Non-Newtonian Fluids in Spout-Fluid Beds: Mass Transfer Coefficient at Low Reynolds Numbers

Following on from the work of Anabtawi et al. (2003), this study examined how the volumetric liquid-phase mass transfer coefficient, k_La, of oxygen in air in three-phase spout-fluid beds was affected by varying the system parameters of bed height, bed diameter, gas velocity, and liquid velocity. The liquid used was 0.1% CMC solution, displaying a pseudo-plastic rheology, with 1.75 mm glass spheres as packing. The values of the Sherwood number were lower than in previous studies (Anabtawi et al., 2003), in the range 9,000-186,000. Gas velocity had a similar effect on k_La as in a bubble column, with results also giving good agreement with previous work on two-phase and three-phase spouted bed systems. The correlation obtained for the effect of liquid velocity on k_La compared well with that of Schumpe et al. (1989). An increase in the height of packing increased k_La to the power of 0.319, with an increase in column diameter also causing an increase in k_La, which is in agreement with the results of Akita and Yoshida (1973).     

PHENOL BIODEGRADATION BY RALSTONIA PICKETTII EXTRACTED FROM PETROLEUM REFINERY OIL SLUDGE

Phenol-degrading bacterial strains have been extracted from oil-sludge samples collected from a local refinery. A selective medium was used to isolate the active strain capable of utilizing phenol as a sole carbon source, which was identified as Ralstonia pickettii. The growth kinetics of mixed and isolated R. pickettii suspensions were investigated using different initial concentrations of phenol in the range of 25 to 200 g m^?3 at 35°C and pH of 8.5. The results were compared to those of a commercially available mixed bacterial suspension, which was either acclimatized to 100 g m^?3 phenol concentration, extracted from PVA particles that were subjected to real petroleum refinery wastewater containing phenol, or an isolated active strain grown on a selective medium that was identified as Pseudomonas putida. The effect of substrate inhibition was observed using all bacterial suspensions, and the growth results were used to determine the parameters of a suitable kinetic model. It was found that the phenol biodegradation ability of the indigenous bacteria, R. pickettii, isolated from refinery sludge was comparable to that of the commercially available bacteria.     

Demanding applications in harsh environment – FeCrMnNiC amorphous equiatomic alloy thin film

An amorphous equiatomic FeCrMnNiC alloy thin film was synthesised on silica and silicon substrates by ion beam sputter deposition. Scanning electron microscopy energy-dispersive X-ray spectroscopy, X-ray diffraction, selected area electron diffraction and nano indentation were used to investigate the material. The produced film is amorphous and uniform on the atomic level without any detectable element segregation. The corrosion properties were assessed in 3.5% NaCl solution. The FeCrMnNiC alloy has corrosion resistance better than corrosion resistance of 304 SS. The thin film has hardness at around 12.3?±?0.5?GPa and reduced Young’s modulus at around 222?±?12?GPa.     

Electrochemical deposition of CuInTe<Subscript>2</Subscript> layers for applications in thin film solar cells

Copper indium ditelluride (CuInTe₂) has been electrochemically deposited from aqueous solution. Cyclic voltammetry analyses were used to determine suitable deposition parameters. As measured by Tallysurf and gravimetric techniques, the thickness of films deposited over a period of 3 h was found to be ~1.5 μm. X-ray diffraction, optical absorption and scanning electron microscopy have been used to investigate the bulk structure, energy bandgap and surface morphology of the material layers respectively. It was found that the material layers have polycrystalline chalcopyrite structure and bandgaps varied between 1.05 and 1.30 eV. Current-voltage characteristics of the CuInTe₂/electrolyte, solid/liquid junctions were measured under dark and illuminated conditions. The layers were found to be photo active and p-type in electrical conduction.     

Teaching water desalination through active learning

Active learning refers to the direct involvement of students in the learning process rather than being passive receptors of materials. This paper evaluates the implementation of active learning in teaching seawater desalination as an elective course in chemical engineering curriculum. Desalination is a multi-disciplinary engineering science that encompasses elements of water chemistry, material science, transport phenomena, thermodynamics, engineering design, and corrosion. Water desalination is an important course in most chemical and mechanical engineering curricula, where the design and analysis of different water desalination processes are addressed. The current teaching method, however, relies heavily on classical lecture-presentation of the course materials, without any direct involvement of the students. A simple approach that utilizes Excel and Ez-Solve in designing and analyzing desalination processes has been developed. Active learning is the central part of this course development, where students are heavily involved in class activities and can directly assess the effect of input variables on the design parameters, allowing them to carry out “What If” or parameter sensitivity analysis.     

