Preparation Of Soil Defluoridators And The Study Of Their Defluordation Properties From Drinking Water

The endemic fluorosis is one of the main endemics in our country. According to statistic, disease areas are all over 28 provinces; the disease area population is about 110,000,000; the sufferers of dental flourosis amount to 37,390,000; the sufferers of skeletal flourosis is about 2,760,000; and the number of sufferers is increaseing continuously. By demotics, disease areas distribute to villages, not cities; distributing to unenlighted areas, not developed areas. So the fluorosis is a kind of poor disease, and social disease. In our country, the research of the mechanisms of cheap adsorbent is on the start stage still. The study of aclive groups which have powerful affinity with fluorin is also on the experienial stage. So many microcosmic mechanisms about defluoridation need to be researched in-depthly. In order to resolve the proplem that high fluorine drinkingwater is widespread existence in our country, we make use of abundant cheap soil resources to produce a kind of cheap, efficacious, safe and new-style defluoridation used and regenerated easily.In the subject, we understood the defluoridation properties of various soils by experiment fistly. Second, we probed into the mechanism of defluoridation. And then, utilizing the characteristics of soil, such as big specific surface area, degree of viscosity, reclaimed easily, we constructed some function keys in the soil, for example -OH, Fe3+, Al3+, thus reclaimed soil could adsorb more fluorin from water. With the principle of simple, easy and cheap technique, we have researched preparation progress, defluoridation properties of reclaimed soils in depth. Concretely, including slecting soils andadditives, pretreating and reclaiming soils, proparation progress, molding, the contrast of the static and continuous-flow defuoridation properties between various reclaimed soils, analyzing mechanism, the contrast of the static and continuous-flow defuoridation properties between zeolite, activated alumina, bone chaocoal and I-5-3, anagenetic methods and results, experiment of the lixiviated quantity of additives from relaimed soils, economic and safe analysis of the drinkingwater.The main conclusions have been summarized as follows: (1) Original soils, baked soils and relaimed soils by ferrie salt are not suitable for defluoridation from the drinkingwater. I-5-3 sorbent is best at defluoridation from the drinkingwater. Some of relaimed soils by ferrie salt and aluminate can be used to remove fluoride from industrial waste water. (2) The soils which were gathered from defferent areas have big defferences in ignition loss and resolvable fluorin and defluoridation properties. Surption capacity is between the 0.03 mg/g and 0.08 mg/g. The reclaimed soil by the same ferrie salt and aluminate almost has the same surption capacity.Additives have the main function in removing fluorine from water, and the additive is suitable for various common soils to reclaim.(3) In the lower concentration of luorine aqua, the sorption isotherms of original soil and various reclaimed soils defluoridators correlate with Langmuir isotherm models. Correlation retio >0.99, n>1, so these sorbents have advantage to adsorb fluorine ion. Because of adsorbing and precipitating reaction, ion exchanges physical adsorption.(4) Baking temperature havocs the defluoridation properties and stability of the adsorbent. The best baking temperature is 400℃to 500℃when wereclaimed soil by ferrie salt; the best baking temperature is 350℃to 450℃when we reclaimed soil by aluminate. On thorough burning, the baking time almost has no effect on the defluoridation properties and stability of the adsorbent.(5) There are big divercity between reclaimed soil by different ferrie salts aluminates salts, especially the stability. In conclusion,aluminates are better than ferrie salts; ferrie salts are btter than ferrous salts; chloride salts are better than sulphates. The reclaimed soils by different vesicants have different stability. NH4HCO3 is best than other vesicants. Appending soluble substances will havoc the stability of sorbents. Na2SiO4 almost has no effect on stability. Although defluoridation properties will be better when we append hydroxids into soil, we cann't control the stability of the soil, and the pH in the water will rise after adsorbing.(6) I-5-3 has best defluoridation property, through water multiple amounts to 80. The sorption capability of the anagenetic sorbent is less than before, but repetitious usage after, the sorption capacity keeping a constant——above 0.1 mg/g. The stability of I-5-3 sorbent in the water is better than most of others. In the piller adsorbing experiment, lixiviated quantity of Al is descending along with the increment of through water quantity. The highest Al concentration is 0.13 mg/l; the lowest Al concentration is below 0.05 mg/l, below national drinkingwater health standard far away.(7) The sorption capacity of I-5-3 sorbent is 1/3 of the sorption capacity of activated alumina and bone charcoal; is 4 times than sorption capacity of zeolite. The sorption capacities of activated alumina, bone charcoal and I -5-3 sorbent are all descending along with the increment of anagenetic times. Thecost of anagenetic I-5-3 sorbent is higher than activated alumina and zeolite, but lower than bone charcoal. At the same time, the cost of preparation of I-5-3 sorbent is lowest than others. Because the preparation craft and regeneretion craft of I-5-3 sorbent are shorter, and the equipment is simpler. The first time investment is least than other sorbents, so this sorbent is a kind of economical and valid defluoridation.The main innovations of this research: First, making use of soil's characteristic, such as big specific surface area, degree of viscosity, and reclaimed easily. The next in order, we did not limit at a certain soil, but many kinds of common soils. Third, we took into account sorbent's stability and machine intensity in the water when we selected additives, and finally we selected AlCl3·6H2O appending vesicants for the very first time, availaly improving phycial and chemic characteristics. Finally, we regenerated the sorbent only by baking, and the sorption capacity is 80% of new sorbent. There are not secondary pollute.This research exploits widely the applied realm of the soil mineral, preparating cheap soil defluoridation. Through further research, this sorbent may be substitute intrinsic sorbent. This research has theoretical meaning and applied value for the development of soil sorbent application in our country.