Design and development of proton exchange membrane (PEM) from synthetic rubber and carbon nanoballs for PEM fuel cell

The need for an alternative source of energy is very urgent. The challenges are to develop a new technology that will produce an efficient and environmentally friendly source of energy other than fossil fuel. A fuel cell system especially proton exchange membrane fuel cell is considered the most promising alternative method of converting and exploiting energy with many benefits including low pollutant emission, sustainability and reliability. However, a number of issues need to be resolved before the proton electron membrane fuel can become commercially and technologically viable. These include the durability and the availability of the membrane among many other factors. In this research, Proton Exchange Membrane (PEM) was synthesized by sulphonation of polystyrene butadiene rubber that is readily available in South Africa, using chlorosulphonic acid as the sulphonating agent. The synthesized membrane was blended with carbon nanoballs (CNBs) produced by the swirled floating catalytic chemical fluid deposition (SFCCVD) method designed and conceptualized by Iyuke (2005). Synthesis of carbon nanoparticles with this reactor was optimized using different experimental conditions of pyrolysis temperature, flow rates of acetylene, hydrogen and argon gases. A maximum production rate of 0.35 g/min was obtained at 1000oC, acetylene flow rate of 370 ml/min, hydrogen flow rate of 180 ml/min and a flow ratio of acetylene to hydrogen equal to five. Since clean nanoparticles are required in this work for membrane synthesis, the SFCCVD reactor was modified to synthesize clean carbon nanoballs via a non-catalytic method. The carbon nanoballs produced were used in the formulation of sulphonated polystyrene butadiene rubber–carbon nanoballs composite membrane. The synthesised membranes and the composite membranes were characterized to determine the ion exchange capacity, degree of sulphonation, thermal stability, water uptake, vi porosity, proton conductivity, solvent uptake, and morphology and methanol crossover. The characterization of the synthesized membrane for methanol cross over is to determine the suitability of the membrane for possible application in direct methanol fuel cell; however hydrogen fuel is used in this work. The results obtained revealed that the blending of the membrane with CNBs improved the thermal stability, water uptake, porosity, solvent uptake, methanol crossover and proton conductivity of the membrane with more than 50 % increase in proton conductivity. The results of various analyses conducted on the synthesized membrane revealed that the synthesized membrane shows better qualities in terms of thermal stability, solvent uptake, porosity to solvent, methanol crossover and water uptake than Nafion 112, which is the commercially available membrane. The synthesized and composite membranes were sandwiched between two electrodes to produce a membrane electrode assembly (MEA), using the hot press method at constant temperature, pressure and time. The performance of the fabricated MEA was tested in a single PEM fuel cell using hydrogen as the fuel gas and oxygen as oxidant at room temperature (about 25oC). The results obtained revealed that the utilization of sulphonated PSBR resulted in higher performance compared to Nafion 112. Nafion 112 produces a maximum power density of 67 mW/cm2 while the membrane synthesized from PSBR generated a maximum power density of 74 mW/cm2. This difference is corresponding to about 10% increment. Also the membrane blended with CNBs exhibited a superior performance to a non-blended membrane. The former gives a maximum power density in the range of 74-97 mW/cm2 depending on the mass of CNBs. These values are about 7-32 % higher than the nonblended membrane

Reagent optimization across a UG2 plant

Reagent optimization is very important in the recovery of valuable metals from their ore via flotation. This is particularly important for large platinum operations where correct reagent regime and addition system can provide improvement opportunities in recovery and grade. Also reagent optimization can reduce reagent costs for the rougher, scavenger and cleaner flotation units. Reagents were optimized in the flotation of hot floats from the plant at laboratory scale. It was found that in order to save cost, the collector and depressant must be reduced in the roughers and cleaners respectively. This report presents results and some practical considerations that must be taken into account to optimise reagent usage

Effect of pH on the recovery and grade of base metal sulphides (PGMs) by flotation

This study investigated the effect of pH on the recovery and grade of the Platinum Group Metals (PGMs) and base metal sulphides from the UG2 ore of the Bushveld Complex. This was achieved through running a series of test work in a Denver flotation cell at varying pH 6-11 at constant reagent dosage. The UG-2 reef is characterized by two predominant gangue phases i.e. chromite and silicate, that have significantly different physical and chemical properties. The test work was aimed at evaluating which pH gives best recoveries, and finding the effect of the chrome content in these recoveries. A pH of 9 gave the highest recovery compared to other pH ranges. However, the highest PGM grade was attained at a pH of 6 which is slightly acidic. Ideally this trend could be expected since the collectors (xanthates) are more stable in alkaline medium. The higher PGM recovery was also accompanied by higher chrome content as a result of their similar chemical properties

Characterization of Baruten Local Government Area of Kwara State (Nigeria) fireclays as suitable refractory materials

