Bi_(2)O_(3)/g-C_(3)N_(4)hollow core–shell Z-scheme heterojunction for photocatalytic uranium extraction

Photocatalytic uranium extraction from radioactive nuclear wastewater and seawater is critical for promoting the sustainable advancement of nuclear industry,but the complexity of real-world environments,particularly the occurrence of anoxic and oxygen-enriched states,presents significant challenges to effective uranium extraction.Here,a layered hollow core–shell structure of Bi_(2)O_(3)/g-C_(3)N_(4)Z-scheme heterojunction photocatalyst has been designed and successfully applied for photocatalytic uranium extraction in both aerobic and oxygen-free conditions,and the extraction efficiency of uranium can reach 98.4%and 99.0%,respectively.Moreover,the photocatalyst still has ultra-high extraction efficiency under the influence of pH,inorganic ions,and other factors.The exceptional capability for uranium extraction is on the one hand due to the distinctive hollow core–shell architecture,which furnishes an abundant quantity of active sites.On the other hand,benefiting from the suitable band gap structure brought by the construction of Z-scheme heterojunction,Bi_(2)O_(3)/g-C_(3)N_(4)exhibits current densities(1.00μA/cm^(2))that are 5.26 and 3.85 times greater than Bi_(2)O_(3)and g-C_(3)N_(4),respectively,and the directional migration mode of Z-scheme carriers significantly prolongs the lifetime of photogenerated charges(1.53 ns),which separately surpass the pure samples by factors of 5.10 and 3.19.Furthermore,the reaction mechanism and reaction process of photocatalytic uranium extraction are investigated in the presence and absence of oxygen,respectively.

Purification of scandium from concentrate generated from titanium pigments production waste

Nowadays 80%of scandium in China is obtained from titanium pigments production waste through a complex purification process.The study mainly focused on the purification of Sc from its concentrate generated from titanium pigments production waste by solvent extraction.Several extractants have been tried and 10%D_(2)EHPA-5%TBP-85%sulfonated kerosene exhibited the best extraction performance towards Sc in 7 mol/L H_(2)SO_(4)solution,so it was selected as the oil phase.0.5%of H_(2)O_(2)was added into the concentrated solution which can effectively inhibit the extraction of Ti.Both the extraction and back extraction parameters are optimized.The preferred extraction conditions were obtained,i.e.,acidity:7 mol/L H_(2)SO_(4),the phase ratio A/O:10,room temperature,mixed contact time:30 min,Sc concentrate:10 g/L,that the extraction rate of Sc in the above conditions was nearly 100%.NaOH was used for back extraction with the stripping rate 99%on the following conditions:5 mol/L NaOH stripping for 30 min at a phase ratio A/O:1 at 90℃.Finally,H_(2)C_(2)O_(4)was used to further purify the back extraction product and Sc_(2)(C_(2)O_(4))_(3)precipitant fo rmed.The final product Sc_(2)O_(3)with a purity over 99.5%was obtained by calcining Sc_(2)(C_(2)O_(4))_(3)at 1000℃for 2 h.A conceptual process for Sc purification was put forward and proved.The total recovery yield of Sc in the whole process is 95%.

Adsorption behavior of Me2-CA-BTP/SiO2-P adsorbent toward MA(Ⅲ) and Ln(Ⅲ) in nitrate solution

A porous Me2-CA-BTP/SiO2-P adsorbent was prepared to separate MA（III） from Ln（III） in high level liquid waste （HLLW）. The adsorption behavior of Me2-CA-BTP/SiO2-P toward 241Am（III） and Ln（III） in 0.01 M HNO3-NaNO3 solution was studied. Me2-CA-BTP/SiO2-P showed high adsorption and selectivity toward 241Am（III） over Ln（III） fission products with the separation factor （SF） reaching to 557, 2355, 1952, 1082, 214, 105, 86, 14 for Y, La, Ce, Nd, Sm, Eu, Gd and Dy respectively in 0.01 M HNO3-0.99 M NaNO3 solution. The adsorption kinetics of both Dy（III） and Eu（III） on Me2-CA-BTP/SiO2-P was studied and followed pseudo-second-order rate equation indicating chemical sorption as the rate-limiting step of the adsorption, and the adsorption isotherm of Dy（III） and Eu（III） matched better with the Langmuir isotherm than the Freundlich isotherm with the adsorption amount around 0.22 and 0.20 mmol/g respectively. Thermodynamic study revealed that the adsorption of both Dy（III） and Eu（III） on Me2-CA-BTP/SiO2-P was spontaneous and endothermic processes with a positive entropy at 298, 308, 313 K.