Heavy metals removal from aqueous solutions by Al₂O₃ nanoparticles modified with natural and chemical modifiers

We prepared novel Al₂O₃ nanoparticles (NPs) modified with humic acid (Al-H), extractant of walnut shell (Al-W), and 1,5-diphenyl Carbazon (Al-C). The present study was conducted to evaluate the feasibility of modified nano-alumina (Al-H, Al-W, and Al-C) for Cd²⁺, Cu²⁺, and Ni²⁺ removal from single and competitive aqueous solutions. The nature and morphology of sorbents were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and Scanning electron microscopy (SEM) analysis. The SEM results revealed that the three modified nanoparticles had larger size in comparison with bare nanoparticles and with an average diameter of around 61 nm. Batch adsorption studies were performed as a function of contact time, initial heavy metals concentration (isotherm), and pH. Heavy metals sorption kinetics was well fitted by pseudo-second-order kinetic model. The maximum uptake values (sum of 3 metals) in competitive component solutions were 92.0, 97.0, and 63.8 mg g⁻¹, for Al-H, Al-W, and Al-C, respectively. The heavy metals sorption has been well explained using Langmuir isotherm model. SEM–EDX before and after metal sorption, and soil solution saturation indices showed that the main mechanism of sorption for Cd²⁺ and Ni²⁺ was adsorption, whereas for Cu²⁺ sorption was due to adsorption and precipitation. Thus, the new nanoparticles are favorable and useful for the removal of Cd²⁺, Cu²⁺ metal ions particularly, in single solutions and with Al-C NPs. The high adsorption capacity makes them good promising candidate materials for heavy metal ions removal from water samples.