Adsorption Sulfate from Underground Water by Zn/Al Layered Double Oxide
|School||Taiyuan University of Technology|
|Keywords||underground water sulfate adsorption LDH adsorption method|
In recent years, our country has been confronted with the shortage of freshwater source, so the urgency of the exploitation of underground water is becoming out. But the underground water in many places of Shanxi province have a high level of SO42-, such as Taiyuan basin and west of Fen river. It was reported that diarrhea may be linked to water that contains high levels of sulfate. And the content of sulfate in water was positively correlated to the sick rate of liver cancer. The most of the methods that study on high levels of sulfate in water is about industry waste water but not the underground water. Based on the advantage of the LDH that has a high adsorbability, we research the feasibility that SO42-removal from high sulfate containing ground water by LDH adsorption method. This paper hope to offer a practicable、economic and safety way for the treatment of high sulfate containing groundwater.In the study of the adsorption of sulfate by Zn/Al-LDO, this paper is mainly explored following aspect:Investigate the synthesis conditions of LDHs by orthogonal experimental method and single factor experiment in order to improve the sulfate adsorption capacity of the Zn/Al-LDHs. The results indicated that sulfate adsorption capacity of LDHs was greatly affected by the compositon of metal ions in LDHs and the synthesis conditions. The best condition was synthesized at75℃, using10%NaOH as the coprecipitant, aged for12h, pH10and then calcined at380℃.ZnAl-380had a good stability and a high phosphate uptake in the water samples at pH7. The amount of the adsorbed sulfate per gram of Zn/Al was decreased with an increase in the LDHs dosage. Agitation speeded up the sulfate by the ZnAl-380, and the sulfate removal ratio reached more than90%.Methods of sulfate desorption and recovery were studied.10%Na2CO3could be a suitable solution for sulfate desorption from the used LDHs and the desorption efficiency was92.3%. The relationship between LDHs structure and the sulfate adsorption capacity, sulfate adsorption kinetics, isotherms and thermodynamic were investigated to explore the mechanisms of sulfate uptake by the LDHs. The mechanisms of sulfate adsorption is ion incorporation during the LDHs rehydration, surface adsorption, ion exchange and surface complexation.Finally, on the basis of the comprehensive comparison of economic performance that many adsorption material perform at sulfate adsorption at the same condition, we come to we come to the conclusion that the LDH have the best performance. Thus provide a scientific basis for the sulfate removal in underground water.