Optimizing ultrasonic-assisted liquid-liquid extraction for an efficient removal of methylene blue dye from wastewater

Liquid-liquid extraction is a fundamental technique used for the removal and recovery of organic compounds from aqueous solutions. This study investigates the efficiency of salicylic acid as an extractant for methylene blue (MB) dye, focusing on both conventional and ultrasonic-assisted extraction methods. At a natural pH and for a load at 25 ppm in BM and an aqueous phase/organic phase W/O ratio of 1/1, the results show that salicylic acid can extract over 67.5% of MB dye within 7 min, with maximum efficiency achieved at a concentration of 0.075 mol L-1 and a stirring speed of 150 rpm. Additionally, low-frequency ultrasonic irradiation significantly enhances extraction efficiency, achieving over 90.2% due to improved mass transfer between immiscible phases. To further optimize the extraction process, a second-order polynomial model was developed, resulting in a maximum extraction yield of 90.36% in the absence of ultrasonic irradiation. The optimal values for the variables were determined to be a salicylic acid concentration of 0.1 mol L-1, an W/O ratio of 0.75, and a stirring speed of 75 rpm. These findings underscore the potential of ultrasonic-assisted extraction for more improving the removal efficiency of organic pollutants in wastewater treatment.