Catalytic Degradation Of P-nitrophenol Research Articles

Efficient degradation of p-nitrophenol by Fe@pomelo peel-derived biochar composites and its mechanism of simultaneous reduction and oxidation process

In this study, waste pomelo peels (PP) mixed with iron salts was treated successively with hydrothermal and pyrolyzing carbonization processes to obtain Fe(0) containing biochar composites (Fe@PP-Hy-Py) and the catalytic degradation of p-nitrophenol (PNP) using these Fe@PP-Hy-Py composites was studied. The results showed that the hydrothermal pre-treatment of the mixture of iron salts and pomelo peels was favorable for the incorporation of iron precursor within biomass network, which enabled copolymerization during the following pyrolysis. Through the pyrolysis process, the iron precursor was reduced in situ to amorphous Fe(0) dopped into the carbonaceous matrix, which conversely decreased the defect and disorder degree of pseudo-graphitic carbons and catalyzed the formation of environmental persistent free radicals (EPFRs). Degradation tests showed that the composites obtained at 600 °C with the theoretical Fe mass loading of 10% exhibited the greatest PNP degradation efficiency. Over 90% of 10 mg/L PNP was removed in 2 min under both N2 and air conditions with 1.0 g/L of catalyst level. The degradation kinetics of PNP were all well fitted by the pseudo-first-order kinetics model with kobs of Fe@PP-Hy-Py600 being 0.953 min−1. HPLC-QTOF/MS analysis demonstrated that both oxidation and reduction of PNP occurred as indicated by the detection of 4-aminophenol and ring opening compounds. The Fe(0) on the Fe@PP-Hy-Py was responsible for the reduction of PNP, while oxidation was induced by EPFRs. This study highlights the feasibility of synthesizing active heterogeneous Fe(0)-biochar composites by hydrothermal-pyrolysis route and the associated mechanisms of pollutant degradation.

Catalytic degradation of p-nitrophenol by magnetically recoverable Fe3O4 as a persulfate activator under microwave irradiation

In this study, Fe3O4 and microwave (MW) were combined to activate persulfate (PS) for the removal of organic matter, resulting in the enhanced degradation of p-nitrophenol (PNP) in solution. During the preparation of Fe3O4, the effect of sodium acetate was examined, and the results showed that the concentration of sodium acetate had little effect on the catalytic activity of the Fe3O4/PS/MW system but did have an effect on the Fe3O4 yield. In addition, with regards to the representative environmental factors, the degradation experiment showed that humic acid and the co-existing anions of chloride, sulfate, nitrate, and phosphate had little effects on p-nitrophenol removal; however, carbonate had a negative effect. In addition, the Fe3O4/PS/MW system performed well in the initial pH range of 3.0–9.0. According to the quenching experiment and electron paramagnetic resonance (EPR) detection, sulfate radicals and a minority of hydroxyl radicals play dominant roles in the degradation process. In addition, the role of Fe3O4 was confirmed to take part in the degradation process by X-ray photoelectron spectroscopy (XPS) analysis. Because of the good performance observed in the water matrices of tap water and the Songhua River, these results demonstrate the potential application of the Fe3O4/PS/MW system for wastewater treatment.

Synthesis of CeO2 hollow microspheres with oxidase-like activity and their application in the catalytic degradation of p-nitrophenol

ABSTRACT CeO2 materials have received wide attention given their oxidase-like activity without the need for an unstable oxide substrate in the catalytic process. Nevertheless, their application and mechanism in the catalytic oxidation of refractory organic pollutants needs further study. Herein, CeO2 hollow microspheres (HMS) with an intrinsic oxidase-like activity were synthesised via a template-free hydrothermal method and their effectiveness in degrading p-nitrophenol(p-NP) was investigated. HMS showed a maximum p-NP degradation rate of 76.5% at a CeO2 dosage of 40 mg, 2 h reactive time, at 30°C and pH of 4.8 when the concentration of p-NP was 20 mg L−1. The catalytic activity of CeO2 HMS also exhibited good thermal stability and reusability. These results provide strong evidence that CeO2 HMS can be utilised as an oxidase mimetic for the efficient catalytic degradation of refractory organic pollutants. A possible mechanism for the degradation of p-NP is also discussed.

Catalytic degradation of PNP and stabilization/solidification of Cd simultaneously in soil using microwave-assisted Fe-bearing attapulgite

A novel Fe-bearing attapulgite (Fe/ATP) as microwave (MW) absorber, cadmium (Cd) stabilizer and active catalyst to simultaneously stabilize/solidify Cd and oxidize p-nitrophenol (PNP) in soil was reported. The toxicity characteristic leaching procedure tests showed 80% of Cd was successfully stabilized in soil with Fe/ATP addition, whereas Cd stabilization efficiency of 99.3% was successfully achieved in MW-assisted Fe/ATP system. In addition, the long-term stabilization efficiency of Cd (180-day of curing) increased about 2-fold in MW-assisted Fe/ATP system compared with Fe/ATP system. XRD, FTIR, and XPS studies showed that Cd was more mineral-integrated than surface-bound with Fe/ATP, and a part of the stabilized Cd in Fe/ATP transformed into ferrite or encapsulated in vitrification with MW irradiation. Fe/ATP also showed extremely high catalytic performance for PNP oxidation, achieving complete PNP removal from soil within 20min of MW irradiation. The enhancements of Cd stabilization and PNP removal were attributed to the “hot spots” effect on the Fe/ATP surface with MW excitation. In addition, active species (holes, OH, and O2−) generated from the redox of Fe2+–Fe3+ species were responsible for the PNP degradation. The use of Fe/ATP to catalytic oxidize PNP and stabilize/solidify Cd under MW irradiation was demonstrated to be an effective method for rapid remediation of organic-heavy metal co-contaminated soil.

Photodegradation of p-nitrophenol using octahedral Cu2O particles immobilized on a solid support under a tungsten halogen lamp

Octahedral Cu2O particles were prepared on an indium-tin oxide glass via electrodeposition and were employed in the catalytic degradation of p-nitrophenol in the presence of H2O2. Under irradiation of a warm visible-light source, tungsten halogen lamp, Cu2O particles not only acted as a photocatalyst, but might also act as a thermal-catalyst to induce the decomposition of H2O2 and produce O2 at higher temperatures. The photogenerated electrons and holes could react with H2O2, O2, and H2O to produce abundant OH radicals, resulting in the effective oxidation of p-nitrophenol. High-performance liquid chromatography measurements of degradation intermediates showed that p-nitrophenol was first decomposed into hydroquinone and benzoquinone and then mineralized. The degradation efficiency was dependent on electrodeposition time, light intensity, H2O2 amount, and solution temperature. This catalyst could be easily recycled and used in the efficient degradation of other phenolic compounds.