Poly-Extract Synthesized Silver Nanoparticles Catalysed Rhodamine-B and Methyl Orange Dye Degradation: Influence of Physicochemical Parameters and their Recyclability

Abstract

Poly-extract (equal ratio of tulasi (leaf), neem (leaf) and turmeric (rhizome) aqueous extracts) was used for the synthesis of silver nanoparticles (SNPs). The SNPs were then used for the degradation of rhodamine-B (RhB) and methyl orange (MO) in presence of sodium borohydride (SBH; reducing agent) as na-no-catalysts. Influence of four physicochemical parameters such as: nano-catalyst and reducing agent concentration along with temperature and pH of the degradation process were investigated. Maximum degradation was observed at 100 µg (SNPs amount), 20 mg (SBH amount) and at 70 °C for both RhB and MO dyes. Whereas, pH 8 and pH 6 were found to optimum for RhB and MO dyes, respectively. At optimum conditions, SNPs showed 97.41 ± 2.39% degradation with 0.1554 min-1 under 24 min and 97.32 ± 2.12% degradation with 0.5017 min-1 under 7 min for RhB and MO dyes, respectively. SNPs further showed good recyclability, with 84.22 ± 2.19% (under 7 min) MO dye degradation even after Cycle 6 with 0.2071 min-1 as degradation rate. However, SNPs showed low recyclability for RhB dye degradation with only 71.05 ± 2.14% (under 24 min) degradation after Cycle 4 with 0.0556 min-1. It was observed that degradation kinetics was following pseudo-first order kinetics.