Minerals Engineering

Siderophores are a class of biogenic macromolecules that have high affinities for metals in the environment, thus could be exploited for alternate sustainable metal recovery technologies. Here, we assess the role of siderophores in the extraction and complexation of metals from an iron oxide-rich metallurgical processing residue and a low-grade primary Ni ore. Evaluation of the biological siderophore production by three pseudomonads, P. fluorescens, P. azotoformans and P. putida identified that P. putida could generate the highest siderophore yield, which was characterized as a hydroxamate and catecholate mixed-type pyoverdine PyoPpC-3B. Key physicochemical parameters involved in raw siderophore mediated metal extraction were identified using a fractional factorial design of experiments (DOE) and subsequently employed in purified PyoPpC-3B leaching experiments. Further targeted experiments with hydroxamate and catecholate functional analogues of PyoPpC-3B confirmed their marked abil...

The aim of this project was to investigate ferrosilicon replacement through the use of spherical magnetite in water in a wet heavy medium. By replacing this ferrosilicon with a waste product from titanium sand processing (spherical magnetite), it was hoped that higher density media would be achieved in a fluidized bed without reaching a viscous limit. Investigation on whether fine magnetite suspensions could gain an increased density without meeting the viscosity limit by addition of the coarser spherical magnetite was also done. Separations of coal was then tested. Dense medium of about 2000kg/m3 was prepared using fine magnetite and the setting rates of density tracers were measured. Another dense medium of about 1600kg/m3 was prepared using spherical magnetite and settling rates were again calculated. Spherical magnetite did not completely mix with water to form a required dense medium, thus; it was added to a previously prepared fine magnetite medium in increments of 100 kg/m3 to a final set density of 1500 kg/m3 without reaching a viscous limit.

Settling rates of density tracers in this set density were measured. A sample of shale and coal (feed ash content of 17.32%) was used to measure the separation efficiency of the prepared dense medium. Coal and shale ash content was determined using the furnace and thereafter, the necessary calculations were done to generate the tromp curve. The separation inefficiency EP usually lies in the range of 0.02 – 0.08(Wills, 1997). For this project, an EP value of 0.05 (which is within the required range) was assumed. An EP value of 0.06 was calculated from the generated tromp curve and this translated to 94% separation efficiency.

At a set density of 1500 kg/m3, 88.21 % of material reporting to the floats with 11.79% going to the sinks, and 80.02% mass yield was achieved. It was concluded that; the replacement of fine magnetite by spherical magnetite would be feasible since it could reduce the cost of raw materials for a process, spherical magnetite can be used to be replace ferrosilicon in a heavy medium, spherical magnetite could replace some of the fine magnetite at lower densities since it does not have much effect on the viscosity at higher densities and finally, sharp and efficient separation of coal were possible at lower densities. Furthermore, it was recommended that; fine magnetite must be replaced with spherical magnetite to decrease viscosity and process costs, use a pump capable of pumping high density slurries, an effective stirrer with bigger impellers must be used and a bed or column of bigger diameter must also be used to decrease wall effects.

ABSTRACT Small-scale laboratory tests for sizing and designing disc filters are typically performed by using leaf test equipment. Although the basic tests are fairly simple and quick, the accuracy and repeatability of the results may be poor due to various reasons. In addition to errors caused by variations in the structure of the equipment, also the skills and experience of the person performing the tests is of great importance. This paper introduces an experimental study carried out for defining the most important sources of errors in these kinds of laboratory tests and for estimating their influence on the final test results. The results obtained in this study were utilized for designing an improved version of the test equipment and also for creating a standard procedure for performing the tests. The results acquired with the small-scale laboratory tests were in good agreement with the performance results obtained from full-scale ceramic disc filters operating in industrial processes.

That talk is never disinterested complicates the relationship between the environment and the claims people make about it. Talk about place, and one's self in it, is particularly complex when the environment poses risk or is otherwise problematized. This study, a secondary analysis of interview data, seeks to extend discursive work on place-identity by examining the ways in which 14 residents of a small English village talk about themselves and their locale. The locale accommodates an active quarry, and many residents had lodged complaints to the quarry about dust, noise and vibrations from blasting. Attention to the interactional context of the interviews illustrates the ways in which (simply) interviewing people about their locale can threaten self- and place-identity. When asked about life in the village, interviewees oriented to two main dilemmas in protecting self- and place-identity: (1) how to justify continued residence in a challenging environment and (2) how to complain about the locale whilst maintaining positive place-identity. Discursive responses to these dilemmas drew upon typical identity processes, such as self- and place distinctiveness and the formulation of out-groups, as well as upon constructions of localized power-sharing and morally obligated tolerance of risk. We suggest that research on problematical places, and of environmental risk, needs to be sensitized to how it may constitute a threat to self- and place-identity, and how this may mediate formulations self and place, as well as of environmental risk.