Synthesis and Characterization of Silver Nanoparticles for the Preparation of Chitosan Pellets and Their Application in Industrial Wastewater Disinfection

Abstract

The use of silver nanoparticles (AgNPs) has become popular in several applications due to their bactericidal properties. In this sense, it is ideal that the AgNPs are incorporated into a matrix in order to minimize their release to the environment and to maintain their high reactivity. In view of these facts, the main goal of this work was to synthesize and characterize AgNPs, evaluating the influence of pH on the synthesis, for later incorporation into a chitosan polymeric matrix that will be used in the form of pellets for the disinfection of industrial wastewater. For this purpose, AgNPs were initially synthesized by a chemical route using silver nitrate, sodium borohydride and sodium citrate and then characterized by ultraviolet-visible spectroscopy, transmission electron microscopy and as a function of bacterial growth inhibition against Escherichia coli and Enterococcus faecalis. At the end of this procedure, AgNPs were incorporated in chitosan and the pellets formed were employed in the disinfection process, while assessing their bactericidal activity as well as the amount of silver leached. In general, the results showed that AgNPs synthesized at pH 10.0 were smaller (3.14 ± 0.54 nm) and presented greater dispersion than the AgNPs synthesized at other pH values. Furthermore, it was possible to observe a synergistic effect between chitosan and AgNPs and the chitosan pellets containing AgNPs proved to be effective in wastewater treatment, destroying Escherichia coli after 60 min of treatment. Finally, by considering the ease of application, the low environmental impact and the bactericidal action, it is concluded that the hybrid pellets developed in this work have great potential to be used as auxiliaries in wastewater treatment.