Synergistic effect of surfactant and alkali on the treatment of oil sludge

The oil sludge is considered as a hazardous waste, the improper disposal or insufficient treatment can pose a major problem to the oil production, transportation and processing processes, and may result in serious environmental concerns and human health risks. In the present study, washing treatment with a cleaning solution containing surfactant and alkali was investigated to remove the residual oil from the oil sludge obtained from Tahe Oilfield. The effects of the dosage of surfactant, cleaning temperature, stirring rate, stirring time and liquid-solid ratio on the performance in residual oil removing were analyzed. Sodium nonylphenol polyoxyethylene ether sulfate (AEOS) and alkali were used as the cleaning agents. The results show that the content of the residual oil in the sludge could be lowered from 14.3 wt% to 0.9 wt% after being washed twice under the optimum operation conditions with a 0.6 wt% AEOS and 3 wt% KOH solution for 30 min at 80 °C, a stirring rate of 210 rpm and a liquid-solid ratio of 3:1. Thermogravimetric (TGA) and infrared analyses confirmed that the oil components in the oil sludge can be mostly removed.