Green synthesis of silver nanoparticles using an extract of Ives cultivar (Vitis labrusca) pomace: Characterization and application in wastewater disinfection

Abstract

Traditional methods for synthesizing metallic nanoparticles include the use of toxic chemicals, which can have negative impacts on the environment and human health. A safer alternative to produce these nanomaterials is based on the concept of Green Chemistry, which uses less harmful chemicals from renewable sources. In this work, we describe a specific approach for the green synthesis of silver nanoparticles (AgNPs) using the extract of Ives cultivar (Vitis labrusca) pomace, their characterization, and their immobilization in a polymer matrix of chitosan aiming the disinfection of a raw wastewater sample. The influence of some experimental parameters on synthesis such as pH, stabilization time as well as the temperature has been investigated. The grape pomace extract was initially characterized regarding its content of phenolic compounds and then used as stabilizing-reducing agent. The obtained AgNPs were analyzed by ultraviolet-visible spectroscopy, transmission electron microscopy, zeta potential, scanning electron microscopy coupled with energy dispersive spectroscopy, and raman spectroscopy. In general, the AgNPs were spherical in shape and very stable. Aiming to explain the reaction, we also proposed a mechanism of formation of AgNPs based on gallic acid molecule. Concerning the antimicrobial properties, the results demonstrated the synergistic activity of chitosan-AgNPs pellets against Gram-positive and Gram-negative bacteria. Additionally, these materials led to a reduction of 47% of the bacterial count of Escherichia coli on the disinfection of the wastewater. Finally, it was concluded that the extract of Ives cultivar pomace is capable of producing stable AgNPs that can be used as auxiliaries in wastewater disinfection.