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.

Four cationic surfactants with various length and number of long alkyl chains such as dodecyltrimethylammonium, tetradecyltrimethyl-ammonium, hexadecyltrimethylammonium and didodecyldimethyl-ammonium were intercalated at different concentrations into two natural clays from Burkina Faso via solid-state reaction. Each organoclay was used to explore bisphenol A (BPA) removal from water. Various factors including adsorbent dose, agitation time, concentration, surfactant loading levels, pH and temperature were evaluated. Further, pseudo-first and pseudo-second kinetics, Langmuir and Freundlich isotherms and thermodynamics of adsorption onto organoclays were investigated. The adsorption mechanism was perfectly described by pseudo-second-order kinetic model and Langmuir isotherm. Spontaneous and exothermic processes were associated with BPA removal. This study showed that both physisorption and chemisorption are involved in BPA adsorption. Adsorption capacities ranging from 88 to 127 mg/g were observed at ambient temperature and acidic environment. The ranking of organoclays sorption capacities depends on the surfactant loading level. The pH effect on the adsorption showed a remarkable decrease in the quantity of BPA removed when pH ≥ 10. The BPA amount adsorbed onto the organoclays was not varying significantly for pH < 10. Organoclays prepared via solid-state surfactant intercalation are as effective adsorbents for BPA removal from water as those prepared in aqueous solution through cation exchange.

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.