Sustainable Degradation of Binary Dye Mixtures Using Fe/Co/rGO Nanocomposite: Dual Dye Dynamics, Adsorption and Reusability

In the present study, rGO was used as supporting material to incorporate Fe/Co nanoparticles to form Fe/Co/rGO composite using aqueous extract of Dypsis lutescens leaves. The strong adsorption sites, wide surface areas and oxygen functionalities of reduced graphene oxide (rGO) produced more adsorption and photocatalytic degradation efficiency. Various characterization techniques like UV–visible spectrophotometer, FTIR, XRD, EDX and SEM were performed to analyze the synthesized nanocomposite, which confirmed the crystalline, porous nature of nanocomposite with average size of 5 nm. Degradation mechanism of mixture of cationic (rhodamine B) and anionic (alizarin red) dyes was observed with and without tungsten lamp source. Different parameters (time, pH, dye concentration, Fe/Co/rGO dosage and temperature) affecting adsorption and degradation of dyes were examined. At 5 ppm dyes solution and 10 mg nanocatalyst dosage in time limit of 20 min, without tungsten lamp, % removal of rhodamine B was observed as 62% and that of alizarin R was 59%, while under tungsten lamp % removal was increased upto 95% for rhodamine B and 90% for alizarin R. Kinetics of adsorption mechanism revealed that process followed pseudo-2nd-order reaction. Thermodynamic studies predicted that adsorption process was spontaneous and exothermic in nature. Among different isotherm models applied, the Freundlich isotherm model was best fitted. Moreover, the reusability studied showed that nanocatalyst is effective even after five cycles and hydroxyl radicals were the main specie of degradation mechanism.