Design of a solar reactor for the removal of uranium from simulated nuclear wastewater with oil-apatite ELM system

Development of evaporation technique for concentrating lead acid wastewater from the battery recycling plant, by nanocomposite ceramic substrates and solar/wind energy

Wastewater from car battery recycling plants contains lead ions. This acidic wastewater was treated by the solar steam generation method. In this research, a light porous ceramic substrate (PCS) was made based on clay, human hair, and nano-hydroxyapatite. The physical and chemical characteristics of this PCS were identified by SEM, XRD, FTIR, BET, and TGA. The high porosity in PCSs was created due to the removal of human hair in the calcination process inside the furnace. Microchannels with capillarity and hydrophilicity of nano-hydroxyapatite quickly pump water molecules to the surface of PCSs. The wastewater treatment process was carried out on two laboratory and semi-industrial scales. The temperature of the surface of the PCSs reached 70 °C in less than 60 min with the radiant heat transfer mechanism, and the water molecules were evaporated with an evaporation rate and thermal conversion efficiency were 9.22 Kgm^-2h^-2 and 90%, respectively. The wind blew the vapor away from the system and the rate of evaporation increased. PCSs had the ability to regenerate after several consecutive cycles.

Efficient charge separation in sulfur doped AgFeO2 photocatalyst for enhanced photocatalytic U(VI) reduction: The role of doping and mechanism insights

Photocatalytic reduction of U(VI) in aqueous solutions has been considered as an efficient and promising technology to solve radioactive U pollution. In this work, density functional theory (DFT) calculations were firstly employed to optimize and compare the adsorption configurations combined uranium with four given photocatalysts, then their adsorption energies were - 0.97 eV for AgFeO₂, - 1.15 eV for Zn doped AgFeO₂, - 1.73 eV for Cu doped AgFeO₂ and - 2.66 eV for S doped AgFeO₂, respectively, indicating the sulfur doping plays a major role in U(VI) photoreduction. Herein, a visible light responsive efficient sulfur doped AgFeO₂ photocatalyst (S doped AgFeO₂) was synthesized and utilized to photocatalytic reduction of U(VI) in aqueous solutions. According to XRD, XPS and TEM analysis, the sulfur was successfully doped in AgFeO₂ via the hydrothermal method. The batch experimental showed that S doping enhanced the U(VI) photoreduction activity of AgFeO₂, and the S-AFO-3 photocatalyst exhibited the highest photocatalytic activity (92.57%), which was 1.5 times than that of pure AgFeO₂. ESR, PL and DFT results demonstrated that the enhancement of adsorbed U(VI) photoreduction was attributed to the own unique effect of oxygen vacancy defects and efficient charge separation of S doped AgFeO₂ photocatalyst. Due to its higher adsorption energies, fast-U(VI) photoreduction rate and superior chemical stability, the sulfur doped AgFeO₂ photocatalyst is hoped for water remediation containing U(VI) wastewater.

Bismuth impregnated biochar for efficient uranium removal from solution: Adsorption behavior and interfacial mechanism

In this work, Bi₂O₃ doped horse manure-derived biochar was obtained by carbonizing the H₂O₂-modified horse manure loaded with bismuth nitrate under nitrogen atmosphere at 500 °C. The results showed that there was a sharp response between the as-prepared bismuth impregnated biochar and uranium(VI) species in solution, which resulted in a short equilibrium time (<80 min), a fast adsorption rate (about 5.0 mg/(g·min)), a high removal efficiency (93.9%) and a large adsorption capacity (516.5 mg/g) (T = 298 K, pH = 4, C_i = 10 mg/L and m/V = 0.1 g/L). Besides, the removal behavior of the bismuth impregnated biochar for uranium(VI) did not depend on the interfering ions and ion strength, except Al³⁺, Ca²⁺, CO₃^2- and PO₄^3-. These results indicated that the modified biochar might possess the potential of remediating the actual uranium(VI)-containing wastewater. Moreover, the interaction mechanism between Bi₂O₃ doped biochar and uranium(VI) species was further explored. The results demonstrated that the enrichment of uranium(VI) on the surface of the as-prepared biochar was controlled by various factors, such as surface complexation, ion exchange, electrostatic attraction, precipitation and reduction, which facilitated the adsorption of uranium(VI) on the bismuth impregnated biochar.