| At present, water arsenic pollution is one of the most serious environmental problems in the world due to its threatening environment safity and people's health. Arsenic exists in the minerals widely on the earth. Human activity, such as mining, smelting, chemical industry, maked more and more As enter to water which people are using. Arsenic can be accumulated in human body, which causes the pathological changes of the organ, and even skin cancer. WHO has listed As as one of the carcinogens, and thus USA and China had raised up the concentration of As standard of drinking water from 50μg/L to 10μg/L in 2006.Now, the methods for As remove include physical method, chemical method, and biological method. However, some of those traditional methods have low efficiency of As remove, high cost and long cycle, and are not useful in practical production.In this study, we used titania dioxide (TiO2) to modify natural zeolite to develop an adsorbent with high capacity of As adsorption, low cost, and good efficiency. We utilized the natural zeolite and titania dioxide's advantages to develop a sol-gel method to modify the zeolite, using batch experiment method. The main results were summarized as follows:1. The four natual zeolites from four areas exhibited low As adsorption ability. The As removal percentages were 23.51%-31.76% under the condition of solid/liquid ratio of 1:100, adsorption time of 90 min, and As concentration of 200μg/L. The As adsorption capability of four kinds of zeolites ranked as WenXian>JinYun>DaYe>LiangZi Lake for As(Ⅲ) removal, and WenXian>JinYun>LiangZi Lake>DaYe for As(V) revoval. The result indicated that the ferric oxide, titania and manganese oxide promoted As adsorption ability of natural zeolite.2. Three modifying methods including nano TiO2 mixing, TiCl4 hydrolysing, and Ti(OC4H9)4 hydrolysing, were compared for the operation, safty, cost, and effeicency, and the results showed that the method of Ti(OC4H9)4 hydrolysing was the best one. As removal by heating modified Zeo-Ti and iron modified zeorite (Zeo-Fe), and found that the removal percentages of As(Ⅲ) and As(V) were 9.99% and 45.75% for heating modified Zeo-Ti respectively,54.97% and 13.92% for Zeo-Fe respectively, however 96.57% and 96.79% for Zeo-Ti respectively, under the condition of solid/liquid ratio of 0.2:100, adsorption time of 90 min and As concentration of 1000μg/L.3. The capacity of As adsorption by Zeo-Ti depended on its loading of titania and calcine temperature. The more titania content, the more As adsorbed. Zeo-Ti removed more than 95% of As(Ⅲ) and As(Ⅴ) from the water, when the titania loading content reached 10%, solid/liquid ratio was 0.2:100, adsorption time was 90 minutes,and the concentration of As was 1000μg/L.Zeo-Ti at calcine temperature of 300℃had the best removal efficiency.4. The modifying promoted zeolite's As adsorption capacity. Natural zeolite's adsorption capacity of As(Ⅲ) and As(V) was 0.6960 mg/g and 0.9823 mg/g respectively, however, the Zeo-Ti's adsorption capacity of As(Ⅲ) and As(Ⅴ) was 7.4463 mg/g and 6.3563 mg/g, increasing 10.7 and 6.5 times respectively. The Freundlich isotherm was well fit for the adsorption isothermal curve.5. Batch experiment was used to study influence of adsorption time, pH, temperature, solid/solution ratio, light condition, and concomitant ions on As removal. The results showed that when the solid/solution was 0.1g/50ml and the adsorption time reached 90 minutes, As removal was 95%. The pH (4-10) and temperature (10-40℃) had no distinct influences on As removal. Presence of concomitant ions, such as Mg2+, Ca2+,SO42-,NO3-had no distinct influences on As removal, but H2PO4- and SiO32-decreased the removal of As clearly when their concentrations exceeded 001mg/L6. Sodium hydroxide (O.1mol/L) was used to desorb As adsorbed by Zeo-Ti and regenerate the Zeo-Ti. The result showed that the desorption and regeneration of As(V) for Zeo-Ti was easier than that of As(Ⅲ).7. FT-IR characterization of Zeo-Ti indicated the presence of both As-O-Ti and As-O groups and supported the concept of surface complex formation. X-ray photoelectron spectroscopy (XPS) indicated that As(Ⅲ) and As(V) were adsorbed onto the Zeo-Ti with their own acid radicals. 8. Column test demonstrated that 1 tof Zeo-Ti could treat 60t wasterwater polluted by As and made it satisfy the drinking water standard; and could treat 150 t wasterwater polluted by As and made it satisfy the industry water discharge standard in one hour. In addition, titania was a kind of safe food additive, it could be used in drinking water treatment, and had good application value as substance of As polluted water.treatment. |
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