 and 2.0% weight/weight (w/w) resulting in TPH reductions from 20 to 90%. Gas chromatography with flame ionization detector (GC-FID) chromatograms for hydrocarbons were obtained and presented as chain-length fractions. Sodium percarbonate and hydrogen peroxide achieved the highest TPH reduction. There was little difference between 1 and 10% weight/volume (w/v) for all oxidant doses on TPH removal. Soluble organics in the liquid supernatants after oxidation of the TPH-containing soils were characterized by TPH analysis and excitation-emission matrix fluorescence spectroscopy. Benchmark Soil 1 (BM1) containing 1.6% w/w TPH was more susceptible to solubilization than Benchmark Soil 2 (BM2, containing 2.0% w/w TPH) according to TPH removal data and posttreatment supernatant quality. Some of the oxidants achieving the greater reduction in soil TPH resulted in higher aqueous phase organic content, based upon TPH measurements and fluorescence spectroscopy. Persulfate achieved intermediate TPH reduction in soil, but the separated aqueous phase had lower carbon content. This work showed chemical oxidation can transform and mobilize heavy hydrocarbons in soil and can produce more water-soluble organics. Chemical oxidation alone may achieve regulated TPH soil concentration, or it could also be used in conjunction with other technologies such as bioremediation or surfactant washing to further reduce TPH in soil.