Deep eutectic solvents (DESs)- a New Era in Membranes Preparation

In the last few decades, the concept of ''Green Chemistry'', ''Green Engineering'' and ''Circular Economy'' are often used to describe the development of new technologies and products that have la lower environmental impact and are based on renewable resources. Membrane Science can be identified as a "Green Technology" that offers a lot of advantages such as low cost, energy recovery, possibility of integration with conventional technologies, safety and flexible scaling up [1]. At the same time, the use of well-known toxic solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-methyl-2-pyrrolidone (NMP) and tetrahydrofuran (THF) for the membrane preparation represents a severe problem for both human health and environment. Recently, new alternative solvents attracted a great interest in accordance to the fifth principle of "Green Chemistry" stating that "the use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used" [2]. In this work, for the first time, deep eutectic solvents (DES) were explored as novel alternative solvents for the preparation of membranes thanks to their favourable green properties, such as low flammability, low or absent toxicity, high recycle and reuse capability, chemical and thermal stability, non-flammability, high dissolution ability [3].The research focuses on the possibility of using DESs for solubilizing the most used polymers such as polyvinylidene fluoride (PVDF, Solef® 6012, Solvay Specialty Polymer, Italy), polyethersulfone (PES, Solvay Specialty Polymer, Italy) and polyacrylonitrile (PAN) for the development of porous membranes via non solvent induced phase inversion (NIPS). The effect of the selected DES solvents on the morphology and performance of prepared membranes was investigated. The results confirm the possibility to obtain membranes for microfiltration (MF) and ultrafiltration (UF) applications.