CATALYTIC CONVERSION OF TOXIC ORGANIC COMPOUNDS USING GOLD NANOPARTICLES SYNTHESIZED VIA A GREEN APPROACH

Abstract

Organic dyes such as methylene blue (MB) and bromocresol green (BCG), are significant contributors to
water pollution if discharged untreated. This study explores the catalytic efficiency of gold nanoparticles
(AuNPs) in the reduction reaction of these dyes with NaBH4. AuNPs were synthesized using a green, one-step method employing extracts from Helicteres hirsute Lour containing saponins, tannins, and flavonoids
as both reducing and stabilizing agents. Transmission electron microscopy (TEM) and scanning electron
microscopy (SEM) analyses revealed that the AuNPs are spherical with an average particle size of 12.4 nm
and are uniformly dispersed. The nanoparticles demonstrated high stability, as indicated by a zeta potential
of -29.8 mV, attributed to electrostatic repulsion. Kinetic studies on the catalytic reduction of MB and BCG
showed reaction rate constants of k = 0.4107 min⁻ ¹ and k = 0.3286 min⁻ ¹, respectively. Additionally, the
activation energies for these reactions were calculated as -8.42 kJ/mol for MB and -35.21 kJ/mol for BCG,
indicating effective catalysis and potential application in wastewater treatmen