Green synthesized nanosilver-biochar photocatalyst for persulfate activation under visible-light illumination

This paper presents a novel eco-sustainable wastewater treatment using silver nanoparticles and biochar (AgNPs@BC) synthesized from an Eriobotryra japonica leaf. A simple green pyrolysis method was chosen to activate peroxydisulfate (PDS) for organic pollutant degradation under the action of visible light. Rhodamine B (RhB) was chosen as a typical containment to assess the photocatalytic performance of the AgNPs@BC/PDS system with visible-light illumination (AgNPs@BC/PDS-vis). When Ag@BC750 (referring to the AgNPs@BC pyrolyzed at 750 °C) was added, the photocatalytic activity of PDS for RhB degradation was enhanced (from k_app = 0.165-2.984 min^-1). The result confirmed that 99.9% of the RhB was degraded in the AgNPs@BC/PDS-vis system within 10 min and with a 2.0 g/L photocatalyst, 10 mM PDS and under pH 9.03 (k_app = 6.723 min^-1). Over 100 mg/L of RhB could be degraded completely in the AgNPs@BC/PDS-vis system within 30 min mainly attributed to various free radicals. The possible degradation pathways of RhB were illustrated and the recyclability of the AgNPs@BC photocatalyst was confirmed. The findings in this study reveal the virtue of using the AgNPs@BC/PDS-vis process for advanced water disinfection and its provision as an alternative solution in addressing the green way for further water treatment.