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Graphical abstract Highlights • Cubic perovskite was successfully synthesized by a facile solvothermal method. • Inner-sphere complexation dominated U(VI) sequestration under neutral condition. • Carbonate inhibited the sequestration and photocatalytic reduction of U(VI). Abstract Cubic perovskite (CaTiO 3) was successfully synthesized by a facile solvothermal method and was utilized to sequestrate U(VI) from aqueous solutions. The batch experiments revealed that carbonate inhibited U(VI) sequestration at pH > 6.0 due to the formation of uranyl-carbonate complexes. The maximum sequestration capacity of U(VI) on perovskite was 119.3 mg/g (pH 5.5). The sequestration mechanism of U(VI) on perovskite were investigated by XPS and EXAFS techniques. According to XPS analysis, the presence of U(IV) and U(VI) oxidation states revealed the photocatalytic reduction of U(VI) by perovskite under UV–vis irradiation. In addition, photocatalytic reduction performance significantly decreased in the presence of carbonate. Based on EXAFS analysis, the occurrence of U-Ti and U-U shells revealed the inner-sphere surface complexation and reductive precipitation of U(VI) on perovskite. These findings herein are crucial for the application of perovskite-based composites in the decontamination of U(VI) in aquatic environmental cleanup. [ABSTRACT FROM AUTHOR]

The discharge of microplastics into aquatic environment poses the potential threat to the hydrocoles and human health. The fate and transport of microplastics in aqueous solutions are significantly influenced by water chemistry. In this study, the effect of water chemistry (i.e., pH, foreign salts and humic acid) on the surface charge and aggregation of polystyrene microsphere in aqueous solutions was conducted by batch, zeta potentials, hydrodynamic diameters, FT-IR and XPS analysis. Compared to Na + and K + , the lower negative zeta potentials and larger hydrodynamic diameters of polystyrene microspheres after introduction of Mg 2+ were observed within a wide range of pH (2.0–11.0) and ionic strength (IS, 0.01–500 mmol/L). No effect of Cl − , HCO 3 – and SO 4 2− on the zeta potentials and hydrodynamic diameters of polystyrene microspheres was observed at low IS concentrations (<5 mmol/L), whereas the zeta potentials and hydrodynamic diameters of polystyrene microspheres after addition of SO 4 2− were higher than that of Cl − and HCO 3 – at high IS concentrations (>10 mmol/L). The zeta potentials of polystyrene microspheres after HA addition were decreased at pH 2.0–11.0, whereas the lower hydrodynamic diameters were observed at pH < 4.0. According to FT-IR and XPS analysis, the change in surface properties of polystyrene microspheres after addition of hydrated Mg 2+ and HA was attributed to surface electrostatic and/or steric repulsions. These investigations are crucial for understanding the effect of water chemistry on colloidal stability of microplastics in aquatic environment. [ABSTRACT FROM AUTHOR]

Plasma-and chemical-grafted amidoxime/carbon nanotber hybrids (p-AO/ CNFs and c-AO/CNFs) were utilized to remove2-"U(VI) andL1Am(II1) from aqueous solutions, seawater, and groundwater. Characteristic results indicated more nitrogen-containing groups in p-AO/CNFs compared to c-AO/CNFs. The maximum adsorption capacities of p-AO/CNFs at pH 3.5 and T = 293 K (588.24 mg of mU(VI)/g and 40.79 mg ofw(Am(llI)/g from aqueous solutions, respectively) were sipctifcantly higher than those of c-AO/CNFs (263.18 and 22.77 mg/g for238U(VI) and24 Am(I11), respectively), which indicated that plasma-grafting was a highly effective, low-cost, and environmentally friendly method. Adsorption of 2wU(VI) on AO/CNF5 from aqueous solutions was significantly higher than that of 238U(VI) from seawater and groundwater; moreover, AO/CNF5 displayed the highest effective selectivity for 238U(VI) compared to the other radionuclides. Adsorption of U(VI) onto AO/CNFs created inner-sphere complexes (e.g., U-C shells) as shown by X-ray absorption fine structure analysis, which was supported by surface complexation modeling. Three inner-sphere complexes gave excellent fits to pH-edge and isothermal adsorption of 238U(VI) on the AO/CNFs. These observations are crucial for the utilization of plasma-grafted, AO-based composites in the preconcentration and immobilization of lanthanides and actinides in environmental remediation. [ABSTRACT FROM AUTHOR]

A novel magnesium silicate/diatomite sorbent (MSD) was fabricated using a facile hydrothermal method. The interaction mechanism of U(VI) on MSD was investigated by batch, spectroscopic and modeling techniques. The maximum adsorption capacity of MSD for U(VI) (31.54 mg/g) is significantly higher than that of diatomite (12.74 mg/g). XPS analysis indicated that the oxygen-containing groups (e.g., Si OH) of MSD were responsible for the high efficient removal of U(VI) from aqueous solutions. The fitted results of surface complexation modeling showed that the adsorption of U(VI) on MSD at pH < 4.0 and pH > 4.5 was attributed to cation exchange and inner-sphere surface complexation, respectively. These findings suggested that MSD could be a favorable sorbent for the efficient removal of U(VI) in the environmental cleanup. [ABSTRACT FROM AUTHOR]

The flower-like sodium titanate nanospheres (Na-TNS) were synthesized by the facile and hydrothermal method. The effect of environmental factors on the sorption of U(VI) on as-prepared Na-TNS was conducted by batch techniques. The maximum sorption capacity of Na-TNS for U(VI) fitted by Langmuir model was 189.34 mg/g at pH 5.0 and T = 298 K. It was determined from recycle experiment that Na-TNS was a reusable and steady nanomaterial with the high sorption performance. The analysis of XPS results indicated that the high resolution Ti 2p spectra after sorption shifted to higher binding energy, which was due to the interactions of U(VI) with the TiO 6 octahedron. Therefore, Na-TNS can be utilized as an effective and sustainable sorbent to deal with U(VI) contamination in aqueous environmental cleanup. [ABSTRACT FROM AUTHOR]