Adsorption of Natural Organic Matter onto the Products of Water-Pipe Corrosion

Świetlik, Joanna; Laskowski, Tomasz; Kozyatnyk, Ivan

Adsorption of Natural Organic Matter onto the Products of Water-Pipe Corrosion

2015

Świetlik, Joanna | Laskowski, Tomasz | Kozyatnyk, Ivan

Natural organic matter (NOM) interaction with corrosion sediments is important because it can adversely affect the behaviour of many organic and inorganic pollutants in drinking water distribution systems. NOM accumulation onto corrosion sediments can cause serious problems for water supply, such as bacteria regrowth and deterioration of water quality. Corrosion sediments have different structures from the well-known iron oxides. The interaction among corrosion sediments and water organic matter can also differ. The main goal of this work was to understand the adsorption mechanism of the processes of NOM interaction with corrosion sediments. Fulvic acid (FA) isotherms on corrosion sediments in logarithmic coordinates of the Freundlich equation have different segments with different slopes, representing the non-adsorbed and adsorbed conditional component of the FA. The formation of structures with a molecular weight higher than the initial FA was observed. FA adsorption on corrosion sediments depends on time. Almost 60–70 % of the FA was removed during the first 10 min of contact. Such rapid adsorption indicates that FA was accumulated onto corrosion sediments mainly due to physical-chemical interaction. The pseudo-second-order kinetics model was demonstrated to better describe the adsorption of FA onto corrosion sediments than the pseudo-first-order model. External mass transfer is the limiting stage of the process of FA adsorption onto corrosion sediments. This knowledge is useful for understanding of corrosion processes and biological regrowth in water supply pipes and thus further decrease of drinking water quality.

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