Role of bioinorganic metal nanoparticles as catalyst for the treatment of dyes polluted wastewater

Abstract

Bioinorganic silver nanoparticles preparation was carried out by using the leaf extract of Epiphyllum oxypetalum as reducing and capping agent while AgNO3 salt was used as precursor of Ag+ ions. Change in color of the reaction mixture from dark green to brown and appearance of SPR band at 400 nm in UV–Visible spectra confirmed the successful fabrication of AgNPs. FTIR, UV–Visible, DLS, TGA and SEM analysis were performed to characterize the AgNPs. Reduction of Congo red (CR) was adopted as a benchmark reaction to evaluate the catalytic potential of AgNPs while using NaBH4 as a reducing agent. Reaction was completed in 22 min with the value of kapp found as 0.218 min−1. Controlled reactions were also performed to confirm the role of biogenic NPs as catalyst in the reduction reactions. Biogenic synthesized AgNPs also exhibited the capability to speed up the rate of reduction of some other toxic dyes such as crystal violet (CV), CR, methyl orange (MO) and Rhodamine B (RhB). Kinetic study illustrated that reduction reactions followed pseudo first order model with the value of kapp found as 0.301, 0.251, 0.106 and 0.039 min−1 for CV, CR, MO and RhB, respectively. Bioinorganic NPs also showed catalytic potential for the simultaneous reduction of mixture of CV, CR, MO and RhB dyes under same reaction conditions. Reported catalyst also exhibited excellent activity for the treatment of dyes polluted textile industry wastewater. Activity of catalyst was maintained up to three cycles with slight increase in reaction completion time with the increase of reusability cycles.