| dc.description.abstract | The mechanism of organic compound chlorination during drinking water purification process is complicated. General speaking, in presence of cation in either clay or solution may cause a significant increase in formation of disinfection by-products(DPBs). In our earlier studies, the effects of the different exchangeable cations on clay surface to catalyze chlorinated reaction of organic compounds have ever been elucidated. However, the importance for the exchangeable cation amount in the chlorination reaction needs to be described further. For this reason, the montmorillonite with Ca2+ exchanged by different amounts of cation, including Cu2+, Fe3+,and Ti4+, was employed as the catalyst to examine the product using the NaOCl chlorination humic acid or polymer under a series of batch experiments. A comparable result between cation on the montmorillonite and free cation in the solution was observed to discuss the mechanism of organic compound chlorination.
The results indicated that the total formation potential of disinfection by-products (DBPs) for cation-montmorillonite is in the following order :Ti-Mont> Fe-Mont> Cu-Mont> Mn-Mont> Ca-Mont. For the free cation, the order is TiCl4 > FeCl3> FeCl2> CuCl2> MnCl2 >CaCl2> CuCl. The similar result was attributed to that the transition-mental cations process an empty d-orbital, especially in a higher valence state, to act as strong Lewis acid sites and electron acceptors, leading to higher valence state, on the other hand, although the higher amount of the exchange cation can promote the DBPs, the increase trend is unapparent relative to different metal species. The result can be concluded that cation species on the clay is a dominant factor due to they offer a catalytic center where the reaction occur | en_US |