scholarly journals Geochemical characterization and assessment of fluoride sources in groundwater of Siloam area, Limpopo Province, South Africa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tobiloba Onipe ◽  
Joshua N. Edokpayi ◽  
John O. Odiyo
Keyword(s):  
Dental Fluorosis ◽  
Fluoride Concentration ◽  
Limpopo Province ◽  
Water Type ◽  
X Ray Diffraction ◽  
Kaolinite Clay ◽  
X Ray ◽  
High Incidence ◽  
High Fluoride ◽  
Fluoride Ion Selective Electrode

AbstractSiloam’s groundwater is reportedly characterized by high fluoride. In response to the reported high incidence of dental fluorosis in the area, sources of elevated fluoride in the groundwater were investigated. Total fluoride (TF) was determined using Ion Chromatograph and Fluoride Ion Selective Electrode. The mineral composition of rocks and soils were determined using X-ray Fluorescence and X-ray diffraction, respectively. Results revealed that groundwater fluoride concentration ranged from 3.92 to 4.95 mg/L. Na-Cl water type was found to be dominant in the water samples. TF content of the rocks and soils ranged from 10 to 2000 mg/L. Leachates were obtained by making a slurry from the samples at a predetermined temperature and time. TF in leachates ranged between 0.27 and 14.88 mg/L and 0.05 to 10.40 mg/L at induced, and non-induced temperatures, respectively. The possible source of fluoride has been previously inferred to be caused by fluorite minerals occurring at greater depth. However, this study proves that fluoride decreases with depth and the elevated fluoride in the groundwater is caused by smectite-kaolinite clay, muscovite and chlorite minerals abundant in the area. Geothermal temperature exhibited by the groundwater in the area is a major factor enhancing the release of fluoride from the clay materials.

scholarly journals Characterisation of smectite-rich clay soil: Implication for groundwater defluoridation

2016 ◽  
Vol Volume 112 (Number 11/12) ◽  
Author(s):  
Rabelani Mudzielwana ◽  
Mugera W. Gitari ◽  
Titus A.M. Msagati ◽  
◽  
◽  
...  
Keyword(s):  
South Africa ◽  
Rural Areas ◽  
Contact Time ◽  
Clay Soil ◽  
Dental Fluorosis ◽  
Fluoride Concentration ◽  
Limpopo Province ◽  
World Health ◽  
Fluoride Removal ◽  
X Ray

Abstract Groundwater is a widely used and affordable source of drinking water in most of the rural areas of South Africa. Several studies have indicated that groundwater in some boreholes in South Africa has a fluoride concentration above the level recommended by the World Health Organization (1.5 mg/L). Fluoride concentrations above the permissible limit (>1.5 mg/L) lead to dental fluorosis, with even higher concentrations leading to skeletal fluorosis. In the present work, we evaluate the application of smectite-rich clay soil from Mukondeni (Limpopo Province, South Africa) in defluoridation of groundwater. The clay soil was characterised by mineralogy using X-ray diffraction, by elemental composition using X-ray fluorescence and by morphology using scanning electron microscopy. Surface area and pore volume was determined by the Brunauer–Emmett–Teller surface analysis method. Cation exchange capacity and pHpzc of the soil were also evaluated using standard laboratory methods. Batch experiments were conducted to evaluate and optimise various operational parameters such as contact time, adsorbent dose, pH and initial adsorbate concentration. It was observed that 0.8 g/100 mL of smectite-rich clay soil removed up to 92% of fluoride from the initial concentration of 3 mg/L at a pH of 2 with a contact time of 30 min. The experimental data fitted well to a Langmuir adsorption isotherm and followed pseudo second order reaction kinetics. Smectite-rich clay soil showed 52% fluoride removal from field groundwater with an initial fluoride concentration of 5.4 mg/L at an initial pH of 2 and 44% removal at a natural pH of 7.8. Therefore smectite-rich clay soil from Mukondeni has potential for application in defluoridation of groundwater. Chemical modification is recommended to improve the defluoridation capacity.

