An in situ formed Fe–Mn binary oxide (FMBO) was successfully fabricated for efficient removal of 17α-ethinylestradiol (EE2) from water. Moreover, manganese oxide (MnO2) and ferric oxide (FeOOH) were also studied for the comparison of EE2 removal efficiency and FMBO showed a better removal capacity towards EE2 than both MnO2 and FeOOH. Various removal conditions including contact time, pH and coexisting ions were investigated. The results showed that the best removal capacity was obtained at pH 6.0 and FMBO rapidly reached a removal efficiency of approximately 96% in 30 min at pH 6.0. The retarded first-order kinetic model was able to simulate the entire removal kinetics (R2 = 0.96). Besides, it was found that the investigated coexisting ions (SO42−, Ca2+, Mg2+, Fe3+) did not have an obvious effect on EE2 removal, while phosphate, carbonate, and manganous ions reduced the removal efficiency, especially phosphate. Fourier transform infrared and X-ray photoelectron spectroscopy results were investigated and they revealed that EE2 was adsorbed through hydrogen bonding and then oxidized by MnO2 on FMBO, which contributed to further degradation of EE2. Besides, the intermediates during removal were studied by gas chromatography-mass spectroscopy, indicating that the products still kept the core ring structure of estrogen while lowering estrogen activity. Above all, FMBO can be used as a promising material to remove EE2.

An in situ formed Fe–Mn binary oxide (FMBO) was successfully fabricated for efficient removal of 17α-ethinylestradiol (EE2) from water. Moreover, manganese oxide (MnO2) and ferric oxide (FeOOH) were also studied for the comparison of EE2 removal efficiency and FMBO showed a better removal capacity towards EE2 than both MnO2 and FeOOH. Various removal conditions including contact time, pH and coexisting ions were investigated. The results showed that the best removal capacity was obtained at pH 6.0 and FMBO rapidly reached a removal efficiency of approximately 96% in 30 min at pH 6.0. The retarded first-order kinetic model was able to simulate the entire removal kinetics (R2 = 0.96). Besides, it was found that the investigated coexisting ions (SO42−, Ca2+, Mg2+, Fe3+) did not have an obvious effect on EE2 removal, while phosphate, carbonate, and manganous ions reduced the removal efficiency, especially phosphate. Fourier transform infrared and X-ray photoelectron spectroscopy results were investigated and they revealed that EE2 was adsorbed through hydrogen bonding and then oxidized by MnO2 on FMBO, which contributed to further degradation of EE2. Besides, the intermediates during removal were studied by gas chromatography-mass spectroscopy, indicating that the products still kept the core ring structure of estrogen while lowering estrogen activity. Above all, FMBO can be used as a promising material to remove EE2.

•First report on the use of a fungal-bacterial consortium for the biodegradation of CB.•The biodegradation rate of consortium was 1.5 times more than that of single one.•The addition of fungus LW-1 could relieve the inhibition of 2-CP to bacterium L2.•RT-PCR analysis confirmed the strains growing with different rates at various times.•The interactions within the different microorganisms led to the enhanced biodegradation.A defined consortium of Ralstonia pickettii L2 (bacterium) and Trichoderma viride LW-1 (fungus) was selected to assess its potential for the enhanced biodegradation of mono-chlorobenzene (CB). At an initial concentration of 220 mg L−1 CB, the developed consortium showed an enhanced degradation rate of 0.50 mg CB·g−1protein·h−1, while the individual Ralstonia sp. L2 and Trichoderma sp. LW-1 showed average degradation rates of 0.34 and 0.32 mg CB·g−1protein·h−1, respectively. A CO2 conversion level of up to 86.3% reflected a possible high mineralization extent of CB by the co-culture. The estimated μmax and vmax values were 0.36 h−1 and 0.41 h−1 for the consortium, which were much higher than the values obtained by each strain individually. 2-Chlorophenol (2-CP) accumulated in the growth medium of strain L2 and inhibited its growth, but it could be consumed quickly by the fungus LW-1, providing a possibility to reach complete biodegradation of CB in a short time. Real-time PCR revealed that bacterium L2 played a major role in the initial stage, and that fungus LW-1 grew well if 2-CP was generated. These results suggest that the fungal-bacterial consortium might be effectively applied for complete biodegradation of CB and have a potential environmental implication in purification of CB-contaminated environments.Download high-res image (271KB)Download full-size image

