Difficult separation of oil−solid phase and high fine content of the recovered oil were two problems in the treatment of oily sludge from the tank bottom by the hot water-based extraction process. To solve the problems, one technology with "ball milling + ozone-catalyzed oxidation" as the core was studied, and the process parameters of ball milling and ozone-catalyzed oxidation were respectively optimized. After ball milling treatment, the oil content of dry oily sludge decreased from 33.9 to 10.2%. Then, an ozone catalytic oxidation treatment technology with aluminum ore as the catalyst was developed to further treat this stubborn oily sludge. Under the optimal conditions, the oil content of oily sludge could be further reduced to 0.28%, which met the treatment and disposal requirements stipulated in GB4284-2018. For further research on the contribution of the catalyst to the ozone catalytic oxidation system, the reaction activation energy and reaction rates of ozone oxidation and ozone catalytic oxidation were compared from the perspective of kinetics. The results showed that, with the catalyst addition, the reaction rate constants increased about three times and the reaction activation energy reduced 82.26%, which showed the effectiveness of the catalyst on the kinetics quantitatively. The combined process with "ball milling + ozone-catalyzed oxidation" as the core can solve the two problems in the treatment of oily sludge from the tank bottom by hot water-based extraction and provides a reference for the harmless and resourceful treatment of oily sludge from the tank bottom.

The properties including oil content, density, high viscosity, and corresponding components were analyzed in the samples of the oil-contaminated soil from one country in the Middle East; also, chemical composition of the solids in the oil-contaminated soil was analyzed by using the X-ray deflection structure analysis method. Characterization results of obtained samples showed the similarities of the oil-contaminated soil with the Canadian oil sand, and then the hot water-based extraction technology that is successfully used in commercial oil sand operation in Canada was fine-tuned to be a novel cleaning technology to clean up oil-contaminated soils. Then, the different cleaning agents, cleaning agent dosage, liquid–solid ratio, temperature, stirring rate, and time as the primary parameters that would affect the cleaning effect were all optimized. Under the optimum conditions, the oil removal results demonstrated that oil removal by this technology was very effective; the oil content of the cleaned soils could be reduced to less than 0.3 wt %, which met the treatment and disposal requirements stipulated in GB4284-2018, and the reaction process was theoretically analyzed by a kinetic method. The oil phase obtained by water washing after further solvent purification treatment has a higher recycling value. This study provides a cost-effective way to recover and deal with the oil-contaminated soil from the perspective of economic efficiency and environmental protection.

Oil-contaminated soil of a dry oil lake which was taken from Kuwait included two types of samples, namely, oil sludge and oil soil. Through the analysis of physical and chemical properties, the results show that both of them with high oil content had a certain recycling value combined with a poor dispersion effect in water. Then, a new process based on countercurrent extraction was designed to treat the oil-contaminated soil. Through a series of laboratory-scale experiments, the optimal processing conditions were found, in which the oil content of tails was lower than 0.5% and the oil obtained from the organic phase by evaporating could be reused. Furthermore, the reaction conformed to the kinetic characteristics of the quasi-first-order reaction; the activation energy (E a) was 27.425 kJ/mol (oil sludge) and 51.839 kJ/mol (oil soil), and the extraction mechanism of the compound extractant was expounded. The proposed countercurrent extraction method shows well performance to recover oil from oil-contaminated soil which is economically efficient and supports environmental protection.

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