The strong promoting effects of thin layer Al2O3 on FeCu Fenton-like components: Enhanced electron transfer.

The Fe(III)/Fe(II) redox cycle is the main factor limiting the effectiveness of Fe-mediated advanced oxidation processes (AOPs) for the degradation of organic pollutants. In this study, the promoting effects of thin-layer Al2O3 (t-Al2O3) between the frequently used FeCu components and the mesoporous silica support were studied to reduce Fe(III) to promote the activity of the Fenton-like catalyst. After modification by t-Al2O3, the mesoporous silicon-loaded FeCu catalyst removed 97% of Rhodamine B at pH 7, which was superior to the unmodified sample with a removal rate of 62.4% under the same conditions. Morphological characterization and X-ray diffraction patterns indicated that the Fe-Cu/t-Al2O3 active components were highly dispersed. Pyridine infrared spectra suggested that all of the acid sites were Lewis acids, and the t-Al2O3-loaded samples provided moderate/strong Lewis acids. The loading of t-Al2O3 between the FeCu complex and mesoporous silica support facilitated electron transfer during the Fe(III)/Fe(II) redox cycle by enhancing the dispersion of Fe-Cu/t-Al2O3 and the Lewis acidity. The results of this study provide insight into how t-Al2O3 promoted the interactions between the active components and silica support and how it can be used to aid in the selection of suitable wastewater treatment technologies.

Effective defect generation and dual reaction pathways for phenol degradation on boron-doped carbon nanotubes.

A new type of metal-free catalyst was successfully prepared by doping boron (B) in the carbon nanotube. The catalyst had 99.4% removal of phenol in 60 min at pH 7 by activating peroxymonosulfate (PMS). In order to explore the origin of the high catalytic activity, the samples were characterized by Raman and electron paramagnetic resonance (EPR), and the reactive oxygen species (ROS) in the process of catalytic degradation were investigated. The Raman results showed that the defect sites increased after doping, which indicated that the B doping increases the active sites on the surface of the carbon nanotubes. Identification experiments of ROS found that not only hydroxyl radicals (·OH) and sulfate radical (SO4-∙), but also singlet oxygen (1O2) exist in the system. The presence of multiple free radicals indicated the existence of free radical reaction pathway, and the presence of 1O2 confirmed the existence of non-radical reaction pathway. These results indicated that there were dual reaction pathways for the activation of persulfate by B-doped carbon nanotubes, which was the intrinsic nature for the high catalytic activity of the system.

Insights into the peroxomonosulfate activation on boron-doped carbon nanotubes: Performance and mechanisms.

Preparation of carbonaceous catalysts by doping with boron (B) is one of the most promising strategies for substitution of toxic transition metal catalysts in advanced oxidation processes. This study was dedicated to reveal the intrinsic structure-performance relationship of peroxomonosulfate (PMS) activation by B-doped carbon nanotubes toward catalytic oxidation of pollutants. Performance tests showed the catalyst realized more than 95% phenol removal at pH 7 in 1 h and 69.4% total organic carbon removal. The catalysts were characterized using scanning electron microscopy (SEM), transmission electron microscope (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Characterization results indicated that the topography of carbon nanotube was not significantly changed after B doped, while the defect sites increased from 1.05 to 1.23. The newly formed active sites may be presented in the form of C3B, CBO2 and CBO3, and reactive oxygen species (ROS) including OH, SO4-•, O2-• and 1O2 might be generated after activation by the active sites. Furthermore, B-MWNT-PMS∗ was also be detected by In-situ Raman, confirming the non-radical pathway and electron transfer mechanism. Beside of phenol, the reaction system of B-MWNT/PMS also can remove methylene blue, bisphenol S and diuron at pH = 7, confirming the universality and promising of this advanced oxidation technology.