Development of polymeric nanocomposite membranes for effective elimination of pharmaceuticals from aqueous media
Funding period: 01.03.2023 – 31.08.2024
The European Union (EU) Directive 2013/39/ EU considers water contamination with pharmaceutical residues as an emerging environmental concern. The presence of pharmaceuticals and their primary active metabolites have been observed in rivers, streams, groundwater, and wastewater and drinking water. Pharmaceuticals are recognized as contaminants of emerging concern (CEC) because they are compounds of continuous use, recalcitrant to conventional processes, detected at very low concentrations (ng L−1 - μg L−1) in water bodies, their environmental effects are not completely known, and in most cases are unregulated in wastewaters.
Membranes that can separate pharmaceutical compounds based on molecular properties can revolutionize the water treatment industry. Hence, the aim of the project is to create new polymer nanocomposite membranes that are able to perform separations with the selectivity of emergency water contaminants while having a mechanical strength and productivity of state-of-the-art artificial membranes. Furthermore, the creation of such a polymer composition could radical improve the permeability and selectivity of commercially available membranes.
To achieve this aim the objects of research were acrylic aqueous dispersion, crosslinking agent and inorganic nanoparticles. For this, nanosized TiO2 and ZnO will be used as nanoparticles. TiO2 nanocomposite-based polymeric membranes have already been well-studied and reviewed [9]. Zinc oxide (ZnO) nanoparticles, with one-fourth of the cost of TiO2, present comparable physical and chemical properties with TiO2. Therefore, ZnO nanoparticles are believed to be a competitive alternative to TiO2 nanoparticles in the formation of antifouling organic–inorganic composite membranes [10].
Acrylate polymers will be used as a polymer matrix due to their properties. Main advantages of acrylic polymers are: the ability to allow for a quick polymerization on the surface while forming a crosslinked structure, low cost and environmental safety of polymer dispersions. Acrylic copolymers can be effective modifiers of the membrane surface for the sorption of pharmaceuticals. Many acrylic copolymers are actually polyelectrolytes that can form ions when exposed to an aqueous medium, causing significant volumetric swelling due to the formation of hydrogen bridges or covalent bonds [11]. A specifically developed polymer nanocomposition will be used for an improvement of the permeability and selectivity of commercially available membranes. In this context, the pore size distribution of the substrate surface should preferentially be sharp and free from large defects, so that the intrusion of coating solution can be prevented. In fact, the degree of porosity of the substrate should be sufficiently high so that the membrane resistance can mainly be controlled by the coated selective layer [12].
Three pharmaceuticals that planned to be studied in this research are metoprolol, ibuprofen and diclofenac. They are widely used but hard to remove from the environmental water as they have low removal efficiency. Therefore, they are frequently detected in surface water, groundwater and drinking water, and their concentration is relatively high. The maximum concentrations measured in water samples are for ibuprofen, 159 ng/l, for metoprolol 1000 ng/l and 54 ng/l for diclofenac. Furthermore, the three chosen pharmaceuticals have different molar masses and show different charges in aqueous solution.
Membrane structure will be correlated regarding the flux dynamics and selectivity of chosen pharmaceuticals. The reproducibility and comparability will be improved by controlling of the quantity of ingredients in polymer nanocomposition. Primary methods of membrane preparation will be focused on elucidating the role of roughness, surface charge, surface chemistry, crosslink density and monomer chemistry on the interfacial and internal dynamics of the membrane. An approach for synthesizing model crosslinked polymer nanocomposite membranes will be developed based on acrylic polymers and ZnO and TiO2 nanoparticles, enabling precise control over network structure, surface chemistry, residual charge, and roughness and film thickness. Nanoparticles surface will be functionalized in order to authorize an optimal dispersion in the polymer matrix. With this knowledge, the industry will get next-generation, energy-efficient, high-flux membranes with good selectivity to pharmaceuticals, as could be created new material with positive or negative charged active groups on the surface, that can easily catch opposite charged pharmaceuticals.