Lignocellulose biomatrix zero-valent cobalt nanoparticles: a dip-catalyst for organic pollutants degradation

Pollutant removal based on natural materials got comprehensive spread utilization because of their high efficiency in degrading toxic organic pollutants in an aqueous medium. In this work, a redox dip-nanocatalyst based on cobalt nanoparticles (Co NPs) at a size of approximately 100 nm anchored on lignocellulose biomatrix via wet impregnation was used for the degradation of model pollutants. The cobalt ions immobilized on rice husk (RH) biomass fibers were reduced to their respective zero-valent state by treatment with sodium borohydride (NaBH4). The as prepared catalyst was named as RH@Co NPs. Various analytical characterization techniques viz. Fourier transforms infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), X-Ray photoemission spectroscopy (XPS), and X-ray diffraction analysis (XRD) were used to examine functional group analysis, morphological characteristics, stability, elemental composition, and crystalline nature of the as-prepared RH@Co nanocatalyst respectively. The catalytic properties of the RH@Co NPs were tested using different nitrophenols viz. 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), and dyes viz. congo red (CR), methyl orange (MO), methylene blue (MB), and rhodamine B (RB). It was found that kinetic data followed zeroth order kinetics for the degradation of model pollutants. The RH@Co showed good catalytic activity for 2-NP, 3-NP, and 4-NP with apparent rate constants (kapp) of 0.019 min−1, 0.029 min−1, and 0.0416 min−1, respectively. Similarly, in the case of CR, MO, RB, and MB dyes, the kapp was 0.067 min−1, 0.12 min−1, 0.16 min−1, and 0.085 min−1, respectively. These results present the potential application of RH@Co as a sustainable and retrievable nanocatalyst for the remediation of pollutants. Furthermore, the results are general and can be used for the reduction of other organic pollutants.