Latest ArticlesIn this study, α-Bi2O3/g-C3N4 nanocomposite with direct Z-scheme was successfully prepared through calcination of BiOCOOH/g-C3N4 precursor at different temperature. Meanwhile, the effect of calcination temperature on the physicochemical properties of α-Bi2O3/g-C3N4 was studied. All results confirmed that calcination temperature greatly influences structural, morphology, surface states, photoelectrochemical property and photocatalytic (PC) performance of α-Bi2O3/g-C3N4 composite. Furthermore, the α-Bi2O3/g-C3N4 composite was applied as photocatalyst to degrade amido black 10B dye under visible light irradiation. It was found that the composite synthesized at 400 ℃ exhibited the highest PC performance due to the intense visible light absorbance and high separation efficiency of electron and hole pairs. Besides, the possible PC mechanism was proposed that the photo-generated charge carrier migration in α-Bi2O3/g-C3N4 photocatalyst followed a Z-scheme structure. Finally, the stability test also manifest that the α-Bi2O3/g-C3N4 composite photocatalyst has good stability and reusability, which was a promising candidate for wastewater treatment.
The heterogeneous reaction of SO2 on mineral dust surfaces is generally considered as an important chemical pathway for secondary sulfate formation in the troposphere. To this day, there are no reported studies that assess the impact of atmospheric CO2 in sulfate production on mineral dust surfaces. In this work, we investigate the impact of CO2 on SO2 uptake on dust proxy aluminum oxide particles using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). CO2 is demonstrated to suppress the heterogeneous oxidation of SO2 on alpha-Al2O3. Compared to that measured in the CO2-free case, the uptake coefficient is decreased by nearly 57% when Al2O3 particles are exposed to the gas flow with atmospheric CO2 at a relative humidity (RH) of 25%. It is also found that there is a balance between the yield of active moiety —OH provided by Al(OH)3(CO)(OH)2 clusters and the loss of basic hydroxyl group on aluminum oxide surfaces blocked by CO2-derived (bi)carbonate species. This work, for the first time, reveals a negative effect of atmospheric CO2 on the sulfate formation, which potentially decreases solar-radiation scattering and further exacerbates global warming.
The development in technology of synthetic azo dyes, has led to excessive water resources pollution. Even at lower concentration they can impart the quality of water and human life. Herein, we have developed a novel synthesis strategy via introducing salicylic acid (SA) for the synthesis of a leachy crystalline material H-MIL-53(Fe) with hierarchical pores (HP) and exposed coordination unsaturated sites (CUS), which had higher surface area and larger pore volume than the as synthesized MIL-53(Fe). Due to these characteristics, H-MIL-53(Fe) was competent removal of orange G (OG, one of the frequently used azo dyes) with equilibrium in 300 min and the maximum adsorption capacity of 163.9 mg/g. The adsorption mechanism of OG onto H-MIL-53(Fe) was mostly based on electrostatic attraction between CUS of H-MIL-53(Fe) along with HP as active species to OG diffusion and bind. By comparing H-MIL-53(Fe) with other adsorbents for OG adsorption, it is undoubtedly that H-MIL-53(Fe) can be used as a promising adsorbent for OG removal from aqueous solutions.
The contamination of antibiotics in aqueous environment causes increasing concerns recently. Light-assisted activation of peroxydisulfate (PDS) has been demonstrated as an efficient technology for removal of contamination in water. Herein, a hollow sphere of CuWO4 (h-CuWO4) was employed as a visible light-activated photocatalyst for the activation of PDS, and following with high removal efficiency (98%) of antibiotic sulfamethoxazole (SMX). Under visible light irradiation, the degradation rate on hollow structures system is nearly 2 times higher than the traditional solid CuWO4 spheres. Furthermore, the underlying mechanism and detailed pathway of SMX degradation were proposed based on density functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC–MS). This work provides a new feasible way for advanced oxidation processes to remove antibiotics SMX in heterogeneous system, and open up new application possibilities of CuWO4-based materials.
