Facile synthesis of novel nanocomposite composed of Co3O4, MgO, and Mg3B2O6 for malachite green dye decontamination from aqueous media.

Malachite green is a hazardous chemical that poses serious threats to aquatic ecosystems due to its toxicity and persistence in the environment. Additionally, it is harmful to human health, recognized as a carcinogenic and mutagenic agent that can cause long-term adverse effects. Hence, in this study, malachite green dye was efficiently removed from aqueous media using Co₃O₄/MgO/Mg₃B₂O₆ novel nanocomposites, known as CBM600 and CBM800. The CBM600 and CBM800 nanocomposites were facilely fabricated through the Pechini sol-gel procedure at 600 and 800 °C, respectively. Besides, X-ray diffraction analysis showed their crystalline structures, including Co₃O₄ and MgO in cubic systems, and Mg₃B₂O₆ in an orthorhombic system. For the CBM600 and CBM800 nanocomposites, the average crystal sizes are 40.76 nm and 57.43 nm, with BET surface areas of 74.25 m²/g and 57.59 m²/g, respectively. The highest uptake capacities for malachite green dye by the CBM600 and CBM800 nanocomposites are 492.61 mg/g and 440.53 mg/g, respectively. The pseudo-second-order model and Langmuir isotherm were the best fits for the adsorption data. Also, the uptake of malachite green dye by the CBM600 and CBM800 nanocomposites is spontaneous, physical, and exothermic. The nanocomposites were regenerated using 6 M HCl and repeatedly used to remove malachite green dye with very small loss in efficiency, demonstrating their robust reusability.