Activated carbon (AC) is widely used in pollutant removal , due to its adsorption capacity, conductivity and catalytic performance. However, few studies focus on the redox activity of AC and its role in pollutant transformation. In this study, we found that AC could efficiently mediate the oxidation of As(III) and the process of As(III) oxidation was pH and oxygen concentration dependent. In general, the presence of O 2 promoted As(III) oxidation at pH 3.0–9.5. Acidic and alkaline conditions favored As(III) oxidation regardless of whether there was oxygen, but the mechanisms involved were quite different when there was oxygen. At pH 3.0, reactive species (H 2 O 2 and ·OH) were generated and accounted for As(III) oxidation; at pH 9.5, As(III) was directly oxidized by O 2 (electron transfer from As(III) to O 2 mediated by carbon matrix) under aerobic conditions . Pre-oxidation and cyclic experiments results indicated the ability of AC to oxidize As(III) at pH 9.5 was sustainable and recyclable. This study provided a new insight in pollutant oxidation by AC in the environment.
Two-dimensional (2D)-interface engineering for designing effective electron-rich catalyst center is pivotal in manipulating the catalytic behaviors and activity, but still challenging. Here, we’ve successfully twisted the surfaces of the 2D layered FeOCl, fulfilling the targeted fine-tuning of its Fe sites. The obtained new catalyst can boost peroxymonosulfate activation for reactive species with much lower energy barriers and efficiently oxidized target organic with almost 41 orders of magnitude faster reaction kinetics than pristine FeOCl. The increased degree of freedom of electron around Fe site has been identified as the key driver. The distorted geometry structure around Fe has led to an increased polarization of charge distribution, associating with less symmetric electron valence cloud and higher electron mobility. Thus, the twisted surfaces enable a much enhanced interfacial charge transfer between Fe site and the electron-deficient peroxymonosulfate. This work highlights the concept of twisted surface construction toward efficient advanced oxidation catalyst design.
Prussian blue analogs (PBAs) are promising catalysts in heterogeneous oxidation processes. The catalytic activity of PBAs relies on exposed crystal facets and accessible active sites on the PBA framework. Employing a heteroatom doping strategy using a rare earth element (La), we regulated the crystal structure and optimized the catalytic activity of CoFe PBA for peroxymonosulfate (PMS)-driven degradation of the antibiotic norfloxacin (NOR). The La atoms were mainly doped in the interstitial sites of the CoFe PBA cubic lattices, without affecting the electron distributions of Co and Fe metals or the face-centered cubic crystal phase of the coordination skeleton. La doping dominated the (1 1 1) and (1 0 0) as the main exposed facets of CoFeLa PBA, increasing the affinity of CoFeLa PBAs for PMS adsorption due to the higher surface energy of the two facets. Consequently, the activation energy considerably declined from 77.57 kJ/mol in CoFe PBA to 51.66 kJ/mol in CoFeLa PBA and the catalytic activity for PMS-driven NOR degradation was largely improved, which can reach 76.4 % removal of NOR within 15 min, with an increased initial rate constant k of 0.095 min −1 . 1 O 2 was proven as the main reactive specie responsible for NOR degradation in the PMS/CoFeLa system, and O 2 · − and SO 4 · − were verified as the important intermediates to generate 1 O 2 . Thus, La doping can effectively enhance the catalytic performance of PBA-based catalysts for organic pollutant removal.
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