Chlorobenzene removal was investigated in a non-thermal plasma reactor using CeO2/HZSM-5 catalysts. The performance of catalysts was evaluated in terms of removal and energy efficiency. The decomposition products of chlorobenzene were analyzed. The results show that CeO2/HZSM-5 exhibited a good catalytic activity, which resulted in enhancements of chlorobenzene removal, energy efficiency, and the formation of lower amounts of by-products. With regards to CO2 selectivity, the presence of catalysts favors the oxidation of by-products, leading to a higher CO2 selectivity. With respect to ozone, which is considered as an unavoidable by-product in air plasma reactors, a noticeable decrease in its concentration was observed in the presence of catalysts. Furthermore, the stability of the catalyst was investigated by analyzing the evolution of conversion in time. The experiment results indicated that CeO2/HZSM-5 catalysts have excellent stability: chlorobenzene conversion only decreased from 78% to 60% after 75 hr, which means that the CeO2/HZSM-5 suffered a slight deactivation. Some organic compounds and chlorinated intermediates were adsorbed or deposited on the catalysts surface as shown by the results of Fourier Transform Infrared (FT-IR) spectroscopy, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses of the catalyst before and after the reaction, revealing the cause of catalyst deactivation.Download high-res image (83KB)Download full-size image

•Typical transition metal cobalt (Co) modified PbO2 electrode was prepared.•Co2+ improved the catalytic activity of PbO2 electrode.•Co-PbO2 electrode was characterized by the steady-state polarization curves and cyclic voltammetry.•Electrochemical method is proved to be a useful way of degrading metronidazole.•The main metronidazole electrochemical degradation pathway was proposed.This study presents an electrochemical method for the degradation of metronidazole (MNZ) in aqueous solution with novel PbO2 electrode, which was prepared via electrodeposition in nitrate solution. The influencing factors on electrochemical decomposition of pollutants were evaluated and the removal of MNZ and chemical oxygen demand (COD) reached 78.09% and 21.77% after 120 min treatment under the optimal conditions with the concentration of supporting electrolyte, the initial concentration of MNZ, the pH and the current density were 0.10 mol/L, 100 mg/L, 6.4 and 10 mA/cm2, respectively. Then, the Co doped PbO2 electrodes were prepared and used to degrade MNZ under the optimal conditions. Relatively good performance was achieved when the molar ratio of Pb and Co was 100:1. Compared to pure PbO2 electrode, the steady-state polarization curves and cyclic voltammetry analysis showed that 1.0% Co-PbO2 electrode had a higher oxygen evolution potential and greater current of reduction and oxidation peaks, which increased the electrochemical activity and decreased the energy consumption. Finally, based on the intermediate products identified by IC and GC/MS, the main degradation pathway of MNZ was proposed including ring open, denitrification and radical reactions.

In this study, the kinetics and mechanism of direct ozonation organics in aqueous solution were explored. Phenoxyacetic acid was selected as the model pollutant and ozonation experiments were performed in a bubble batch reactor to determine the rate constants for the direct reaction. Two kinetic methods were used for determination of different kinetic rate constants (kapp and ki). The first group of results showed that degradation of phenoxyacetic acid followed pseudo-first-order kinetics. A simplified model was derived related to the operational parameters on phenoxyacetic acid degradation, and the apparent rate constant kapp was obtained. The reaction was proved in the slow kinetics of the gas–liquid reaction, and the kinetic constant ki was built. Influence of pH on kapp and ki, the O3 dosage, and the initial phenoxyacetic acid concentration were carefully analyzed.

•The effects of different parameters were studied.•A possible degradation pathway of PAA by ozonation was proposed.•The kinetic mechanism in the initial stage of ozonation was analyzed.This study aims to investigate degradation mechanisms and kinetics of phenoxyacetic acid by ozonation in aqueous solution. The optimized operating condition was achieved by phenoxyacetic acid and total organic carbon (TOC) removal based on the studies of the effects of various parameters, such as pH value (4–12), the initial concentration of phenoxyacetic acid (100–2000 mg L−1) and the ozone dosage (16–48 mg min−1). A series of intermediates were formed in the ozonation process and detected by GC/MS and HPLC analysis, such as phenyl formate, salicylic acid, phenol, oxalic acid and small molecule acids. A possible degradation pathway of phenoxyacetic acid was proposed. The kinetic analysis showed that phenoxyacetic acid degradation was in slow kinetic regime based on the results of Ha. This paper can provide basic data and theoretical reference for pharmaceutical wastewater treatment by ozonation.

Chemical absorption–biological reduction (BioDeNOx), which uses FeII(EDTA) as a complexing agent for promoting the mass transfer efficiency of NO from gas to water, is a promising technology for removing nitric oxide (NO) from flue gases. The carbon source and pH are important parameters for FeII(EDTA)-NO (the production of absorption) reduction and N2O emissions from BioDeNOx systems. Batch tests were performed to evaluate the effects of four different carbon sources (i.e., methanol, ethanol, sodium acetate, and glucose) on FeII(EDTA)-NO reduction and N2O emissions at an initial pH of 7.2 ± 0.2. The removal efficiency of FeII(EDTA)-NO was 93.9 %, with a theoretical rate of 0.77 mmol L−1 h−1 after 24 h of operation. The highest N2O production was 0.025 mmol L−1 after 3 h when glucose was used as the carbon source. The capacities of the carbon sources to enhance the activity of the FeII(EDTA)-NO reductase enzyme decreased in the following order based on the C/N ratio: glucose > ethanol > sodium acetate > methanol. Over the investigated pH range of 5.5–8.5, the FeII(EDTA)-NO removal efficiency was highest at a pH of 7.5, with a theoretical rate of 0.88 mmol L−1 h−1. However, the N2O production was lowest at a pH of 8.5. The primary effect of pH on denitrification resulted from the inhibition of nosZ in acidic conditions.

