"Joint laboratory on green separation processes for the wastewaters treatment and recovery of contaminating species". Rapp. Int. 01/2018

Description of the 1st year activity on "Joint laboratory on green separation processes for the wastewaters treatment and recovery of contaminating species". The activity was devoted to the development of asymmetric polymeric membranes for filtration/separation processes (MF, UF, NF).The main objective of the project consists into the realization of a joint research on sustainable and non-polluting separation techniques for the purification of industrial waste-waters with recovery of contaminants species (metal ions, etc.) using membrane systems of different type, morphology and properties (solid, liquid membranes, ATPS, ILs). In this first year of the project, starting from the experience of CNR- ITAE (Italy) and the University of Guanajuato partner (UGto., Mexico) on polymers, their functionalization, solid membranes development (Italy), biphasic liquid systems, separation/filtration methods (Mexico), the starting point was individuated into the development of asymmetric membranes based on polysulfone (PSF), named AM-PSF, particularly suitable for industrial grade wastewaters purification applications. For this aim, the definition of the following intermediate objectives was pursued: -state of the art on materials and methods; -preparation procedure of the asymmetric PSF membranes (AM-PSF) with suitable morphology and pore size control (using SEM and BET) to determine the selective capacity of the first prototypes of membranes; -synthesis parameters for membranes manufacturing determining the AM-PSF morphology; -experimental operative conditions for membranes manufacturing; -the role of additives/surfactants to be added to the polymer matrix in order to improve the hydrophilic properties, morphology of the cross section and water permeability behaviour; -characterization of the developed AM-PSF membranes in terms of XRD, TG-DSC, water retention, dimensional analysis, mechanical properties by dynamo mechanical analysis (DMA) for glass transition (Tg) determination, cross-section and surface SEM, surface area and pore-size distribution by BET device (Itae); contact angle, permeability tests to water flow (UGto.); zeta-potential and IR measurements (UGto., in progress). As required by the project, these measurements were carried out jointly performed by both work teams. The starting polymer (PSF), its solvent (DMAc), the preparation procedure (phase inversion method by non-solvent coagulation bath technique) and casting method (doctor-blade) were defined. Particularly, four parameters determining the morphology were evaluated and varied, here following listed: concentration of the starting PSF solution (5-18wt.%), non-solvent (H2O, EtOH, their 1:1 mixture), "de-mixing time" (Dt) into non-solvent medium generating the membrane formation (20, 600s), two different concentrations of surfactant (1:1 and 1:2 PSF/P123 ratios). P-123 is well known due its ability to supply hydrophilicity to the membranes. Through a standardised procedure, eleven membrane samples (PSF2-1 to PSF2-11) were synthesised varying the four investigated parameters. The membranes were jointly characterised from two research teams in terms of XRD, TGA-DSC, water retention and dimensional analysis @rT and 60°C into three spatial directions, DMA, BET, cross-section and surface SEM (Itae); contact angle, permeability tests (UGto.); Z-potential and IR measurements (UGto.) are, actually, in progress. In particular, the different characterisation techniques have been devoted to the individuation of membranes morphology, to goodness of the manufacturing, the asymmetry definition into the transversal dimension of membranes, to the size, shape and pores/channels distribution, surface porosity in order to identify the characteristics suitable for the different processes (MF, UF, NF) that the partners will intend to adopt for final aims of the project. The characterisation results were jointly evaluated, crossed between them reaching the first conclusions, here following briefly summarised: -miscibility and fast solvent/non-solvent exchange guarantee the correct "finger-like morphology"; -the most performing asymmetric membranes were obtained when lower de-mixing times (Dt) and water as a non-solvent are used (PSF2-3 and PSF2-11); -mesoporous membranes (2nm<pores<50nm) obtained with CA<90°C (hydrophilic character); -a good trend (permeability) obtained in terms of Darcy's law for some of the samples; -asymmetry with "finger-like morphology" obtained and determining parameters identified; -surface porosity (500nm-2micron) for different samples with channels of about 1-2 micron obtained; -two membranes identified as the best prototypes to be further optimized. Crossing permeabilty, CA together to BET and SEM results, PSF2-3 sample (without surfactant) and PSF 2-11 (with surfactant) seem good candidates for final application. It's surely necessary to improve the membranes manufacturing and reduce the pores and channels size as well as to better connect the synthesis parameters to the manufacturing quality of the corresponding membranes in order to select the optimal membrane, but, in any case, important starting points for 2nd year activity were identified. Dissemination of results (2017), expected experimental activity (2018), necessary experimental corrective actions, expected results (2018), expected dissemination results (2018) are in it described.