Changes in Spectral Characteristics and Copper (II)-Binding of Dissolved Organic Matter in Leachate from Different Water-Treatment Processes

Abstract

The aim of the present study was to investigate the fluorescence properties of dissolved organic matter (DOM) from four leachate samples, which were disposed by regulating tank (RTK), anaerobic treatment (ATT), oxidation ditch (ODH), and membrane bioreactor and to assess their binding capacities and stability constants by Cu(II). The results showed that five fluorescent peaks, including three humic-like peaks (peaks A, C, and E) and two protein-like peaks (peaks B and D), were identified. Most fluorescent components can be degraded after ODH. Fluorescence-quenching titration showed that the modified Stern-Volmer model can be used to fit the quenching data and calculate conditional stability constants (log K) and the % of fluorophores (f %) between DOM and Cu(II). DOM-Cu(II) complexes had relatively high log K values in the RTK and ATT disposals. After the ODH-treatment process, log K values showed a marked decrease. The f % values of protein-like materials were evidently greater than those of humic-like substances. The results showed the impact of the water treatment on the metal-binding ability of various fractions.