The interaction between effluent organic matter fractions and Al2(SO4)3 identified by fluorescence parallel factor analysis and FT-IR spectroscopy

Abstract

Colloidal organic matter (OC fraction), hydrophobic organic matters (HPO fraction), transphilic matters (TPI fraction) have been extracted and fractionated from Effluent Organic Matter (EfOM). FT-IR spectroscopy and Fluorescence Excitation-Emission Matrix parallel factor (EEM-PARAFAC) analysis have been performed to characterize the chemical structure of fractions. The coagulation performance of EfOM fractions with Al2(SO4)3 was investigated in terms of turbidity reduction and dissolved organic carbon (DOC) removal. FT-IR spectroscopy and Fluorescence have also been introduced to identify the interaction between fractions and Al2(SO4)3. The results showed the main component in different fractions and that HPO fractions can be representative of natural organic matter (NOM), whereas OC fractions is representative of EfOM. The dissolved organic matters (DOMs) like HPO fraction showed better removal efficiency during coagulation. The relationship between zeta potential and DOC removal suggested that the coagulation mechanism of EfOM fractions were different. A new intensity peak showed up in Region V and the enhancement of Fluorescence intensity in humic-like substance exhibited after coagulation, which due to the complex with aluminum salts. The –COO–Al asymmetric stretch in FT-IR spectroscopy confirmed the complexation between aluminum salts and carboxyl groups. As the interaction of Effluent Organic Matter can cause enhancement in fluorescence intensity, fluorescence-EEM was not an appropriate method to evaluate the coagulation performance of secondary effluent with aluminum salts.