Flocculation and mechanism of self-flocculating lipid producer microalga Scenedesmus quadricauda for biomass harvesting

In this study, the extracellular polymeric substance of Scenedesmus quadricauda called EPS-S.q and its bioflocculatoin mechanism were investigated. Results showed EPS-S.q was successfully used as bioflocculating agent for S. quadricauda biomass harvesting and flocculation efficiency of up to 86.7% to S. quadricauda cells could be achieved in presence of Zn²⁺. EPS-S.q was the flocculating agent for self-flocculating microalga S. quadricauda and bioflocculation mechanism was polymer bridging. The sugar and protein mass fraction of dry EPS-S.q was sugar 56.7% and protein 41%. The infrared spectrum further indicated the presence of hydroxyl, carboxyl and amino groups. Moreover, pH decrease induced the flocculation of S. quadricauda and 78.4% of flocculation efficiency was the highest at pH 3. In addition, chemical flocculant FeCl₃ was efficiently used for S. quadricauda harvesting and up to 96.8% of flocculation efficiency could be achieved for S. quadricauda culture with biomass concentration 0.21–0.39 g L⁻¹ at pH 7.     

Improved transfer of chemical-vapor-deposited graphene through modification of intermolecular interactions and solubility of poly(methylmethacrylate) layers

Clean chemical vapor deposition (CVD)-grown graphene surfaces with intrinsic electrical properties were obtained by a modified poly(methylmethacrylate) (PMMA) transfer method. The modified method entails UV irradiation, followed by wet cleaning of the UV-irradiated PMMA layer using a mixture of isopropyl alcohol (IPA), acetone, and methyl isobutyl ketone (MIBK). The chemical structure of the PMMA layer degrades following UV irradiation under atmospheric conditions, via side-chain cleavage of the ester groups, resulting in reduced intermolecular interactions between the PMMA layer and the underlying graphene film. Furthermore, the IPA/MIBK/acetone mixture is shown to be a powerful solvent that can effectively remove the PMMA layer without leaving any PMMA residue, which could act as a source of cracks and scattering centers for charge carrier transport, on the graphene surface. Graphene transistors fabricated by this modified transfer method show high electron and hole mobilities with ideal threshold voltages of near 0 V.     

Effect of seed layer on the growth of rutile TiO2 nanorod arrays and their performance in dye-sensitized solar cells

In order to improve the performance of TiO₂ photoanode-based dye sensitized solar cells (DSSCs), rutile TiO₂ nanorod arrays (NRAs) were grown on SnO₂:F (FTO) conductive glass coated with TiO₂ seed layer by a hydrothermal method. The TiO₂ seed layer was obtained by spin-coating titanium tetraisopropoxide (TTIP) isopropanol solution with concentration in the range of 0~0.075 M. Then the effect of the thin TiO₂ seed layer on the crystal structure and surface morphology of TiO₂ NRAs and the photoelectric conversion properties of the corresponding DSSCs were investigated. It is found that TiO₂ NRAs are vertically oriented, about 1.7 μm long and the average diameter is about 35 nm for the samples derived from TTIP in the range of 0.005~0.05 M, which are more uniform and better separated from each other than those without TiO₂ seed layer (average diameter 35~85 nm). The photoelectric conversion efficiency of DSSCs based on TiO₂ NRAs with TiO₂ seed layer is larger than that without TiO₂ seed layer. Typically, the energy efficiency of DSSCs obtained from the seed solution of 0.025 M TTIP is 1.47%, about 1.8 times greater than that without TiO₂ seed layer. The performance improvement is attributed to the thinner, denser and better oriented NRAs grown on seeded-FTO substrate absorbing more dye and suppressing charge recombination at the FTO substrate/electrolyte interface.     

Supercritical fluid CO<Subscript>2</Subscript>-extraction regeneration of nickel–molybdenum catalyst for hydrotreatment

Results from studying the supercritical fluid СО₂-extraction regeneration of DN-3531 industrial nickel–molybdenum hydrotreatment catalyst in the temperature range of 323.15–383.15 K, at pressures of up to 30 MPa, and with modification of the basic extragent with such polar compounds as chloroform, methanol, ethanol, acetone, and dimethylsulfoxide (DMSO), are presented. The order of modifiers corresponds to the increase in the solubilizing ability of modified supercritical carbon dioxide (SC-СО₂) with respect to catalyst- deactivating deposits. With DMSO as the most efficient modifier, however, not only are deactivating compounds removed but nickel and molybdenum as well, considerably reducing the final activity of a regenerated sample. During extraction regeneration, the content of coke in the catalyst is reduced by two-thirds, while the specific surface area and the pore volume grow. The activity of the deactivated catalyst in dibenzothiophene hydrodesulfurization (HDS) and naphthalene hydrogenation grows by several hundred per cent after one-time SC-CO₂ treatment and is 2.5 times higher than for a sample regenerated using the traditional oxidative method.     

