Integration of natural deep eutectic solvent in a bulk liquid membrane system for tetracycline removal from wastewater

The presence of tetracycline (TC) in aquatic environments poses significant ecological and public health risks, requiring the development of effective and sustainable methods for its removal. This research details the selective extraction and removal of TC from wastewater using natural deep eutectic solvent (NADES) with a bulk liquid membrane (BLM). NADES was synthesized through mixing thymol (THY), a hydrogen-bond donor, and oleic acid (OA), a hydrogen-bond acceptor, and was further utilized as a green carrier in the BLM system. Extraction parameters, i.e., extraction time, NADES concentration, and mixing speed, were optimized via response surface methodology in order to maximize TC extraction and stripping efficiencies. The conductor-like screening model for real solvents (COSMO-RS) was also utilized for the verification of TC removal, as well as for characterizing the molecular interactions. Under the optimized conditions, the integrated NADES-BLM system attained notable TC extraction and stripping efficiencies of 79.4% and 78.5%, respectively. Moreover, the extraction efficiency was confirmed using COSMO-RS molecular interactions, which was investigated through sigma profile and a sigma potential between the TC molecules and the system phases. This research implies a novel green approach via utilizing NADES as a carrier in the BLM extraction system.