Green-synthesized Fe–Ni bimetallic nanoparticles for Peroxodisulfate-activated degradation of Allura Red

A green and sustainable approach was developed for the synthesis of Fe–Ni bimetallic nanoparticles (BMNPs) using Ocimum tenuiflorum leaf extract as a natural reducing and stabilizing agent, which achieved 95–98% degradation of Allura Red (AR) within 60 min in a Peroxodisulfate (PDS)-activated system. The biosynthesized nanoparticles were comprehensively characterized using UV–Visible spectroscopy, FTIR, XRD, SEM–EDS, TEM, SAED, DLS, and zeta potential analyses. XRD results confirmed the formation of a crystalline FCC structure with an average crystallite size of ∼44 nm, while FTIR spectra indicated the involvement of plant-derived phytochemicals in nanoparticle stabilization. Microscopic analyses revealed predominantly cubic to quasi-spherical nanoparticles with uniform elemental distribution of Fe and Ni. The catalytic performance of Fe–Ni BMNPs was evaluated for the oxidative degradation of AR in aqueous solution using PDS as an oxidant. Kinetic investigations demonstrated that the degradation process follows pseudo-first-order kinetics under the studied conditions. The effects of operational parameters, including PDS concentration, dye concentration, catalyst dosage, pH, and coexisting inorganic ions, were systematically examined. Increased PDS and catalyst loadings enhanced degradation efficiency due to improved sulfate radical generation, while higher dye concentrations reduced the reaction rate because of radical scavenging and surface saturation effects. The presence of inorganic anions showed inhibitory effects in the order NO 3 - < Cl - < HCO 3 - . LC–MS analysis suggested that degradation proceeds through initial azo bond cleavage followed by aromatic ring opening and subsequent mineralization to CO 2 , H 2 O, SO 4 2- , and NO 3 - . These findings demonstrate that green-synthesized Fe–Ni BMNPs are efficient and environmentally friendly catalysts for advanced oxidation-based treatment of dye-contaminated wastewater.