Introducing Reverse Osmosis and Membrane Distillation in the Recovery Process of N-Methylmorpholine N-Oxide in Cellulose Fiber Production

This study serves as a proof of concept for the evaluation of two membrane technologies, reverse osmosis combined with membrane distillation, for the recovery of N-methylmorpholine N-oxide (NMMO) and water from generated wastewater by the textile manufacturing “Lyocell process”. This method utilizes NMMO to dissolve cellulose for the production of cellulosic yarn, resulting in wastewater that contains 1–2 %w/w NMMO. After an initial pretreatment to remove suspended solids, followed by a mixed ion-exchange resin, the stream was fed into a reverse osmosis membrane unit, concentrating the solution to approximately 10 %w/w NMMO. Following this step, the RO concentrate was introduced to a DCMD setup equipped with a PTFE microporous membrane, achieving a final concentration of a 70.5 %w/w NMMO aqueous solution, which is considered suitable for reuse. The main contribution of the present study is to establish, in principle, that the newly proposed method can be a modular and scalable alternative to the dominant multi-stage evaporation technologies.