Study of the Stabilizing Agent Influence in the Catalytic Degradation of Methylene Blue using Silver Nanoparticles

Water shortage is currently a serious problem that was aggravated by the contamination of rivers and lakes by industrial waste, such as organic dyes. Inadequate or inexistent treatment allows the contaminants to disseminate through rivers and seas, impacting Human health and aquatic biodiversity. One of the most used industrial dyes is methylene blue (MB), which is toxic in high doses and prevents solar radiation to penetrate the water's surface. To reduce water contamination and environmental impact, the organic dyes could be degraded, generating less harmful and colourless substances. The use of nanoparticles as catalysts has been shown potential since they have excellent catalytic activity due to their high surface-to-volume ratio. In this context, this work aims to prepare silver nanoparticles (AgNPs) and use them in the degradation of MB. AgNPs were prepared in water by the chemical reduction strategy, using NaBH4 as the reducing agent. Four different organic stabilizers were used: sodium citrate, ascorbic acid, polyvinylpyrrolidone, and poly(vinyl alcohol). The MB degradation in the presence of the AgNPs was monitored by UV-Vis absorption spectroscopy, for a maximum of 30 minutes of reaction. The results showed the formation of AgNPs with a spherical shape for all the stabilizers used. All the AgNPs prepared were efficient in the degradation of MB, having degraded more than 90%. However, the AgNPs stabilized with sodium citrate and polyvinylpyrrolidone presented the best catalytic performance. Nevertheless, the four AgNPs prepared are potential catalysts for the degradation of organic dyes of wastewater.