Water pollution has invaded seas, rivers, and tap water worldwide. This work employed commercial Mesquite charcoal as a low-cost precursor for fabricating Mesquite carbon nanoparticles (MUCNPs) using a ball-milling process. The scanning electron energy-dispersive microscopy results for MUCNPs revealed a particle size range of 52.4–75.0 nm. The particles were composed mainly of carbon with trace amounts of aluminum, potassium, calcium, titanium, and zinc. The X-ray diffraction peaks at 26.76 and 43.28 2θ° ascribed to the (002) and (100) planes indicated a crystalized graphite phase. Furthermore, the lack of FT-IR vibrations above 3000 cm⁻¹ showed that the MUCNPs were not functionalized. The MUCNPs’ pore diameter, volume, and surface area were 114.5 Ǻ, 0.363 cm³ g⁻¹, and 113.45 m² g⁻¹. The batch technique was utilized to investigate MUCNPs’ effectiveness in removing chlorohexidine gluconate (CHDNG) from water, which took 90 min to achieve equilibrium and had an adsorption capacity of 65.8 mg g⁻¹. The adsorption of CHDNG followed pseudo-second-order kinetics, with the rate-limiting step being diffusion in the liquid film. The Langmuir isotherm dominated the CHDNG adsorption on the MUCNPs with a correlation coefficient of 0.99. The thermodynamic studies revealed that CHDNG adsorption onto the MUCNPs was exothermic and favorable, and its spontaneity increased inversely with CHDNG concentration. The ball-milling-made MUCNPs demonstrated consistent efficiency through regeneration–reuse cycles.

This study has successfully developed a practical and straightforward approach for synthesizing nanocomposites with excellent dye removal potential. The SEM inspection of γ-Al₂O₃ (γ-Al) and MgO/MgAl₂O₄ (Mg/MgAl) nanocomposite showed a mean size of 59.0 and 46.4 nm, respectively, while the TEM results show particles with an average size of 26.63 and 13.4 nm, respectively. The surface area of γ-Al and Mg/MgAl was 50.0 and 69.5 m² g⁻¹, respectively. The study of adsorbing indigo carmine (IC) sorption onto γ-Al and Mg/MgAl presented sorption capacities of 41.6 and 55.9 mg g⁻¹, respectively, and both adsorbents attained equilibrium at 90 min. The highest IC sorption onto Mg/MgAl took place at pH 6.0. It is worth mentioning that raising the IC solution’s temperature from 20 °C to 50 °C increased the q_t to 268 mg g⁻¹. The IC sorption onto γ-Al and Mg/MgAl agreed with the pseudo-second-order model, and the liquid-film diffusion controlled the IC sorption. The Mg/MgAl showed an average removal of 98.2% when tested for removing six dyes at 10 mg L⁻¹, particularly malachite green, methylene blue, fast green, methyl orange, rhodamine B, and basic fuchsin, and the removal efficiency was 93.3% when their concentration increased to 20 mg L⁻¹. The Mg/MgAl nanocomposite performed exceptionally well in natural water samples (seawater and groundwater), indicating its potential applicability in managing water contamination.