Study On The Adsorption Performance Of Modified Vermiculite To Fluoride Ions In Water

Fluorine is a widely distributed element in the natural environment,mainly in the form of fluoride ions in water and soil,which is closely related to human health.The right amount of fluoride is good for human health,but excessive fluoride can cause fluorosis in human body,and fluorine has a dual nature to human health.Local fluorosis is caused by drinking water-type high-fluorine water,which has the characteristics of wide incidence area,large number of patients and difficult treatment in our country.It has had a certain negative impact on the health and economic development of the people and has therefore become a problem that cannot be ignored.This paper introduces a variety of fluorine removal methods at home and abroad.On this basis,we select non-toxic,harmless,low-cost,abundant reserves of meteorites as research materials for fluorine adsorption control technology,through acid modification and load modification of vermiculite.The treatment was carried out and the adsorption experiment was carried out to investigate the effect of the modification method of vermiculite on the amount of fluorine adsorption..Firstly,using microwave expanded vermiculite as raw material,the experimental results show that the better modification effect was obtained when the concentration of 150 mesh vermiculite and hydrochloric acid was 6 mol/L.The adsorption performance of hydrochloric acid modified vermiculite on fluorine is obviously improved.In the experiment of adsorbing fluorine by hydrochloric acid modified vermiculite,the optimal adsorption conditions were:NaF solution concentration was 30 mg/g,adsorption temperature was20℃,pH value was 6-7,the solid-liquid ratio of NaF solution to expanded vermiculite was 1:50,and the adsorption equilibrium time was 2h.Compared with the original vermiculite and microwave-expanded vermiculite,the adsorption amount of fluorine by hydrochloric acid-modified vermiculite was 0.96 mg/g,which was significantly improved.The characterization results show that the structure of the vermiculite is not destroyed after the hydrochloric acid modified vermiculite,the wafer was broken,the interlayer cations were dissolved and a large number of pits and pores appear,which greatly increased the adsorption amount of fluorine.The hydrochloric acid modified vermiculite was defluorinated,although the adsorption amount was greatly improved,but the fluorine removal rate was only 64.03%,which cannot meet the requirements of fluorine content in drinking water standards in China.On this basis,the loading modification of vermiculite can improve its adsorption capacity and achieve better adsorption effect.Therefore,the paper is loaded and modified on the basis of hydrochloric acid modified vermiculite.Through screening,it was determined that Al₂（SO₄）₃,FeCl₃,CaCl₂,MgCl₂ and chitosan were selected as loading agents.Through the adsorption test,obtained Al₂（SO₄）₃ modified vermiculite was the best adsorption effect on fluorine in the five kinds of load modifiers.The initial concentration of NaF solution was 30mg/g,after the modified of hydrochloric acid modified vermiculite with Al₂（SO₄）₃ with a solution concentration of 0.06mol/L,the adsorption amount of fluorine to the fluoride was up to 1.47 mg/g in 40minutes,the rate of the fluorine removal was 98.29%,the remaining NaF concentration in the solution is only 0.73mg/L,less than 1mg/L,reaching the national drinking water standard.The modified meteorite retains the original structure and frame characteristics of the vermiculite.After the vermiculite is modified by the load,the ions in the solution are exchanged to the outer surface of the vermiculite and the inner surface of the pore.The surface of the vermiculite covers a large number of particles,and the surface of the vermiculite becomes rough and rough,which increases the active site of the vermiculite and forms an adsorption active center,thereby improving the adsorption performance of the vermiculite.It can be seen from the research that in the adsorption process of fluorine by Al₂（SO₄）₃ loaded modified vermiculite,in addition to physical adsorption,there are also chemical adsorption and ion exchange adsorption,the three methods also act together in the process of fluorine adsorption,thus improving the fluorine adsorption performance significantly,and vermiculite price is low,which has broad prospects in practical application.