A dissertation submitted to the Faculty of Science, University of the Witwatersrand in fulfilment of the requirements for the award of Master of Science degree, 2017. / Mining is an integral sector of most developing countries and it is a highly lucrative industry that has been in existence for centuries, and assumes an essential part in their economies. However, the legacy of mining in these countries has posed a threat to underground and surface water as a result of contamination arising from Acid Mine Drainage (AMD). Bearing in mind the environmental and ecological impairment posed by AMD there is a need for innovation in the treatment of AMD, to enable financially savvy treatment of the contaminated waters. This research is focused on the extraction of U(VI), As(III) and As(V) from synthetic metal solutions as well as field removal of these metal ions by application of iron hydroxide/oxide-modified zeolite. Batch experiments were performed to evaluate the effectiveness of iron hydroxide/oxide-modified zeolite as a potential low-cost sorbent for extracting As(III), U(VI) and As(V) from AMD. The research approach was based on the possible changes that can occur to a zeolite surface that has been in contact with an iron-laden solution. Zeolite is a commonly used adsorbent, but fewer studies have explored changes that it undergoes as an adsorbent on contact with iron solutions. Thus, the study involved modifying zeolite with iron hydroxide/oxide, which are the main precipitates of iron in the environment and which can possibly alter the adsorption properties of zeolite. Batch extraction studies were performed using the modified zeolite. In paper I, the synthesis of iron (hydr) oxide modified zeolite was achieved through precipitation of iron on the zeolite. The kinetic data for As(V) adsorption by iron (hydr) oxide-modified zeolite model fit well into pseudo second-order and the adsorption capacity was obtained as 0.080 mg g-1. The application of iron (hydr) oxide modified zeolite on AMD for As(V) recovery showed that > 99% of As(V) was extracted from the solution. The high removal efficiency of oxyanionic arsenic species was attributed to arsenic forming complexes with iron oxyhydroxide surface on the surface of the sorbent. Paper II dealt with adsorption of U(VI) from aqueous solution by application of iron hydro (oxide)-modified zeolite in a single-component system. Parameters such as: solution pH, contact time, adsorbent dosage, initial concentration and temperature were optimized before field application to real acid mine drainage. The optimum parameters for U(VI) adsorption were: adsorbent dosage (3.0 g), solution pH (6 ±0.1) and contact time (30 min). Optimum parameters where then applied to acid mine drainage were the effluent was found to be cleaner than the influent. In Paper III, iron oxide-coated zeolite (IOCZ) nanocomposite was prepared and fully characterized. This sorbent was then used for extraction of U(VI) and As(III) from aqueous solutions by application of batch techniques. Batch study results were modelled best by the pseudo second-order kinetic model and Freundlich isotherm. The adsorption capacity of both U(VI) and As(II) was dependent on the temperature. The presence of Cd2+, Co2+ and Cr3+ ions enhance the adsorption of As(III) whereas the opposite trend was observed for U(VI) sorption onto IOCZ nanocomposite. / XL2018

The use of algae as heavy metal bioindicators in aquatic environments has received much attention. In this study, the performance of a common freshwater living green alga, Cladophora sp. as a mercury bioindicator and its potential for phytoremediation applications was assessed by various parameters which included the influence of contact time, pH, initial mercury concentration and the presence of competing metal cations. A rapid uptake of mercury by Cladophora sp. was displayed. More than 99% of mercury in solution was removed within the first 5 min of contact and equilibrium was attained after 10 min. High adsorption capacities of 800 mg kg-1, 530 mg kg-1 and 590 mg kg-1 at pH 3, 6.5 and 8.5 respectively were obtained at the optimum mercury concentration of 1.0 mg l-1. Competitive adsorption studies showed that the selectivity of heavy metal cations by Cladophora sp. was in the following order: Hg2+ ˃Fe2+˃Cu2+˃ Zn2+ ˃ Co2+. These results indicate that living Cladophora sp. algae are suitable for use as mercury bioindicators in AMD waters and are also suitable for the removal of mercury in AMD conditions.

No description available.

