Wentao Li

Synthesis of akageneite (beta-FeOOH)/reduced graphene oxide nanocomposites for oxidative decomposition of 2-chlorophenol by Fenton-like reaction

In this work, the composite of reduced graphene oxide and akageneite (Ak/rGO) was synthesised by co-precipitating and reduction processes. The morphological and structural features of the synthesized composites (Ak/rGO) were characterized by XRD, SEM, BET, FTIR, Zeta potential and XPS. The results revealed that (1) beta-FeOOH was successfully loaded on the reduced graphene oxide (rGO); (2) the presence of strong interfacial interactions (Fe-O-C bonds) between rGO and beta-FeOOH was observed; (3) the reduction of graphene oxide may be inhabited in the formation process of beta-FeOOH, producing rGO sheets rather than rGO sphere. In the heterogeneous Fenton-like reaction, the degradation rate constants of 2-chlorophenol (2-CP) increased 2-5 times after the addition of rGO probably due to the Fe-O-C bond. The increase of the content of rGO could contribute to the removal of 2-CP, due to the synergy of catalysis and 2-CP adsorption towards Ak/rGO. In this study, the Ak/rGO composite has exhibited great potential and significant prospects for environmental application.

Synergistic effect of humic and fulvic acids on Ni removal by the calcined Mg/Al layered double hydroxide

Discharge of Ni(II) containing wastewater to terrestrial environment can lead to serious pollution issues. This study presents a facile, cost-effective and highly efficient method to rapidly remove Ni(II) from wastewater using a calcined Mg/Al layered double hydroxide (LDH), which is a pioneering investigation of using the calcined LDH to remove the positively charged Ni(II) ions. The kinetic studies showed that the removal of Ni(II) was very rapid with a pseudo first order k of up to 3.6 ± 0.5 h−1, and maximum removal of Ni(II) was up to 204.2 ± 10.6 mg g−1. In addition, our results reveal that both humic (HA) and fulvic acids (FA) can strongly bind to the surface of the LDH, which demonstrates that the calcined LDH can effectively remove both cationic and anionic pollutants in a single process. With the increase of pH up to 7.5, the removal of Ni, HA and FA by the calcined LDH are all drastically enhanced. Our study also demonstrated a strong synergetic effect of FA and HA on the Ni(II) removal by the calcined LDH, with a maximum Ni(II) removal of 290.6 ± 16.4 mg g−1 and 480.4 ± 21.3 mg g−1 at pH 7, respectively. The possible mechanism of the Ni(II) removal can be due to the incorporation of Ni into the layered structure by replacing the leached Mg in the layers of the LDH during the process of rehydration of the calcined LDH. The HA or FA bound on the surface of the rehydrated LDH can induce an additional Ni(II)-HA or -FA complexation consequently leading to the enhancement of the Ni removal. The trial of treating a high Ni-containing wastewater in practice indicates that the calcined LDH is a promising material for metal containing wastewater treatment.

Investigation of adsorption and photocatalytic activities of in situ cetyltrimethylammonium bromide-modified Bi/BiOCl heterojunction photocatalyst for organic contaminants removal

Bi/BiOCl heterojunction was prepared via a hydrothermal method, using cetyltrimethylammonium bromide (CTAB) as a stabilizing agent. The structure and chemical properties of Bi/BiOCl with the three different CTAB contents were thoroughly analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), UV-vis diffuse reflectance spectra (UV-vis DRS), zeta potential, and carbon element analysis, the results indicates that there are some important interactions between CTAB and Bi/BiOCl, resulting in decreasing the band gap of Bi/BiOCl with the increase of CTAB content. Two typical dyes, rhodamine B (RhB) and methyl orange (MO) which has different surface charges, were choosed as the target pollutants. Under the visible light (λ = 420 nm), the photocatalytic efficiency of Bi/BiOCl with a higher CTAB (Bi/BiOCl-a) was 3.72-fold more than that of Bi/BiOCl with a lower CTAB (Bi/BiOCl-c) to remove RhB. Bi/BiOCl heterojunction alone exhibited a poor degradation capability for the MO such as 5% of MO photodegradation with Bi/BiOCl-c. In contrast, MO removal efficiency by the Bi/BiOCl-a was 100%. Hence, the CTAB could play an important role to enhance the removal of dyes. Firstly, CTAB could absorb the target pollutants near the surface of Bi/BiOCl due to the electrostatic attraction and dispersion interaction; then Bi/BiOCl could degrade the pollutants via the in situ h+ or ˙O2− under the visible light. The proposed mechanism was supported by the FTIR and adsorption analysis.

