A Study On Removal Of Fluorine Ion From Wastewater By Adsorption Processing

The source of wastewater containing fluorine ion is extensive, and excessive fluoride of water is a severe hazard to environment and human health. Therefore it is of significance to study and exploit methods of defluoridation of water.As an important physico-chemical wastewater treatment method, adsorption has already been used widely because it is simple and efficient, especially effective in treating wastewater containing low concentration pollutants. And adsorption is one of the most extensively used treatment methods for removing fluoride from wastewater. The key to successfully adopt the adsorption in treating wastewater 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 interest of many scholars in environmental engineering.To explore and manufacture the wastewater treatment adsobents of defluoridation with high adsorption efficiency, we adopt all the three materials as fly ash of Pingguo Aluminum Industry Company, steel slag from Liuzhou Steel Company and bentonite of Ningming, Guangxi Zhuang Autonomous Region, to remove fluorine ions from water. The steel slag and its modification products have the adsorption capacity greatly, and they are investigated intensively to treat the wastewater containing F~-.Through the study, the following conclusions can be obtained.(1)Steel slag has great adsorption capacity in absorbing F , while fly ash is the weaker, and bentonite is the weakest. Sulphated steel slag can be improved and enhanced in its adsorption capacity. But the processing with steel slag and its modification products are the most prospective new methods of defluoridation because it is simple to treat, easy to handle, little time comsuption and energy comsuption, rapidly and effectively to separate liquid and solid of the treated solution, most important of all, its product has high adsorption capacity.(2) Under the conditions of the experiment, defluoridation effect with steel slag is relevant to the initial fluoride concentration. With the increment of the initial fluoride concentration, the removal of F~- is enhanced.(3)The pH value of waste water is large range in using steel slag to remove fluorine ion, and the optimum pH was found to be about 6.6. In the acidic range, the removal efficiency of F~- is increasing with the growing of pH, but in the alkaline range, the result is reverse, and that is to say the removal efficiency of F~- is reducing with the growing of pH. The suitable pH value is 4-10 in eliminating F~- with steel slag.(4) Absorption time is an important factor that influence the removal efficiency of F~- Under the conditions of the experiment, the optimum reacting time of the steel slag and its modification products is 90 min. With the increment of the steel slag dosage, the removal of F~- is enhanced. With the increasing of rotation time, the removal efficiency is increased.(5)The mechanism of steel slag is ion exchange, inner-layers combination and surface combination. The adsorption of F~- is fit with Freundlich equation and Langmuir equation, but it is more suitable for the former.