•An ozone-assisted photodegradation was developed to convert a binary mixture of VOCs.•The introduction of ozone enhances the photonic efficiency and the conversion of VOCs.•The appearance of CB has a positive effect on EB conversion under various RHs.•Different ozone additions influence the solubility and toxicity of intermediates.•Residual ozone combined with products could regulate the surface of the biofilm.In the present study, we investigated ozone-assisted photodegradation (UV254nm) of two common VOCs in a mixture, ethylbenzene (EB) and chlorobenzene (CB). Our results demonstrated that the photodegradation method was most efficient when ozone was introduced into the reaction system. When using this system, a significant combined effect from ozone and hydroxyl radicals was observed in the conversion of targets. The Cl radicals could suppress ozone and hydroxyl radical reactions, and thus the inhibition on EB conversion caused by higher relative humidity (RH) levels was not present. When the ratio of ozone to VOCs was 2 and RH was 75–80%, many lighter carbonyls (benzoic acid, benzaldehyde, formic acid, etc.) were observed. Under these conditions their contributions to the carbon mass balance was 43.2%. According to the toxicity results, the optimal reaction condition was the same as the condition which generated the largest amount of total organic carbon. Here, the main product was chlorophenol and thus must be controlled.

•The first study to catalyze ozonation of p-TSA by Ce/AC catalyst.•The properties of Ce/AC catalyst were analyzed by SEM, EDX, BET and XRD.•Ce/AC catalyst exhibits good heterogeneous activity in the degradation of p-TSA.•A possible degradation pathway of p-TSA by catalytic ozonation was proposed.The catalyst of cerium supported on activated carbon (Ce/AC) for ozonation was prepared and the catalytic activity was evaluated by the degradation of p-toluenesulfonic acid (p-TSA). The results showed that Ce/AC catalyst could not only greatly enhance the degradation of p-TSA but also significantly increase the efficiency of COD removal by ozonation. The COD removal could reach 74.1% with the Ce/AC catalyst at 60 min, while the effects of activated carbon (AC) catalyst and without catalyst were only 62.4% and 50.8%, respectively. The superiority of Ce/AC catalyst was attributed to the fact that cerium increased the generation of hydroxyl radicals (OH), which could react with p-TSA and intermediate to form oxidized products rapidly. Based on the intermediates detected by GC/MS, IC and HPLC, a possible degradation pathway of p-TSA was proposed. Our aim is to provide basic data and theoretical support for pharmaceutical wastewater treatment by catalytic ozonation.

The degradation of p-acetamidophenol (APAP), which is a typical component in pharmaceuticals and personal care products (PPCPs), in aqueous solution by ozonation process was studied. The effects of factors that affected the reaction rate, including the initial concentration of APAP, pH value, and O3 dosage were investigated, and the degradation products and mechanism of ozonation were also discussed. The results showed that the degradation of APAP was affected by the initial concentration of APAP, pH value, and O3 dosage. The optimized degradation condition was observed at pH 12.0. Under the same condition, increasing the pH value and ozone dosage would improve the degradation efficiency of APAP, while the degradation rate of APAP increased as the initial concentration of APAP decreased. Under the conditions of pH 2.0–12.0, an ozone dosage of 16–64 mg min–1, a pollutant concentration of 200–3000 mg L–1, and a temperature of 25 °C, the degradation followed the pseudo-first-order kinetics. Moreover, the kinetic model was proposed with the function of C = C0 exp(−11.359QO31.3475C0–0.8487[OH–]0.0343t).

