Efficient and sustainable generation of high-valent metal-oxo species (HVMs) is critical for selective decontamination via Fenton-like catalysis, however, maintaining electron density balance at the active sites remains challenging. In this study, a zeolite-supported CuO catalyst was found to induce complete and selective Cu(III) oxidation of organics through persulfate (PDS) activation. PDS activation and pollutant oxidation occurred simultaneously at the electron-rich ≡Cu sites and electron-deficient ≡Al centers, respectively. Notably, zeolite could successfully serve as an electron buffer by creating dual active centers with distinct electron densities, stabilizing the generation and retention of ≡Cu(III) for exceptional anti-interference capacity. Strong metal-support interactions tuned the ≡Cu d-band center closer to the Fermi level, efficiently promoting electron transfer to ≡Cu sites through the Al/Si-O-Cu bond for the formation of ≡Cu(III). This study unveils a zeolite-based electron buffering strategy and presents an advanced approach for developing highly efficient catalysts in PDS activation and HVMs-mediated water purification.
In recent years, there has been growing interest in the mechanism (radical or nonradical) of persulfate activation processes. In this study, the enhancement of naproxen (NPX) degradation in a Cu 0 /peroxymonosulfate (PMS) system by complexing reagents was investigated. Surprisingly, neocuproine (NCP) alters the nature of reactive species in the Cu 0 /PMS system. A high-valent copper species, Cu(III)-NCP, was found to dominate NPX degradation rather than radicals under acid conditions for the first time. Moreover, systematically designed experiments revealed that the Cu(III)-NCP complex was a strong selective oxidant that reacted with organics through a single electron transfer pathway. Meanwhile, the degradation efficiency of NPX was highly dependent on the solution pH and dosage of Cu 0 and NCP, but was irrelevant to the concentration of NPX. Additionally, the enhancement of NCP on other copper based PMS activation systems (i.e., Cu 2+ /HA/PMS and Cu 0 /HA/PMS systems) was investigated. Considering that the released copper can be removed by a simple precipitation method to meet the effluent standards, the new complex-enhanced Cu 0 /PMS system provided a new method to enhance the degradation efficiencies of pollutants by a copper-catalyzed Fenton-like system.
Zhiwei Yang,Xiaonan Tan,Daojian Tang,Jing Li,Jiahai Ma
In this study, the contrasting activities and pathways of Mn2+/Cu2+–HCO3− systems for Congo red (CR) dye degradation are presented. The Mn2+–HCO3− system (with the well-known MnIVO as the reactive species) did not degrade CR, while the Cu2+–HCO3− system (with high-valent Cu proposed as the reactive species) had a good oxidizing ability for CR. Further, HO radicals in the classic Fenton-like system made no contribution to CR degradation with both Cu and Fe ions as catalysts. The results indicate that reactive species in metal–HCO3− AOPs need prudent examination and better understanding of the underlying mechanism would benefit the development of more efficient AOPs.
The development of coordination complexes to activate hydrogen peroxide (H 2 O 2 ) selectively is a goal that has long been pursued. As highly reactive intermediates, the high-valent metal-oxo species play important roles in many biological and industrial catalytic oxidation processes. To improve the catalytic efficiency of metal complexes, the peroxide O O bond should be cleaved heterolytically to decrease the decomposition of H 2 O 2 into O 2 and H 2 O. In this work, we provide a simple method to obtain coordination complex catalysts based on iminodiacetic acid (IDA), copper(II) ions and pyridine derivatives. Catalytic activity tests showed that the introduction of 4-aminopyridine ligands resulted in an enhanced catalytic activity of the IDA/Cu(II)/4-ampy complex. A series of designed experiments proved that high-valent copper-oxo species ([ O Cu III (IDA)(4-ampy) 2 ] species) were formed in the IDA/Cu(II)/4-ampy complex system in the presence of hydrogen peroxide. The [ O Cu III (IDA)(4-ampy) 2 ] species were detected by in-situ high-definition electrospray ionization mass spectrometry, and has been considered as the possible active species during H 2 O 2 activation catalyzed by the IDA/Cu(II)/4-ampy complex (with the molar ratio of IDA/Cu(II)/4-ampy being greater than 1:1:2). A mechanism has been proposed based on the results of electron paramagnetic resonance and density functional theory calculations.
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