One-step synthesis of aluminum magnesium oxide nanocomposites for simultaneous removal of arsenic and lead ions in water

Aluminum magnesium oxide nanocomposites were prepared via a one-step microwave assisted solvothermal method, and they showed high adsorption capacities for the removal of both of As(V) and Pb(II) ions in water.

Effect of in situ Fe(II)/Fe(III)-doping on the visible light-Fenton-like catalytic activity of Bi/BiOBr hierarchical microspheres

Novel Fe(II)/Fe(III) doped Bi/BiOBr (FBB) visible light photocatalysts with heterojunctions were successfully prepared by a facile solvothermal method. The as-prepared samples were characterized via XRD, FESEM, XPS, UV-vis absorption spectroscopy and N2 adsorption–desorption. The results demonstrate that Fe doping plays key roles in the transformation of amorphous to crystal phase for Bi metal nanoparticles and the increase of specific surface areas for FBB. The degradation of rhodamine B (RhB) was studied using FBB with hydrogen peroxide (H2O2) under visible light irradiation (λ = 420 nm); it was found that the degradation rate constant for 0.2-FBB (Fe/Bi molar ratio = 0.2) is 4-fold more than that for pure BiOBr. The presence of visible light enhances the Fenton-like reaction by the reduction of Fe(III) to Fe(II), producing more holes and hydroxyl radicals to degrade RhB. This result is confirmed by ESR spectroscopy, H2O2 consumption and surface Fe(II) concentration experiments. Radical scavenger experiments demonstrated that the active species follow the order holes > hydroxyl radicals. After five cycles, 0.2-FBB retains stable catalytic activity.

Separation and determination of estrogen in the water environment by high performance liquid chromatography-fourier transform infrared spectroscopy

The components for connecting high-performance liquid chromatography (HPLC) with Fourier-transform infrared spectroscopy (FTIR) were investigated to determine estrogen in the water environment, including heating for atomization, solvent removal, sample deposition, drive control, spectrum collection, chip swap, cleaning and drying. Results showed that when the atomization temperature was increased to 388 K, the interference of mobile phase components (methanol, H2O, acetonitrile, and NaH2PO4) were completely removed in the IR measurement of estrogen, with 0.999 of similarity between IR spectra obtained after separation and corresponding to the standard IR spectra. In experiments with varying HPLC injection volumes, high similarity for IR spectra was obtained at 20 ul injection volume at 0.01 mg/L BPA while a useful IR spectrum for 10 ng/L BPA was obtained at 80 ul injection volume. In addition, estrogen concentrations in the natural water samples were calculated semi-quantitatively from the peak intensities of IR spectrum in the mid-infrared region.

Inspection of Feasible Calibration Conditions for UV Radiometer Detectors with the KI/KIO3 Actinometer

UV radiometers are widely employed for irradiance measurements, but their periodical calibrations not only induce an extra cost but also are time‐consuming. In this study, the KI/KIO3 actinometer was applied to calibrate UV radiometer detectors at 254 nm with a quasi‐collimated beam apparatus equipped with a low‐pressure UV lamp, and feasible calibration conditions were identified. Results indicate that a washer constraining the UV light was indispensable, while the size (10 or 50 mL) of a beaker containing the actinometer solution had little influence when a proper washer was used. The absorption or reflection of UV light by the internal beaker wall led to an underestimation or overestimation of the irradiance determined by the KI/KIO3 actinometer, respectively. The proper range of the washer internal diameter could be obtained via mathematical analysis. A radiometer with a longer service time showed a greater calibration factor. To minimize the interference from the inner wall reflection of the collimating tube, calibrations should be conducted at positions far enough away from the tube bottom. This study demonstrates that after the feasible calibration conditions are identified, the KI/KIO3 actinometer can be applied readily to calibrate UV radiometer detectors at 254 nm.

