Membrane Processes Based on Complexation Reactions of Pollutants as Sustainable Wastewater Treatments

Water is today considered to be a vital and limited resource due to industrialdevelopment and population growth. Developing appropriate water treatment techniques,to ensure a sustainable management, represents a key point in the worldwide strategies. Byremoving both organic and inorganic species using techniques based on couplingmembrane processes and appropriate complexing agents to bind pollutants are veryimportant alternatives to classical separation processes in water treatment. SupportedLiquid Membrane (SLM) and Complexation Ultrafiltration (CP-UF) based processes meetthe sustainability criteria because they require low amounts of energy compared topressure driven membrane processes, low amounts of complexing agents and they allowrecovery of water and some pollutants (e.g., metals). A more interesting process, on theapplication point of view, is the Stagnant Sandwich Liquid Membrane (SSwLM),introduced as SLM implementation. It has been studied in the separation of the druggemfibrozil (GEM) and of copper(II) as organic and inorganic pollutants in water.Obtained results showed in both cases the higher efficiency of SSwLM with respect to theSLM system configuration. Indeed higher stability (335.5 vs. 23.5 hours for GEM; 182.7vs. 49.2 for copper(II)) and higher fluxes (0.662 vs. 0.302 mmol·h-1·m-2 for GEM; 43.3 vs.31.0 for copper(II)) were obtained by using the SSwLM. Concerning the CP-UF process,its feasibility was studied in the separation of metals from waters (e.g., from soil washing),giving particular attention to process sustainability such as water and polymer recycle, freemetal and water recovery. The selectivity of the CP-UF process was also validated in theseparate removal of copper(II) and nickel(II) both contained in synthetic and real aqueous effluents. Thus, complexation reactions involved in the SSwLM and the CP-UF processesplay a key role to meet the sustainability criteria.