Distribution and dispersion of metals and their economic potential: a case of the Fumani Tailings Dam, Limpopo Province, South Africa

Abstract

The study was conducted at the Fumani Tailings Dams 1 and 2 located in Malamulele, Mtititi village and the area surrounding it to investigate the distribution and dispersion of gold and metals such as Pb, Zn, Cu, As, Co, Cd, Cr and Ni, and also to determine their pollution status, whilst looking at possibilities of reprocessing the tailings as well as using tailings for brick production. A total of 84 and 63 tailings samples were collected from tailings dams 1 and 2 respectively. 3 profiles were set on each tailings dams, with 4 and 3 boreholes set on each profile of Fumani Tailings Dams 1 and 2 respectively. All boreholes were drilled by a hand auger up to a depth of 7 m, collecting samples of approximately 5 kg at each 1 m interval. The samples were prepared at the University of Venda MEG laboratory where they were analysed for pH using pH meter, metals and major elements using X-ray Spectrometry, Gold using AAS as well as geotechnical tests using sieve analysis. Profile logs as well as pH logs revealed that the tailings dams were highly oxidized at the surface of the tailings dams to about 2 m. The average pH revealed that the entire tailings is slightly acidic to neutral. X-ray fluorescence spectrometry confirmed the presence of Pb, Zn, Cu, As, Co, Cd, Cr and Ni. The pollution status conducted revealed that As and Ni pollutes the tailings dams whilst the remaining metals are within the required standard. Gold values within the tailings dams showed a very erratic trend with depth, with an average concentration of 1.34 ppm and 1.44 ppm at tailings dams 1 and 2 respectively. The study ascertained that there is about 299.1 kg and 225.5 kg of gold within Fumani Tailings Dams 1 and 2 respectively. Soil samples were collected in four directions from the Fumani tailings Dams at an interval of 200 m. The samples were prepared and analysed using XRF for Pb, Zn, Cu, As, Co, Cd, Cr and Ni at the university of Venda. The Study showed that Zn and Cd do not contaminate the soil whilst Pb, As, Cu, Cr and Co highly pollutes the soil. These might be from a different source since they are low within the tailings dams. The Major oxides, sieve analysis, liquid limit test and the plastic limit test were used to classify the tailings using USCS and AASHTO Classification system. The USCS revealed that the tailings were ML and/or CL fine grained silty clay, whilst AASHTO Classification system revealed that the Fumani Tailings Dams 1 and 2 were in class A-4(3) and A-4(1) respectively. The tailings had low LL, low PI, and low alumina content required for brick production. The tailings, therefore, had a low compressibility, slight to low plasticity, and no cohesion, and therefore were not suitable for brick production on their own. Clay and cement bricks of different tailings to soil and cement ratios were made at Tshidino Bricks. All bricks were tested for dimension tolerance test, water absorption test, compressive strength test, hardness test as well as the impact test. All clay bricks failed these tests. The cement bricks passed the hardness test, water absorption test, and hardness test. This was not enough to make them suitable for brick production as they failed the dimension tolerance test and compressive strength test.