Lifen Liu

Covalent assembly of 3D graphene/polypyrrole foams for oil spill cleanup

Functionalized graphene oxide (KGO) sheets were covalently assembled with pyrrole and reduced to form a 3D foam structure via a multistep route through the hydrolytic condensation (cross-linking), polymerization reactions and hydrothermal reduction of graphene oxide (GO). The formed graphene/polypyrrole foam and its structures were analyzed using Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The specific surface area and the total pore volume of the samples were measured using N2 adsorption. The graphene composite foams have a special 3D structure, with a wide range of macropores (from sub-μm to several hundred μm) and mesopores within. Due to the intrinsic covalent bonding between graphene sheets and the special 3D structure, not only were the sorption capacities of the graphene/polypyrrole foams determined to be very high for oil (>100 g g−1) and solvent, but also the sorption rate was very high.

Hydrophobic modification of polyurethane foam for oil spill cleanup

To improve the oleophilic/hydrophobic properties of polyurethane (PU) foams for oil spill cleanup, PU samples were modified by grafting with oleophilic monomer Lauryl methacrylate (LMA) in solvent and/or coating with LMA microspheres through heating and curing. Modified PU cubes were characterized by field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FTIR). The water sorption of modified PU cubes was decreased by 24-50%, while the diesel or kerosene sorption of modified PU cubes was increased by 18-27%. In water-oil system, compared with blank PU cubes, the sorption capacity of PU cubes grafted with LMA was increased by 44% for diesel and 100% for kerosene. The sorption capacity of PU cubes coated with LMA microspheres was increased by 20% for diesel and 7% for kerosene. The solvent sorption of modified PU cubes could reach 50-69 g/g. The modified PU cubes can be effectively used in oil/solvent spill cleanup.

Effects of COD/N ratio and DO concentration on simultaneous nitrification and denitrification in an airlift internal circulation membrane bioreactor

The effects of chemical oxygen demand and nitrogen (COD/N) ratio and dissolved oxygen concentration (DO) on simultaneous nitrification and denitrification (SND) were investigated using an airlift internal circulation membrane bioreactor (AIC-MBR) with synthetic wastewater. The results showed that the COD efficiencies were consistently greater than 90% regardless of changes in the COD/N ratio. At the COD/N ratio of 4.77 and 10.04, the system nitrogen removal efficiency became higher than 70%. However, the nitrogen removal efficiency decreased to less than 50%, as the COD/N ratio shifted to 15.11. When the operating DO concentration was maintained at 1.0 mg/L in AIC-MBR, a satisfying SND was achieved. Either low or high DO concentration could restrain SND.

TiO2 and polyvinyl alcohol (PVA) coated polyester filter in bioreactor for wastewater treatment.

Prepared by coating TiO(2)/polyvinyl alcohol (PVA) on a low cost polyester filter cloth (22 μm), a composite membrane (10 μm pore size) was successfully used in an anoxic/oxic membrane bioreactor (A/O-MBR) for treating a simulate wastewater in removing nitrate/ammonium for water reuse in a polyester fiber production plant. Its permeate flux and the anti-fouling properties against extracellular polymeric substances (EPS) were studied. Comparing with a commercial (0.1 μm) PVDF (polyvinylidene fluoride) membrane, similar effluent qualities were achieved, meeting the basic COD requirements for reuse. Anti-EPS accumulation, the TiO(2)/PVA Polyester composite membrane had higher sustained permeability and required less frequent cleaning. Its filtration time was 4 times longer when operated at a higher flux than the PVDF membrane. The nano-TiO(2) enhances the interaction between PVA and polyester, forms a more hydrophilic surface, drastically reduces the contact angle with water and reduces EPS fouling. The slow (trans-membrane pressure) TMP rise, loose cake layer, the low filtration resistances, and the EPS, SEM analysis confirmed the advantage of the composite membrane. Potential in lowering the membrane cost, the operation and maintenance cost, and in enhancing MBR waste water treatment efficiency is expected by the use of this new composite membrane.

Non-UV Based Germicidal Activity of Metal-doped TiO2 Coating on Solid Surfaces

A stain-based screening method was developed to screen different catalyst coatings for their germicidal activity. A Baclight dead/live bacteria viability kit (invitrogen, molecular probes) was used for staining the cell. The screening was carried out following a standard procedure. This included loading cell suspension to solid surface and maintaining contact for 30 min, then staining with a mixture containing dyes. The stained cells were observed using an epifluorescent microscope and photographed with a CCD camera under UV. Metal-doped TiO2 coatings on Al plates were prepared and tested for non-UV germicidal activity without using UV. It was tested using model microorganisms such as Bakers Yeast (Saccharomyces cerevisiae), Bacillus subtilis, Pseudomonas putida, and Escherichia coli. On the basis of the germicidal activity of catalyst and the degree of damage caused to the cells, the stained cells may appear green (viable), green with red or yellow nuclei and yellow (compromised) or red (nonviable). According to their stained color, cells were counted to calculate the percentage of dead, live, and compromised cells. Compromised cells are cells that grow very slowly after reculturing indicating a degree of reversible cell damage. Screening the germicidal activity using this staining method is accurate and efficient, and requires less time than the culture-based method. A modification to the procedure for measuring germicidal activity of rough surfaces or fibrous coatings was developed. Both TiO2 and metal-doped TiO2 (Ag, Pt, Au, Cu) possess non-UV based germicidal activity. The germicidal activity of TiO2 was found to be related with its wetting property and can be improved by UV irradiation before testing. It is not greatly affected by contact time, indicating a fast acting germicidal activity.