Physico-Chemical and Morphological Changes of Sayong Kaolinite Clay Treated with Sulphuric Acid for Enzyme Immobilization

2013 ◽  
Vol 832 ◽  
pp. 589-595 ◽  
Author(s):  
N.A. Edama ◽  
A. Sulaiman ◽  
K.H. Ku Hamid ◽  
M.N. Muhd Rodhi ◽  
Mohibah Musa ◽  
...  
Keyword(s):  
Surface Area ◽  
Sulphuric Acid ◽  
Enzyme Immobilization ◽  
Morphological Changes ◽  
Chemical Properties ◽  
X Ray Diffraction ◽  
Kaolinite Clay ◽  
X Ray ◽  
Mineral Oxides ◽  
Physico Chemical

This study analyzed the effects of sulphuric acid (H2SO4) treatment on pysico-chemical properties and morphological changes of clay obtained from Sg. Sayong, Perak. The clay was ground and sieved to <150μm and treated with different concentrations of H2SO4. The treatment was completed by refluxing the clay with different concentration of H2SO4 (1M, 5M and 10M ) at 100 °C for 4 hours and followed by calcination at 500 °C for 1 hour. The physic-chemical properties and morphological changes of the untreated and treated clay were compared using Surface Area Analyser, X-Ray Diffraction (XRD), Field Emission Scanning Electron Micrograph (FESEM), X-Ray Diffraction (XRD) and Fourier Transformed Infrared Spectroscopy (FTIR). The results showed that acid treatment of 5M increased the surface area from 25 m2/g to 75 m2/g and the pore volume increased from 0.1518 cc/g to 0.3546 cc/g. The nanopore size of the clay decreased from 24.8 nm to 19.4 nm after treated with acid. This can be explained due to the elimination of the exchangeable cations and generation of microporosity. The results of XRF showed SiO2 increased from 58.34% to 74.52% and Al2O3 reduced from 34.6% to 18.31%. The mineral oxides such as Fe2O3, MgO, CaO, K2O and TiO2 also reduced. This concluded that H2SO4 treatment has led to significant removal of octahedral Al3+, Fe3+ cations and other impurities. In conclusion, this study showed the physico-chemical properties and morphology of Sayong clay were improved once treated with H2SO4 and therefore suggests better supporting material for enzyme immobilization.

scholarly journals Biomarkers for the Assessment of Fluoride Exposure in Children

2020 ◽  
Vol 54 (2) ◽  
pp. 134-143
Author(s):  
Oladipo S. Idowu ◽  
Ralph M. Duckworth ◽  
Ruth A. Valentine ◽  
Fatemeh Vida Zohoori
Keyword(s):  
Significant Positive Correlation ◽  
Dental Fluorosis ◽  
Fluoride Concentration ◽  
Strong Correlations ◽  
Positive Correlation ◽  
Validated Questionnaires ◽  
Fluoride Exposure ◽  
Fluoride Intake ◽  
Whole Saliva ◽  
High Fluoride

Due to practical difficulties in quantifying fluoride exposure, the ability of various biomarkers to predict exposure has been investigated previously. However, the results are inadequate for validation of their application and usefulness. This study aimed to investigate the association between contemporary/recent biomarkers of fluoride exposure and total daily fluoride intake (TDFI) of children with large differences in fluoride exposure through drinking water. TDFI was assessed in 61 healthy 4- to 5-year-old children who provided at least 1 biomarker sample; 32 lived in a low-fluoride area (0.04 mg F/L) and 29 lived in a high-fluoride area (3.05 mg F/L). Validated questionnaires were administered to evaluate fluoride intake from diets (including water) and toothpaste ingestion. Daily urinary fluoride excretion (UFE) and fluoride concentrations in plasma, fasting whole saliva, hair, and nails (toenails/fingernails) were evaluated and related to total fluoride exposure. TDFI, UFE, and fluoride concentrations of biomarkers were statistically significantly higher in the high-fluoride area than in the low-fluoride area. There was a strong statistically significant positive correlation between TDFI and UFE (ρ = 0.756, p < 0.001); plasma fluoride concentration (ρ = 0.770, p < 0.001); and toenail fluoride concentration (ρ = 0.604, p < 0.001). The statistically significant positive correlation between TDFI and fingernail fluoride concentration (ρ = 470, p < 0.001) as well as between TDFI and fasting whole saliva fluoride concentration (ρ = 0.453, p = 0.001) was moderate, whereas it was weak between TDFI and hair fluoride concentration (ρ = 0.306, p = 0.027). In conclusion, the current study confirmed the suitability of 24-h urine samples for estimating fluoride exposure in children. The strong correlations between TDFI and fluoride in plasma and toenails also suggest these biomarkers may be considered for health risk assessments of fluoride in children who are susceptible to development of dental fluorosis.

scholarly journals Dielectric and electrical properties of a mullite/glass composite from a kaolinite clay/mica-rich kaolin waste mixture

