Contaminated drinking water is the leading cause of diseases such as diarrhea, typhoid fever, hepatitis A and E, poliomyelitis, and cholera. The main objective of this project was the development of PVA-based hydrogels loaded with silver nanoparticles (Ag-NPs) synthesized through a green synthesis process, with biocidal activity for the treatment of contaminated water.
To achieve this objective, silver nanoparticles were synthesized through the reduction of silver nitrate (AgNO₃) using fungal exudates obtained from Macrophomina phaseolina, Trichoderma harzianum, and Penicillium bilaiae. The process began with the cultivation of these fungi on Petri dishes with suitable culture medium, incubated at 28ºC. The fungal exudate, which contains reducing enzymes, was then extracted by agitation in liquid medium at 28ºC for 3 days. This exudate was used to reduce AgNO₃ to silver nanoparticles in a controlled process at 28ºC and in darkness, with constant agitation.
Subsequently, the exudates were centrifuged at 10,000 rpm to remove organic compounds, resulting in a suspension of clean silver nanoparticles. These nanoparticles were concentrated and weighed to be used in the formulation of the hydrogels. Starch was used in some cases to stabilize the nanoparticles during synthesis. The Ag-NPSs were characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS), and biocidal capacity tests in diffusion on culture medium.
The procedure for obtaining PVA hydrogels involved dissolving the polymers in distilled water as the solvent. The solutions were poured into suitable molds, such as Petri dishes, to apply the corresponding characterization techniques. To obtain stable hydrogels with a proper structure, the samples were subjected to several freeze-thaw cycles at -20°C and room temperature (~25°C). Between 2 and 8 freeze-thaw cycles were performed to ensure the formation of a porous matrix with a regular structure. The characterization techniques employed included scanning electron microscopy (SEM) to observe the morphology of the hydrogels, rheological analysis to evaluate the mechanical properties, and gravimetric analysis to study the swelling behavior of the hydrogels.
The successful optimization of Ag-NP synthesis and PVA hydrogels allowed for the advancement in material production, considering their properties, functionality, and the inputs used. The next stage will focus on the production and characterization of PVA hydrogels loaded with different concentrations of Ag-NPs, aiming to evaluate their potential for water disinfection.