Cellulose acetate was selected as a cost-effective and market available bio-based polymer.
A wide range of cellulose acetate membranes, differing in pore sizes and pore size distribution, was achieved by optimization of the fabrication conditions without chemical or structural modifications. The basic fabrication was carried out using phase inversion of casted membranes, in which pure deionized water was used as a main coagulation medium. The speed of the film applicator and the thickness of the casted films were found to be important parameters to be controlled during the fabrication process. The produced membranes were porous in their upper and lower surfaces. The fabrication conditions were found also to have a significant effect on the cross-section morphology of the membranes, which were found to be typically anisotropic, with different pore shapes and sizes in a finger like pattern.
Further modifications to control the microscopic structure of the produced membranes were carried out by mixing the polymer solution with a water-soluble surface-active agent (surfactant) before the casting of the membrane. The produced membranes presented a sponge like structure instead of a finger like one, in addition to a more uniform pore size distribution.
Another modification was introduced by using a salt coagulation bath instead of the fresh water bath: the result was a reduction of the pore sizes of the produced membranes, which widened their filtration range (ultrafiltration, nanofiltration).
The previously mentioned modifications were also combined together, providing an enhanced membrane with small pore sizes and a narrower pore size distribution in an overall more homogeneous microscopic structure.
All the produced membranes were structurally characterized and investigated for their water permeability and organic dye removal efficiency (using representative models for organic water pollutants).
The optimized preparation conditions, chosen on the bases of the previous results, were then employed to prepare membranes containing photosensitizers (PSs). The PS was added to the polymer solution prior to proceed with the casting and phase inversion procedure. Several PSs, differing in structure and charge/polarity were tested in different loadings, and the obtained membranes were optically characterized by means of steady-state and time-resolved photophysical techniques. The singlet oxygen production capacity of the PSs embedded in the polymeric membranes was analysed by means of an innovative method that makes use of a colorimetric singlet oxygen trap in a solid-liquid interface setup.
All the modified membranes were structurally characterized and investigated for their water permeability.
The outcomes of the project have been presented at five national and international conferences. At least two papers will be shortly submitted. Participation of the ER and the Supervisor to the European Researchers’ Night event in 2019 in Bologna with a stand, presentations and activities allowed dissemination to the large public of the innovation brought by the use of polymeric membranes to desalinate and remove pollutants from water. Moreover, the ER has been invited to present the project results at the “Aquatech 2019” Exhibition in Amsterdam, with a lecture at the “Meet the Expert Stage” of the InnovationLab and a poster at the EU Innovation Project Pavillon. The latter exhibition is a unique event in Europe with a 100% focus on water (process, drinking and wastewater), with an estimation of 25,000 visitors from 140 countries and over 1000 exhibitors.
