Using Log-transformed Differential Spectra To Analyse The Influence Of Chlorination On Metal Binding By Dissolved Organic Matter

Reactions between dissolved organic matter (DOM) and chlorine are extremelyimportant for drinking water and wastewater processes. This study probe interactions ofSuwannee River fulvic acid (SRFA) and Aldrich humic acid (AHA) affected by chlorinationwith Fe(III), Al(III), and Cu(II) ions. Using differential optical absorption spectroscopy tostudy DSlope325-375values, the results to compare the NICA-Donnan model predictionssituation, and as a model parameters predictive to describe the case of metal complexationwith DOM. Cl2/DOC ratios of0.2and1.0(mg/mg) were selected to represent chlorine dosesthat are commonly used in pre-chlorination and disinfection. Spectroscopic data wereinterpreted based on NICA-Donnan modeling that employed modified constants describingrelevant complexation equilibria. The data demonstrated that effects of chlorination onDOM-metal interactions depend on the metal, chlorine dose and intrinsic DOM properties.Fe(III) was observed to form strong complexes with DOM and relatively little change ofFe(III) binding were observed both SRFA and AHA affected by chlorine. The amount ofbound Al(III) decreased significantly at total Al(III) concentrations>5μM. The amount ofbound Al(III) decreased only slightly for chlorinated SRFA but for AHA Al(III) bindingincreased at total Al concentrations <1μM due to the generation of additional carboxylicgroups after chlorination. It is different from Fe(III) and Al(III), the dominant involvement ofCu-DOM binding is carboxylic groups in both fulvic and humic acid, especially for humicacid, the increase of carboxylic group after chlorination for SRFA at low Cl2dose and forAHA at both low and high dose lead to increase the total amount of bound Cu(II).