Volumetric Mass Transfer Coefficient in non‐Newtonian Fluids in Spout Fluid Beds

The volumetric liquid‐phase mass transfer coefficient, k_La, was determined by absorption of oxygen in air using six different carboxy‐methyl cellulose (CMC) solutions with different rheological values in three phase spout‐fluid beds operated continuously with respect to both gas and liquid. Three cylindrical columns of 7.4 cm, 11.4 cm, and 14.4 cm diameters were used. Gas velocity was varied between 0.00154–0.00563 m/s, liquid velocity between 0.0116–0.0387 m/s, surface tension between 0.00416–0.0189 N/m, static bed height between 6.0–10.8 cm, and spherical glass particles of 1.75 mm diameter were used as packing material. A single nozzle sparger of 1.0 cm diameter was used in the spouting line. The volumetric mass transfer coefficient was found to increase with gas velocity, liquid velocity, and static bed height and to decrease with the increase of the effective liquid viscosity of the CMC solution. A dimensionless correlation was developed and compared with those listed in the literature.     

Precursor-directed syntheses and biological evaluation of new elansolid derivatives

The antibiotic elansolid C1 (8) was isolated from Chitinophaga sancti strain FxGBF13 after fermentation in the presence of anthranilic acid. Remarkably, 8 was also obtained by addition of anthranilic acid to a crude fermentation extract containing the macrolide elansolid A2 (1*). This Michael-type conjugate addition allowed us to generate 21 new derivatives of elansolid C1 (9-29) by using various nucleophiles. Biological activities of all derivatives were evaluated against Staphylococcus aureus, Micrococcus luteus, and the mouse cell line L929.     

Structural,optical and electrical properties of SnO<Subscript>2</Subscript>:F thin films deposited by spray pyrolysis for application in thin film solar cells

Fluorine doped tin oxide (FTO) thin films with adequate properties to be used as transparent electrical contact for PV solar cells were synthesised using the spray pyrolysis technique, which provides a low cost operation. The deposition temperature and the fluorine doping have been optimized for achieving a minimum resistivity and maximum optical transmittance. No post-deposition annealing treatments were carried out. The X-ray diffraction study showed that all the FTO films were polycrystalline with a tetragonal crystal structure and preferentially oriented along the (200) direction. The grain size ameliorates with the increase in substrate temperature. The samples deposited with the substrate temperature at 440 °C and fluorine content of 20 wt % exhibited the lowest electrical resistivity (1.8 × 10^?4 Ω cm), as measured by four-point probe. Room-temperature Hall measurements revealed that the 20 wt% films are degenerate and exhibit n-type electrical conductivity with carrier concentration of ~4.6 × 10²⁰ cm^?3, sheet resistance of 6.6 Ω/□ and a mobility of ~25 cm² V^?1 s^?1. In addition, the optimized growth conditions resulted in thin films (~500 nm thickness) with average visible transmittance of 89 % and optical band-gap of 3.90 eV. The electrical and optical characteristics of the deposited films revealed their excellent quality as a TCO material.     

Synergistic effect of pretreatment and hydrolysis enzymes on the production of fermentable sugars from date palm lignocellulosic waste

The sequential addition of the enzymes, laccase for lignin degrading, followed by xylanase for hemicelluloses hydrolysis, then cellulase for cellulose hydrolysis, was compared to the synergistic action of using the three enzymes together. It was shown that the reducing sugars yield increased from 5.6% using cellulase only to 45.6% by pretreatment with laccase and xylanase, prior to the enzymatic hydrolysis. A higher conversion of 60% was achieved by using the three enzymes together for the same incubation period. The proposed synergistic enzymes approach is a simpler and less energy intensive alternative compared to the conventional lignocelluloses pretreatment techniques.     

Biodegradation of phenol by Pseudomonas putida immobilized in polyvinyl alcohol (PVA) gel

Batch experiments were carried out to evaluate the biodegradation of phenol by Pseudomonas putida immobilized in polyvinyl alcohol (PVA) gel pellets in a bubble column bioreactor at different conditions. The bacteria were activated and gradually acclimatized to high concentrations of phenol of up to 300 mg/l. The experimental results indicated that the biodegradation capabilities of P. putida are highly affected by temperature, pH, initial phenol concentration and the abundance of the biomass. The biodegradation rate is optimized at 30 degrees C, a pH of 7 and phenol concentration of 75 mg/l. Higher phenol concentrations inhibited the biomass and reduced the biodegradation rate. At high phenol concentration, the PVA particle size was found to have negligible effect on the biodegradation rate. However, for low concentrations, the biodegradation rate increased slightly with decreasing particle size. Other contaminants such heavy metals and sulfates showed no effect on the biodegradation process. Modeling of the biodegradation of phenol indicated that the Haldane inhibitory model gave better fit of the experimental data than the Monod model, which ignores the inhibitory effects of phenol.