Liquid-liquid equilibrium for recovery of carboxylic acids from wastewater using green solvents

Abstract

Recently, the valorization of organic liquid residues from agroindustry processes to produce chemicals with high-added-value has been gaining worldwide prominence due to economic and environmental concerns. Vinasse, the residue from sugarcane ethanol plants, is characterized by negative environmental impact and the presence of high market value compounds (carboxylic acids: succinic, acetic and lactic) in concentrations of up to 5%, whose recovery can be precursors to the carboxylate platform of the biorefinery concept. The advantage of using vinasse as a raw material is efficient in resource terms and sustainable because it does not compete with food production, agricultural land or deforestation to grow biorefinery crops. Therefore, scientific and technological innovations are needed to use it as renewable resources of carboxylic acids and make it sustainable and economically viable. Liquid-liquid extraction using green solvents, protic ionic liquids (PILs) and deep eutectic solvents (DESs), as promising substitutes for volatile organic solvents may be an alternative to recover carboxylic acids from wastewater (Vinasse), however, for develop the separation process it is necessary a complete understanding of the interactions taking place, and ruling the liquid-liquid equilibrium of complex systems containing water, carboxylic acids, glycerol and green solvents. Considering their extractive properties, low cost, ease of synthesis, recyclability, low toxicity, biodegradability and capacity to form biphasic systems, PILs (hydrophobic and hydrophilic ammonium-based) and DESs will be studied to remove carboxylic acids. In this context, this project proposes: i) experimental evaluation of the extraction capacity (selectivity and partition coefficient) of PILs and DESs; ii) experimental determination of the liquid-liquid equilibrium (LLE) data of quinary mixtures involved in the extraction of carboxylic acids and thermodynamic modeling using the NRTL model or the CPA Equation of State; iii) evaluation of optimal conditions of LLE in real systems containing sugar¬¬¬cane vinasse from sugar-ethanol plant; iv) investigation of the effect of temperature, cations and anions structure, composition of the mixture, pH and addition of inorganic salts in the formation of biphasic systems and extraction efficiency; v) evaluation of technical and economic feasibility for acid recovery by computer simulation using the aspenONE® Engineering. (AU)