In the first stage, as part of Activity Act.1.1 (WP1) of the POLHSYS project, seven hydrophobic fibrous materials based on PVDF-HFP copolymer and various fillers (CoFe2O4 spinel ferrite, graphite, and nanoclay) were prepared using the electrospinning method. The electrospun materials (Fig.1) obtained were characterized by advanced instrumental analysis techniques: SEM, EDAX, VSM, FTIR, and mechanical tests. The porosities and water contact angles were also determined. The oily liquids (hydrophobic pollutants) used in the sorption tests were characterized for density, viscosity, and surface tension. The sorption capacities of the electrospun materials for collecting oily liquids were evaluated.
Fig. 1. SEM micrographs of fibrous membranes produced by the electrospinning technique: (a) PVDF-HFP, (b) PVDF-HFP/CoFe2O4, (c) PVDF-HFP/CoFe2O4/graphite, (d) PVDF-HFP/CoFe2O4/ nanoclay.
Within the framework of Activity Act.1.2 (WP2), three porous membranes based on polyetherimide (PEId, main polymer), polyvinylpyrrolidone (PVP, porogen), and kaolin-type nano-clay (filler) were obtained by the phase-inversion method. The membranes were characterized in terms of mechanical properties, IR spectra, water contact angle, porosity, and water permeation tests. Activity Act.1.3 (WP3) involved the synthesis, morphological and structural characterization, and testing of nanostructured inorganic photocatalysts based on cerium-doped zinc oxide (ZnO:Ce) and dysprosium-doped titanium oxide (TiO2:Dy). Herein, the effect of dopant concentration and sintering temperature on the photodegradation efficiency of recalcitrant organic pollutants was investigated. Supporting activity Act.1.4 (WP4) involved nonlinear regression modeling of the kinetic curves of photodegradation of organic pollutants and the determination of rate constants. For the TiO2:Dy/Ciprofloxacin system (Fig.2), the optimal operating conditions were established through design of experiments (DoE) and a statistical modeling approach relying on the response surface methodology.
Fig. 2. Application of the TiO₂:Dy photocatalyst for the degradation of ciprofloxacin.
In the second stage, under activity Act.2.1 (WP1), a systematic study was undertaken involving the preparation of 17 hydrophobic copolymer-based fibrous composites, using a design of experiments (DoE) approach. The composites were produced by electrospinning, with the amounts of copolymer and fillers varied simultaneously according to the experimental design. The resulting materials were characterized and evaluated for their sorption performance toward petroleum products. Statistical analysis of the SEM micrographs revealed the distributions of both the electrospun ultrathin fiber diameters and the interfibrillar distances within the resulting composites. Furthermore, the composites exhibited both hydrophobic and magnetic properties. For activity Act.2.2 (WP2), a factorial design was applied to prepare eight polyetherimide-based porous membranes via phase inversion, varying six manufacturing process factors. The resulting membranes exhibited asymmetric porosity and hydrophilic character. The optimal membrane was identified using the desirability function approach, establishing a balance between permeate flux and the efficiency of natural organic matter removal from aqueous solutions. Likewise, within WP2, the adsorption kinetics of the anionic dye MO1 onto the surface of montmorillonite (MMT) modified with trimethyl-stearyl-ammonium (TmSA) were investigated. Activity Act.2.3 (WP3) in the second stage focused on the synthesis, morphological and structural characterization, and testing of samarium-doped zinc oxide nanostructured photocatalysts, investigating the effect of the dopant amount on the photodegradation efficiency of dyes. Support activity Act.2.4 (WP4) focused on modeling the adsorption and photodegradation kinetics of organic pollutants using nonlinear regression, including the estimation of rate constants. For the MMT-TmSA/MO1 system (Fig. 3), the adsorption process was modeled and optimized via the RSM methodology, while intermolecular interactions were investigated through molecular modeling.
Fig. 3. Application of MMT-TmSA organoclay adsorbent for MO1 dye removal.
The cognitive impact arising from the performed activities of the project is related, on the one hand, to the elucidation of the relationships between physicochemical properties and sorption capacity in the development of composite materials for oily liquid sorption and, on the other hand, to the exploration of the effects of lanthanide doping on semiconducting oxides intended for photocatalytic applications. From a socio-economic standpoint, the activities developed to date show potential for proposing more performant materials for water purification; the results are currently under evaluation for their applicability and future valorization. The undertaken activities brought together experienced and early-career researchers with complementary skills and expertise, contributing to the formation of a highly competent and ambitious research team.
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