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Partnerships for enhanced engagement in research (PEER) SCIENCE
Cycle 2 (2012 Deadline)

Development of advanced composite materials and geopolymers for the removal of uranium and toxic elements from gold mine-polluted water

PI: Hlanganani Tutu (University of the Witwatersrand)
U.S. Partner: Edward Rosenberg (University of Montana)
Project Dates: August 2013 to February 2015

South Africa Picture A
An abandoned talling storage facility with an efflorescent crust, which leaches metal pollutants into the water at the start of the rainy season (Photo courtesy Dr. Tutu).

The Witwatersrand Basin in South Africa faces challenges of water pollution, largely due to acid mine drainage (AMD) emanating from gold mining activities. AMD in the region includes a wide range of toxic elements such as uranium, arsenic, lead, mercury, and other metals. Most of the AMD emanates from inactive or abandoned mine facilitie, with sources including tailings storage facilities, tailing ponds, waste rocks, abandoned mine shafts, and open pits. Because of lack of funding for treatment of such facilities, surface and groundwater resources are continually contaminated, which has far-reaching implications for communities where these are the only water sources available. Two remediation approaches for the polluted water will be studied in this PEER Science project. The first will focus on the remediation of tap water used by households drawing water from mine-polluted aquifers. Silica polyamine composites (SPC) for the removal of uranium and attendant toxic elements will be developed for use in faucets (tap filters) and in columns that can be inserted into drinking water holding containers such as kettles and water jars. Commercially-available adsorbents tend to be expensive and out of reach for poor communities such as the ones affected by AMD in the study area. Affordable ones such as activated carbon are not very effective for removal of uranium and other elements such as arsenic. To this end, the study will explore ways of augmenting activated carbon with SPC for improved removal of these elements. The second approach will focus on bulk remediation at the sources of contamination. This will entail developing cost-effective geopolymeric materials using fly ash from coal mining, slag from furnace smelters, and a silicate binder. This material will be used in concrete mixes to form porous reactive barriers that will be erected at mine-polluted sites to intercept the polluted water flow, providing an adsorption surface for toxic elements and improving the quality of exiting water.

In the course of the proposed work, particular attention will also be paid to the potential recovery of low levels of precious metals (gold and silver) contained in gold mine-polluted water. Once allowed to load onto the adsorbents over time, these and other metals can be desorbed by an acid leach and concentrated using precious metal and uranium-selective SPC and recovered for economic use, thus providing the possibility of an in situ “smart” mining technique. This way, the costs of remediation can be decreased further or, better still, forgone. The results of this study will have applications in most mining industries in South Africa. In addition, the project will provide an opportunity for students to participate in applied and fundamental academic research.

Summary of Recent Activities

South Africa Picture B
The project team expects to visit more abandoned gold mines to such as this one to collect samples and to characterize elemental speciation and distribution. (Photo courtesy Dr. Tutu).

One of Dr. Tutu’s collaborators, Dr. Raymond Johnson from the U.S. Geological Survey, held a workshop on geochemical modeling at University of the Witwatersrand February 3-7, 2014. The workshop, attended by nine students from the School of Chemistry, covered aspects of elemental speciation and predictive modeling, both of which are important to the PEER project. One of the students working on the project, master’s degree candidate Martin Kgabo Manamela, has submitted his project proposal to the School of Chemistry as per the requirements for new postgraduate students. His work involves addressing the development of geopolymeric materials for use in reactive barriers, which is a goal of the project.
Future plans involve more site visits to collect samples of fly ash, as well as subsequent lab work to characterize elemental speciation and distribution of toxins. This will be helpful in designing the geopolymeric materials needed to remove contaminants from polluted water. The work on adsorption will continue with a special emphasis on how to prevent fly ash from leaching. U.S. partner Dr. Ed Rosenberg will visit the University of Witwatersrand from May 20-June 7 to give a departmental seminar and participate in other project activities. During his visit, the project team is also planning a meeting with the Cancer Association of South Africa to discuss household water filtration systems and their design. The meeting is expected to identify communities in the West Rand area of Johannesburg where these filter systems may be introduced. In early August, Dr. Tutu and a student will present some of their recent findings at the International Mine Water Association Conference in Xuzhou, China.
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