Rapid and Enhanced Adsorptive Removal of Malachite Green Dye by Chemically Synthesized Magnesium Hydroxide Nanomaterials

Abstract The design of resilient and sustainable adsorbents for effective wastewater management has become a key priority in recent times. Herein, we report the preparation of Mg(OH)2 nanostructures by co-precipitation and hydrothermal methods for the evaluation of their adsorption performance for malachite green (MG) dye from aqueous solution. Electron microscopy and diffractometry analysis of the synthesized products confirm the formation of well-crystalline plate-like sheets. The nanomaterials synthesized by the hydrothermal method exhibit uniform morphology but a lower surface area (67.7 m2 g−1) compared to those synthesized by the coprecipitation method (84.0 m2 g−1). Batch adsorption studies under optimized conditions confirm the superior performance of Mg(OH)2 nanomaterials synthesized by the coprecipitation method, with maximum adsorption capacities of 2626.5 mg g−1 and 3601.0 mg g−1 based on the Langmuir and Sips isotherms, respectively. The equilibrium data are best interpreted by the Freundlich and Sips models, indicating heterogeneous multilayer adsorption, while kinetic data followed the pseudo-second-order model, suggesting chemisorption as the dye uptake mechanism. Thermodynamic studies further confirmed that the adsorption process is spontaneous and endothermic. The spent Mg(OH)2 nanomaterials can be effectively regenerated through both thermal and chemical methods, underscoring the high efficiency and economic feasibility of the adsorbent for MG dye removal from water. Moreover, the whole process stands out as environmentally friendly and sustainable in the effective remediation of MG dye from water.