Determination of best possible correlation for gas compressibility factor to accurately predict the initial gas reserves in gas-hydrocarbon reservoirs

Gas compressibility factor or z-factor plays an important role in many engineering applications related to oil and gas exploration and production, such as gas production, gas metering, pipeline design, estimation of gas initially in place (GIIP), and ultimate recovery (UR) of gas from a reservoir. There are many z-factor correlations which are either derived from Equation of State or empirically based on certain observation through regression analysis. However, the results of the z-factor obtained from different correlations have high level of variance for the same gas sample under the same pressure and temperature. It is quite challenging to determine the most accurate correlation which provides accurate estimate for a range of pressures, temperatures, and gas compositions. This paper presents a novel method to accurately estimate GIIP of an Australian tight gas field through identification of the most appropriate z-factor correlations, which can accurately determine the z-factor and other PVT properties for a wide range of gas compositions, temperatures, and pressures. The sensitivity study results demonstrated that a single correlation cannot work across the range of pressures and temperatures for a certain gas sample necessary to calculate z-factor during simulation process and/or other analysis, such as material balance and volumetric estimate.     

A new application of giant reed waste material for ammonium removal

Excess nitrogen is one of the main causes of eutrophication in water bodies. In this study, the undesirable agricultural lignocellulosic material giant reed was used to remove ammonium ions from aqueous solutions. Batch experiments were conducted to investigate the effect of various parameters such as contact time, initial ammonium concentration, adsorbent dosage, pH, particle size, agitation rate and phosphate coexisting during the ammonium adsorption process. The ammonium sorption capacity of fibrous giant reed (FGR) at equilibrium was 12.49?mg?N/g with a maximum removal efficiency of 76% observed within 30?min at pH range of 6.5–9.5. Results revealed that the Freundlich isotherm model fitted better with the sorption process than the Langmuir model, and the adsorption process was well described by pseudo-second-order kinetic model. FT-IR analyses indicated that complexation and ion exchange could be the main mechanisms for the ammonium removal by FGR. Results revealed that FGR has a sorption capacity comparable to that of other natural sorbents with the advantage of greater availability with no cost.     

Kinetic study for phosphate removal from water by recycled date-palm wastes as agricultural by-products

The presence of excessive amounts of nutrients including phosphates in water is undesirable. They cause the deterioration of water quality and problems in many natural and engineering systems. The recycling of agricultural waste materials as biosorbents for contaminants removal provides a cheap and ecological means to reduce wastes. This study explored the use of date palm wastes for the effective removal of phosphate from aqueous solutions. Granular date stones (GDS) and palm surface fibres (PSF) as raw abundant waste materials were examined for PO₄ ^-3 removal from aqueous solution. The experimental work was performed in a batch mode to investigate the influence of initial phosphate concentration, contact time, and pH of solution on phosphate biosorption. The FT-IR spectra for the waste materials display many adsorption peaks, confirming the complex nature of the GDS and PSF. Phosphate percentage removal up to 87 and 85% were obtained at initial PO₄ ^-3 concentration of 50 mg as P/L using GDS and PSF, respectively. Due to their low cost and high capability, these types of waste can be used for cost-effective removal of phosphate from wastewater.     

Recycling of industrial wastes in ceramic manufacturing: State of art and glass case studies

Nowadays, ceramic tile are manufactured at zero emissions permitting to recycle all by-products and part of residues derived from depuration treatments (exhausted lime, glazing sludge and polishing sludge). In addition to this environmentally friendly tendency, in the last years an increasing number of scientific studies demonstrated the feasibility to use alternative raw materials in substitution of different component of the ternary clay-feldspar-quartz system. In the first part of the paper is reported the state of the art of industrial waste recycling in the ceramic sector, with the focus on review studies related to both ceramic tiles and bricks..In the second part of the work are reported two case studies conducted by the authors with the aim to formulate ceramic bodies using alternative raw materials. New tailored compositions were obtained replacing clays, flux and/or inert compounds (higher than 60 wt%) by scraps from packaging waste glass in tiles, and cathode ray tube glasses and packaging waste glass up to 20 wt% in the brick compositions.