Catalytic ozone oxidation toluene over supported manganese cobalt composite: influence of catalyst support.

In this study, the manganese cobalt composite (Mn-Co)-loaded SiO2, MgO, TiO2, γ-Al2O3 and silicalite-1 were prepared by ultrasonic complexation method. The catalysts were characterized by XRD, BET, SEM, TEM, H2-TPR and XPS, and the activity of catalytic oxidation of toluene was evaluated. It was found that Mn-Co loaded γ-Al2O3 (Mn2CoOx/γ-Al2O3) exhibited excellent catalytic activity. When the gas hour space velocity (GHSV) was 45,000 h-1, the removal rate of toluene reached 91.2% within 5.5 h, and the selectivity of CO2 was 71.10% at ambient temperature. The operation of Mn2CoOx/γ-Al2O3 at different temperatures was investigated, and the better toluene removal efficiency more than 80% after reacting 9h was obtained at 50 °C. The characterization results showed that better catalytic activity is related to smaller grain size, higher Mn3+/Mn4+ values and the relative content of active oxygen species (OII + OIII). Increased amounts of low state species easily led to the imbalance of the catalyst surface charge and promoted the formation of more oxygen vacancies.

The stimulatory effect of humic acid on the co-metabolic biodegradation of tetrabromobisphenol A in bioelectrochemical system.

In this paper, the typical organic component of humic acid (HA) was studied to explore its effect on the co-metabolic biodegradation of Tetrabromobisphenol A (TBBPA) in bioelectrochemical systems (BES). The degradation efficiency, intermediate metabolites and microbial diversity were investigated to demonstrate the impact of HA on the biodegradation of TBBPA in BES-HA-T (Bioelectrochemical system with TBBPA as substrate and HA as a stimulating factor). The highest biodegradation rate (93.2%) for TBBPA were obtained, which illustrated that HA played a positive role in the biodegradation of TBBPA. According to the analysis of the intermediate metabolites, it can be concluded that HA has changed the biodegradation pathway of TBBPA. The analysis of microbial diversity showed that the interaction of microorganisms had great effects on the anaerobic biodegradation of TBBPA, especially Trichococcus and Anaerolineaceae. Meanwhile, the abundance of Desulfobulbus in the BES-HA (Bioelectrochemical system with HA as a stimulating factor) had a positive effect on the improvement of electrochemical system performance.

High-efficiency treatment of PTA wastewater using a biogas jet assisted anaerobic fluidized bed reactor.

In this paper, a new type of biogas jet assisted anaerobic fluidized bed reactor loaded with a polypropylene carrier has been proposed. There was a clear improvement in the fluidized state due to the biogas assisted input when the gas/water ratio was set at 1:3 with a suitable carrier loading of 60%. When the circulating water flow is 30 L/min assisted with biogas 10 L/min, the mixing time shortens from 26 to 18 s. The performance of anaerobic biodegradation on wastewater treatment was improved largely. The chemical oxygen demand (COD) and terepthallic acid removal efficiencies were at 85.4% and 84%, respectively, at hydraulic retention time of 20 h, even when the influent COD concentration was as high as 4224 mg/L. In addition, plenty of microorganisms, attached to the carriers and assumed to be the reason behind the organic biodegradation efficiency of the proposed system, were observed using scanning electron microscopy.

Effects of exposure to BPF on development and sexual differentiation during early life stages of zebrafish (Danio rerio).