A Green Method to Determine VUV (185 nm) Fluence Rate Based on Hydrogen Peroxide Production in Aqueous Solution

A mini‐fluidic vacuum ultraviolet/ultraviolet (VUV/UV) photoreaction system (MVPS) was developed in our previous study. Based on the MVPS, a green method to determine VUV fluence rate has been developed using the production rate of H2O2 when water is exposed to 185 nm VUV. The H2O2 production followed pseudo‐zero‐order reaction kinetics well over the first 10 min of VUV/UV exposure. This new method was well calibrated with a standard cis‐cyclooctene cis–trans photoisomerization actinometer as recommended by the International Union of Pure and Applied Chemistry. The apparent quantum yield for H2O2 production by 185 nm VUV irradiation of water was determined to be 0.024 ± 0.002. As the solution pH increased from 5.0 to 8.0, the H2O2 production rate decreased from 0.83 to 0.40 μm min–1. Dissolved oxygen had a negligible influence on the H2O2 production. This study proposes a novel VUV fluence rate determination method with advantages of nontoxicity, low detection limits, low costs and convenience, and it can be used as a good alternative to traditional actinometers.

Experimental Evaluation of Turbidity Impact on the Fluence Rate Distribution in a UV Reactor Using a Microfluorescent Silica Detector

Turbidity is a common parameter used to assess particle concentration in water using visible light. However, the fact that particles play multiple roles (e.g., scattering, refraction, and reflection) in influencing the optical properties of aqueous suspensions complicates examinations of their effects on ultraviolet (UV) photoreactor performance. To address this issue, UV fluence rate (FR) distributions in a photoreactor containing various particle suspensions (SiO2, MgO, and TiO2) were measured using a microfluorescent silica detector (MFSD). Reflectance of solid particles, as well as transmittance and scattering properties of the suspensions were characterized at UV, visible, and infrared (IR) wavelengths. The results of these measurements indicated that the optical properties of all three particle types were similar at visible and IR wavelengths, but obvious differences were evident in the UV range. The FR results indicated that for turbidity associated with SiO2 and MgO suspensions, the weighted average FR (WAFR) increased relative to deionized water. These increases were attributed to low particle photon absorption and strong scattering. In contrast, the WAFR values decreased with increasing turbidity for TiO2 suspensions because of their high particle photon absorption and low scattering potential. The findings also indicate that measurements of scattering and transmittance at UV wavelengths can be used to quantify the effects of turbidity on UV FR distributions.

On-site determination and monitoring of real-time fluence delivery for an operating UV reactor based on a true fluence rate detector

At present, on-site fluence (distribution) determination and monitoring of an operating UV system represent a considerable challenge. The recently developed microfluorescent silica detector (MFSD) is able to measure the approximate true fluence rate (FR) at a fixed position in a UV reactor that can be compared with a FR model directly. Hence it has provided a connection between model calculation and real-time fluence determination. In this study, an on-site determination and monitoring method of fluence delivery for an operating UV reactor was developed. True FR detectors, a UV transmittance (UVT) meter, and a flow rate meter were used for fundamental measurements. The fluence distribution, as well as reduction equivalent fluence (REF), 10th percentile dose in the UV fluence distribution (F10), minimum fluence (Fmin), and mean fluence (Fmean) of a test reactor, was calculated in advance by the combined use of computational fluid dynamics and FR field modeling. A field test was carried out on the test reactor for disinfection of a secondary water supply. The estimated real-time REF, F10, Fmin, and Fmean decreased 73.6%, 71.4%, 69.6%, and 72.9%, respectively, during a 6-month period, which was attributable to lamp output attenuation and sleeve fouling. The results were analyzed with synchronous data from a previously developed triparameter UV monitoring system and water temperature sensor. This study allowed demonstration of an accurate method for on-site, real-time fluence determination which could be used to enhance the security and public confidence of UV-based water treatment processes.