Cerâmica ◽  
2019 ◽  
Vol 65 (373) ◽  
pp. 117-121 ◽  
Author(s):  
J. P. F. Grilo ◽  
H. P. A. Alves ◽  
A. J. M. Araújo ◽  
R. M. Andrade ◽  
R. P. S. Dutra ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Glassy Phase ◽  
Low Cost ◽  
Microstructural Characterization ◽  
Reactive Sintering ◽  
X Ray Diffraction ◽  
Glass Composite ◽  
Kaolinite Clay ◽  
X Ray ◽  
Waste Mixture

Abstract A mullite/glass composite has been prepared by reactive sintering of a kaolinite clay/mica-rich kaolin waste mixture with 25 wt% waste. Phase composition, microstructure, dielectric and electrical properties of the composite fired at 1400 °C were evaluated by X-ray diffraction, scanning electron microscopy and impedance spectroscopy (between 25 and 600 °C in air). The microstructural characterization showed the attainment of dense samples composed of acicular (orthorhombic) mullite (47.6 wt%), glassy phase (50.1 wt%), and residual quartz (2.3 wt%). Electrical conductivity (1.9x10-8 S/cm at 300 °C), dielectric constant (6.7 at 1 MHz, 25 °C) and dielectric loss (0.024 at 1 MHz, 25 °C) results gave evidence that the mullite/glass composite is a promising low-cost material for commercial use in electronics-related applications.

Ultrastructure and Composition of Enamel in Human Dental Fluorosis

1989 ◽  
Vol 3 (2) ◽  
pp. 203-210 ◽  
Author(s):  
T. Yanagisawa ◽  
S. Takuma ◽  
O. Fejerskov
Keyword(s):  
Surface Layer ◽  
Dental Fluorosis ◽  
Fluoride Concentration ◽  
Occlusal Caries ◽  
Electron Microscopic ◽  
High Fluoride Concentration ◽  
High Fluoride ◽  
Materials Used ◽  
High Degree ◽  
Hexagonal Crystals

Materials used in this work were 13 permanent molars exhibiting dental fluorosis (between 5 and 9 on the Thylstrup-Fejerskov scale, 1978) obtained from adults (aged 20-40 years) living in regions with 3.5 ppm fluoride in the water supplies. Small but deep occlusal caries lesions necessitated extraction. Light and polarized microscopic, microradiographic, electron microscopic, and electron-probe- and ion-micro-analytical studies were made. Enamel surfaces were generally cloudy to opaque, with several pits or defects of various sizes and degrees of brown-staining. An extensively hypomineralized area extended from the inner enamel to the surface layer, which was mineralized to a high degree. The hypomineralized area contained sparsely arranged, flattened, hexagonal crystals with either perforated centers or defects extending from the perimeter and indicating either no or low fluoride content. The highly mineralized surface layer, however, was composed of many large, flattened, hexagonal crystals and extremely small, irregularly shaped crystals. Both types were free of central perforations and defects. A high fluoride concentration was determined in the highly mineralized surface layer. These findings suggest that the hypomineralized area undergoes caries-like changes in terms of crystal dissolution and that the highly mineralized surface layer contains hydroxyapatite and fluoridated-hydroxyapatite, or fluorapatite, or both.

Iron Distribution in Geopolymer with Ferromagnetic Rich Precursor

2010 ◽  
Vol 643 ◽  
pp. 131-138 ◽  
Author(s):  
Kelly Cristiane Gomes ◽  
Gabriel S.T. Lima ◽  
Sandro Marden Torres ◽  
Silvio Romero de Barros ◽  
Igor Frota Vasconcelos ◽  
...  
Keyword(s):  
Iron Content ◽  
Systematic Investigation ◽  
X Ray Diffraction ◽  
Kaolinite Clay ◽  
X Ray ◽  
Good Thermal Stability ◽  
Spectroscopy Studies ◽  
Significant Attention ◽  
Proper Analysis

Geompolymers and their engineering applications have attracted significant attention of the scientific community. This is due to properties such as good thermal stability and high resistance to aggressive environments. Most studies on this subject are based on traditional precursor materials such as calcined kaolinite clay (metakaolinite) and fly ash. The iron content is significant, reaching around 10% in metakaolinite, for instance. The role of iron in geopolymers still lacks systematic investigation. This can be attributed to the limitations presenting nuclear magnetic resonance (NMR) spectroscopy, which is a widely used technique to study geopolymers structure. Ferromagnetic elements such as iron, which is often present in some precursors, affect the magnetic response of the material, compromising the proper analysis of its structure by NMR results. Iron content in some industrial residues may be several times higher as it is often found in metakaolinite. This work presents x-ray diffraction, infrared and Mössbauer spectroscopy studies on the distribution of iron species in iron oxide/hydroxide-rich precursor, which was used to synthesized geopolymers.