Bisphenol F (BPF) has become a predominant bisphenol contaminant in recent years. It has significant estrogenic properties in both in vivo and in vitro studies. We have previously studied the disrupting mechanisms of BPF on the hypothalamic-pituitary-gonadal axis of adult zebrafish. However, the effects of BPF exposure on development and sexual differentiation of zebrafish embryos/larvae remain unclear. To determine the effects of BPF on the critical stage of sex differentiation in zebrafish, zebrafish embryos/larvae were exposed to 1, 10, 100, and 1000 µg/L BPF from fertilization to 60 days post-fertilization (dpf). Developmental malformations were induced by exposure to BPF from 2 h post-fertilization (hpf), with a LC50 of 10,030 µg/L at 96 hpf and 9391 µg/L at 120 hpf. Long-term exposure during sex differentiation tended to result in a female sex ratio bias. Histological analyses at 60 dpf indicated that the development of ovo-testes and immature ovaries was induced by 100 and 1000 µg/L BPF. Homogenate testosterone levels decreased and 17ß-estradiol levels increased in zebrafish in a concentration-dependent manner. BPF exposure suppressed gene expression of double sex, Mab3-related transcription factor 1(dmrt1), fushi tarazu factor 1d (ff1d), sry-box containing gene 9a (sox9a) and anti-Mullerian hormone (amh); induced expression of the forkhead box L2 transcription factor (foxl2), leading to increased expression of aromatase (cyp19a1a), which promoted production of estrogens, and further caused phenotypic feminization of zebrafish. These results suggest that developmental exposure to BPF has adverse effects on sexual differentiation, and the results were useful for a BPF risk assessment.

Highly efficient Zr doped-TiO2/glass fiber photocatalyst and its performance in formaldehyde removal under visible light.

Zr-doped-TiO2 loaded glass fiber (ZT/GF) composite photocatalysts with different Zr/Ti ratios were prepared with a sol-gel process. Zr4+ can replace Ti4+ in the TiO2 lattice, which is conducive to forming the anatase phase and reducing the calcination temperature. The glass fiber carrier was responsible for better dispersion and loading of Zr-doped-TiO2 particles, improving the applicability of the Zr-doped-TiO2. The ZT/GF photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis) and Barrett-Joyner-Halenda (BJH). The performance of photocatalysts with different loading was evaluated in formaldehyde degradation under visible light at room temperature. ZT/GF0.2 exhibited the highest activity, with a formaldehyde removal rate as high as 95.14% being observed, which is better than that of the photocatalyst particles alone. The stability of the catalyst was also tested, and ZT/GF exhibited excellent catalytic performance with 94.38% removal efficiency, even after seven uses.

Sludge Reduction in the Activated Sludge Process Strengthened by Enhanced Ozonation Oxidation.

A novel radial-axial mixer and microbubble ozone reactor for enhancing sludge disintegration was designed. In the batch studies, the new reactor was shown to be significantly effective in improving sludge disintegration and increasing ozone utilization. For ozone dosages of 0.02 to 0.3 gO3/gTSS (total suspended solids) at pH = 10, the average sludge disintegration ratio was more than 17 ± 0.83% higher than that of the conventional reactor. An activated sludge process coupled with discharged sludge ozonated was run for 60 days to evaluate the influence of ozonated sludge feeding on the sludge yield coefficient and effluent quality. Although the effluent chemical oxygen demand (COD) and suspended solids (SS) increased slightly, these values were well below the discharge limit. Furthermore, a sludge reduction efficiency of 95% was attained. The experimental results indicated that the combination of sludge ozonation with the activated sludge process could generate a high quality of effluent and a small sludge yield.

Effects of BPF on steroid hormone homeostasis and gene expression in the hypothalamic-pituitary-gonadal axis of zebrafish.

