Nanoneedle-Assembled Copper/Cobalt sulfides on nickel foam as an enhanced 3D hierarchical catalyst to activate monopersulfate for Rhodamine b degradation

Boosting elimination of sunscreen, Tetrahydroxybenzophenone (BP-2), from water using monopersulfate activated by thorny NanoBox of Co@C prepared via the engineered etching strategy: A comparative and mechanistic investigation

As sunscreens, benzophenones (BPs), are regarded as emerging contaminants, most of studies are focused on removal of 2-hydroxy-4-methoxybenzophenone (BP-3), which, however, has been employed for protecting skin. Another major class of BPs, which is used to prevent UV-induce degradation in various products, is completely neglected. Thus, this present study aims to develop a useful advanced oxidation process (AOP) for the first time to eliminate such a class of BP sunscreens from contaminated water. Specifically, 2,2',4,4'-Tetrahydroxybenzophenone (BP-2) would be focused here as BP-2 is intensively used in perfumes, lipsticks, and plastics for preventing the UV-induced degradation. As monopersulfate (MPS)-based AOP is practical for degrading emerging contaminants, a facile nanostructured cobalt-based material is then developed for maximizing catalytic activities of MPS activation by immobilizing Co nanoparticles onto carbon substrates. In particular, ZIF-67 is employed as a template, followed by the etching and carbonization treatments to afford the thorny nanobox of Co@C (TNBCC) with the hollow-nanostructure. In comparison to the solid (non-hollow) nanocube of Co@C (NCCC) from the direct carbonization of ZIF-67, TNBCC possesses not only the excellent textural features, but also superior electrochemical properties and highly reactive surfaces, making TNBCC exhibit the significantly higher catalytic activity than NCCC as well as Co₃O₄ in activating MPS to degrade BP-2. Mechanisms of BP-2 degradation are also elucidated and ascribed to both radical and non-radical routes. These advantageous features make TNBCC a useful catalyst of activating MPS in BP-2 degradation.

Peroxymonosulfate-Activation-Induced Phase Transition of Mn3O4 Nanospheres on Nickel Foam with Enhanced Catalytic Performance

The transformations of physicochemical properties on manganese oxides during peroxymonosulfate (PMS) activation are vital factors to be concerned. In this work, Mn₃O₄ nanospheres homogeneously loaded on nickel foam are prepared, and the catalytic performance for PMS activation is evaluated by degrading a target pollutant, Acid Orange 7, in aqueous solution. The factors including catalyst loading, nickel foam substrate, and degradation conditions have been investigated. Additionally, the transformations of crystal structure, surface chemistry, and morphology on the catalyst have been explored. The results show that sufficient catalyst loading and the support of nickel foam play significant roles in the catalytic reactivity. A phase transition from spinel Mn₃O₄ to layered birnessite, accompanied by a morphological change from nanospheres to laminae, is clarified during the PMS activation. The electrochemical analysis reveals that more favorable electronic transfer and ionic diffusion occur after the phase transition so as to enhance catalytic performance. The generated SO₄^•- and •OH radicals through redox reactions of Mn are demonstrated to account for the pollutant degradation. This work will provide new understandings of PMS activation by manganese oxides with high catalytic activity and reusability.

Peroxymonosulfate Activation by CuO-Fe2O3-Modified Ni Foam: A 1O2 Dominated Process for Efficient and Stable Degradation of Tetracycline

The post-separation of powder catalysts restricts the practical application of peroxymonosulfate (PMS)-based advanced oxidation technology. Hence, we fabricated CuO-Fe2O3-modified Ni foam (CFO-NF) using a facile hydrothermal method for an efficient PMS activation. The CFO-NF/PMS system could achieve a 97.9% tetracycline hydrochloride (TC) removal efficiency in 60 min with four pieces of CFO-NF and 0.4 mmol L−1 of PMS. The removal efficiency was maintained at ˃85% even after five cycles, indicating the excellent stability of CFO-NF composites. The conversion among Fe(III)/Fe(II), Cu(II)/Cu(I), and Ni(III)/Ni(II) accelerated the PMS decomposition, verifying the synergy between CuO-Fe2O3 and Ni foam. The trapping experiments and EPR detection confirmed that abundant active species (•OH, SO4•−, O2•−, and 1O2) were produced in the CFO-NF/PMS system, accounting for the existence of radical pathways and a non-radical pathway, in which 1O2 (non-radical pathway) was dominated. This study developed a novel CuO-Fe2O3-modified Ni foam with a superior PMS activation performance, a high stability, and a recoverability for eliminating refractory organic pollutants.