In bioelectrochemically reductive dechlorination of chlorinated organic compounds (COCs), the electrons transfer from enzyme in the electrode to COCs was the key step, which determined the average current efficiency (CE) and was influenced by the pH and temperature of the systems. In this work, the effect of temperature (288–318 K) and pH (2–11) of the electrolyte on decholrination of trichloroacetic acid (TCA) was investigated in the sodium alginate/hemoglobin-multiwalled carbon nanotubes-graphite composite electrode (Hb/SA–MWCNT–GE). The results showed that the most favourable degradation conditions for TCA by Hb/SA–MWCNT–GE were found to be pH 3 and 310 K. By varying the pH of the systems, it was found that a proton accompanied with an electron transfer between the electrode and heme Fe(III)/Fe(II) of Hb during the reaction. Additionally, the activation energy of 26.2 kJ mol−1 was also calculated by the Arrhenius equation for the reaction. The total mass balance of the reactant and the products was in the range of 97–105% during the bioelectrochemically reductive reaction. The CE only decreased from 87% to 83% when the Hb/SA–MWCNT–GE was used 5 times. Based on the intermediates detected, a pathway was proposed for TCA degradation in which it underwent dechlorination process. The main degradation mechanism described by a parallel reaction rather than by a sequential reaction for dechlorination of TCA in Hb/SA–MWCNT–GE system was proposed. These data provided relevant information about the applicability of bioelectrocatalytic systems for treatment of wastewater contaminated by COCs.Graphical abstractHighlights► The electrons transfer from enzyme in the electrode to COCs was the key step. ► The average current efficiency was influenced by pH and temperature of the systems. ► The most favourable degradation conditions for TCA were found to be pH 3 and 310 K. ► The activation energy of 26.2 kJ mol−1 was also calculated by the Arrhenius equation. ► Bioelectrocatalytic mechanism of TCA was verified by kinetic expressions.

In this study, the novel PbO2 electrodes co-doped with rare earth (La and Ce) were prepared by electrodeposition technique. The rare earth co-doped electrode applied as an anode was carefully studied for the degradation of cationic gold yellow X-GL, in sono-electrochemical oxidation system. Optimal degradation conditions were achieved by investigating the effects of different parameters, such as initial concentrations, pH levels, electrolyte concentrations, current densities, on the constant frequency and power of ultrasound. Under the optimal conditions, removal rates of cationic gold yellow X-GL and COD were about 99.95% and 74.03%, respectively, after 2 h degradation. Moreover, the synergistic effect in sono-electrochemical oxidation system was also certificated and discussed. In addition, SEM images indicated that the surface of Ti/SnO2–Sb2O3/PTFE-La-Ce-β-PbO2 electrode had the dense structure and the preferred crystalline orientation, which could be helpful to improve the mass transportation and mineralization of cationic gold yellow X-GL.Highlights► Typical rare earth and PTFE co-doped PbO2 electrode was prepared. ► The modification mechanism of rare earth doped on electrode surface was discussed. ► The novel PbO2 electrode was introduced in sono-electrochemical oxidation system. ► The sono-electrochemical oxidation system possessed an obvious synergistic effect. ► The degradation mechanism and pathway of X-GL was explored.

Paracetamol (4′-hydroxyacetanilide, N-acetyl-p-aminophenol, acetaminophen, and paracetamol) is a widely used over-the-counter analgesic and antipyretic drug. Paracetamol and structural analogs are ubiquitous in the natural environment and easily accumulate in aquatic environment, which have been detected in surface waters, wastewater, and drinking water throughout the world. Paracetamol wastewater is mainly treated by chemical oxidation processes. Although these chemical methods may be available for treating these pollutants, the harsh reaction conditions, the generation of secondary pollutants, and the high operational cost associated with these methods have often made them not a desirable choice. Biodegradation of paracetamol is being considered as an environmentally friendly and low-cost option. The goal of this review is to provide an outline of the current knowledge of biodegradation of paracetamol in the occurrence, degrading bacteria, and proposed metabolic/biodegrading pathways, enzymes and possible intermediates. The comprehensive understanding of the metabolic pathways and enzyme systems involved in the utilization of paracetamol means will be helpful for optimizing and allowing rational design of biodegradation systems for paracetamol-contaminated wastewater.

The photodegradation of gaseous α-pinene by a vacuum ultraviolet (VUV) light was investigated under different process parameters and reaction media. The degradation of α-pinene was examined at nominal concentrations ranging from 50 to 1000 ppm, and resulted from the combination of direct photolysis, OH oxidation and O3 oxidation, in which O3 oxidation played a dominant role. A high conversion efficiency of α-pinene was achieved at a moderate relative humidity (RH) of 35–40% with an efficient utilization of the electrical energy. The conversion of α-pinene were remarkably reduced while a RH was increased to 75–80% since a higher RH inhibited the production of ozone and further affected the conversion of α-pinene adversely. The α-pinene conversion followed the first-order kinetic model at the low initial concentrations (50–200 ppm), and the second-order kinetic model provided a good fit to the data at the high concentrations (400–1000 ppm). The kinetic models including the initial target concentrations and the produced ozone amounts were developed to describe their mutual relationships. Preliminary results indicate that the VUV photooxidation was an appropriate technology for conversion of α-pinene not only as a single treatment but also as a pretreatment followed by the subsequent biodegradation.Graphical abstractThe conversion of gaseous α-pinene in the VUV system was attributed to the combination of the direct photolysis, hydroxyl radical oxidation and ozone oxidation. A complex interaction between O3 and OH was present in the system with the introduction of water molecule. A high relative humidity of 75–80% inhibited O3 generation, and further reduced the total conversion of α-pinene. Thus, a moderate relative humidity of 35–40% should be controlled during the photodegradation process.Research highlights▶ Higher relative humidity would affect the ozone formation and α-pinene conversion. ▶ In the combination role of direct photolysis, O3 and OH oxidation, O3 could play the dominant role. ▶ The developed kinetics models predicted well the conversion behaviors of α-pinene. ▶ The results provided a possibility for the combination of VUV technology and biodegradation.

