[Variation characteristics of relative molecular mass of different fractions of dissolved organic matter from landfill leachate during photocatalytic degradation].

ABSTRACT

Gel permeation chromatography was applied to analyze the variation characteristics of molecular mass of DOM six fractions during photocatalytic degradation. The results showed that most of DOM with average relative molecular mass was below 10(4). Large molecular fractions higher than 10(4) mainly containing HIB and HIN, accounted for nearly 20% of total DOM. Relative molecular mass of other fractions was mainly from 10(3) to 10(4). Fractions with relative molecular mass less than 500 were little. Most of DOM in leachate was yellow humic acid with moderate relative molecular mass and that is difficult to be biologically degraded. Relative molecular mass distribution of DOM fraction in different effluent broadened gradually during photocatalytic process, while polydispersity distribution coefficient (D) increased gradually. Relative molecular mass of HOB, HIB, HIA and HON decreased notably after photocatalytic treatment, especially HOB which relative molecular mass decreased from initial (4-25) x 10(3) to (0.4-1) x 10(3) after 72 h degradation. On the contrary, relative molecular mass of HOA and HIN tended to increase, and the more obvious is HOA which relative molecular mass increased from (2-20) x 10(3) of raw leachate to (20-50) x 10(3) of 72 h effluent. RID peak signal intensity of each DOM fraction decreased with the treatment time, which illustrated that the concentration decreased. As a whole, all fractions of DOM can be photocatalytically transformed efficiently.