•The catalyst RFAM displayed excellent catalytic activity for the VLD photo-Fenton process at neutral pH.•Excellent capacity of RFAM ascribed to synergistic effects of α-FeOOH, rGO and the Al-MCM-41 support.•The effects of the contents of loading and bubbling gas were studied.•The energy utilization factor at different parameters and the degradation intermediates were studied.In this study, α-FeOOH on reduced graphene oxide (rGO-α-FeOOH) supported on an Al-doped MCM-41 catalyst (RFAM) was optimized for the visible-light photo-Fenton oxidation of phenol at neutral pH. The stability of the catalysts, effect of bubbling aeration, and degradation intermediates were investigated. Results indicated that RFAM with a large Brunauer-Emmett-Teller (BET) area and mesoporous structure displayed excellent catalytic activity for the visible-light-driven (VLD) photo-Fenton process. Phenol degradation was well described by a pseudo-first-order reaction kinetics model. Raman analysis demonstrated that an rGO-α-FeOOH (RF) composite is formed during the ferrous-ion-induced self-assembly process. Al-MCM-41 could uniformly disperse RF nanosheets and promote the mobility and diffusion of matter. The activity of the main catalyst α-FeOOH was enhanced after the incorporation of rGO nanosheets. The α-FeOOH crystal in RFAM showed catalytic activity superior to those of Fe3O4 and Fe2O3. The RFAM catalyst, with an optimal GO-Fe2+mass ratio of 2.33, exhibited a larger BET area, pore size, and pore volume, and thus exhibited high performance and energy utilization efficiency in the VLD photo-Fenton reaction with remarkable stability. Bubbling N2 inhibited catalytic performance, while bubbling O2 or air only slightly accelerated the phenol degradation. Visible light played an important role in accelerating the formation of reactive oxygen species (·OH) for the highly efficient phenol degradation. Analysis of degradation intermediates indicated a high phenol mineralization level and the formation of low-molecular-weight organic acids. This work would be helpful in providing an insight into a new type of catalyst assembly and a possible route to a promising heterogeneous catalyst applicable in the visible light photo-Fenton process for effective wastewater remediation at neutral pH.

A Co-doped modified PbO2 electrode was prepared to electrocatalytically oxidize IBU in aqueous solution. The effects of initial IBU concentration (40–320 mg L−1), initial pH (4–10), current density (3–30 mA cm−2), natural organic matter and small molecular organic acid were investigated. The structure, morphology and electrochemical properties of the electrode were studied by X-ray diffraction, scanning electron microscopy, linear sweep voltammetry and cyclic voltammograms. The doping of Co may decrease the particle size and increase the lifetime of PbO2, which favors the electrocatalytic activity. The results indicated that the Co-PbO2 electrode exhibited a highly effective oxidation capacity for IBU. After 60 min of electrolysis, the removal of IBU and COD at a current density of 3 mA cm−2 for 80 mg L−1 of IBU reached 98.7% and 32.1%, respectively, and the degradation of COD was 53.6% after 180 min of reaction. The reaction apparently followed a first-order kinetics model. When the IBU initial concentration was 80 mg L−1, the highest reaction rate and energy efficiency were observed. Considering the energy demand and space efficiency, the applied current density of 3 mA cm−2 was the most suitable. Lower pH favored degradation because the oxygen evolution reaction was restrained. The addition of low concentrations (10 mg L−1) of humic acid and fulvic acid could promote the degradation of IBU, whereas high concentrations (20–40 mg L−1) inhibited the degradation of IBU. Moreover, the addition of oxalic acid and citric acid (0.1–0.5 mmol L−1) could inhibit IBU degradation. Finally, the possible reaction pathways were proposed.

A new heterogeneous Fenton catalyst, mesoporous MCM-41 supported reduced graphene oxide-Fe (rGO-Fe/MCM-41), was synthesized via a hybrid hydrothermal-calcination treatment. The physicochemical characteristics of the catalyst were evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FT-IR) and surface area (BET) analysis. The results indicated that the rGO-Fe/MCM-41 possessed a mesoporous structure. The effective reduction of GO to rGO and a high degree of α-Fe2O3 loading were observed. After the incorporation of rGO, the activity and stability of the catalyst in phenol degradation significantly increased. The kinetics of phenol degradation fit the first order kinetic model well. The effects of Fe and GO dosage, as well as calcination temperature, were investigated. The XRD and the Raman scattering demonstrated that the reduction of GO was more effective, and the α-Fe2O3 crystal structure was formed when calcination temperature is 550 °C, which beneficially increased the catalytic activity.