A Ralstonia pickettii species able to degrade chlorobenzene (CB) as the sole source of carbon and energy was isolated from a biotrickling filter used for the removal of CB from waste gases. This organism, strain L2, could degrade CB as high as 220 mg/L completely. Following CB consumption, stoichiometric amounts of chloride were released, and CO2 production rate up to 80.2% proved that the loss of CB was mainly via mineralization and incorporation into cell material. The Haldane modification of the Monod equation adequately described the relationship between the specific growth rate and substrate concentration. The maximum specific growth rate and yield coefficient were 0.26 h−1 and 0.26 mg of biomass produced/mg of CB consumed, respectively. The pathways for CB degradation were proposed by the identification of metabolites and assay of ring cleavage enzymes in cell extracts. CB was degraded predominantly via 2-chlorophenol to 3-chlorocatechol and also partially via phenol to catechol with subsequent ortho ring cleavage, suggesting partially new pathways for CB-utilizing bacteria.

Methylibium petroleiphilum PM1, which is capable of degrading of methyl tert-butyl ether (MTBE), was immobilized in calcium alginate gel beads. Various applications were explored to increase the mechanical strength of these gel beads. The introduction of 0.3 mol/L calcium chloride into the crosslinking solution, 0.002 mol/L calcium chloride into the growth medium, and 0.2% polyethyleneimine (PEI) as chemical crosslinking agent increased the stability of the Ca-alginate gel beads under the operation conditions of the bioreactor. The degradation rates of MTBE by the immobilized cells in the bioreactor system operated in batch and continuous mode , respectively, were compared. A MTBE biodegradation rate of 5.79 mg/L·h was reached for over 400 h (50 batches), and the immobilized cells in the bioreactor removed >96% MTBE during 50 days of operation. Molecular analysis of the PM1 cells revealed that microbial growth occurred predominantly as microcolonies in the outer area of the beads during the first 20 days of operation. The results of this study show that a continuous-mode, fixed-bed bioreactor reactor coupled with PM1-immobilized cells is a promising technology for remediating MTBE-contaminated groundwater.

TiO2 nanomaterial is widely used for catalytic ozonation. In the present work, TiO2 nanostructures with various morphology and crystallite phases were synthesized by a hydrothermal method, followed by calcination using Degussa P25 as precursor. The nanotube, nanorod, and nanowire forms were obtained by varying the hydrothermal temperature, and the anatase/rutile ratios were adjusted by controlling the annealing temperature. The catalytic activity of the samples was evaluated by degradation of phenol in aqueous solution in the presence of ozone. We found that the initial degradation rates (IDR) of phenol were dominated primarily by the surface OH groups. Thus, with the help of transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauer−Emmett−Teller (BET) analyses, the number of surface OH groups per unit area of TiO2 was correlated with the morphology and crystallite phases. Finally, we conclude that the vast surface area and higher rutile phase ratios are favorable for the catalytic ozonation of phenol and the morphology of TiO2 had negligible effect in our experiments.

The role of platinum deposited on iodine-doped titanium dioxide (Pt/I-TiO2) catalyst during photodegradation of phenol under irradiation with visible light was investigated. The results of this study demonstrate that the Pt/I-TiO2 photocatalyst enhanced the phototransformation of phenol, with a negligible increase upon photomineralization. The results of the phototransformation of para substiuted phenols (p-methylphenol, phenol, p-chlorophenol, and p-nitrophenol) show that the phenol−TiO2 interaction, influenced by the Hammett constants, has the principal role in photodegradation. Furthermore, the action of scavengers (iodide ion, tert-butyl alcohol, fluoride ion, and persulfate ion), as well as N2 purge on the photodegradation of phenol prove that the phototransformation of phenol occurs on the surface of the photocatalyst and is initiated mostly by a valence band hole (hvb+), and the degradation process is limited by the keto−enol tautomeric equilibrium between hydroquinone and quinone. On the basis of these experimental results, we conclude that the role of platinum on the I-TiO2 surface is to inhibit the recombination of electron−hole pairs and promote a more efficient diffusion of the hvb+, which was propitious to the phototransformation of phenol. Nonetheless, the tautomeric equilibrium restrains the degree of mineralization. Additionally, identification of the main products showed that more quinone, formic acid, and oxalic acid were found in solution after reaction for 4 h using the Pt/I-TiO2 photocatalyst in comparison to the I-TiO2 photocatalyst, which could further explain the insignificant action of platinum for the photomineralization of phenol.