Bisphenol F (BPF) has been frequently detected in various environmental compartments, and previous studies found that BPF exhibits similar estrogenic and anti-androgenic effects on the mammalian endocrine system to those of bisphenol A (BPA). However, the potential disrupting effects of BPF on aquatic organisms and the underling disrupting mechanisms have not been investigated. In this study, the potential disrupting mechanisms of BPF on the hypothalamic-pituitary-gonadal (HPG) axis and liver were probed by employing the OECD 21-day short-term fecundity assay in zebrafish. The results show that BPF exposure (1 mg/L) impaired the reproductive function of zebrafish, as exemplified by alterations to testicular and ovarian histology of the treated zebrafish. Homogenate testosterone (T) levels in male zebrafish decreased in a concentration-dependent manner, and 17ß-estradiol (E2) levels increased significantly when fish were exposed to 0.1 and 1 mg/L BPF. The real-time polymerase chain reaction was performed to examine gene expression in the HPG axis and liver. Hepatic vitellogenin expression was significantly upregulated in males, suggesting that BPF possesses estrogenic activity. The disturbed hormone balance was enhanced by the significant changes in gene expression along the HPG axis. These alterations suggest that BPF leads to adverse effects on the endocrine system of teleost fish, and that these effects were more prominent in males than in females.

[Treatment of PTA Wastewater by Modified Anode Microbial Fuel Cell].

The purpose of this study was to investigate the effect of different modified anodes on the microbial fuel cell(MFC) and the effect of MFC on the treatment of refractory wastewater. Based on a single room air cathode, the anode of MFC was modified by 0.10 g of tourmaline, 75% manganese bioxide/halloysite nanotube(MnO2/HNT) and multi-walled carbon nanotube-carboxyl(MWCNT-COOH), respectively. The results showed that, the removal rate of purified terephthalic acid(PTA) was higher than 70%, and the chemical oxygen demand(COD) removal rate was more than 79% in MFC with different modified anodes. Compared with others, MFC with MWCNT-COOH modified anode obtained the maximum output voltage and maximum power density, which were 529 mV and 252.73 mW·m-2, respectively.

Anaerobic co-metabolic biodegradation of tetrabromobisphenol A using a bioelectrochemical system.

Tetrabromobisphenol A(TBBPA), a pollutant in industrial wastewaters, needs to be removed due to its high toxicity and persistence. The main biodegradation pathway for TBBPA has been studied, and bisphenol A(BPA), which is toxic to the environment, is recognized as the general terminal product. In this study, we explored a new approach for the anaerobic biodegradation of TBBPA in a bioelectrochemical system (BES) through co-metabolic degradation of TBBPA with glucose. The half-life of TBBPA was significantly reduced to 13.5h-1 at 25µg/l of TBBPA. With an increase in the concentration of TBBPA, the removal rates of TBBPA rose to more than eighty percent. Based on the analysis of the products, we found that the degradation products of TBBPA were 2,6-dibromo-4-(1-methyl-1-phenylethyl) phenol, (double-benzenes product) and 2,6-dibromo-4-(prop-1-en-2-yl) phenol (single-benzene product), rather than BPA. Simultaneously, we proposed two degradation pathways for TBBPA in a BES system. According to the microbial diversity analysis of the anode biofilm, we speculated that the microorganism responsible for the biodegradation of TBBPA was Azoarcus. Additionally, we briefly analyzed the effect of TBBPA on the performance of BES system to pave the way for the further analysis of the interaction between the TBBPA and the BES system.

The performance of a two-layer biotrickling filter filled with new mixed packing materials for the removal of H2S from air.

In the work described here, a two-layer biotrickling filter filled with new packing materials was used to remove H2S from air. The upper layer of the filter was packed with activated carbon-loaded polyurethane, whereas the lower layer was filled with modified organism-suspended fillers. The effects of inlet load, empty bed residence time (EBRT) from 79 s to 53 s, pH and contaminant starvation time were investigated. For loads of 15-50 g/(m(3) h), the average removal efficiency (RE) was higher than 96% under a consistent supply of pollutants. The critical elimination capacity was 39.95 g/(m(3) h) for an EBRT of 53 s with an RE of 99.9%. The two-layer BTF was capable of withstanding contaminant starvation periods for 1.5 d and 7 d with only a few hours of recovery time. The biodegradation kinetics was studied using Michaelis-Menten type equations under different EBRTs. At an EBRT of 66 s, the optimal kinetic constants rmax and Km were 333.3 g/(m(3) h) and 0.93 g/m(3), respectively. During the operation, the two-layer BTF performed well under various reasonable conditions.

