Optimization and mechanism of oily sludge treatment by a synergistic approach of high-speed stirring cleaning integrated with thermal-activated Na2S2O8 oxidation

Abstract

Oily sludge not only seriously pollutes the ecological environment, but also endangers human health. Additionally, the complex properties pose significant challenges in its treatment. The single technology has limited capacity and poor treatment effect. Consequently, the combined technology is being developed due to the exceptional treatment effect. Herein, a new combined technology was proposed to treat oily sludge, which combined high-speed stirring cleaning with thermal-activated Na₂S₂O₈ oxidation. The bulk of petroleum pollutants were efficiently removed by high-speed stirring cleaning firstly, and the residual petroleum pollutants were decomposed by thermal-activated Na₂S₂O₈. After treatment, the oil content of the oily sludge decreased from 13.81 % to 0.47 % with the removal rate of 96.6 % under the optimal conditions, which had reached the discharge and reuse standards. The high-speed stirring had remarkable removal effect on saturated hydrocarbons, aromatic hydrocarbons and resins. In addition to the three components mentioned above, thermal-activated Na₂S₂O₈ also had excellent removal effect on asphaltenes in the cleaned oily sludge based on the strong oxidation effect of SO₄⁻· and OH·. This work demonstrates a new method to treat oily sludge efficiently, which not only reduces the burden of petrochemical industries and provides support for their green development, but also has important scientific significance for environmental protection and environmental management.