ZnO-Co3O4/N-C Cage Derived from the Hollow Zn/Co ZIF for Enhanced Degradation of Bisphenol A with Persulfate

Cobalt doped g-C3N4 activated peroxymonosulfate for organic pollutant degradation: Alterations in cobalt species and reactive oxygen species

Cobalt-based materials are promising catalysts for activating peroxymonosulfate (PMS) to degrade organic pollutants. Among various cobalt-based catalysts, the alteration in cobalt species and the reactive species produced are not fully understood. Herein, four materials were synthesized by controlling synthesis methods and doping of g-C3N4 to regulate cobalt species. Through two methods, ZIF/Co and Co3O4, whose main cobalt species are Co-O/Co-N and CoO/O-CoO, were synthesized. On this basis, ZIF/Co-CN and Co3O4-CN were synthesized by adding g-C3N4. Then, the four materials were used to activate PMS for carbamazepine (CBZ) degradation, focusing on the correlation between active sites and reactive species. CoO/O-CoO mainly led to the formation of free radicals, while Co-N tended to produce non-free radicals. The addition of g-C3N4 would facilitate non-free radical catalysis by promoting the conversion of Co-O to Co-N and enhancing the catalytic role of C and N. Finally, the systems with a high proportion of non-free radicals showed better degradation performance when multiple pollutants co-existed, and reactive species may be selective to different pollutants. The findings have significance for the synthesis design of cobalt-based catalysts and the regulation of reactive species to degrade different pollutants practically.

Hollow NiCo2O4-ZnO-Co3O4-/N-C Micro-Cage for Synergistic Bisphenol A Degradation by Activating Persulfate

The NiCo₂O₄-ZnO-Co₃O₄-/N-C micro-cage was successfully synthesized by calcination of the precursor obtained from a hollow ZIF-8/ZIF-67 with nickel nitrate. The preparation process concerning ion exchange and leaching was illustrated by the investigation of the composition and structure of the composites. As a catalyst for the activation of persulfate (PDS) to degrade bisphenol A (BPA), it was discovered that the BPA degradation in the presence of NiCo₂O₄-Co₃O₄-ZnO/N-C was more efficient than the solids obtained by ZIF-67 with nickel nitrate, indicated by the sevenfold increase of the apparent reaction rate. The further electrochemical analysis evidenced that the electron transfer was more easily accomplished in the system of BPA-PDS-NiCo₂O₄-Co₃O₄-ZnO/N-C. This enhanced activity of NiCo₂O₄-Co₃O₄-ZnO/N-C was mainly due to the hollow structure, the synergistic effect of NiCo₂O₄, as well as the smaller size of the active species, which facilitated the transportation of molecules and ions as well as the activation of PDS.

Hollow CdS-ZnS-ZIF-8 Polyhedron for Visible Light-Induced Cr(VI) Reduction

By loading a small amount of cadmium acetate dihydrate on the zeolitic imidazolate framework-8 (ZIF-8), a hollow CdS-ZnS-ZIF-8 composite was facilely synthesized by rapid solid-phase grinding with thioacetamide. The evolution of the structure, composition, and photoelectrochemical properties was studied by a series of methods. When it was used as a photocatalyst, the hollow CdS-ZnS-ZIF-8 composite demonstrated a highly visible light response as well as a robust ability and reusability for Cr(VI) reduction, which could be ascribed to the hollow structure and ultrasmall CdS nanoparticles. Notably, the presence of ZIF-8-S (ZIF-8 ground with thioacetamide) could also obviously enhance the stability of CdS by promoting the separation of the photogenerated charge during light irradiation.