A novel chemical/biological combined technique for N, N-dimethylformamide wastewater treatment.

N, N-Dimethylformamide (DMF) is a widely used organic solvent whose wastewater is difficult to biodegrade directly. In this paper, a novel chemical/biological combined technique consisting of alkaline hydrolysis stripping, activated sludge and a bio-trickling filter (BTF) was developed for DMF wastewater treatment. The main pollutant, DMF, was decomposed to dimethylamine and formate under alkaline conditions, and the dimethylamine was stripped out by the BTF. The pretreated wastewater was then degraded in an activated sludge process. The operation performances of alkaline hydrolysis, activated sludge and BTF processes were investigated separately. At the optimal conditions of an alkali dosage of 40 g/L, an air/liquid ratio of 3000:1 and 5 h in the air-stripping process, the removal of total organic carbon and DMF was found to be 58% and 96%, respectively. A chemical oxygen demand removal efficiency of 80-90% was obtained in the activated sludge process. The performance of BTF was excellent with a dimethylamine removal efficiency close to 90% even at a high loading of 16 g/d.

Hydrogen production and wastewater treatment in a microbial electrolysis cell with a biocathode.

The broad application of microbial electrolysis cells (MECs) requires a system characterized by low cost and high operational sustainability. Biocathode MECs, which only require bacteria as the cathode catalysts, can satisfy these demands and have attracted considerable attention in recent years. In this study, we have examined biocathode alternatives to the typical platinum cathode in a single-chamber, membrane-free MEC. This biocathode MEC has been used for simultaneous hydrogen production and wastewater treatment. The results showed that hydrogen production rates increased in response to an increase in voltage. At an applied voltage of 0.9 V, the biocathode MEC achieved a hydrogen production rate of 0.39 m3 m(-3) d(-1), with a current density of 134 Am(-3), chemical oxygen demand (COD) removal of 90%, a coulombic efficiency of 63%, a cathodic hydrogen recovery of 37%, and an energy efficiency based on an electricity input of 67%. The biocathode demonstrated sufficient electrocatalytic activity and achieved a performance level comparable to that of the platinum cathode. Moreover, the substrate that was used to simulate wastewater in this study was efficiently treated by the MEC.

Anaerobic degradation of purified terephthalic acid wastewater using a novel, rapid mass-transfer circulating fluidized bed.

The anaerobic treatability of purified terephthalic acid (PTA) wastewater in a novel, rapid mass-transfer fluidized bed reactor using brick particles as porous carrier materials was investigated. The reactor operation was stable after a short 34 day start-up period, with chemical oxygen demand (COD) removal efficiency between 65 and 75%, terephthalate (TA) removal efficiency between 60% and 70%, and system organic loading rate (OLR) increasing from 7.37 to 18.52 kg COD/m(3) d. The results demonstrate that the reactor is very efficient, and requires a low hydraulic retention time (HRT) of 8 h to remove both TA and COD from the high-concentration PTA wastewater. The system also has high resistance capacity to varied OLR.

Phenol biodegradation and simultaneous nitrogen removal using a carbon fiber felt biofilm reactor.

Phenol biodegradation and its effect on the biological nitrogen removal were studied in a biofilm reactor (15 L) packed with carbon fiber felt carriers. Meanwhile, the effects of the effluent internal recirculation ratios (0, 100% and 200%) and the air flow rates (0.42, 0.83, 1.46, 2.08 and 3.33 L/min) on the performance of system were tested. The system exhibited an excellent capacity for simultaneous phenol biodegradation and biological nitrogen removal without effluent internal recirculation when the influent phenol concentration was as high as 1,000 mg/L (organic loading rate of 9.54 kg COD/(m(3) d)) and the ammonia loading rates of 0.20, 0.32 and 0.40 kg NH(4)(+)-N/(m(3) d) respectively). Nitrification process was inhibited at the influent phenol concentration of 1,200-1,300 mg/L with average ammonia removal efficiency of 26.9%. The nitrifiers activity could be recovered in the perfect performance of system for phenol biodegradation. However, denitrification was not affected by the process of phenol biodegradation. In the air flow rates of 1.46-2.08 L/min, the system manifested stable operation for phenol elimination and nitrogen removal. Dissolved oxygen (DO) distributions in carbon fiber felt biofilm descended gradually from the external to the center of the carrier in all air flow rates.