The natural estrogen 17β-estradiol (E2) is a major endocrine disruptor, with adverse effects on wildlife and humans. The aim of this study was to isolate microorganisms able to effectively remove E2 from wastewater. Accordingly, five E2-degrading strains of bacteria were isolated from activated sludge collected from a wastewater treatment plant. Based on their 16S RNA gene sequences, these five strains belonged to the genus Bacillus. All five isolates were capable of converting E2 to estrone (E1), greatly reducing total estrogenic activities in wastewater during E2 biodegradation. However, only two strains (strain E2Y1 and E2Y4) were able to further transform E1, whereas it accumulated in the culture medium of the other isolates. Among all isolates, strain E2Y4, with 100% of the 1,400 bp 16S RNA gene matched that of B. subtilis CICC10075, exhibited the highest E2 and E1 degradation capacities, degrading 1 mg E2/l completely within 4 days and further transforming 40% of the metabolite E1. Furthermore, the E2 degradation rates of strain E2Y4 increased with increasing initial concentrations of the steroid, with a high degradation capacity maintained even at initial concentrations up to 50 mg/l. These results demonstrate the potential significance of strain E2Y4 in biological remediation applications.

The adsorption of methyl tert-butyl ether by granular activated carbon was investigated. The experimental data were analyzed using the Freundlich isotherm and the Langmuir isotherm. Although equilibrium data were found to follow Freundlich isotherm model, it were fitted better by the Langmuir model with a maximum adsorption capacity of 204.1 mg/g. The kinetic data obtained at different concentrations were analyzed to predict the constant rate of adsorption using three common kinetic models: pseudo-first-order, pseudo-second-order equation and intraparticle diffusion equation. The pseudo-second-order model was suitable for describing the adsorption kinetics for the removal of methyl tert-butyl ether from aqueous solution onto granular activated carbon. Both the Lagergren first-order rate constant k1 and pseudo-second-order rate constant k2 decrease with increasing initial concentrations of methyl tert-butyl ether and the intraparticle diffusion rate constant kp shows the reverse characteristic. Analysis of sorption data using a boyd plot confirmed that external mass transfer is the main rate-limiting step at the initial stage of adsorption. Results illustrate that granular activated carbon is an effective adsorbent for methyl tert-butyl ether and also provide specific guidance into adsorption of methyl tert-butyl ether on granular activated carbon in contaminated groundwater.

Dichloromethane (DCM)-degrading bacterium strain wh22 (GenBank accession number FJ418643) was isolated and identified as Lysinibacillus sphaericus based on standard morphological and physiological properties, cellular fatty acid composition, mole percent guanine–cytosine content, and nucleotide sequence analysis of enzymatically amplified 16S ribosomal deoxyribonucleic acid. The strain also grew on many other halocarbons found in the waste gases of industrial effluents, such as 1,2-dichloroethane, chlorobromomethane, methylene bromide, 1,1,1-trichloroethane, trichloroethylene, and hexachlorobenzene. The strain harbored a novel degradative plasmid, pRC11 (48.8 kb). The genes coding for the metabolism of DCM were found to be plasmid-borne, and a physical map of the plasmid has been established. The purified plasmid was transformed to dcm−Escherichia coli DH5 at a rate of 1.65 × 105. The transformed cells were able to grow on DCM at a concentration of 5–16 mM and can be further used as an excellent source for genetic manipulations leading to the construction of genetically modified microbial strains or genetically engineered microorganisms.

17β-Estradiol (E2) is known as a natural endocrine disruptor and often found in municipal sewage. Batch experiments were conducted to assess the oxidative transformation of E2 in aqueous solutions by MnO2 and the probable degradation pathway. The results suggested that E2 could be degraded by MnO2, and the oxidation reaction deviated from pseudo-first-order kinetics due to the accumulation of reaction products in mineral surfaces and a gradual change of the surface site distribution toward less reactive sites. MnO2 dosage had a positive effect on oxidative transformation of E2, and both the initial reaction rate and the adsorption of E2 to oxide surfaces increased as the pH decreased. Two products, estrone and 2-hydroxyestradiol, were detected by gas chromatography coupled with mass spectrometry, and the probable degradation pathway was proposed. Results suggest that E2 can be oxidatively transformed by MnO2, which will provide some new insights into the interaction of estrogens with manganese oxides in natural soils and sediments.

The gene dehalA encoding a novel dichloromethane dehalogenases (DehalA), has been cloned from Bacillus circulans WZ-12 CCTCC M 207006. The open reading frame of dehalA, spanning 864 bp, encoded a 288-amino acid protein that showed 85.76% identity to the dichloromethane dehalogenases of Hyphomicrobium sp. GJ21 with several commonly conserved sequences. These sequences could not be found in putative dichloromethane (DCM) dehalogenases reported from other bacteria and fungi. DehalA was expressed in Escherichia coli BL21 (DE3) from a pET28b(+) expression system and purified. The subunit molecular mass of the recombinant DehalA as estimated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis was approximately 33 kDa. Subsequent enzymatic characterization revealed that DehalA was most active in a acidic pH range at 30°, which was quite different from that observed from a facultative bacterium dichloromethane dehalogenases of Methylophilus sp. strain DM11. The Michaelis–Menten constant of DCM dehalogenase was markedly lower than that of standard DCM dehalogenases.

