Charge reconstruction from simultaneous Fe coordination and P/O co-doping in g-C3N4 for efficient photo-reductive recovery of uranium(VI)

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-09, Vol.496, p.154319, Article 154319
• Main Authors: Zhang, Xiao, Zhang, Menglin, Li, Xinyuan, Xin, Baoping, Hao, Jie, Li, Jinying, Li, Hansheng, Zhang, Dongxiang, Wu, Zijie, Xu, Xiyan, Zhang, Jiatao
• Format: Article
• Language: English
• Subjects: Charge reconstruction; Fe coordination; P/O co-doping; Photoreduction; Uranium(VI) recovery
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.154319

[Display omitted] •Simultaneous Fe coordination and P/O co-doping in g-C3N4 was achieved by a novel one-step thermal polymerization method;•Electrons migration driven by coordinated Fe and lone electron pairs delocalization from doped P/O promoted charge transfer;•Uranium capture rate increased by 3-folds over original g-C3N4 through simultaneous introduction of Fe, P and O;•A higher uranium capture was achieved with the lowest catalyst consumption compared with previously reported g-C3N4-based photocatalysts;•The presence of dissolved O2 in this system facilitated photoreduction of uranium(VI) instead of inhibiting; The risk of radionuclide leakage always threats ecological security and human health, making the recovery of uranium from nuclear wastewater a meaningful and urgent issue. However, the low-cost and efficient capture of uranium remains a challenge at present. In this study, a homemade photocatalyst of iron coordinated graphitic carbon nitride (g-C3N4) co-doped with phosphorus and oxygen (OPFCN), which was facilely synthesized through a novel one-step thermal polymerization method, exhibited superior photoelectric efficiency and photocatalytic activity towards the photo-reductive capture of uranium(VI). The simultaneous Fe coordination and P/O co-doping in framework of g-C3N4 played a synergistic effect in charge reconstruction, in which electrons migration driven by coordinated Fe and lone electron pairs delocalization from doped P/O enormously increased electron density and enhanced charge transfer, thus effectively promoting the separation of photogenerated charge carriers. The specific surface area, pore volume and average pore size of OPFCN reached 70.2 m2·g−1, 0.157 cm3·g−1 and 7.78 nm, respectively, exhibiting a trend increasingly beneficial for photocatalytic adsorption and mass transfer with successive introduction of Fe, P and O into original g-C3N4. With the simultaneous introduction of Fe, P and O, the optical absorption edge underwent a significant redshift and fluorescence emission intensity dropped by 75 % compared to that of CN, demonstrating the enhanced visible light capturing ability and significantly inhibited recombination of photogenerated charge carriers in OPFCN. As a result, a uranium capture rate of over 98 % was achieved with catalyst dosage of only 5:1 at pH 5 with OPFCN, demonstrating its competitive photo-reductive activity towards uranium(VI) uptake compared with previously reported g-C3N4-based photocatalysts. Mea