A review of emerging adsorbents and current demand for defluoridation of water: Bright future in water sustainability
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Potable water
Activated alumina
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Activated alumina
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To estimate fluoride concentration in drinking water, cow's milk and buffalo's milk and to correlate the concentration of fluoride in cow's milk and buffalo's milk with varying levels of fluoride concentration in drinking water.Ten households having both cows and buffalo's were selected by convenience in each of the 3 zones (below optimum fluoride <0.7 ppm (parts per million), optimum fluoride 0.7-1.2 ppm and above optimum fluoride areas > 1.2 ppm). From these selected households, 200 ml of fresh milk of both cows and buffaloes was collected along with 200 ml of drinking water for estimation of fluoride concentration by using a fluoride ion selective electrode method. The data was analysed using SPSS, version 11.5 for windows.The mean fluoride concentration of drinking water, cow's milk and buffalo's milk in three different fluoride zones was 0.89±0.39, 0.09±0.07, 0.09±0.08 respectively. Pearson's correlation found a statistically significant correlation between fluoride concentrations in cow's and buffalo's milk with varying levels of fluoride concentration in drinking water in zone B and zone C. However, this correlation was not statistically significant in zone A.With an increase in fluoride concentration in drinking water there was an increase in concentration of fluoride in cow's and buffalo's milk. We conclude that this association is seen in conjunction to not only a single factor but rather due to culmination of several other aspects. So, there is a need to elucidate the other factors that might be contributing to this increase and dental fluorosis.
Water buffalo
Cow milk
Positive correlation
Negative correlation
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The aim of the study is to assess the occurrence of fluoride in the groundwater of Kaltungo area and environs. Consumption of high fluoride waters clearly manifests in the majority inhabitant of the area in form of dental fluorosis especially in the majority of the populace. Thirty groundwater samples were collected from hand-dug wells and boreholes using standard method and were analyzed to determine the fluoride level. The results revealed that the Fluoride in the waters ranges from 0.8 to 1.94 mg/l with a mean value of 1.65 mg/l. No clear variations in fluoride content have been observed in both the borehole samples and those from the hand-dug wells. Ca-Mg-HCO3 and Ca-Mg-Cl are the two major water types obtained in the area, which have a good association with fluoride. Negative correlation is observed between fluoride and temperature, fluoride and magnesium, fluoride and potassium and poor correlation is observed between fluoride and chloride, fluoride and nitrate, fluoride and phosphates which rules out the possibility of anthropogenic source of the fluoride in the waters. Positive correlation between fluoride and iron, indicates that the presence of fluoride in the water is as a result of dissolution of biotite within the host rock (Basalt).
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Activated alumina
Skeletal fluorosis
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Activated alumina
Hydrous ferric oxides
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The range of fluoride levels in the drinking-water of cities and villages in South Africa was determined during the transition from a very dry (1983) to a wet (1984/85) period. The combination fluoride ion selective electrode was employed for the determination of the fluoride concentration. It was found that fluoride levels in drinking-water changed for 93% of the cities and villages studied during the period 1983-1985. Furthermore, it became clear that when the water volume of the supplying source increased, the fluoride level decreased significantly (P less than 0.01). Boreholes showed significantly higher fluoride levels (P less than 0.01) than rivers or dams. The impact of the variation in drinking-water fluoride concentrations on supplementary fluoride dosage is discussed and recommendations made.
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Fluoride contamination of drinking water and groundwater is a worldwide concerned issue, and technologies are needed for the treatment of aqueous fluoride. In this study, Ti(IV) species-modified granular activated carbon (Ti(IV)-GAC) was prepared and tested for fluoride removal from aqueous solution. Batch experiments were performed to investigate the equilibrium, kinetics, and mechanism of fluoride adsorption onto the prepared Ti(IV)-GAC. The results showed that the spontaneous fluoride adsorption process followed the Langmuir isotherm model and the pseudo-second-order kinetic model. Fluoride adsorption onto the Ti(IV)-GAC was enhanced as the initial fluoride concentration and contact time increased. Alkaline pH and elevated solution temperature did not favor the adsorption of fluoride. Anion exchange between the fluoride ions and the hydroxyl groups of the adsorbents was the major adsorption mechanism. Both batch experiments and flowing column experiments demonstrated that the Ti(IV)-GAC adsorbent can effectively remove the aqueous fluoride with high efficiency, and bring down the fluoride concentration lower than the permissible limit of fluoride in drinking water in China (1.0 mg/L). Experiments also showed that the Ti(IV)-GAC material had favorable regenerability, and can be used as a versatile adsorbent for treating mixed contamination of fluorides and organic pollutants.
Langmuir adsorption model
Activated alumina
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Some commonly used remediation methods of heavy metal-contaminated soils were summarized,such as physical remediation,chemical remediation and bioremediation.The applicability and limitations of different remediation methods were analyzed.The general situation of zero-valent iron remediation and the problems in zero-valent iron remediation were elaborated,which was the new direction for future development of metal-contaminated soil remediation.
Zerovalent iron
Soil Remediation
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