Edison Muzenda

Effect of pH on the Floatability of Base Metal Sulphides PGMs

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 produces the best recoveries, and finding the effect of the chrome content in these recoveries. A pH of 9 produced the highest recovery compared to other pH values. 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.

Mechanical Properties and Chemical Resistance of Short Tamarind Fiber/Unsaturated Polyester Composites: Influence of Fiber Modification and Fiber Content

In the present work, tamarind fibers were extracted from ripened fruits by the water retting process. Using these fibers as reinforcement and unsaturated polyester as matrix, composite samples were prepared by the hand lay-up technique. The effect of chemical surface treatments (alkali and silane) of tamarind fibers on the mechanical properties, chemical resistance, and interfacial bonding was studied. The mechanical properties of the composites with surface modified fibers were found to be higher than those with unmodified fibers. Morphological studies indicated improvement of interfacial bonding by alkali and silane coupling agent treatments of the fibers. The composites were found to be resistant to many chemicals.

TENSILE AND THERMAL PROPERTIES OF POLYCARBONATE-COATED TAMARIND FRUIT FIBERS

In this work agro-based waste natural tamarind fibers were extracted from ripened fruit, and alkali treatment and polycarbonate coating were used to improve the properties of the chemically modified fibers. The tensile properties of these chemically modified fibers were found to be improved by polymer coating. Scanning electron micrographs indicated better interfacial bonding between the fiber and matrix. Thermogravimetric analysis showed that the thermal stability of the coated fibers was lower than that of polycarbonate but higher than that of uncoated fibers. The moisture absorption of the polycarbonate-coated fibers was lower than that of uncoated fibers.

Effect of Chemical Treatment and Fiber Loading on Mechanical Properties of Borassus (Toddy Palm) Fiber/Epoxy Composites

The aim of the present study was to investigate and compare the mechanical properties of untreated and chemically modified Borassus fiber–reinforced epoxy composites. Composites were prepared by the hand lay-up process by reinforcing Borassus fibers with epoxy matrix. To improve the fiber-matrix adhesion properties, alkali (NaOH) and alkali combined with silane (3-aminopropyltriethoxysilane) treatment of the fiber surface was carried out. Examinations through Fourier transform-infrared spectroscopy and scanning electron microscopy (SEM) were conducted to investigate the structural and physical properties of the Borassus fibers. Tensile properties such as modulus and strength of the composites made with chemically modified and untreated Borassus fibers were studied using a universal testing machine. Based on the experimental results, it was found that the tensile properties of the Borassus-reinforced epoxy composites were significantly improved as compared with the neat epoxy. It was also found that the fiber treated with a combination of alkali and silane exhibited superior mechanical properties to alkali-treated and untreated fiber composites. The nature of the fiber/matrix interface was examined through SEM of cryo-fractured samples. Chemical resistance of composites was also found to be improved with chemically modified fiber composites.

Extraction and Characterization of Cellulose from Pretreated Ficus (Peepal Tree) Leaf Fibers

In this work, we carried the physicochemical characterization of the cellulose extracted from the forestry residue of ficus leaves using chemical method. Detailed chemical composition of the ficus leaf fibers (both untreated and pretreated) and extracted cellulose was carried out. The chemical analysis confirmed the sequential removal of the lignin and hemicellulose components from the ficus leaves fibers. The morphology of the ficus leaf fibers and extracted cellulose was investigated using scanning electron microscopy. Structural analysis was carried out by Fourier transform infrared and nuclear magnetic resonance spectroscopy. The studies indicated that on chemical treatments the lignin and hemicellulose were removed extensively from the ficus leaf fibers. X-ray diffraction studies reveal that extracted cellulose was more crystalline than the ficus leaf fibers. The thermal stability of ficus leaf fibers and extracted cellulose was investigated by thermogravimetric analysis and the extracted cellulose had good thermal stability.

A Comparative Study of Modified and Unmodified High-Density Polyethylene/Borassus Fiber Composites

In this work, composite samples were prepared using Borassus fibers and a high-density polyethylene matrix. Alternatively, a chemically modified matrix (maleic anhydride grafted HDPE) was also used to improve fiber-matrix compatibility. The effect of fiber loading on the mechanical properties was investigated. Borassus fiber/modified HDPE composites exhibited improved mechanical performance as compared to pure HDPE composites. SEM studies on the fractured specimens of unmodified HDPE fiber composites reveal the poor fiber-matrix interaction, whereas the interaction is strong with enhanced mechanical properties for modified HDPE fiber composites. This is due to an improvement of the chemical bonding between the modified HDPE matrix and the Borassus fiber as also supported by Fourier transform infrared spectroscopy results. Thermal stability was also found to be enhanced slightly for modified HDPE composites.

