Novel Donor-Acceptor g-C3N4 Organic Semiconductor Photocatalytic Separation of Uranium

Abstract

The extraction of uranium from nuclear wastewater through photocatalysis represents a highly viable, environmentally friendly, and sustainable approach, contributing significantly to mitigating environmental degradation while facilitating the efficient recovery of uranium resources. Nonetheless, the development of highly efficient photocatalysts with rapid charge carrier migration and surface reaction kinetics for the effective removal of U(Ⅵ) from uranium-containing wastewater remains a formidable challenge. This study successfully employed template-free self-assembly techniques to fabricate hollow tubular g-C3N4(TCN) and synthesized a tubular donor-acceptor(D-A) organic semiconductor photocatalyst, B-TCNx, by incorporating hydroquinone into the framework of TCN. This innovative photocatalyst was utilized for the photocatalytic removal of U(Ⅵ) under ambient air conditions. The construction of an intra-molecular D-A system enables the separate accumulation of electrons and holes in the acceptor and donor moieties, thereby significantly reducing electron-hole recombination. Furthermore, the spatial separation of electrons and holes in the acceptor and donor moieties leads to the formation of an intrinsic electric field, which facilitates the migration of charge carriers. The research findings indicate that B-TCN60 achieved a remarkable removal rate of 96.8% for U(Ⅵ) within 120 minutes, with a kinetic constant(0.03114 min−1) that is 2.58 times higher than that of TCN(0.01215 min−1). Moreover, negligible performance variation was observed after five consecutive cycles, demonstrating the excellent stability and reproducibility of the photocatalyst. The enhanced performance of B-TCN60 can be attributed to its unique structural and electronic properties. The hollow tubular structure of TCN provides a high surface area, which is beneficial for the adsorption of uranium ions. Additionally, the incorporation of hydroquinone into the TCN framework not only improves the light absorption properties of the photocatalyst but also plays a crucial role in the formation of the D-A system. The effective separation of charge carriers within the D-A system minimizes recombination losses and maximizes the efficiency of the photocatalytic process. The study’s findings underscore the potential of D-A organic semiconductor photocatalysts in addressing environmental challenges associated with nuclear waste, while also enhancing the recovery of valuable uranium resources. The novel approach of utilizing a D-A system in the photocatalyst design opens new avenues for the development of advanced materials with superior photocatalytic performance. The innovative use of template-free self-assembly techniques to fabricate hollow tubular g-C3N4 and the successful synthesis of the B-TCNx photocatalyst represent significant advancements in the field. The high removal efficiency, stability, and reproducibility of B-TCN60 highlight its potential for practical applications in environmental remediation. This work not only contributes to the field of environmental remediation but also offers a sustainable solution to the global issue of nuclear waste management.

Keywords

• g-c3n4
• resorcinol
• donor-acceptor photocatalysts
• u(ⅵ) photocatalytic reduction