Gamma-alumina nanoparticles (γANPs) were obtained from a low-cost process by using natural bauxites. The γANPs materials were characterized by X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) theory, scanning electron microscopy (SEM), atomic force microscopy (AFM), and were functionalized with N-cetyl-N, N, N, trimethylammonium bromide (CTAB), leading to CTAB modified γ-alumina nanoparticles (γANPs-CTAB). These novel functionalized γANPs-CTAB were characterized by XRPD, FTIR, and were used as an adsorbent for bisphenol-A (BPA) removal from water. Batch investigations were conducted under different experimental conditions (e.g., adsorbent dose, agitation time, initial concentration, and pH and surfactant loading) in order to optimize BPA adsorption and to identify the adsorption mechanisms in the system γANPs-CTAB-BPA. The effect of pH on the adsorption showed that the quantity of BPA removed increased remarkably until the pH value was 4, then remained almost constant until the pH value was up to 10, and then decreased for pH values greater than 10. For an initial BPA concentration of 20 mg/L and an adsorbent dose of 12.5 g/L at a pH value of 10, the removal efficiency achieved was 91.80 ± 0.21%. The adsorption mechanism was perfectly described by pseudo-second-order kinetics and the Langmuir isotherm. γANPs-CTAB materials were found to be effective adsorbents for BPA removal from water.

Thallium (I) was removed from aqueous solution by using gamma-alumina nanoparticles (γANPs) materials as nano adsorbents. Varied experimental conditions such as adsorbent dose, agitation time, initial concentration, pH, and temperature effects were carried out in batch conditions in view of the optimization of thallium (I) adsorption and the identification of the adsorption mechanisms in the system γANPs-Tl. The pH effect indicated a remarkable increase in the quantity of Tl(I) removed for pH values ranging from 4 to 8, an almost constant magnitude for pH values between 8 and 10, and a decrease for pH values above 10. Considering an initial Tl(I) concentration of 20 µg/L and an adsorbent dose of 1 g/L at a pH value of 8.5, the removal was achieved at 95.12 ± 0.02% efficiency. The pseudo-second-order kinetics and the Freundlich isotherm perfectly described the adsorption mechanism. The process of thallium (I) adsorption reaction, as highlighted by thermodynamic investigations, was found to be spontaneous and exothermic with coexistence of physisorption and chemisorption with a dominance of physisorption. The diffusion model predicted multi-linearity, suggesting an involvement of surface spread and intraparticle diffusion in the sorption process. Thallium removal was effective by using γANPs as nano adsorbents.

The growing interest in local materials as natural adsorbents stems from their abundance, low cost, and eco-friendliness, offering an effective, economical, and sustainable alternative to commercial options. The present work investigates the removal performance of lead (Pb2+) and copper (Cu2+) ions from synthetic aqueous solutions using both raw and activated laterite (KN-Ac) under batch conditions. The experiments were carried out to examine the effects of contact time, adsorbent dose, temperature, pH, and initial metal-ion concentration. High determination coefficients obtained from the pseudo-second-order kinetics and Langmuir isotherm models indicate that these models reliably describe the experimental adsorption behavior of the metal ions. The diffusion model-adjusted data revealed that adsorption occurred rapidly at the beginning, with fast adsorption on the outer surface followed by slower adsorption controlled by intraparticle diffusion. The KN-Ac, designated KN-Ac, proved to be highly effective in removing both heavy metals, achieving removal percentages of 97.81 ± 0.23% (4.07 ± 0.01 mg/g) for Pb2+ and 94.24 ± 0.18% (1.18 ± 0.02 mg/g) for Cu2+ at an initial concentration of 10 mg/L. The ΔG values obtained for the metal ions were all negative, indicating that the adsorption process is feasible and spontaneous for Pb(II) and Cu(II) ions on the adsorbents, following the order of thermodynamic stability: Pb2+(KN-Ac) > Cu2+(KN-Ac) > Pb2+(raw laterite [KN]) > Cu2+(KN) in the temperature range of 303–333 K. The positive ΔH values for all metal ions suggest that adsorption onto the adsorbents is endothermic and involves physisorption. The energy values derived from the Dubinin–Radushkevich equation are all below 8 kJ/mol, indicating that the adsorption of Pb2+ and Cu2+ is physical in nature. Furthermore, the Fourier transform infrared spectra of adsorbent residues loaded with heavy metals show no changes compared to the spectra of the unloaded adsorbents, confirming physisorption as the main adsorption mechanism.