The porous g-C3N4 (PCN) nanosheets are successfully synthesized and further modified with nano-sized Ag by a simple wet-chemical process. Interestingly, the Ag-modified porous g-C3N4 (Ag-PCN) nanosheets exhibit competitive fluorescence detection performance of chloride ion (Cl-) in aqueous solution. Under the optimized conditions, the concentration of Cl- could be quantitative analyzed with the Ag-PCN in a wide detection range from 0.5 mmol/L to 0.1 mol/L, with a low detection limitation of 0.06 mmol/L. It is confirmed that the fluorescence of PCN could be effectively decayed by the photoinduced charge transfer via the adsorbed Cl- for trapping holes, mainly by means of the time-resolved fluorescence and surface photovoltage spectra. The porous structure and modified Ag promote the adsorption of Cl- on resulting Ag-PCN, leading to excellent fluorescence detection for Cl-. This work provides a feasible route to develop a fluorescence detection of Cl- with g-C3N4 nanosheets in environment water.
In this study, Fe2O3/Mn2O3 composite was synthesized by a facile two-step technique, and several methods were carried out to characterize it. Then, the decomposition experiments of tartrazine (TTZ), a kind of refractory organic pollutant, were conducted under various environmental condition to detect the catalyst performance, such as reaction system, the dosage of catalyst, peroxymonosulfate (PMS) concentration, initial pH, different natural water substances. The results exhibited that Fe2O3/Mn2O3 composite with the mole rate 2:3 had the best PMS activation performance and the removal efficiency was 97.3% within 30 min. Besides, the optimum degradation conditions of TTZ were also discussed, that is catalyst dosage (0.6 g/L), PMS concentration (0.8 g/L) and the initial pH 11. In addition, proved by the natural water substances adding experiments, HPO42-, HCO3-, NO3- and NOM (nature organic matter) could slow down the experiments progressing, but Cl- could boost it. Then inhibitor experiments indicated both the HO· and SO4·- played a vital role in the experiments. Reusability and ions leaching experiments as well as the used catalyst physical characterization images exhibited the excellent stability and cyclicity of the Fe2O3/Mn2O3 composite. Finally, based on the XPS (X-ray photoelectron spectroscopy) and the experiments results, the possible mechanism of TTZ degradation was proposed. This system might provide a novel thought for the decomposition of refractory organic pollutant and had potential in promotion of actual sewage treatment technology.
One of the core issues in the photocatalytic oxidation of nitric oxide is the effective conversion of NO into the final product (nitrate). More than just improving the visible light photocatalytic performance of BiOCl, we aim to inhibit the generation of toxic by-product NO2 during this process. In this study, we demonstrate that the oxygen vacancies (OVs) modulate its surface photogenerated carrier transfer to inflect the NO conversion pathway by a facile mixed solvent method to induce OVs on the surface of BiOCl. The photocatalytic NO removal efficiency under visible light increased from 5.6% to 36.4%. In addition, the production rate of NO2 is effectively controlled. The effects of OVs on the generation of reactive oxygen species, electronic transfer, optical properties, and photocatalytic NO oxidation are investigated by combining density functional theory (DFT) theoretical calculations, the in situ FTIR spectra and experimental characterization. The OVs on the surface of BiOCl speed the trapping and transfer of localized electrons to activate the O2, producing O2·-, which avoid NO2 formation, resulting in complete oxidation of NO (NO + O2·- → NO3-). These findings can serve as the basis for controlling and blocking the generation of highly toxic intermediates through regulating the reactive species during the NO oxidation. It also can help us to understand the role of OV on the BiOCl surface and application of photocatalytic technology for safe air purification.