The spatial distributions and sources of polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Yangtze Estuary were systematically analyzed. The results indicated significant spatial variations. The mean of ∑PAHs in different sampling times in a year varied from 128.5 ± 51.4 to 307.8 ± 108.9 ng g−1. Samples collected during the flood season showed higher PAH concentrations and larger PAH fluctuations compared with those collected during the dry season. This variation was mainly ascribed to the change in the river flow rate. Higher values of ∑PAHs were observed in the inner estuary than the adjacent coastal area over a year because of diffusion and degradation effects. Analysis of PAH abundance revealed a predominant proportion of light PAHs with two to three rings, with phenanthrene being the most abundant. Based on principal component analysis, vehicular emissions, coal and biomass combustion were the main sources of PAHs.

Magnetic Cu2+-chelated silica particles using polyacrylamide as a metal-chelating ligand was developed and used for the immobilization of laccase by coordination. The effect of pH and temperature on the enzymatic property of immobilized laccase and its catalytic capacity for pentachlorophenol (PCP) degradation were evaluated systemically. Compared with free laccase, the immobilized laccase showed improved acid adaptability and thermal stability. The immobilized laccase prepared in this work exhibited a good catalytic capacity for PCP removal from aqueous solutions.

The erbium (Er)–chitosan–fluorine (F) modified PbO2 electrode was prepared by electrodeposition method, and its use for adsorption and electrochemical degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution was compared with F–PbO2 and Er–F–PbO2 electrodes in a batch experiment. The electrodes were characterized by scanning electron microscopy, X-ray diffraction and cyclic voltammetry. Degradation of 2,4-DCP depending on Er and chitosan contents was discussed. The results showed that Er2O3 and chitosan were scattered between the prevailing crystal structure of β-PbO2 and thus decreased the internal stress of PbO2 film. Prior to each electrolysis, the modified PbO2 anode was first pre-saturated with 2,4-DCP solution for 360 min to preclude the 2,4-DCP decrease due to adsorption. Among the electrodes examined in our study, the highest adsorption and electrochemical degradation for 2,4-DCP and TOC removals that are due to oxidation and adsorption of the organic products onto the chitosan was observed on Er–chitosan–F–PbO2 electrode. At an applied current density of 5 mA cm−2, the removal percentages of 2,4-DCP and TOC (solution volume: 180 mL, initial 2,4-DCP concentration: 90 mg L−1) were 95% after 120 min and 53% after 360 min, respectively. At Er amount of 10 mM in the precursor coating solution, the degradation and mineralization removal for 2,4-DCP on the Er–F–PbO2 electrode reached a maximum. At chitosan amount of 5 g L−1, the highest TOC removal on the Er–chitosan–F–PbO2 electrode was observed. Intermediates mainly including aliphatic carboxylic acids were examined and a possible degradation pathway for 2,4-DCP in aqueous solution involving dechlorination and hydroxylation reactions was proposed.

The adsorption of phosphorus (P) onto three industrial solid wastes (fly ash, red mud and ferric–alum water treatment residual (FAR)) and their modified materials was studied systematically via batch experiments. Compared with two natural adsorbents (zeolite and diatomite), three solid wastes possessed a higher adsorption capacity for P because of the higher Fe, Al and Ca contents. After modification (i.e., the fly ash and red mud modified by FeCl3 and FARs modified by HCl), the adsorption capacity increased, especially for the modified red mud, where more Fe bonded P was observed. The P adsorption kinetics can be satisfactorily fitted using the pseudo-second-order model. The Langmuir model can describe well the P adsorption on all of the samples in our study. pH and dissolved organic matter (DOM) are two important factors for P adsorption. Under neutral conditions, the maximum adsorption amount on the modified materials was observed. With the deviation from pH 7, the adsorption amount decreased, which resulted from the change of P species in water and surface charges of the adsorbents. The DOM in water can promote P adsorption, which may be due to the promotion effects of humic-Fe(Al) complexes and the pH buffer function exceeds the depression of competitive adsorption.Download high-res image (242KB)Download full-size image

