Contribution of 1O2 in the efficient degradation of organic pollutants with Cu0/Cu2O/CuO@N-C activated peroxymonosulfate: A Case study with tetracycline.

Peroxymonosulfate-mediated advanced oxidation processes (PMS-AOPs) degrading organic pollutants (Tetracycline (TC) as an example) in water with singlet oxygen (1O2) as the main reactive oxygen has received more and more attention. However, the generation mechanism of 1O2 is still unclear. Consequently, this study investigates the 1O2 formation mechanism during the activated PMS process using a nitrogen-copper-loaded carbon-based material (Cu0/Cu2O/CuO@N-C), synthesized by thermally decomposing organobase-modified HKUST-1 via a one-pot method. It was discovered that incorporating an organobase (Benzylamine) into the metal organic framework (MOF) precursor directs the MOF's self-assembly process and supplements its nitrogen content. This modification modulates the Nx-Cu-Oy active site formation in the material, selectively producing 1O2. Additionally, 1O2 was identified as the dominant reactive oxygen species in the Cu0/Cu2O/CuO@N-C-PMS system, contributing to TC degradation with a rate of 70.82%. The TC degradation efficiency remained high in the pH range of 3-11 and sustained its efficacy after five consecutive uses. Finally, based on the intermediates of TC degradation, three possible degradation pathways were postulated, and a reduction in the ecotoxicity of the degradation products was predicted. This work presents a novel and general strategy for constructing nitrogen-copper-loaded carbon-based materials for use in PMS-AOPs.

Anisotropic Deformation Behavior and Indentation Size Effect of Monocrystalline BaF2 Using Nanoindentation.

In this study, our objective is to investigate the anisotropic deformation behavior and the indentation size effect (ISE) of monocrystalline barium fluoride (BaF2) using nanoindentation experiments with a diamond Berkovich indenter. BaF2 is known for its anisotropy, which results in significant variations in its mechanical properties. This anisotropy poses challenges in achieving high processing quality in ultra-precision machining. Through our experiments, we observed numerous pop-in events in the load-displacement curves, indicating the occurrence of plastic deformation in BaF2 crystals, specifically in the (100), (110), and (111) orientations; these pop-in events were observed as the indentation depth increased to 56.9 nm, 58.2 nm, and 57.8 nm, respectively. The hardness-displacement and elastic modulus-displacement curves were obtained from the tests exhibiting the ISE. The nanoindentation hardness of BaF2 is found to be highly dependent on its crystallographic orientation. Similarly, for BaF2 in the (100) orientation, the range is from 2.43 ± 0.74 and 1.24 ± 0.12 GPa. For BaF2 in the (110) orientation, the values range from 2.15 ± 0.66 to 1.18 ± 0.15 GPa. For BaF2 in the (111) orientation, the values range from 2.12 ± 0.53 GPa to 1.19 ± 0.12 GPa. These results highlight the significant influence of crystallographic orientation on the mechanical properties of BaF2. To better understand the ISE, we employed several models including Meyer's law, the Nix-Gao model, the proportional specimen resistance (PSR) model, and the modified PSR (mPSR) model, and compared them with our experimental results. Among these models, the mPSR model demonstrated the best level of correlation (R2>0.9999) with the experimental measurements, providing a reliable description of the ISE observed in BaF2. Our reports provide valuable insights into the anisotropic mechanical characteristics of BaF2 materials and serve as a theoretical guide for the ultra-precision machining of BaF2.