Síntese verde de nanopartículas de prata a partir de flores de Manacá-da-Serra e incorporação em uma matriz polimérica biodegradável de quitosana para o tratamento terciário de efluentes industriais

Abstract

The increasing generation of industrial wastewater, combined with intensive water use and climate change, represents an environmental challenge, contributing to water scarcity and contamination of receiving bodies. Conventional treatment methods, such as chlorination, ozonation, and ultraviolet radiation, present limitations, including high costs, the formation of toxic by-products, and low sustainability. In this context, metallic nanoparticles (NPs), particularly silver nanoparticles (AgNPs) obtained through green routes, have shown promise due to their antimicrobial potential. Considering this scenario, this study aimed to synthesize AgNPs using an aqueous extract of Manacá-da-Serra (Pleroma sellowianum) flowers and to incorporate them into a biodegradable chitosan polymer matrix, with the purpose of obtaining composites applicable to tertiary wastewater treatment. The floral extract, rich in phenolic compounds, enabled an efficient green synthesis at pH 12.0, 25 °C, and using a 0.01 mol L-1 AgNO3, resulting in spherical AgNPs (20-30 nm) with moderate colloidal stability (ZP= -14 mV) and high antimicrobial activity (MIC of 5 uL mL-1 against E. coli and S. aureus). Characterization of the composite (FEG-SEM/EDS, FTIR, and TGA) confirmed successful integration of AgNPs into the polymeric matrix, revealing homogeneous distribution, specific molecular interactions, and enhanced thermal stability. Antimicrobial assays showed inhibition halos of 11 ± 1 mm for S. aureus and 9 ± 1 mm for E. coli. In disinfection tests, the composite promoted a reduction greater than 99.9% of total coliforms within 180 min, with silver leaching of only 0.01 mg L-1, a value within regulatory limits. These results highlight the synergistic effect between chitosan and green-synthesized AgNPs, confirming the potential of Manacá-da-Serra for NP synthesis and the applicability of the composite as a safe, efficient, and sustainable solution for the disinfection of industrial wastewater. [resumo fornecido pelo autor]