•Novel SLD Fenton catalyst was synthesized via in-situ induced self-assembly process.•RGO improved light-harvesting capacity and enhanced electro-transport performance.•Visible light irradiation accelerated reaction and extended operating pHs (4.0–8.0).•H2O2 reduction and H2O oxidation yielded ·OH in FeⅡ/FeⅢ and FeⅢ/FeⅣ cycling process.A novel solar-light-driven (SLD) Fenton catalyst was developed by reducing the ferrous-ion onto graphene oxide (GO) and forming reduced graphene oxide/α-FeOOH composites (RF) via in-situ induced self-assembly process. The RF was supported on several mesoporous supports (i.e., Al-MCM-41, MCM-41 and γ-Al2O3). The activity, stability and energy use for phenol oxidation were systematically studied for a wide pH range. Furthermore, the catalytic mechanism at acid and alkaline aqueous conditions was also elucidated. The results showed that Fe(II) was reduced onto GO nanosheets and α-FeOOH crystals were formed during the self-assembly process. Compared with Fenton reaction without SLD irradiation, the visible light irradiation not only dramatically accelerated the rate of Fenton-based reactions, but also extended the operating pH for the Fenton reaction (from 4.0 to 8.0). The phenol oxidation on RF supported catalysts was fitting well with the pseudo-first-order kinetics, and needed low initiating energy, insensitive to the reacting temperature changes (273–318 K). The Al-MCM-41 supported RF was a more highly energy-efficient catalyst with the prominent catalytic activity at wide operating pHs. During the reaction, OH radicals were generated by the SLD irradiation from H2O2 reduction and H2O oxidation in the FeⅡ/FeⅢ and FeⅢ/FeⅣ cycling processes.Schematic of the preparation of RF supported catalysts and the reaction mechanism for SLD Fenton catalytic degradation of aqueous phenol.Download high-res image (148KB)Download full-size image

•The characteristics of DOM extracted from four particle-size sediments were compared.•Particle size obviously influenced the quality and quantity of extracted DOM.•Protein-like material dominated in DOM and processed a stronger complex capacity with As/Sb.•The binding capacity of DOM with As/Sb decreased with the increasing particle size.•A positive correlation between complexation capacity and acidic functional group content.The characteristics of dissolved organic matter (DOM) extracted from sediments with four particle sizes (< 25, 63–25, 200–63 and > 200 μm) in the Yangtze Estuary were compared. The differences in their binding capacities for individual fluorescent components with As/Sb were studied using fluorescence-quenching titrations combined with excitation–emission matrix (EEM) spectra. The results indicated that the particle size influenced the quality and quantity of extracted DOM. With increasing particle size, the extracted DOM content, value of UV280 and acidic functional group content of the DOM decreased. Three protein-like components (C2, C3 and C4) and one humic-like component (C1) were identified using the parallel factor analysis (PARAFAC) model. Wherein, protein-like material dominated in DOM on different particle-size fractions and possessed a stronger complex capacity with As/Sb. A significant positive correlation between the complexation capacity of extracted DOM from samples, as well as with the acidic functional group content, was observed.

The spatial distributions and sources of polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Yangtze Estuary were systematically analyzed. The results indicated significant spatial variations. The mean of ∑PAHs in different sampling times in a year varied from 128.5 ± 51.4 to 307.8 ± 108.9 ng g−1. Samples collected during the flood season showed higher PAH concentrations and larger PAH fluctuations compared with those collected during the dry season. This variation was mainly ascribed to the change in the river flow rate. Higher values of ∑PAHs were observed in the inner estuary than the adjacent coastal area over a year because of diffusion and degradation effects. Analysis of PAH abundance revealed a predominant proportion of light PAHs with two to three rings, with phenanthrene being the most abundant. Based on principal component analysis, vehicular emissions, coal and biomass combustion were the main sources of PAHs.