This study aimed to investigate and explore the possibility of using ground sea shell powder (Donax trunculus) (SSP) for sorption of Sr(II) ions from aqueous solutions. The maximum removal of Sr(II) removal in SSP was 60% at initial Sr(II) concentration of 25 mg/L, at pH 6.0, contact time 120 min, temperature 25 °C and volume/mass ratio equivalent to 500. Sorption data were interpreted considering the adsorption isotherms and thermodynamic parameters calculated. The maximum Sr(II) adsorption on SSP was 25.45 mg/g at pH 6.0. Freundlich isotherm and Dubinin–Radushkevich models were seen to be more compatible with the sorption equilibrium. The nature of the process was spontaneous and exothermic. The results suggest that SSP could be used as an efficient and cost-effective adsorbent to remove strontium ion.

In this study, for the first time ZnO nanoparticles and diatomite-supported ZnO nanocomposite have been utilized as adsorbent for the removal of Th(IV) ions from aqueous solutions under different experimental conditions. The Langmuir, Freundlich, Temkin and Dubinin– Radushkevich (D–R) isotherms were used to analyze the equilibrium data. The sorption equilibrium data were fitted well to the Langmuir isotherm with maximum sorption capacities values was found to be 1.105 mmol/g and 0.320 mmol/g for ZnO nanoparticles and diatomite supported ZnO nanocomposite, respectively. Pseudo-first and pseudo-second order equations, Intraparticle diffusion and Bangham’s models were considered to evaluate the rate parameters and sorption mechanism. Sorption kinetics were better reproduced by the pseudo-second order model (R ² > 0.999), with an activation energy (E _a) of +99.74 kJ/mol and +62.95 kJ/mol for ZnO nanoparticles and diatomite-supported ZnO nanocomposite, respectively. In order to specify the type of sorption reaction, thermodynamic parameters were also determined. The evaluated ΔG ^* and ΔH* indicate the non-spontaneous and endothermic nature of the reactions. The results of this work suggest that both of the used materials are fast and effective adsorbents for removing Th(IV) from aqueous solutions and chemical sorption plays a role in controlling the sorption rate.

Graphene oxide (GO) and zinc oxide (ZnO) were synthesized via the Tour’ and sol-gel methods, respectively. Adsorption potentials of Th(IV) ions were investigated with the functionalization of GO with ZnO nanoparticles (GO-ZnO) and compared with the GO. Studies concerning factors affecting the adsorption process, kinetics, adsorption isotherms, and thermodynamic properties were carried out. In this study, the optimum pH for the adsorption of Th(IV) ions is 3.0, and quickly reaching equilibrium is an indication of the high efficacy of the sorbent. A pseudo-second order adsorption model fits the kinetic data well. Experimental results were compared with Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. These results show that the Langmuir model fits the data well. Measured thermodynamic parameters, Gibbs free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) indicate that the adsorption of Th(IV) on GO−ZnO is spontaneous and endothermic in nature. According to the linear fit in the Langmuir isotherm model, the maximum adsorption capacity of GO and GO-ZnO at 298 K occurs at 109.89 mg/g and 243.90 mg/g, respectively. The results show that decoration with ZnO nanoparticles is a good method to improve the adsorption capacity of GO for Th(IV) removal.