Evaluation of Technological Properties of Ceramic Bodies Made of Kaolinite Clay and Steatite

2015 ◽  
Vol 820 ◽  
pp. 564-569
Author(s):  
Harlley Sander Silva Torres ◽  
Angélica Fortes Drummond Chicarino Varajão ◽  
Antônio Claret Soares Sabioni
Keyword(s):  
Flexural Strength ◽  
Industrial Waste ◽  
Ceramic Industry ◽  
Compact Surface ◽  
Technological Properties ◽  
Sintering Process ◽  
Icp Oes ◽  
X Ray Diffraction ◽  
Kaolinite Clay ◽  
X Ray

Ceramic bodies composed of steatite residues from workshops from the region of Ouro Preto (MG-Brazil) and 15, 20 and 25% of kaolinite clay were fired at 1000 and 1200 °C for 2hrs in air to evaluate their technological properties. Essays of flexural strength and water absorption showed that ceramic bodies have a performance for their use as commercial bricks with values in accordance to those defined by the Brazilian standards. The mixture material, raw and fired, was analyzed using X-ray diffraction, ICP/OES and SEM. After fired, the samples showed a more compact surface and an advanced sintering process. Talc and kaolinite are the dominant minerals in raw ceramics. After being fired, talc changes to enstatite and at 1200°C, mullite, periclase and cordierite appear. These minerals affect the physical properties of the ceramic bodies such as reduction of the porosity, increase of the sintering process and consequently, increased flexural strength. The results show that mixtures kaolinite clay and steatite have potential for application in ceramic industry which can also contribute to reducing the environmental impact of industrial waste from steatite.

scholarly journals 3D printing of kaolinite clay with small additions of lime, fly ash and talc ceramic powders

2019 ◽  
Vol 13 (3) ◽  
pp. 287-299 ◽  
Author(s):  
Carlos Revelo ◽  
Henry Colorado
Keyword(s):  
Fly Ash ◽  
Density Measurement ◽  
Surface Finishing ◽  
X Ray Diffraction ◽  
Ceramic Powders ◽  
Kaolinite Clay ◽  
X Ray ◽  
Direct Ink Writing ◽  
Ceramics Industry ◽  
Traditional Ceramics

Direct ink writing technique, an extrusion based additive manufacturing process, has been used to fabricate kaolinite clay based-ceramics with several inexpensive ceramic powders: lime, fly ash and talc. All the above materials are commonly used in the traditional ceramics industry, in both small and large industries, and therefore available worldwide. This research shows the simplicity of the process feasible not only for companies but also for individual users. The samples were fabricated with water to clay ratios (W/C) between 0.68 and 0.72. Additives were tested in 3.0, 5.0 and 7.0wt.% with respect to the clay contents, although 3 wt.% of additives worked best. Cylindrical samples were fabricated with 20mm in diameter and 20mm in height in order to test their compressive strength and density. Measurement samples were previously cured for three days at room temperature and then exposed to 1100?C for 1 h. The powdered additives and their corresponding mixtures with clay were characterized with scanning electron microscopy, X-ray fluorescence and X-ray diffraction techniques. Results showed that samples with 0.70 W/C ratio and using fly ash as an additive were the best in terms of workability, mechanical properties and surface finishing.

scholarly journals FLUORIDE IN GROUNDWATER AND ITS EFFECTS ON HUMAN HEALTH

2017 ◽  
Vol 6 (2) ◽  
pp. 51 ◽  
Author(s):  
Ayse Dilek ATASOY ◽  
Mehmet İrfan YEŞİLNACAR ◽  
Benan YAZICI ◽  
Müge ÖZDEMİR ŞAHİN
Keyword(s):  
Human Health ◽  
Dental Fluorosis ◽  
Fluoride Concentration ◽  
World Health ◽  
Negative Effects ◽  
School Students ◽  
The World ◽  
High Fluoride ◽  
Permissible Levels ◽  
Recommended Level

Fluoride contents higher than the permissible levels lead to negative effects on the human health. More than 200 million people in the world were adversely affected from the fluoride. Fluoride levels in water were higher than the World Health Organization’s (WHO) recommended level. Endemic fluorosis originating from the consumption of high fluorine water was observed also in some parts of Anatolia. Volcanic formations are found in areas with high fluoride concentrations in ground waters. In this study, fluoride concentration of water was researched in Şanlıurfa where comprised generally sedimental formations and where the fluorosis cases were identified on the primary school students. High fluoride levels were assigned in water samples from the wells in Sarım and Karataş villages in Şanlıurfa. Keywords: Fluoride, hydrogeochemistry, dental fluorosis, Şanlıurfa   

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