Preparation of Fe-Cu catalysts and treatment of a wastewater mixture by microwave-assisted UV catalytic oxidation processes.

Microwave-assisted UV catalytic oxidation (MW/UV) is a potential method to treat organic pollutants that have non-biological degradability and high toxicity. To achieve high treatment efficiency, it is crucial to prepare heterogeneous photocatalysts with a high activity. Iron-copper catalysts were prepared by four different methods. Synthetic wastewater containing aniline and nitrophenol (TOC = 1000 mg/L) was treated. The key parameters including the proportion of Fe2O3 and CuO and the total content of the active components are discussed. The optimum catalyst dosage and the whole catalytic oxidation process were investigated, and different catalytic oxidation systems were also compared. The catalyst prepared by impregnation was best: the highest TOC removal efficiency reached 78%. The optimum proportion of Fe2O3 and CuO and the content of the total active composition were 4:1 and 30%, respectively. The catalyst preparation method had a greater influence on the MW/UV system than on the microwave (MW) system, and the synergistic effect between MW and UV was verified. The MW/UV system was more susceptible to catalyst dosage than was the MW system, and the optimum catalyst dosage was 5 g/L. The catalyst and H2O2 had a synergistic effect. The presence of a possible non-thermal microwave effect could be expected.

High yield hydrogen production in a single-chamber membrane-less microbial electrolysis cell.

The single-chamber membrane-less MEC exerted much better hydrogen production performance while given higher applied voltages than it did at lower. High applied voltages that could shorten the reaction time and the exposure of anode to air for at least 30 min between cycles can significantly suppress methanogen and increase hydrogen production. At an applied voltage of 1.0 V, a hydrogen production rate of 1.02 m(3)/m(3)/day with a current density of 5.7 A/m(2) was achieved. Cathodic hydrogen recovery and coulombic efficiency were 63.4% and 69.3% respectively. The hydrogen concentration of mixture gas produced of 98.4% was obtained at 1.0 V, which was the best result of reports. The reasons that such a high hydrogen concentration can be achieved were probably the high electrochemical activity and hydrogen production capability of the active microorganisms. Increase in substrate concentrations could not improve MEC's performance, but increased the reaction times. Further, reactor configuration and operation factors optimisation should be considered to increase current density, hydrogen production rate and hydrogen recovery.

[Electricity generation using high concentration terephthalic acid solution by microbial fuel cell].

The high concentration terephthalic acid (TA) solution as the substrate of microbial fuel cell (MFC) was studied to generate electricity. The open circuit voltage was 0.54 V after inoculating for 210 h with anaerobic activated sludge, which proved that TA can be the substrate of microbial fuel cell to generate electricity. The influence of pH and substrate concentration on generating electricity was studied deeply. The voltage output of external resistance (R = 1,000 Omega) was the highest when pH was 8.0. It increased as the substrate concentration increasing and tended towards a maximum value. The maximum voltage output Umax was 0.5 V and Ks was 785.2 mg/L by Monod equation regression. When the substrate concentration (according to COD) was 4000 mg/L, the maximum power density was 96.3 mW/m2, coulomb efficiency was 2.66% and COD removal rate was 80.3%.

[Influences of inorganic anions on oxidation of phenol by CuO-H2O2].

