MESHWR / Department of Hydrology and Water Resources / Siloam, a village in the Northern province of South Africa has groundwater reportedly characterised by concentration of fluoride greater than 1.5 mg/L permissible limit. Regional investigation has been done to determine the possible fluoride sources in the northern province of South Africa, but no localised investigation has been documented. The World Health Organization and South Africa National Standard permissible limit is 1.5 mg/L for a duration of time. Therefore, this study focuses on investigating the sources of fluoride in the groundwater of Siloam village in response to reported high incidences (80%) of dental fluorosis in Siloam village. This study also elaborates more on the hydrochemical and geochemical processes favouring the release of fluoride into the groundwater of Siloam village. Two (2) surface rocks, one (1) surface clay deposit, twelve (12) borehole cuttings and four (4) groundwater samples were used for this study. Temperature, total dissolved solids (TDS), conductivity (EC) and pH of the groundwater were determined using a combined multimeter because these parameters are proxy indicators of geogenic influence on groundwater fluoride concentration. Total fluoride in the groundwater samples and the leachates obtained during a leaching experiment were determined using Ion Chromatograph (IC) and Fluoride Ion Selective Electrode (FISE). X-ray fluorescence spectrometry is the most preferred method for rock analysis by earth scientists because it is faster and does not require ambiguous training on the part of the analyst, therefore, it is mostly the standard methods used in whole rock chemistry. Elemental composition and mineralogy were determined using X-ray Fluorescence (XRF) and X-ray diffraction (XRD), respectively. Clay, greywacke, argillaceous sedmients and basalt were analysed. Results obtained indicated that the groundwater fluoride concentration ranges from 3.92 to 4.95 mg/L, which are far above the WHO permissible limit and South African standard. Insitu temperature reading obtained ranges from 25 to 48°C thus classifying the groundwater to be hot and tepid. The groundwater pH ranges from 8.1 to 9.1 which indicates an alkaline water condition. The groundwater conductivity ranges from 330 to 730 μS/cm while the Total dissolved solids ranges from 130.12 to 423.07 mg/L. Groundwater proxy indicators showed geologic sources to be responsible for the high fluoride concentration in the groundwater of Siloam village. Hydrochemical investigation revealead that the mineralisation of groundwater in Siloam village is as a result of rock water interaction and the process of groundwater enrichment is through base ion exchange and reverse ion exchange. The dominant water type in the village was identified to be Na-Cl water type and the abundance of sodium (Na) is due to the heavy weathering of plagioclase of the parent rocks. Total fluoride content of the rocks and soils of the village ranges from 10 to 2000 mg/L. The leachable fluoride, however, ranged in concentration from 0.27 to 14.88 mg/L under induced temperature v and 0.05 to 10.40 mg/L without temperature. Mineralogical investigation revealed the abundance of smectite clay, which is known for its enrichment and leaching of fluoride into groundwater sources, thus, the research question and assumption about the possible source of fluoride and the assumption that fluoride increases downwards towards the aquifer were answered. Leaching experiments identified the main contributors of fluoride to groundwater in Siloam village as smectite clays and the muscovite present in the sandstone, greywacke and basalt. Time based leaching experiment, geochemical modelling and dating of different hydrogeological unit was recommended / NRF

MENVSC / Department of Ecology and Resource Management / Fluoride is one of the anionic contaminants which is found in excess in groundwater because of geochemical reaction or anthropogenic activities such as the disposal of industrial wastewaters. Among various methods used for defluoridation of water such as precipitation, ion-exchange processes, membrane processes, the adsorptions process is widely used. It offers satisfactory results and seems to be a more attractive method for the removal of fluoride in terms of cost, simplicity of design and operation. In this work, the preparation of clay polymer nanocomposites (CPNCs) used in defluoridation began by modifying the original natural Mukondeni clay to render the layered silicate miscible with the chosen polymer, microcrystalline cellulose. Clay polymer nanocomposites (CPNCs) were synthesized using the melt intercalation method. Mukondeni black clay with microcrystalline cellulose as polymers was melt mixed at 220 °C for 10 minutes in an extruder for exfoliation of the resulting composite. Physicochemical characteristics and mineralogical characteristics of the CPNC was determined using XRD, XRF, BET, FTIR and SEM. Batch adsorption experiments were conducted to determine the efficiency of CPNCs in defluoridation of groundwater. The pH, EC, TDS and fluoride concentration of field water was determined using the CRISON MM40 multimeter probe and the Orion versastar fluoride selective electrode for fluoride concentration. Elemental analysis revealed that CPNC 1:1 is mainly characterized of cellulose, Quartz and Albatite as the major minerals with traces of Montmorillonite, Ednite and Magnesium as minor minerals constituting CPNC 1:1. The structure of 1:4 CPNC was partially crystalline and partially amorphous showing increased cellulose quantity (1:4 clay to cellulose) as compared 1:1 CPNC, 1:2 CPNC and 1:3 CPNC. Maximum adsorption of fluoride was attained in 10 minutes using 0.5g of 1:4 CPNC removed 22.3% of fluoride. The initial fluoride concentration for the collected field groundwater was 5.4 mg/L, EC 436 μS/cm, and TDS 282 mg/L. The regeneration potential of CPNCs was evaluated through 3 successive adsorption desorption cycles. Fluoride removal decreased after the first cycle for all ratios of CPNCs, a continued decreased can be observed following the second cycle. CPNC 1:2 decreased from 9.32 % at the 1st cycle to 2.84 % and 0.56 % on the 2nd and 3rd cycle respectively. CPNC 1:4 decreased from 8.22 % at the 1st cycle to 4.80 % and 0.72 % on the 2nd and 3rd cycle respectively. The fluoride-rich Siloam groundwater had a slightly alkaline pH of 9.6. iv The low adsorptive characteristic displayed by all 4 CPNCs can be deduced from the BET analysis that revealed low surface area, pore volume, and pore size, it is evident from the BET analysis that less fluoride will be absorb as adsorption sites will be limited. Based on the findings of this study, recommendations are designing of correct preparation techniques to obtain nanocomposites with desirable properties, polymer melting points and evaporation point of the binder should be taken into consideration. / NRF