Carboxyl-functionalized biochar derived from walnut shells with enhanced aqueous adsorption of sulfonamide antibiotics.

The novel HNO3-modifitied biochar (NBC) was synthesized from walnut shell. The NBC was characterized from scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectrum. The NBC was then used in the adsorption of sulfadiazine, sulfamethazine and sulfachloropyridazine from aqueous solution. The material surface has carbon/oxygen-contained groups, which is benefit for the adsorption. The results showed the adsorption ability of NBC on three sulfonamides were 32, 46, and 40 mg g-1, respectively. The kinetic was found to follow the Elovich model and the isotherm conformed Freundlich. Adsorption was more favorable at weak acidic solution. The interactions mainly include π-π EDA, electrostatic interaction, Lewis acid-base interaction, hydrophobic interaction and H-bond.

Magnetic Solid-Phase Extraction Based on Fe3O4/g-C3N4 Nanocomposite for the Determination of Polychlorinated Biphenyls and Polychlorinated Diphenyl Ethers in Environmental Waters.

The graphitic carbon nitride (g-C3N4) and the Fe3O4/g-C3N4 magnetic materials were synthesized in this paper. The structures of the materials were confirmed by a series of analysis. The Fe3O4/g-C3N4 was then used as a sorbent to adsorb polychlorinated diphenyl ethers and polychlorinated biphenyls. Different extraction conditions were examined, including adsorbent amount, salinity, pH of the sample matrix, adsorption time, reaction temperature, elution solvent and preconcentration factor. The maximum recoveries were obtained by employing methanol to desorb pollutants on 40.0 mg Fe3O4/g-C3N4 in 120.0 mL environmental water with a salinity of 5% (w/v) at a pH of 7 at 25 °C within 10 min. Using the optimized parameters, the detection limits of the method are between 0.01 and 0.04 µ · L-1 with a satisfying linear relationship. The adsorbent can be recycled at least 10 times with no significant reduction in the extraction efficiency.

Fabrication of Novel Z-Scheme Bi2WO6/NaBiO3 Nanocomposites with Enhanced Photocatalytic Activity in the Degradation of 2,3-Dichlorophenol.

The Z-scheme Bi2WO6/NaBiO3 nanocomposites were first fabricated by a facile hydrothermal method, and were then characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive spectrometer, Fourier-transform-infrared spectroscopy, X-ray photoelectron spectroscopy and N2 adsorption-desorption. The as-prepared Bi2WO6/NaBiO3 nanocomposites exhibit outstanding photocatalytic activity and recyclability. A 98.4% photodegradation of 2,3-dichlorophenol (50 mg·L-1) was attained in the presence of Bi2WO6/NaBiO3 (1:10) under the visible-light irradiation in 30 min. In particular, the photocatalytic mechanism has been discussed in detail, based on four aspects: (1) oxidative species, (2) photoelectrochemical performance, (3) conduction band and valence band energy levels and (4) possible transition states and reactions. In conclusion, O-2 is the main active oxidative species in the Bi2WO6/NaBiO3 nanocomposite. The material has higher photocurrent and visible light adsorption but lower electron-hole pairs recombination, which contributes to distinguished photocatalytic efficiency. The Z-scheme photocatalytic path was proposed and the possible degradation process and routes have been summarized.

Synthesis of Bi2MoO6/Bi2Ti2O7 Z-Scheme Heterojunction as Efficient Visible-Light Photocatalyst for the Glycolic Acid Degradation.

A novel Bi2MoO6/Bi2Ti2O7 heterojunction photocatalyst was firstly prepared by a simple solvothermal route. The as-synthesized photocatalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy and photoluminescence spectra. The effect of the material ratio, solution pH, and the salinity on glycolic acid degradation were discussed. The Bi2MoO6/Bi2Ti2O7 (2:1) nanocomposite exhibits highest photocatalytic performance and chemical stability. The glycolic acid degradation efficiency can reach 99.9% at pH 4 after 150 min irradiation under visible light. The enhanced photocatalytic activity can be ascribed to the heterojunction interface in the composite, which is beneficial to the efficient charge carriers transfer. The degradation conforms to the pseudo-first-order kinetics. According to the oxidation species trapping experiments, the ·O2-, h+ and ·OH are found to play important roles in the photocatalytic degradation and ·O2- is the main active species. The possible photocatalytic mechanism was further discussed on account of valence band, conduction band positions and possible transition states.

Magnetic adsorbent based on mesoporous silica nanoparticles for magnetic solid phase extraction of pyrethroid pesticides in water samples.

Mesoporous KIT-6-magnetite composite (Fe3O4@SiO2@KIT-6) was successfully prepared and characterized by transmission electron microscopy, scan electron microscopy, elemental mapping, energy dispersive X-ray spectrum, Fourier transform infrared spectroscopy, thermal gravimetric analysis, X-ray powder diffraction, Brunauer Emmett Teller analysis and magnetic property analysis. It was then applied as adsorbent for magnetic solid phase extraction of fenpropathrin, lambda-cyhalothrin, S-fenvalerate and bifenthrin from water samples before analyzed by high performance liquid chromatography-ultraviolet detector. A few factors impacting extraction were studied. The optimal results were acquired by using acetonitrile to eluent the targets adsorbed on 40 mg of Fe3O4@SiO2@KIT-6 adsorbent in 100 mL water samples at a pH of 7 at 25 ℃ within 10 min. The experimental limit of detections of fenpropathrin, cyhalothrin, S-fenvalerate and bifenthrin are 0.01 × 10-3, 0.006 × 10-3, 0.01 × 10-3 and 0.005 × 10-3 mg∙L-1, respectively. Good relative recoveries (86.58-98.80%) and reproducibility values are also obtained. The kinetic experiment shows that the adsorption follows pseudo-second order, while the isotherm experiment follows Langmuir isotherm model. Trace pyrethroid pesticides in water samples can be detected by the developed magnetic solid phase extraction technique followed by high performance liquid chromatography, which is simple, easy, environmental friendly and efficient.