Phenol was selected as a model pollution substrate. The influences and mechanism of inorganic anions on its oxidation were investigated in neutral solution at low temperature and atmospheric pressure. Results showed that phenol could be removed efficiently by CuO and H2O2 with 94.7% removal rate in 10 min, which followed hydroxyl radical oxidation mechanism. Inorganic anions influenced the oxidation with different mechanisms. Higher concentration would lead to more significant influences. HCO3(-) accelerated the inefficient decomposing of H2O2. The decomposing rate constants increased from 0.3738 min(-1) at concentration of 0 mmol x L(-1) to 0.5347 min(-1) at concentration of 20 mmol x L(-1). The TOC removal rate constants decreased from 0.267 min(-1) to 0.0194 min(-1) correspondingly. HPO4(2-) retarded the H2O2 decomposing and inhibited the phenol oxidation. The decomposing rate constants of H2O2 and the removal rate constants of TOC decreased from 0.3738 min(-1), 0.267 min(-1) to 0.0338 min(-1), 0.0338 min(-1) respectively. Cl(-) was good at H2O2 decomposing and phenol removal with simultaneously increasing the H2O2 decomposing rate constants and the TOC removal rate constants from 0.3738 min(-1), 0.267 min(-1) to 0.6040 min(-1), 0.3879 min(-1) respectively. NO3(-) and SO4(2-) had few influences on H2O2 decomposing and phenol removal.

Enhancement of microwave-assisted covalent immobilization of penicillin acylase using macromolecular crowding and glycine quenching.

In order to create macromolecular crowding resembling cells in mesopores and improve the covalent immobilization of penicillin acylase (PA), macromolecular reagents were covalently assembled on the walls of mesocellular silica foams (MCFs) and paralleled enzyme molecules under microwave irradiation at low temperatures. The effects of kind and content of macromolecules on immobilization and the characteristics of the immobilized enzyme were investigated carefully. The maximum specific activities of PA assembled with Dex 10 (Dextran, Mw 10000) (85.3 U/mg) and BSA (Bovine Serum Albumin) (112.7 U/mg) in MCFs under microwave irradiation were 1.73 and 1.31 times, respectively, that of PA solely immobilized by the conventional method. The optimum reaction temperature rose from 45-55 degrees C. Moreover, amino acids were used to quench excess activated groups in order to improve the thermostability of the immobilized enzyme. PA coassembled with Dex 10 in mesopores retained 88% of its initial catalytic activity after heating at 50 degrees C for 6 h, as a result of glycine quenching the excess activated groups. This biomolecule enhanced the thermostability of the enzyme preparation by 2-fold. A crowding environment resembling cells made from macromolecular reagents would be suitable for stabilizing the structure of PA and improving its catalytic activity. Glycine, a small biocompatible molecule, quenched the excess activated groups and modified the surface chemical properties of the mesoporous support, which would further favor the stability of PA at higher temperatures. Combining macromolecular crowding with glycine quenching was one of the efficient strategies adopted to improve microwave-assisted covalent PA immobilization.

Penicillin acylase immobilization depending on macromolecular crowding and catalysis in aqueous-organic medium.

To enhance penicillin acylase (PA) performance, it was immobilized in mesocellular silica foams (MCFs) depended on macromolecular crowding and applied to catalysis in non-aqueous medium. Ficoll 70, dextran 10,000, dextran 40,000 and bovine serum albumin were co-assembled with PA. It was observed that specific activity of PA assembled in MCFs with dextran 10,000 in 80% cyclohexane (v/v) was 233.2 U/mg, 200% as that of PA assembled in MCFs in 80% cyclohexane and 323.5% as that of free PA in full aqueous medium. As content of alkane increased, activity of PA in MCFs with macromolecules varied slightly. In addition, PA co-immobilized with dextran 10 in MCFs retained 58.2% of its initial activity after heating at 50 degrees C for 4 h, 1.2 times higher than that of PA immobilized alone in MCFs. The results showed that macromolecular crowding was favorable for immobilization of PA and its catalysis in suitable aqueous-organic medium.