Templating agent-mediated Cobalt oxide encapsulated in Mesoporous silica as an efficient oxone activator for elimination of toxic anionic azo dye in water: Mechanistic and DFT-assisted investigations

While Azorubin S (AZRS) is extensively used as a reddish anionic azo dye for textiles and an alimentary colorant in food, AZRS is mutagenic/carcinogenic, and it shall be removed from dye-containing wastewaters. In view of advantages of SO₄^•--related chemical oxidation technology, oxone (KHSO₅) would an ideal source of SO₄^•- for degrading AZRS, and heterogeneous Co₃O₄-based catalysts is required and shall be developed for activating oxone. Herein, a facile protocol is proposed for fabricating mesoporous silica (MS)-confined Co₃O₄ by a templating agent-mediated dry-grinding procedure. As the templating agent retained inside the ordered pores of MS (before calcination) would facilitate insertion and dispersion of Co ions into pores, the resulting Co₃O₄ nanoparticles (NPs) would be grown and confined within the pores of MS after calcination, affording Co@MS. On the contrary, another analogue, Co/MS, is also prepared using the similar protocol without the templating agent-mediated introduction of Co, but Co₃O₄ NPs seriously aggregate as clusters on MS. Therefore, Co@MS outperforms Co/MS for activating oxone to eliminate AZRS. Co@MS shows a noticeably lower activation energy of AZRS elimination than the existing catalysts, revealing its advantage over the reported catalysts. Moreover, the mechanistic investigation of AZRS elimination by Co@MS-activated oxone has been also elucidated for identifying the presence of SO₄^•‒, ^•OH, and ¹O₂ in AZRS degradation using scavengers, electron paramagnetic resonance spectroscopy, and semi-quantification. The AZRS decomposition pathway is also investigated and unveiled in details via the DFT calculation. These results validate that Co@MS appears as a superior catalyst of oxone activation for AZRS degradation.

Modulating Direct Growth of Copper Cobaltite Nanostructure on Copper Mesh as a Hierarchical Catalyst of Oxone Activation for Efficient Elimination of Azo Toxicant

As cobalt (Co) has been the most useful element for activating Oxone to generate SO4•-, this study aims to develop a hierarchical catalyst with nanoscale functionality and macroscale convenience by decorating nanoscale Co-based oxides on macroscale supports. Specifically, a facile protocol is proposed by utilizing Cu mesh itself as a Cu source for fabricating CuCo2O4 on Cu mesh. By changing the dosages of the Co precursor and carbamide, various nanostructures of CuCo2O4 grown on a Cu mesh can be afforded, including nanoscale needles, flowers, and sheets. Even though the Cu mesh itself can be also transformed to a Cu-Oxide mesh, the growth of CuCo2O4 on the Cu mesh significantly improves its physical, chemical, and electrochemical properties, making these CuCo2O4@Cu meshes much more superior catalysts for activating Oxone to degrade the Azo toxicant, Acid Red 27. More interestingly, the flower-like CuCo2O4@Cu mesh exhibits a higher specific surface area and more superior electrochemical performance, enabling the flower-like CuCo2O4@Cu mesh to show the highest catalytic activity for Oxone activation to degrade Acid Red 27. The flower-like CuCo2O4@Cu mesh also exhibits a much lower Ea of Acid Red 27 degradation than the reported catalysts. These results demonstrate that CuCo2O4@Cu meshes are advantageous heterogeneous catalysts for Oxone activation, and especially, the flower-like CuCo2O4@Cu mesh appears as the most effective CuCo2O4@Cu mesh to eliminate the toxic Acid Red 27.

Multimetallic CuCoNi Oxide Nanowires In Situ Grown on a Nickel Foam Substrate Catalyze Persulfate Activation via Mediating Electron Transfer

In situ growth of nanostructures on substrates is a strategy for designing highly efficient catalytic materials. Herein, multimetallic CuCoNi oxide nanowires are synthesized in situ on a three-dimensional nickel foam (NF) substrate (CuCoNi-NF) by a hydrothermal method and applied to peroxydisulfate (PDS) activation as immobilized catalysts. The catalytic performance of CuCoNi-NF is evaluated through the degradation of organic pollutants such as bisphenol A (BPA) and practical wastewater. The results indicate that the NF not only plays an important role as the substrate support but also serves as an internal Ni source for material fabrication. CuCoNi-NF exhibits high activity and stability during PDS activation as it mediates electron transfer from BPA to PDS. CuCoNi-NF first donates electrons to PDS to arrive at an oxidized state and subsequently deprives electrons from BPA to return to the initial state. CuCoNi-NF maintains high catalytic activity in the pH range of 5.2-9.2, adapts to a high ionic strength up to 100 mM, and resists background HCO₃^- and humic acid. Meanwhile, 76.6% of the total organic carbon can be removed from packaging wastewater by CuCoNi-NF-catalyzed PDS activation. This immobilized catalyst shows promising potential in wastewater treatment, well addressing the separation and recovery of conventional powdered catalysts.