光催化降解渗滤液DOM不同组分的相对分子质量变化特征

采用凝胶色谱技术研究了光催化氧化处理过程中垃圾渗滤液DOM 6种组分的分子质量变化规律.结果表明,垃圾渗滤液DOM的相对分子质量大多在104以下,平均在104以上的大分子物质主要是HIB和HIN,仅占渗滤液DOM总量的20%左右.其余组分大多位于(1～10)×103之间,低于500的组分含量很少.说明垃圾渗滤液DOM是以中等相对分子质量的黄腐酸类物质为主,难以生物降解.光催化处理过程中渗滤液DOM的相对分子质量分布范围逐渐变宽,多分散系数D逐渐增大.HOB、HIB、HIA以及HON组分在光催化处理后,相对分子质量显著减小;其中HOB减小最为明显,由初始的(4～25)×103,减小为72 h的(0.4～1)×103之间.而HOA和HIN组分的相对分子质量呈增加趋势,其中HOA增加最为明显,在垃圾原液中分布于(2～20)×103,在72 h光催化处理液中位于(20～50)×103之间.随着处理时间延长,DOM各组分的RID信号均降低,说明其浓度下降.整体上看,渗滤液DOM各组分均发生了明显光催化转化.

Variation Characteristics of Relative Molecular Mass of Different Fractions of Dissolved Organic Matter from Landfill Leachate During Photocatalytic Degradation

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 10⁴.Large molecular fractions higher than 10⁴ mainly containing HIB and HIN, accounted for nearly 20% of total DOM. Relative molecular mass of other fractions was mainly from 10³ to 10⁴.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)×10³ to (0.4-1)×10³ 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)×10³ of raw leachate to (20-50)×10³ 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.