Response surface methodology to optimize ultrasonic-assisted extraction of crude oil from oily sludge

Abstract

This study is the first to use a response surface method to optimize the main parameters of ultrasonic-assisted recovery of oil from oily sludge. The solvent with the highest oil recovery (xylene) and most suitable process (Ultrasonic Assisted Extraction) were first selected based on the highest oil recovery rate. Then, single-factor experiments were performed to determine the best parameter range of solvent sludge ratio, frequency, duration, and temperature. Box-Behnken response surface methodology was used to study the influence of each variable on oil recovery. Solvent sludge ratio, frequency, and duration were found to have significant effects. The model optimization results show that the best conditions for Ultrasonic Assisted Extraction are as follows: a solvent to sludge ratio of 7.56:1, frequency of 31.48 kHz, duration of 23.67 min, and temperature of 45.87 °C. Under optimum conditions, the oil recovery predicted by the model and the actual oil recovery were 87.21 and 83.77%, respectively. The relative error between the predicted and actual values was 3.44%. These results indicate that the model results are reliable. Finally, the characteristics of the recovered oil and residue were analyzed. This research provides the possibility to utilize difficult-to-handle crude oil tank bottom sludge.