Tungsten oxide encapsulated phosphate-rich porous alginate composites for efficient U(VI) capture: Insights into synthesis, adsorption kinetics and thermodynamics.

In this work, novel monoclinic tungsten oxide (WO3)-encapsulated phosphate-rich porous sodium alginate (PASA) microspherical hydrogel beads were prepared for efficient U(VI) capture. These macroporous and hollow beads were systematically characterized through XRD, FTIR, EDX-mapping, and SEM-EDS techniques. The O and P atoms in the PO and monoclinic WO3 offered inner-spherical complexation with U(VI). The in situ growth of WO3 played a significant role inside the phosphate-rich biopolymeric network to improve its chemical stability, specific surface area, adsorption capacity, and sorption rate. The phytic acid (PA) served for heteroatom doping and crosslinking. The encapsulated WO3 mass ratio was optimized in different composites, and WO3/PASA3 (the microspherical beads with a mass ratio of 30.0 % w/w) exhibited remarkable maximum sorption capacity qm (336.42 mg/g) computed through the best-fit Langmuir model (R2 ≈ 0.99) and rapid sorption equilibrium, teq (150 min). The isothermal sorption studies were conducted at different temperatures (298, 303, and 308 K) and thermodynamic parameters concluded that the process of U(VI) sorption using WO3/PASA3 is endothermic and feasible having ΔHo (8.19 kJ/mol), ΔGo (-20.75, -21.38, and - 21.86 kJ/mol) and proceeds with a minute increase in randomness ΔSo (0.09 kJ/mol.K). Tungsten oxide (WO3)-encapsulated phosphate-rich porous microspherical beads could be promising material for uranium removal.

Macroporous and ultralight polyethyleneimine-grafted chitosan/nano-TiO2 foam as a novel adsorbent with antibacterial activity for the efficient U(VI) removal.

The radioactive contamination from the excessive discharge of uranium-containing wastewater seriously threatens environmental safety and human health. Herein, macroporous and ultralight polyethyleneimine-grafted chitosan/nano-TiO2 composite foam (PCT) with antibacterial activity was synthesized, which could quickly remove U(VI) from solution. Among different PCT adsorbents, PCT-2 had the best adsorption performance for U(VI), which could be due to its honeycomb macroporous structures and the presence of abundant amino/imine groups. The kinetics and adsorption isotherms data were found in agreement with the pseudo-second-order model and the Langmuir model, respectively, indicating chemisorption or complexation as the main adsorption mechanism. The saturated adsorption capacity of PCT-2 for U(VI) reaches 259.91 mg/g at pH 5.0 and 298 K. The PCT-2 also presents good selectivity for U(VI) with the coefficient (ßU/M) order of Na+ > K+ > Mg2+ > Ca2+ > Ni2+ > Co2+ > Mn2+ > Al3+ > Fe3+ > Cu2+. The adsorption mechanism was explored using FT-IR and XPS analysis, indicating that amino/imine groups and hydroxyl groups are responsible for U(VI) complexation. Thermodynamic calculations show that U(VI) adsorption is endothermic and spontaneous. The ease of preparation, excellent adsorption performance and environmental friendliness of PCT-2 make it a novel adsorbent with antibacterial activity for radioactive contamination control.