Preparation, Chemical Composition, Characterization, and Properties of Napier Grass Paper Sheets

In this study, perennial fast growth Napier grass fibers were used for pulp and papermaking. Chlorination and alkaline processes were carried out using sodium chlorite and sodium hydroxide respectively, for pulp extraction from Napier grass. Detailed chemical composition analysis of the Napier grass fibers and the extracted pulp was carried out and a comparison with other perennial grasses was made. The extracted fibers and pulp obtained from Napier grass were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. The physical, optical, and mechanical properties of Napier grass pulp handmade paper sheets produced in the laboratory were investigated by finding the opacity, brightness, tensile index, breaking length, and burst index. Handmade paper sheets made from Napier grass pulp were compared to paper made from other perennial grasses. The superior properties of paper produced from Napier grass pulp indicate the suitability of Napier grass as an alternative non-wood source for papermaking.

Designing of sampling programmes for industrial effluent monitoring

IntroductionMonitoring of effluent discharges from industrial establishments discharging directly into municipality sewers is one of the major water pollution control activities conducted by municipalities. For largely industrialised municipalities, the task can be quite expensive and not effective if sampling programmes are not properly designed. In most cases, samples are randomly collected without proper knowledge of the discharge patterns of various industries. As a result, the information obtained does not give a good reflection of the quality of effluent being discharged.MethodsThese problems can be resolved by adapting a statistical approach to the design of sampling programmes. This approach is useful in determining the frequency of sampling, the number of samples needed to estimate the average concentration of target pollution indicator parameters and the magnitude of the uncertainty involved.ResultsThe benefits and applications of this approach are demonstrated by a case study presented in this paper. It was found that the number of samples and cost of sample analysis can be greatly reduced by the use of systematic instead of random sampling.ConclusionThe statistical approach greatly improves the estimate of monthly means of pollution indicator parameters and is an effective approach for pollution control when coupled with the “polluter pays principle”.

Parametric effects on leaching behavior of nickel-copper matte in ammonia

Leaching, which is described as the extraction of soluble constituents from a solid by means of a solvent, is an important separation technique in the refining of precious metals from their matte. It is, therefore, important to investigate the extraction behavior of metals from the matte, which is the focus of this study. This study reports the influence of concentration of the solvent (ammonia), leaching temperature, leaching time, and pH on the recovery of nickel and copper from the matte. The elemental composition analysis of the matte indicated that it contains 23% copper, 37% nickel and 1.1% ferrous compound. The analysis also showed that the major mineral phases present in the matte were heazlewoodite (Ni3S2), chalcocite (Cu2S), djurleite (Cu1.9S), and nickel alloy. The leaching parameters studied were concentration of ammonia (1.5, 2.0, 2.5, and 3.0 M), leaching time (0–270 min, at 15 min sampling interval), leaching temperatures (50°C, 60°C, and 70°C), and pH (9.3–11.2). The results obtained revealed that the recovery of nickel and copper from the matte was greatly influenced by the concentration of ammonia, leaching time, leaching temperature, and pH. It was established from this study that the highest dissolution of nickel and copper was obtained at 3 M and 2 M ammonia concentration, respectively. The results also revealed that a decrease in the pH of the solution resulted in a decrease in both nickel and copper recovery, with maximum leaching time of 270 min. It was observed that less than 50% of both nickel and copper was leachable due to the presence of metal alloys. The analyses of the results also showed that as the leaching temperature increased from 50°C to 60°C, the amount of nickel and copper that was recovered from the matte significantly increased. However, there was reduction in the amount of nickel and copper recovered from the matte as the temperature was increased from 60°C to 70°C, due to loss of ammonia by evaporation. The shrinking core model was used to explain the behavior of the recovery of these metals at different temperatures, and both metals were found to be favored by diffusion controlled reaction.

Temperature effect on volatile organic compounds – polydimethylsiloxane Interactions

og V ) of 13 volatile organic compounds (VOCs) of environmental importance between the gas and liquid stationary phase (polydimethysiloxane) (PDMS) were studied using the gas liquid chromatographic technique (GLC). Temperature was varied from 303.15K to 423.15K to allow transport calculations for different seasons. Four PDMS polymers with average molecular weight ranging from 760 to 13 000 were used as solvents. The results of this work confirm that PDMS is well suited for VOCs scrubbing from waste gas streams. Linear plots of log g V against T 1 were obtained in all cases permitting predictions and interpolations to temperatures not studied here. Also dependable enthalpies and entropies of solute transfer from the mobile phase to the stationary phase can be calculated. The specific retention volumes reported in this work are in agreement with literature for similar systems. Efforts were taken to ensure the best possible accuracy and trace the possible sources of error. A gas liquid chromatographic system which secured a simple retention mechanism and showed reproducible solute retention over a long period of time was devised.