Bioreduction (Ag+ to Ag0) and stabilization of silver nanocatalyst using hyaluronate biopolymer for azo-contaminated wastewater treatment

A facile and well-known eco-friendly strategy has been used to synthesize colloidal silver nanoparticles (AgNPs) and applied for the catalytic reduction of azo dyes. Herein, AgNPs were produced using silver nitrate (AgNO3) as a metal precursor and sodium hyaluronate (SH) as both reducing and stabilizing agents without the assistance of any other toxic reagents. The different characterizations were employed to investigate the morphology, crystallinity, surface plasmon resonance (SPR), particle size/distributions, and composition of particles. The investigation revealed that the AgNPs were mostly spherical/oval shape with an average size of 13.3 ± 4.7 nm, highly crystalline with a d-spacing of 0.233 – 0.257 nm, and coated with SH-macromolecules layer of cladding. In application of wastewater treatment, the AgNPs showed an excellent catalytic reduction (more than 99% rate of degradation) of two carcinogenic pollutants, i.e., reactive red 195 (RR195) and reactive yellow 145 (RY145) azo-dyes, with the support of sodium borohydride. The azo-dye catalysis has followed the model of pseudo-first-order kinetics reactions, with a kinetic constant (k) of 0.0948 min−1 (r2 = 0.9889) and 0.0222 min−1 (r2 = 0.9877) for RR195 and RY145, respectively. The present study not only provides a facile synthesis of AgNPs without toxic chemicals but also can be a potential candidate to meet the actual demand for textile wastewater treatment.