Removal of aqueous Hg(II) and Cr(VI) using phytic acid doped polyaniline/cellulose acetate composite membrane.

Conductive composite membrane-phytic acid (PA) doped polyaniline (PANI)/cellulose acetate (CA) (PANI-PA/CA) was prepared in a simple and environmental-friendly method, in which aniline was blended with CA/PA solution and polymerized before the phase conversion. The resultant composite membranes were characterized by SEM, EDX, FTIR-ATR, BET and electrical resistance measurements. When used as adsorbent for Hg(II) and Cr(VI) ions, the prepared composite membrane exhibits excellent adsorption capability. The adsorption of Hg(II) and Cr(VI) follows a pseudo-second-order kinetic model and best fits the Langmuir isotherm model, with the maximum adsorption capacity reaching 280.11 and 94.34 mg g(-1), respectively. The heavy metal loaded composite membrane can be regenerated and reused after treatment with acid or alkali solution, making it a promising and practical adsorbent for Hg(II) and Cr(VI) removal. Tests with river water were also carried out, indicating good performance and application.

Wet air oxidation of pretreatment of pharmaceutical wastewater by Cu2+ and [PxWmOy]q- co-catalyst system.

This study concentrates on the pretreatment of real wastewater using catalytic wet air oxidation (CWAO). WO(3-) and PO(4)(3-) contained in fosfomycin pharmaceutical wastewater (FPW) and Cu(2+) contained in berberine pharmaceutical wastewater (BPW) were studied as CWAO influent. Mixture of this two streams were reused to form Cu(2+) and [P(x)W(m)O(y)](q-), namely polyoxometalates (POMs) as co-catalyst system to treat themselves. Experiments were conducted to investigate the effects of the initial oxygen pressure and temperature on the COD (chemical oxygen demand), TOC (total organic carbon) removal and biodegradable enhancement, it was discovered that over 40% of COD and TOC removal can be easily realized in an hour of WAO oxidation at 523 K, 1.4 MPa. The BOD(5)/COD (BOD(5), biochemical oxygen demand in 5 days) of this two pharmaceutical mixture ascended from nonexistent to maximum 0.41 depends on the optimal FPW:BPW volume ratio 4:1, to compose POM co-catalyst system. Organic pollutants were incompletely oxidized to propionic acid and other intermediates. Some properties (e.g., TGA, IR, XRF) of POM catalyst separated from effluent, were obtained to provide additional information.

Non-UV germicidal activity of fresh TiO2 and Ag/TiO2

Abstract Fresh TiO2 was found to possess a strong germicidal activity even without UV irradiation. Live Yeast (Saccharomyces cerevisiae) cells in contact with fresh TiO2 were found deformed and dead after 15 min contact. The cause of germicidal activity was discussed from the observed cell deformation, lysis and increased absorption at 1680 cm−1 in FT-IR spectra of the affected cells, which proved the oxidizing effect of fresh TiO2 to cells. The deformation caused by the stretching of cell wall and pressure built-up inside the cell, led to cell burst and release of intracellular materials. The degree of cell deformation was found positively related with the wetting property of TiO2. Cells are negatively charged, for Gram-negative cell (thinner cell wall), a higher germicidal effect was observed than Gram-positive cells. The germicidal effect of TiO2 gradually decreased after exposure to air at room temperature, as the wetting property decreased. This kind of germicidal activity was more effective compared to other germicidal process such as UVA/TiO2 or Ag+. This shed light on designing new germicidal material either maintained by visible light irradiation, or by oxidation effect generated by reactive oxygen species.

阳极TiO 2 /g-C 3 N 4 与阴极WO 3 /W纳米催化剂之间扩大的异质结自偏压系统去除污染物

Abstract An anodic TiO2/g-C3N4 hetero-junction and cathodic WO3/W were used to build a self-sustained catalytic fuel cell system for oxidizing rhodamine B or triclosan and reducing NO3−-N to N2 simultaneously. The WO3 nano-catalyst was formed in situ by heating and oxidizing a tungsten wire in air. Cyclic voltammetry and current-time curves were used to characterize the electrochemical properties of the electrodes and system. Aeration and activation of molecular oxygen by self-biased TiO2/g-C3N4 led to the formation of reactive oxidizing species in the fuel cell. The mechanism of simultaneous anodic oxidation of pollutants and cathodic reduction of nitrate was proposed. The spontaneously formed circuit and tiny current were used simultaneously in treating two kinds of wastewater in the reactor chambers, even without light illumination or an external applied voltage. This new catalytic pollution control route can lower energy consumption and degrade many other kinds of pollutants.

Development of a novel proton exchange membrane-free integrated MFC system with electric membrane bioreactor and air contact oxidation bed for efficient and energy-saving wastewater treatment

A novel combined system integrating MFC and electric membrane bioreactor (EMBR) was developed, in which a quartz sand chamber (QSC) was used, replacing expensive proton exchange membrane (PEM). An air contact oxidation bed (ACOB) and embedded trickling filter (TF) with filled volcano rock, was designed to increase dissolved oxygen (DO) in cathodic EMBR to save aeration cost. Membrane fouling in EMBR was successful inhibited/reduced by the generated bioelectricity of the system. The combined system demonstrated superior effluent quality in removing chemical oxygen demand (>97%) and ammonia nitrogen (>93%) during the stable operation, and the phosphorus removal was about 50%. Dominant bacteria (Nitrosomonas sp.; Comamonas sp.; Candidatus Kuenenia) played important roles in the removal of organic matter and ammonia nitrogen. The system has good application prospects in the efficient use of water and the development of sustainable wastewater recycling technology.