Drainage systems on cold-based glaciers are often thought to be simple systems that can be approximated from the supraglacial components of temperate glaciers. Most studies concerning cold-based glacier drainage systems have only considered one facet of the system, with little regard for how the system components interact. Studying each component independently of the whole system constrains our ability to model drainage system function and development. This in turn restricts our potential to predict how drainage systems of cold glaciers may respond to environmental change. The overarching aim of this thesis was to understand drainage system development of a cold-based glacier, and to assess whether our current understanding of supraglacial hydrological systems is consistent with the drainage systems that form on cold-based glaciers. This thesis evaluated the drainage system of the Wright Lower Glacier, McMurdo Dry Valleys, Antarctica, during the 2004/05, 2005/06 and 2006/07 ablation seasons. The study incorporated field, laboratory and numerical analyses, which resulted in a deeper understanding of the spatial and temporal variability of meltwater generation, drainage pathways, water stores and bulk discharge from the glacier. The findings showed that melt variability was driven by sediment and topographic variations, and that water storage in the form of cryoconite holes, intergranular flow, supraglacial ponds and refreezing dictated meltwater transmission to the glacier outlet. These results indicated that the structure, function and variability of the drainage system were inherently more complex than previous studies on supraglacial drainage systems had suggested. These new insights were combined together to construct a new conceptual model of the drainage system structure of a cold-based glacier. However, before the conceptual model can be used to produce a numerical model of drainage system function or development on cold-based glaciers, several issues need to be addressed. These include: refined methods for quantifying meltwater generation in cold, arid environments; methods to measure water storage on and under the glacier surface; further understanding of the development of permeable ice; and a better technique to quantify cryoconite hole connectivity.

Thesis (M.S.)--Ohio State University, 1983. / Includes bibliographical references (leaves 91-93). Available online via OhioLINK's ETD Center

This thesis presents modeling of bilinear flow in tight gas wells and its behavior on single matrix block drainage. The objectives of this research are to: simulate a tight gas well using matrix block drainage under constant production pwf and with a constant production rate; be able to predict the behavior of matrix block drainage; study the effect of natural fracture(s) near a well; examine the matrix block drainage in a natural fracture network; and to validate a matrix block drainage model with a hydraulic fracture analytical solution. Two different production scenarios, constant pwf and constant rate, are assigned to a tight gas well in matrix block drainage. Matrix block drainage has two distinct permeabilities; a low permeability matrix serves as the tight gas reservoir with a high permeability streak surrounding the matrix. A well only produces from the high permeability fracture. Models were run with different sensitivity cases toward fracture half length, xf, and fracture permeability kf,. The fracture half-length reflects on a/b aspect ratio. The analytical solution for hydraulic fracture developed by Cinco-Ley and Guppy serves as the validation of matrix block drainage. Analysis on the flow regimes which occurred for different geometries and properties are provided. The log-log diagnostic plot of pseudo-pressure drop/gas rates and the log-log plot of dimensionless pressure derivatives and dimensionless reciprocal production rates are presented. Finally, an attempt to normalize the late time and early time of all geometries and properties is presented to obtain one analytical solution.

This thesis presents modeling of bilinear flow in tight gas wells and its behavior on single matrix block drainage. The objectives of this research are to: simulate a tight gas well using matrix block drainage under constant production pwf and with a constant production rate; be able to predict the behavior of matrix block drainage; study the effect of natural fracture(s) near a well; examine the matrix block drainage in a natural fracture network; and to validate a matrix block drainage model with a hydraulic fracture analytical solution. Two different production scenarios, constant pwf and constant rate, are assigned to a tight gas well in matrix block drainage. Matrix block drainage has two distinct permeabilities; a low permeability matrix serves as the tight gas reservoir with a high permeability streak surrounding the matrix. A well only produces from the high permeability fracture. Models were run with different sensitivity cases toward fracture half length, xf, and fracture permeability kf,. The fracture half-length reflects on a/b aspect ratio. The analytical solution for hydraulic fracture developed by Cinco-Ley and Guppy serves as the validation of matrix block drainage. Analysis on the flow regimes which occurred for different geometries and properties are provided. The log-log diagnostic plot of pseudo-pressure drop/gas rates and the log-log plot of dimensionless pressure derivatives and dimensionless reciprocal production rates are presented. Finally, an attempt to normalize the late time and early time of all geometries and properties is presented to obtain one analytical solution.

Thesis (M.S.)--Ohio State University, 1955. / Includes bibliographical references (leaves 41-42). Available online via OhioLINK's ETD Center

No description available.

No description available.