Diclofenac recovery by means of using Emulsion Liquid Membranes: A possible role of surfactant in the mass transfer process

Emulsion Liquid Membranes (ELM) are a useful method for drug extraction in aqueous solution, as they allow their recovery in a highly concentrated acceptor phase after passing through a membrane phase with a high surface area. The success of this process depends on system formulation and operation conditions. One of the most important aspects in the formulation is the addition of a surfactant that stabilizes the system, which can also participate in the mass transfer process. Recently, resistance to mass transfer caused by the use of polymeric surfactants, such as Abil® EM 90, has been reported. To verify this phenomenon observed in previous studies, the effect of various factors on the recovery of diclofenac (DCF) dissolved in an aqueous medium was analyzed using the ELM technique. The study concluded that using a membrane consisting of Abil® EM 90 (2 % w/V), trioctylamine (5 % w/V), and dodecane, along with a stripping phase formed by NaOH (0.10 mol/L), results in successful DCF removal. When emulsified at 15,000 rpm for 10 minutes at room temperature, it is possible to remove over 99 % of DCF after 15 minutes and recover 18.45 % after 30 min. Furthermore, it was determined that the action of the surfactant is the main cause of the resistance to the passage of DCF to the internal phase and its retention in the organic phase, as had already been observed. This is probably due to strong intermolecular interactions between Abil ® EM 90 and DCF and the formation of a complex and stable interfacial structure, similar to a hydrated bilayer, which favors the rigidity of the interface and keeps the drug trapped. A better understanding of the role surfactants play in the system is essential for the future design of more efficient and stable ELMs. This knowledge will enable the adaptation of the technology to a wider range of processes, including drug recovery. As a result, the maximum benefits of this technology can be fully realized.