Extraction of salicylic acid from wastewater using ionic liquid-based green emulsion liquid membrane: COSMO-RS prediction and experimental verification

Abstract

Salicylic acid is an important component in cosmetics and skincare products and is widely found in aqueous streams as waste material. The present study reported the extraction of salicylic acid from wastewaters using a new technique termed as ‘ionic liquid-based emulsion liquid membrane’ (IL-ELM). Ionic liquids were introduced as carriers in IL-ELMs to enhance the emulsion stability. COSMO-RS simulation tool was employed to identify the effective IL among the 45 ILs composed of different cations and anions. It was found that IL [TMAm][Cl] (tetramethylammonium chloride) was found to be the most effective extracting agent for the extraction of salicylic acid that possesses the higher capacity, selectivity and lower activity coefficient towards analyte molecules. The COSMO-RS prediction results were in good agreement with the experimental data. Furthermore, this study optimized several operating conditions, including surfactant concentration, stripping agent concentration, IL concentration, emulsification time, homogenization speed and extraction time that affected the extraction efficiency. Overall, the proposed IL-ELM showed 90.04% extraction efficiency for salicylic acid under the optimized conditions of 0.005 M NaOH as stripping agent, 1.0 wt% Span-20 as emulsifier, 0.2 wt% [TMAm][Cl], 4000 rpm homogenization speed, 3:1 treat ratio and 25 min of extraction time.