Abstract
Establishing a heterojunction for two kinds of semiconductor catalysts is a promising way to enhance photocatalytic activity. In this study, nanodiamond (ND) and CuFe-layered double hydroxide (LDH) were hybridized by a simple coprecipitation method as a novel heterojunction to photoactivate H2O2. The ND/LDH possessed a hydrotalcite-like structure, large specific surface area (SBET = 99.16 m2/g), strong absorption of visible-light and low band gap (Eg = 0.94 eV). Under the conditions of ND/LDH dosage 0.0667 g/L, H2O2 concentration 19.6 mmol/L, and without initial pH adjustment, 93.5% of 10 mg/L methylene blue (MB) was degraded within 120 min, while only 78.3% of MB was degraded in the presence of LDH instead of ND/LDH. The ND/LDH exhibited excellent stability and maintained relatively high activity, sufficient to photoactivate H2O2 even after five recycles. The mechanism study revealed that in the heterojunction of ND/LDH, the photoelectrons transferred from the valence band of LDH (Cu/Fe 3d t2g) to the conduction band of LDH (Cu/Fe 3d eg) could spontaneously migrate onto the conduction band of ND, promoting the separation of photo-induced charges. Thus, the photoelectrons had sufficient time to accelerate the redox cycles of Cu3+/Cu2+ and Fe3+/Fe2+ to photoactivate H2O2 to produce hydroxyl radicals, resulting in excellent photo-Fenton efficiency on MB degradation.
Highlights
IntroductionWater pollution with synthetic organics (e.g., dyes, pesticides, pharmaceuticals) is a worldwide problem because these unnatural organic pollutants are difficult to degrade with traditional chemical or biochemical processes [1,2]
Water pollution with synthetic organics is a worldwide problem because these unnatural organic pollutants are difficult to degrade with traditional chemical or biochemical processes [1,2]
These results suggested that the as-prepared ND/layered double hydroxide (LDH) possessed a hydrotalcite-like structure, and that the ND was hybridized with LDH successfully
Summary
Water pollution with synthetic organics (e.g., dyes, pesticides, pharmaceuticals) is a worldwide problem because these unnatural organic pollutants are difficult to degrade with traditional chemical or biochemical processes [1,2]. Advanced oxidation processes (AOPs) possess excellent oxidizing abilities for decomposing refractory organic pollutants, due to the oxidation of highly active radicals such as hydroxyl radical (HO·) [3,4,5,6]. As a typical AOP, Fenton technology is a simple and effective method for treating organic wastewater [7,8]. The Fenton assisted by photoirradiation (photo-Fenton) is more efficient than the traditional Fenton [11,12]. Improving the utilization efficiency of visible-light is vital for the photo-Fenton because it can make full use of solar-light in which visible-light is absolutely dominant [3,13]
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