Oxidative treatment of algogenic organic matter

Abstract

Nowadays, removal of organic substances from natural waters (NOM) is getting greater concern gradually because they form carcinogenic substances (DBP, THM, HAAs, etc.). Consequently, alternative methods have been tried to treat organic substances. Advanced treatment methods like titanium dioxide and photocatalytic oxidation are used as alternative methods through their non by-product formation characteristics. Experimental studies showed that, natural water content of organic materials contains humic acid, fulvic acid, hydrophilic acid, protein, lipid, amino acid and hydrocarbons. The objective of this research was to characterize the spectroscopic properties of algal organic matter (AOM) which comes from the algae degradation as model compounds to represent the natural organic matter (NOM) in aquatic systems. The photocatalytic oxidation of AOM aqueous solution was carried out using TiO2 Degussa P-25 as the photocatalyst. The degradation kinetics was assessed based on pseudo first order kinetic models. The related data for all working solutions were comparatively presented in terms of UV-vis parameters such as Color436, Color400, UV365, UV280 and UV254. Furthermore, the molecular and structural characteristics of the AOM solution were monitored by spectroscopic techniques during photocatalytic oxidation. For all of the working solutions, higher removal rates were achieved in terms of UV254 values compared to that of Color436. According to obtained data, the aqueous solution of AOM was efficiently oxidized by photocatalytic due to TiO2 amount and dilution rates. However degradation time did not significantly affect removal efficiencies. Moreover, considering the complexity of the algal derived organic macromolecules; they were fractionated into well defined subcomponents of known molecular sizes using ultrafiltration through membranes in the range of 1-100 kDa. The effect of photocatalytic oxidation on the molecular size fractions of algal organic matter was also evaluated on a comparative basis by UV-vis and fluorescence spectroscopy. As confirmed by the spectroscopic evaluation of the molecular size distribution data, photocatalytic degradation of algal organic matter aqueous solution results in the formation of higher UV-absorbing compounds.