Degradation Mechanism of PVA & HEC by Ozonation

Abstract

In the past, PVA (polyvinyl alcohol) and HEC (hydroxyethyl cellulose) were used in the chemical industry, especially in the expandable polystyrene manufacturing process They remained in the environment for a long time and could not be destroyed effectively by conventional wastewater treatment processes. In this study, PVA and HEC were treated with ozone. PVA was completely removed in 20 min. by ozonation, and about 75% of HEC was removed at pH 12. Increased pH enhanced the ozonation efficiency of PVA and HEC. From molecular weight distribution tests, the fraction of m.w. from 10000 to 30000 amu decreased, but the portion of m.w. from 1000 to 10000 amu increased to 50%. It was concluded that the removal of PVA and HEC was not due to complete mineralization but to the breakdown of macromolecules to micromolecules.