Studies have shown that adequate attention needs to be paid on processing of solid minerals that are potentially available in Nigeria to address its economic problem. Clays from five major towns in Baruten Local Government Area, Kwara State, Nigeria were examined using ASTM guidelines to determine their suitability for refractory applications. The clay samples were classified as Alumino-Silicate refractories due to high values of Al2O3 and SiO2. The results showed apparent porosity (19.4-25.6%), bulk density (1.83-1.90 g/cm3), cold crushing strength (38.7-56.1 N/mm2), linear shrinkage (4.4 – 9.3%), clay contents (52.71-67.83%), moisture content (17.0-23.6%), permeability (68-82 cmsec-1), plasticity (16.7-30.4%), refractoriness (>1300oC) and Thermal Shock Resistance (23-25 cycles) for the clay samples, which were measurable with the established standards for fireclays, refractory clays/brick lining or alumina-silicates and kaolin. Hence, the natural clays could suitably replace imported clays in some refractory applications. Appropriate use of information from this study would improve Nigeria’s industrialization and economic diversification.Keywords: Apparent Porosity, Bulk Density, Clay, Shrinkage and Refractor

Development and Evaluation of an Interactive Instructional Package for Teaching Engineering Graphics Skills

Exposure to modern pedagogical approaches and methods with appropriate instructional media can enhance the development of high-level critical thinking and technical skills. This study examined the development of an interactive instructional software package for teaching engineering graphics and evaluated its relative effectiveness on second-year undergraduate engineering students' academic achievement, skill transfer, and retention. In this study, the quasi-experimental, pre-test, post-test, control group design was employed. 45 research participants were sampled, employing two-stage stratified sampling technique, which comprises the simple random sampling to assign students into three groups from the study population and systematic sampling with k = 3 to select 15 students from each group to a control group and experimental groups A and B. The control group was exposed to conventional classroom instruction (CI), group A to computer-aided instruction (CAI); and group B to conventional and computer-aided instructions (CCAIs). A computer-aided learning package on engineering graphics was developed using the Camtasia software package, which served as the treatment instrument. The pre-test and post-test data used for analysis stemmed from a validated Engineering Graphics Achievement Test instrument. Analysis of covariance and Sidak post hoc test statistical analysis of the groups' performance provided the results on the comparative effects of the treatment conditions. Findings indicated significant differences between the academic achievement, skill transfer, and retention of students, exposed to CCAIs, and CI or CAI strategies. When used together, a significant improvement in students' academic achievement, transfer, and retention of engineering graphics skills occurred than either the CI or CAI strategy used alone

Optimisation of Synthesis Parameters for Co-Mo/MgO Catalyst Yield in MWCNTs Production

This study examined the impact of synthesis parameter on Cobalt-Molybdenum supported with magnesium oxide (Co-Mo/MgO) catalyst yield in production of multiwall carbon nanotube (MWCNT). Wet impregnation was used to synthesis the Co-Mo/MgO bimetallic catalyst, while a catalytic chemical vapour deposition reactor (CCVD) was used for the synthesis of carbon nanotubes (CNTs). Factorial and central composite design techniques were used to optimise the catalyst and multi-wall carbon nanotubes (MWCNTs). Thermogravimetric analysis/ Differential thermal analysis (TGA/DTA), selected area (electron) diffraction (SAED), X-Ray diffraction analysis (XRD), and Brunauer–Emmett–Teller (BET) were used to characterise the catalyst and MWCNTs that were produced. The Co-Mo/MgO catalyst had an optimal yield of 93.22%, 247.30 m2/g of specific surface area at 120 oC drying temperature, 16 g of mass support, and a 10-hour drying time. The maximum catalyst yield of 40.62% was obtained at calcination temperature of 500 oC and a holding period of 2 hours. The catalyst with the highest degradation temperature of 398.21 oC was observed at 600 oC, when calcined for 4 hours. It was discovered that the surface area of Co-Mo/MgO catalyst from the BET analysis under ideal conditions varied depending on the holding time. The XRD and SAED revealed the growth of CNTs of concentric graphene pattern with the Co-Mo/MgO catalyst

Optimization and characterization of biofuel from waste cooking oil

Abstract: Waste cooking oil (WCO) is regarded as one of the cheapest feedstock for the production of biodiesel. The waste cooking oil used in this study was prepared in the laboratory by adding 5 wt. % of oleic acid into 95 wt. % of soybeans oil. 10 wt. % of titania-supported-magnesium oxide catalyst (MgO/TiO2) used was prepared by incipient wetness impregnation and characterized using XRF and XRD. These materials were tested and used as catalyst for the conversion of waste vegetable oil to biodiesel in the presence of methanol and hexane as co-solvents. Methanol to hexane mole ratio of 1:1 was employed in the transesterification process. The effects of reaction time, reaction temperature and hexane co-solvent on the waste vegetable oil conversion have been established. The 1HNMR analysis was used to estimate the waste vegetable oil conversion and the average molecular formula of fatty acid methyl esters (FAME) produced. It was observed that the oil conversion increased with the increase in reaction time, reaction temperature and use of hexane as co-solvent