Catalytic potential of cobalt oxide and agar nanocomposite hydrogel for the chemical reduction of organic pollutants.

In this study, cobalt oxide nanoparticles (Co ₃ O ₄ NPs) were synthesized by precipitation method from cobalt sulphate solution with basic pH, followed by calcination. The ex-situ synthesized Co ₃ O ₄ NPs were mixed with hot agar (AG) aqueous solution. The preparation of AG- Co ₃ O ₄ nanocomposite hydrogel was carried out by self-association method promoted by thermal denaturation. The quenching of hot suspension from 80 °C to room temperature resulted in the formation of AG-Co ₃ O ₄ nanocomposite hydrogel. The as-synthesized AG-Co ₃ O ₄ was characterized by FTIR, XRD and SEM techniques. In order to test the catalytic activity, AG-Co ₃ O ₄ was used as a heterogeneous catalyst for the reduction of methylene blue (MB), congo red (CR) and 4-nitrophenol (4-NP). The excellent performance of the AG-Co ₃ O ₄ was shown by the reaction rate constant (k _app ) values of 0.3623, 0.2114 and 0.2893 for MB, 4-NP and CR, respectively. All these results were obtained with R ² above 94 and utilization of an AG-Co ₃ O ₄ catalyst. Furthermore, the catalytic reduction was studied with varying dye concentration and catalyst dose. This study showed that AG-Co ₃ O ₄ catalyst has high potential for remediation of environmental pollutants in wastewaters.
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