Experimental Study On Flroride Removal By New Adsorbents

Fluoride is toxic, but at the same time it is beneficial for calcification of dental enamel and bone formation. Excess intake of fluoride would lead to various diseases such as osteoporosis, arthritis, brittle bones, cancer, infertility in women, brain damage, Alzheimer syndrome, and thyroid disorder. There are 29 nations in the world suffering such a problem to different extent that their drinking water contains more fluoride than the norm recommended. Especially in China, more than 260 million people are drinking the water with high concentration of fluoride. Therefore, it is necessary to explore effective and economical defluoridation processes.Nowadays, the main defluoridation process include adsorption, ion exchange, reverse osmosis, chemical precipitation and electrodialysis. As an important physico-chemical water treatment method, adsorption has already been used widely because it is simple and efficient, especially effective in treating water containing low concentration pollutants. And adsorption is one of the most extensively used treatment methods for removing fluoride from water. The key to successfully adopt the adsorption in treating water is to use the suitable adsorbents. In recent years, the exploitation of the novel, cheap and effective adsorption materials in treating wastewater to save the cost has attracted the interests of many scholars.In this paper, zirconium hydroxide and activated titanium were firstly investigated and their adsorption performance for fluoride removal is evaluated. The behavior of adsorbents for removing fluride were studied by static method. Use a series condition experiment to analyze the influeneing faetors of fluoride removal one by one, get the optimum reaction condition. Experiment results show that the adsorption capacity increases rapidly with the increasing of the equilibrium concentration. The inference of pH is significant on adsorption capacity and speed of zirconium hydroxide. The optimum pH for adsorption is 2.5～5.0. The adsorption capacity and speed decreases rapidly with pH increasing. The results show that the zirconium hydroxide is suitable for disposal of acidity solution. The largest adsorption capacity is obtained within fifteen minutes contact-time, which shows that the adsorbent has great affinity to fluoride and rapid speed of defluoridation within a short contact-time. We use 0.02g adsorbent to deal with 50mL of fluoride solution, when the original concentration is 10mg/L, the equilibrium concentration is less than 1.0mg/L, the treated solution meets the drinking water quality standards. the largest adsorption capacity is 195.87 mg/g. There is very little effect on the adsorption capacity and speed of active titanium. The largest adsorption capacity is obtained within fifteen minutes contact-time too. We use 0.10g activated titanium to deal with 50mL of fluoride solution, when the original concentration is 10mg/L, the equilibrium concentration is less than 1.0mg/L, the treated solution meets the drinking water quality standards. The largest adsorption capacity is 25.9mg/g .Fluoride removal from water by the zirconium hydroxide is mainly due to the ion- exchange between the–OH from the adsorbent and the F-in the solution. The mechanism of activated titanium removal fluoride is very perplexing and under ulteriorly research and development. The adsorptions equilibrium was studied. The results show that the adsorption of fluoride fit Langmuir adsorption isotherm better. The adsorption capacity increases rapidly with the increasing of the equilibrium concentration. There are higher adsorption capacith when the equilibrium concentration are very lower. Experiment indicates that adsorbents have great affinity to fluoride and the rapid speed of defluoridation, which is a prominence character for adsorbents.The adsorbents with higher removal capacity not only effective but also no secondary pollution, are simple and practicable methods of defluoridation. Their will have bright application foreground.