A coupled ultrasound/electrocatalysis (US/EC) process was used to enhance the decomposition efficiency of organics. The synergetic kinetics and the mechanism of 2-chlorophenol (2-CP) decomposition with coupled US/EC were studied. It was found that in a US/EC process 2-CP is attacked by active radicals (such as hydroxyl radicals) to form 2-chloro-p-benzoquinone, and the latter is oxidized to simple organic acids when the ring is opened. The enhancement factor expressed by the apparent rate constant of 2-CP decomposition with coupled US/EC is 1.324 at a current density of 20 mA · cm−2, an ultrasonic frequency of 20 kHz, an ultrasonic intensity of 0.27 W · cm−2, and a 2-CP initial concentration of 200 mg · L−1, which means that a synergetic effect exists. A model derived from Langmuir adsorption theory of solid surface and reaction kinetics equations can describe exactly the decomposition of 2-CP with coupled US/EC. The numerical values are in good agreement with the experimental data. The model parameters are associated with reaction conditions.

Aerobic granules efficient at degrading methyl tert-butyl ether (MTBE) were successfully developed in a well-mixed sequencing batch reactor (SBR). Treatment efficiency of MTBE in the reactor during the stable operations exceeded 99.8%, and effluent MTBE was consistently below 800 μg/L. The specific MTBE degradation rate was observed to increase with increasing MTBE initial concentrations from 25 to 400 mg/L, peaked at 18.2 mg-MTBE/g-VSS h, and declined with further increases in MTBE concentration as substrate inhibition effects became significant. There was a good fit between these biodegradation data and the Haldane equation (R2 = 0.976). Microbial community DNA profiling was carried out using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction amplified 16S rDNA. The aerobic granule was found to contain a wide diversity of microorganisms. More than 70% similarity among the samples in the time period examined indicated a highly stable microbial community as the reactor reached the stable operation.

Aerobic granules efficient at degrading methyl tert-butyl ether (MTBE) with ethanol as a cosubstrate were successfully developed in a well-mixed sequencing batch reactor (SBR). Aerobic granules were first observed about 100 days after reactor startup. Treatment efficiency of MTBE in the reactor during stable operation exceeded 99.9%, and effluent MTBE was in the range of 15–50 μg/L. The specific MTBE degradation rate was observed to increase with increasing MTBE initial concentration from 25 to 500 mg/L, which peaked at 22.7 mg MTBE/g (volatile suspended solids)·h and declined with further increases in MTBE concentration as substrate inhibition effects became significant. Microbial-community deoxyribonucleic acid profiling was carried out using denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 16S ribosomal ribonucleic acid. The reactor was found to be inhabited by several diverse bacterial species, most notably microorganisms related to the genera Sphingomonas, Methylobacterium, and Hyphomicrobium vulgare. These organisms were previously reported to be associated with MTBE biodegradation. A majority of the bands in the reactor represented a group of organisms belonging to the Flavobacteria–Proteobacteria–Actinobacteridae class of bacteria. This study demonstrates that MTBE can be effectively degraded by aerobic granules under a cosubstrate condition and gives insight into the microorganisms potentially involved in the process.

A novel dichloromethane (DCM)-degrading bacterial strain named WZ-12 (GenBank accession no. EF100968) was isolated and identified as Bacillus circulans based on standard morphological and physiological properties and nucleotide sequence analysis of enzymatically amplified 16S ribosomal deoxyribonucleic acid. DCM dehalogenase from B. circulans WZ-12 was purified to 8.27-fold with a yield of 34.83%. The electrophoretically homogeneous-purified enzyme exhibited a specific activity of 118.82 U/mg. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis of purified DCM dehalogenase gave a distinct band with an estimated molecular mass of 20,000 ± 1,000.

Bacillus sp. Z018, a novel strain producing epoxide hydrolase, was isolated from soil. The epoxide hydrolase catalyzed the stereospecific hydrolysis of (R)-phenyl glycidyl ether to generate (R)-3-phenoxy-1,2-propanediol. Epoxide hydrolase from Bacillus sp. Z018 was inducible, and (R)-phenyl glycidyl ether was able to act as an inducer. The fermentation conditions for epoxide hydrolase were 35°C, pH 7.5 with glucose and NH4Cl as the best carbon and nitrogen source, respectively. Under optimized conditions, the biotransformation yield of 45.8% and the enantiomeric excess of 96.3% were obtained for the product (R)-3-phenoxy-1,2-propanediol.

