Enhancing Commercially Iron Powder Electron Transport by Surface Biosulfuration to Achieve Uranium Extraction from Uranium Ore Wastewater.

The zero-valent iron (ZVI) has attracted increasing attention due to the enhanced reactivity of ZVI to uranium wastewater. However, ZVI practical application is hampered due to its susceptibility to oxidation and the formation of passivation layers during storage and in situ restoration. To address these issues, we used a biosulfuration approach to modify ZVI for application in uranium ore wastewater treatment. A series of physicochemical characterization tools and photoelectronic analyses showed that BS-ZVI considerably increased carrier separation efficiency and visible light absorption capacity, resulting in a significant photoassisted enhancement effect on uranium extraction. Accordingly, the uranium removal efficiency of BS-ZVI reached 91% within 60 min, and its maximum adsorption capacity was 336.3 mg/g. By analyzing the mechanism, the improved U(VI) removal performance was mostly responsible on the dissolution of the passivation layer on the surface of ZVI, the generation of Fe(II) and FeS, and the important role of Shewanella putrefaciens extracellular polymers (EPS). Overall, the BS-ZVI biohybrid merges with the high activity of ZVI, bio-FeS, and self-regeneration ability of bacteria, expanding a promising new approach for sustainable treatment of uranium mine wastewater.

Introduction of cation vacancies and iron doping into TiO2 enabling efficient uranium photoreduction.

The reduction of U(VI) to U(IV) in wastewater by semiconductor photocatalysis has become a new highly efficient and low-cost method for U(VI) removal. However, due to the weak absorption of visible light led by wide band gap and low carrier utilization rate resulted from the severe electron-holes recombination, the photoreduction performance of U(VI) is limited. Herein, the Ti vacancies and doped Fe atoms were simultaneously introduced into TiO2 nanosheet (labeled as 4%Fe-Ti1-xO2) as a highly active and stable catalysis for U(VI) photoreduction. Without adding any hole sacrifice agent, 4%Fe-Ti1-xO2 nanosheets achieved 99.7% removal efficiency for U(VI) within 120 min. And the 92.1% removal efficiency of U(VI) via 4%Fe-Ti1-xO2 nanosheets was still maintained after 5 cycles. Moreover, 4%Fe-Ti1-xO2 exhibited dramatic removal rate, 81.6% U(VI) in the solution was removed in 10 min. Further study on the mechanism showed that simultaneously introducing the Ti vacancies and doped Fe atoms in 4%Fe-Ti1-xO2 nanosheets improved the visible light utilization and decreased the recombination of photogenerated electron-hole pairs, contributing to the highly efficiency removal of U(VI).

Interface assembly of specific recognition gripper wrapping on activated collagen fiber for synergistic capture effect of iodine.

Efficient capture of radioactive iodine (129I, 131I) is of great significance in spent fuel treatment. In this paper, a new adsorbent named Catechin@ACF was successfully prepared through interface assembly of specific recognition gripper with plant polyphenols (catechin) on activated collagen fiber (ACF), and the catechin membrane with specific grip on iodine was successfully constructed on the surface of ACF. The results showed that the adsorbent assembled catechin membrane was rich in aromatic rings, hydroxyl groups and imine adsorption sites, and possessed specific recognition and capture characteristics of iodine. Moreover, the as-prepared Catechin@ACF showed excellent capture capacity for iodine vapor and iodine in organic solution with the maximum capture capacity of 2122.68 mg/g and 258.29 mg/g, respectively. In iodine-cyclohexane solution, the adsorption process was in according with the Pseudo first order kinetic and Langmuir isothermal model. In addition, the specific recognition and capture mechanism analysis indicated that the aromatic rings, phenolic hydroxyl groups and imine groups in the catechin membrane were the specific and effective grippers for iodine, and finally iodine formed a stable conjugated system with the adsorbent in the form of I- and I3-. Therefore, the as-prepared specific iodine capturer Catechin@ACF was expected to play a vital role in the capture of radioactive iodine in spent fuel off-gas because of its specific recognition, high capture capacity, large-scale preparation, and environment-friendly.

Efficient Photocatalytic Extraction of Uranium over Ethylenediamine Capped Cadmium Sulfide Telluride Nanobelts.

The photocatalysts for hexavalent uranium (U(VI)) reduction suffered from the low uranium uptake capacity and weak long-wavelength light absorption. Herein, we synthesized the CdSxTe1-x nanobelts capped by ethylenediamine (EDA), which provided amino groups as the adsorption sites. With the increase of the Te content, the amino groups on the CdSxTe1-x nanobelts decreased because of the variation of the electron density of Cd2+, whereas the light adsorption was enhanced due to the narrowed bandgap. In photocatalytic reduction of U(VI), the CdS0.95Te0.05-EDA nanobelts exhibited a considerable U(VI) removal ratio of 97.4% with a remarkable equilibrium U(VI) extraction amount on per weight unit of the adsorbent (qe) of 836 mg/g. The bandgap structure and Fourier transform infrared spectroscopy (FT-IR) spectra analysis revealed that the optimum photocatalytic activity of CdSxTe1-x nanobelts was achieved at a 5% of Te2- doping, which balanced the factors of amino groups and bandgap. This adsorption-photoreduction process offers an ultrahigh uranium extraction capacity over wide uranium concentrations.

Bio-inspired and assembled fungal hyphae/carbon nanotubes aerogel for water-oil separation.

Carbon nanotube (CNT)-based materials have attracted tremendous interest for their high performance in oil separation. However, the preparation of CNT based materials always require harmful and expensive chemicals. Here, a biological assembly route was applied to assemble CNTs onto a fungal hyphae (FH) to produce FH/CNTs composites, followed by pyrolysis to obtain a hydrophobic CNT based aerogel for oil separation, which is a more environmentally friendly process. The as-prepared FH/CNTs-800 aerogel (pyrolyzed at 800 °C) showed hydrophobicity with a water contact angle of 143° and high specific surface area (1041.2 m2 g-1). The oil absorption results showed that the as-prepared FH/CNTs aerogels could absorb a wide range of oils with high absorption capacities ranging from 48 to 138 times their own weight. Furthermore, the oil-loaded aerogel was recycled through burning with little reduction in the oil absorption capacity. In addition, FH/CNTs-800 provided a high specific capacitance of 232 F g-1 at 1 A g-1 and maintained a capacity retention of 70.62% at 20 A g-1. Therefore, this study offers a simple, low-cost and environmentally friendly bioassembly route for large-scale assembly of CNTs into macroscopic 3D hydrophobic aerogels for highly efficient water-oil separation.