A simple method employing dextrose as a capping agent was adopted for making MgAl2O4@MgO (AM), 5%NiO-MgAl2O4@MgO (AMNi), 5%CoO-MgAl2O4@MgO (AMCo), and 5%CuO-MgAl2O4@MgO (AMCu) nanocomposites. The average particle sizes, determined via SEM, were in the range of 21.6–51.4 nm, 9.8–13.8 nm, 19.1–32.2 nm, and 9.2–31.2 nm for AM, AMCu, AMNi, and AMCo, respectively. The nanosorbents exhibited type IV isotherm curves and type H3 hysteresis loops, signifying mesoporous properties. The AM, AMCu, AMNi, and AMCo exhibited surface areas of 69.47, 95.87, 86.23, and 75.87 m2/g, respectively. The pseudo second order described the indigo carmine (IDC) sorptions onto AM, AMCu, AMNi, and AMCo. The liquid film diffusion regulated IDC sorption on AMNi and AMCo, whereas the intraparticle diffusion was the dominant model on AM and AMCu. The AMCu’s showed a qt value of 127 mg g−1 from a 50 mg L−1 IDC solution at 20 °C, and 286.2 mg g−1 from a 200 mg L−1 IDC solution at 50 °C, establishing its capability for treating contaminated water. The IDC sorption onto AMCu aligns with the Freundlich model, which may elucidate the elevated qt value of AMCu. Elevating the temperature induced the IDC sorption on AMCu, indicating its endothermic nature, and the negative ΔG° implied that the IDC sorption by AMCu was spontaneous. A 5.0 and 10.0 mg L−1 IDC concentration in natural water samples was treated by the AMCu, which showed 100.0% efficacy for both groundwater samples; however, its efficacy toward the 5 and 10 mg L−1 IDC in seawater was 99.23% and 89.78%, respectively. The MACu’s efficiency throughout four reuse cycles decreased by only 7.21%, demonstrating excellent stability and reusability performance.
Elhory et al. (Fri,) studied this question.