The contamination of methyl tert-butyl ether (MTBE) in underground waters has become a widely concerned problem all over the world. In this study, a novel closed culture system with oxygen supplied by H2O2 was introduced for MTBE aerobic biodegradation. After 7 d, almost all MTBE was degraded by a pure culture, a member of β-Proteobacteria named as PM1, in a closed system with oxygen supply, while only 40% MTBE was degraded in one without oxygen supply. Dissolved oxygen (DO) levels of the broth in closed systems respectively with and without H2O2 were about 5-6 and 4 mg/L. Higher DO may improve the activity of monooxygemase, which is the key enzyme of metabolic pathway from MTBE to tert-butyl alcohol and finally to CO2, and may result in the increase of the degrading activity of PM1 cell. The purge and trap GC-MS result of the broth in closed systems showed that tert-butyl alcohol, isopronol and acetone were the main intermediate products.

•Anoxybacillus contaminans can simultaneously reduce Fe(II)EDTA-NO and Fe(III)EDTA•Strain HA possessed much higher tolerance to high temperature than mesophiles.•Efficient removal of Fe(II)EDTA-NO at 55 °C under anaerobic conditions.•Fe(II)EDTA is important to serve as electron donor and the formation of Fe(III)EDTA.•The strain have a μmax and a max reaction efficiency at 55 °C.The reduction of Fe(II)EDTA-NO is one of the core processes in BioDeNOx, an integrated physicochemical and biological technique for NOx removal from industrial flue gases. A newly isolated thermophilic Anoxybacillus sp. HA, identified by 16S rRNA sequence analysis, could simultaneously reduce Fe(II)EDTA-NO and Fe(III)EDTA. A maximum NO removal efficiency of 98.7% was achieved when 3 mM Fe(II)EDTA-NO was used in the nutrient solution at 55 °C. Results of this study strongly indicated that the biological oxidation of Fe(II)EDTA played an important role in the formation of Fe(III)EDTA in the anaerobic system. Fe(II)EDTA-NO was more competitive than Fe(III)EDTA as an electron acceptor, and the presence of Fe(III)EDTA slightly affected the reduction rate of Fe(II)EDTA-NO. At 55 °C, the maximum microbial specific growth rate μmax reached the peak value of 0.022 h− 1. The maximum NO removal efficiency was also measured (95.4%) under this temperature. Anoxybacillus sp. HA, which grew well at 50 °C–60 °C, is a potential microbial resource for Fe(II)EDTA-NO reduction at thermophilic temperatures.

The photocatalytic oxidation of gaseous chlorobenzene (CB) by the 365 nm-induced photocatalyst La/N–TiO2, synthesized via a sol–gel and hydrothermal method, was evaluated. Response surface methodology (RSM) was used to model and optimize the conditions for synthesis of the photocatalyst. The optimal photocatalyst was 1.2La/0.5N–TiO2 (0.5) and the effects of La/N on crystalline structure, particle morphology, surface element content, and other structural characteristics were investigated by XRD (X-ray diffraction), TEM (Transmission Electron Microscopy), FTIR (Fourier transform infrared spectroscopy), UV–vis (Ultraviolet–visible spectroscopy), and BET (Brunauer Emmett Teller). Greater surface area and smaller particle size were produced with the co-doped TiO2 nanotubes than with reference TiO2. The removal of CB was effective when performed using the synthesized photocatalyst, though it was less efficient at higher initial CB concentrations. Various modified Langmuir-Hinshelwood kinetic models involving the adsorption of chlorobenzene and water on different active sites were evaluated. Fitting results suggested that competitive adsorption caused by water molecules could not be neglected, especially for environments with high relative humidity. The reaction intermediates found after GC–MS (Gas chromatography–mass spectrometry) analysis indicated that most were soluble, low-toxicity, or both. The results demonstrated that the prepared photocatalyst had high activity for VOC (volatile organic compounds) conversion and may be used as a pretreatment prior to biopurification.Download high-res image (145KB)Download full-size image

This study was performed to investigate the variables that influence chlorobenzene (CB) degradation in aqueous solution by electro-heterogeneous catalysis. The effects of current density, pH, and electrolyte concentration on CB degradation were determined. The degradation efficiency of CB was almost 100% with an initial CB concentration of 50 mg/L, current density 15 mA/cm2, initial pH 10, electrolyte concentration 0.1 mol/L, and temperature 25°C after 90 min of reaction. Under the same conditions, the degradation efficiency of CB was only 51% by electrochemical (EC) process, which showed that electro-heterogeneous catalysis was more efficient than EC alone. The analysis results of Purge-and-Trap chromatography-mass spectrometry (P&T/GC/MS) and ion chromatography (IC) indicated that in the reaction process, the initial .OH attack could occur at the C–Cl bond of CB, yielding phenol and biphenyl with the release of Cl−. Further oxidation of phenol and biphenyl produced ρ-Vinylbenzoic acid and hydroquinol. Finally, the compounds were oxidized to butenedioic acid and other small-molecule acids.