Anionic Layered Structure Of Water Treatment Functional Materials

In order to deal with problems of water pollution and shortage of water resources, layered double hydroxides ( LDHs) and their calcined products ( CLDHs ),which have a 'memory effect' and adsorption properties, have been used as water treatment chemicals in many areas.In this thesis, the chemical composition, crystalline structure, thermal behavior and specific surface areas of commercial LDHs and CLDHs were characterized. The LDHs which had been pretreated had good layered crystalline structure. During the process of calcining, LDHs lost water and CO32- gradually with increasing temperature, and also the crystalline structure of the LDHs was lost.Using the 'memory effect', the removal of Cl- , PO43~ and phenol were studied using LDHs and CLDHs. It was found that MgAl-CLDHs, especially Mg4Al-CLDH, which had been calcined at 5 00-600 C were more effective than those calcined at other temperatures. After reaction, CLDHs calcined at 500-600 C reconstituted the original layered structure and the solution became basic. The reaction temperature had influence on the efficiency of the removal of the ions.Using their adsorbtion properties, the removal of organisms in water was studied using LDHs and CLDHs. It was found that the CLDHs that had been calcined at 500 C had a better effect than the uncalcined LDHs in removing COD and turbidity in water.Using ZnAl-LDHs and ZnAl-CLDH to sterilize water, it was found that the ZnAl-CIDH calcined at 500"C had the best effect. Zn3Al-CLDH was better than Zn2Al-CLDH, and the greater the amount of CLDHs consumed, the better the effect of sterilization.