Schiff base functionalized polyamidoamine (PAMAM) dendrimer/silica were prepared for the adsorption of aqueous Mn(Ⅱ) and Co(Ⅱ). The effects that influence the adsorption were investigated systematically and the adsorption mechanism was illustrated by theoretical calculation. The optimum adsorption pH are 4 and 6 for Mn(Ⅱ) and Co(Ⅱ). Adsorption kinetics follow pseudo-second-order model and the rate-controlling step is film diffusion process. Adsorption isotherm shows that high initial metal ion concentration facilitates the uptake of metal ions. The adsorption capacity increases first and then decreases in the temperature range of 15–35 ℃. Density functional theory (DFT) calculation demonstrates that Schiff base functionalized PAMAM dendrimer tends to coordinate Mn(Ⅱ) and Co(Ⅱ) with the oxygen atoms of hydroxyl and carbonyl groups, nitrogen of tertiary amine and imino groups. The imino and tertiary amine groups mainly dominate the adsorption. The reproducibility of the adsorbents indicates they can be regenerated by 5% thiourea and 0.5 mol/L HNO3 solution efficiently.
Graphitic carbon nitride (g-C3N4)-based materials are regarded as one of the most potential photocatalysts for utilizing solar energy. In this work, we reported a facile one step in-situ hydrothermal-roasting method for preparing honeycomb-like g-C3N4/CeO2 nanosheets with abundant oxygen vacancies (g-C3N4/CeO2-x). The hydrothermal-roasting and incomplete-sealed state can (ⅰ) generate an in-situ reducing atmosphere (CO, N2, NH3) to tune the concentration of oxygen vacancies in CeO2; (ⅱ) beneficial to prevent continuous growth of g-C3N4 and results in honeycomb-like g-C3N4/CeO2-x hybrid nanosheets. What is more, the g-C3N4/CeO2-x photocatalyst exhibited extended photoresponse range, increased specific surface area and obviously enhanced separation efficiency of photogenerated electron-hole pairs. As a proof-of-concept application, the optimized g-C3N4/CeO2-x nanosheets could achieve 98% removal efficiency for Cr(Ⅵ) under visible light irradiation (λ ≥ 420 nm) within 2.5 h, which is significantly better than those of pure g-C3N4 and CeO2. This work provides a new idea for more rationally designing and constructing g-C3N4-based catalysts for efficient extended photochemical application.
Electrochemical analysis is a promising technique for detecting biotoxic and non-biodegradable heavy metals. This article proposes a novel composite electrode based on a polyaniline (PANi) framework doped with bismuth nanoparticle@graphene oxide multi-walled carbon nanotubes (Bi NPs@GO-MWCNTs) for the simultaneous detection of multiple heavy metal ions. Composite electrodes are prepared on screen-printed electrodes (SPCEs) using an efficient dispensing technique. We used a SM200SX-3A dispenser to load a laboratory-specific ink with optimized viscosity and adhesion to draw a pattern on the work area. The SPCE was used as substrate to facilitate cost-effective and more convenient real-time detection technology. Electrochemical techniques, such as cyclic voltammetry and differential pulse voltammetry, were used to demonstrate the sensing capabilities of the proposed sensor. The sensitivity, limit of detection, and linear range of the PANi-Bi NPs@GO-MWCNT electrode are 2.57×102 μA L μmol-1 cm-2, 0.01 nmol/L, and 0.01 nmol/L–5 mmol/L and 0.15×10-1 μA L μmol-1 cm-2, 0.5 nmol/L, and 0.5 nmol/L–5 mmol/L for mercury ion (Hg(Ⅱ)) and copper ion (Cu(Ⅱ)) detection, respectively. In addition, the electrode exhibits a good selectivity and repeatability for Hg(Ⅱ) and Cu(Ⅱ) sensing when tested in a complex heavy metal ion solution. The constructed electrode system exhibits a detection performance superior to similar methods and also increases the types of heavy metal ions that can be detected. Therefore, the proposed device can be used as an efficient sensor for the detection of multiple heavy metal ions in complex environments.
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