Open Access Original Research Article
Aims: Streakline and its visualization and production techniques are one of important indices for fluid dynamics, civil engineering, material engineering, and so on. In chaotic or turbulent flow field where global mixing occurs, fluid trajectory exponentially expands in particular directions. Consequently, it is quite difficult to visualize streak as a “line” because experimental streak behaves as a “sheet” that has rounded surface. In the present study, to product and visualize a vivid and distinct streakline, a non-ionic surfactant was utilized.
Study Design: Experimental study containing simulation.
Place and Duration of Study: Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, between December 2010 and October 2011.
Methodology: The novel production and visualization technique for vivid streakline in three-dimensional (3D) flow field was developed. The innovative characteristic of visualization technique is that the expansion of streak can be suppressed by the surface tension with the self-assembly of surfactant molecules in the tracer fluid. The impeller-agitated tank was adopted as an unsteady 3D flow system. A non-ionic surfactant, "Emulgen (Kao Co., Ltd., polyoxyethylenelaurylether) was adopted, whose concentration was optimized at about 9 mass% in advance.
Results: The obtained streakline could keep the linear form for a long time not to expand, and there was little leakage of colored component due to the effect of molecular diffusion. The streakline could circulate freely in the tank; nevertheless its linear structure was maintained for a long time even if the streakline collided with the tank wall and impeller blades. The periodical consistency of streakline structure could be confirmed, which was one of necessary and sufficient conditions for the movement of streakline with flow field.
Conclusion: This study clearly demonstrates the production method of vivid streakline with the help of surfactant. While this technique has a little room for additional refinement, the present technique may be used and developed for future science and practical applications.
Open Access Original Research Article
Aims: The study is aimed to develop an indigenous heterogeneous based catalyst and evaluate kinetic mechanism for the synthesis of ethyl acetate by esterification of acetic acid and ethanol.
Study Design: Batch reactor system.
Place and Duration of Study: Department of Pure and Industrial Chemistry, Faculty of Science, University of Port Harcourt, Rivers State. Nigeria. The study was carried out between February to August, 2011.
Methodology: A sample of the natural clay was collected from the open clay deposit in Ezinachi, Okigwe Local Government Area, Imo state, Nigeria. The clay sample was washed and dried under sunshine for two days. Titanium pillared bentonite was produced by modification of natural bentonite clay using titanium pillaring solution at 500á¶¿C. X-Ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) and BET gas sorption analysis were employed to characterize the pillared material. Esterification reactions were carried out in a batch mode using a three-necked round bottom glass flask of 250 ml capacity fitted with a reflux condenser and mercury in glass thermometer to monitor the temperature. Heating and stirring was achieved using a magnetic hot plate with a stirrer. Pre-determined amount of acetic acid (for 1:1, 2:1, 3:1, 4:1 acid: alcohol mole ratio) and the clay catalyst were charged into the reactor and heated to 90 ±0.5ºC. After the desired temperature has been reached, a known amount of ethanol preheated separately using heating mantle was added into the reactor. About 2 ml of the reaction mixture was taken immediately using Pasteur pipette and titrated against 0.1 M NaOH solution using phenolphthalein indicator. All the experimental runs were designed by varying the amount of the catalyst, the acid to alcohol mole ratios, and the reaction period to obtain various kinetic parameters while keeping the temperature constant for all the runs.
Results: The result revealed that significant improvement on physicochemical characteristics of the bentonite samples occurred as a result of pillaring. The results obtained revealed that the conversion of acetic acid was dependent on the catalyst weight, reaction time and mole ratio. The maximum conversion of acetic acid was obtained for mole ratio (acid: alcohol) of 2:1 with optimum catalyst weight of 2.0g at a reaction temperature of 368K and 90 minutes time on-stream. The pillared clay material was shown to be more active in the conversion of acetic acid than the unpillared counterparts. Kinetics studies revealed that the esterification reaction is second-order and follows the single step Eley-Rideal reaction mechanism.
Conclusion: The esterification results showed that the conversion of acetic acid increased as a result of pillaring than the zero and unpillared catalyst. The mechanism involves a nucleophilic attack between adsorbed acetic acid and unadsorbed or competitively adsorbed ethanol to give ethyl-acetate and water. This research has demonstrated that titanium pillared clay has potential for esterification and trans-esterification of carboxylic acids.
Open Access Original Research Article
Aims: This work aimed at using B. cereus strain to decolourize a textile dye and also to study the influence of various environmental parameters on the decolourization processes.
Study Design: Decolourization efficiency of B. cereus.
Place and Duration of Study: Department of Microbiology, Ahmadu Bello University, Zaria, Nigeria; Department of Medical Microbiology, Faculty of Medicine, Ahmadu Bello University, Zaria, Nigeria and Department of Textile Science and Technology, Ahmadu Bello University, Zaria, Nigeria, between March 2011 and September 2011.
Methodology: The B. cereus strain used was isolated from contaminated food by using a selective media (Mannitol egg yolk polymyxin agar) and then culturing and storing on nutrient agar slants at –20ºC after biochemical tests were done to identify the isolate. All the microbial batch experiments were carried out at ambient conditions in 250ml Erlenmeyer flasks. Nutrient broth was autoclaved at 121ºC at 15psi for 15min and nutrient agar plates were also used in the isolation of the B. cereus strain. Effects of various parameters, including initial dye concentration (0, 0.5, 1.0 and 2.0g/l), glucose concentration (50, 100, 200 and 500mg/l), pH (4.0, 7.0 and 10.0) and temperature (20, 27 and 40ºC), on dye decolourization were investigated. Decolourization extent was determined by measuring the absorbance of the culture supernatant at 591nm using a Unicam UV9100-visible spectrophotometer. Decolourization extent was calculated using a standard equation as specified by Giwa et al., 2011.
Results: The bacteria culture exhibited 95% decolourization ability within 72 hours. The optimum dye decolourizing activity of the culture was observed at pH 7.0 and incubation temperature of 27ºC. Maximum dye decolourizing efficiency was observed at 200 mg/l concentration of RB19. The dye solution showed high peak at the wavelength of 591nm.
Conclusion: The results thus obtained have characterized and identified the dye degrading ability of the B. cereus. The presence of a co-substrate (glucose) is an essential condition for attaining maximum decolourization efficiency. Reactive blue 19 was completely and rapidly decolourized by B. cereus after 3days of incubation with different effects on the dye as seen in the result.