Characteristic transformation of humic acid during photoelectrocatalysis process and its subsequent disinfection byproduct formation potential

Abstract

Disinfection byproduct formation potential Structure variationFunctional groups a b s t r a c tIn this study, degradation of humic acid (HA) via photoelectrocatalysis (PEC) process and corresponding disinfection byproduct formation potential (DBPFP) were investigated.Particularly, structure variation and subsequent DBPFP of HA during PEC treatment were correlated. The PEC process was found to be effective in reducing dissolved organic carbon concentration by 75.0% and UV absorbance at 254 nm by 92.0%. Furthermore, 90.3% of haloacetic acids formation potential and 89.8% of trihalomethanes formation potential were reduced within 180 min. Based on molecular weight and resin fraction results, it was demonstrated that HA with large aromatic, hydrophobic and long aliphatic chain organics were transformed into small and hydrophilic organics during PEC process. Combined with the fourier transform infrared spectra and 13 C nuclear magnetic resonance spectra analysis of HA fractions, it was concluded that phenolic hydroxyl and conjugated double bonds tended to be attacked by hydroxyl radicals during PEC process; these groups were reactive with chlorine to produce disinfection byproducts (DBP), especially trihalomethane and trichloroacetic acid. By contrast, amino, carboxyl and alcoholic hydroxyl groups were relatively difficult to be oxidized during PEC process; these groups had the potential to form dichloroacetic acid during chlorination. Results of these studies confirmed that PEC process was a safe and effective technique to decrease DBP formation significantly in water treatment plant. ª

Transformation of humic acid and halogenated byproduct formation in UV-chlorine processes

“…In the UV-chlorine processes, the formation of more OH inhibits the incorporation of chlorine into HA due to the non-selectivity of OH oxidation, leading to lower TCM formation. This indicates that OH radicals are prone to attack precursors such as those with unsaturated CeC bonds, conjugated double bonds and aromatic groups, because phenolic hydroxyl and conjugated double bonds are primarily responsible for TCM and TCAA formation according to previous works (Li et al, 2011;Tian et al, 2013).…”

“…However, a higher amount of DCAA was formed in the former condition, while more TCAA was formed in the latter. Some studies have shown that the DCAA precursor is mainly compounds with carboxyl and alcohol hydroxyl groups (Li et al, 2011), while the TCAA precursor is mainly those with phenolic hydroxyl and conjugated double bonds. Based on the transformation of HA in UVchlorine and chlorine, carboxyl and alcohol hydroxyl intermediates are predominant, leading to higher DCAA formation for UV-chlorine treatment, while phenolic hydroxyl and conjugated double bonds are dominant in intermediates, leading to higher TCAA formation in chlorination.…”

Characterization of dissolved organic matter from surface waters with low to high dissolved organic carbon and the related disinfection byproduct formation potential

“…Tran et al reported that the Ho fraction generally contained a large proportion of aromatic structures [25]. However, the Hi fraction contained many aliphatic carbon and nitrogenous compounds [26]. Thus, SUVA appeared to be a better indicator for the reactivity of the compounds that comprise aquatic humic substances than for the DOC present in the whole water samples.…”

Enhanced removal for humic-acid (HA) and coagulation process using carbon nanotubes (CNTs)/polyalumium chloride (PACl) composites coagulants

“…HA molecules are not only a major source of foulant during ultrafiltration process, but also can compete for adsorption sites with target contaminants during activated carbon adsorption to decrease the pollutant removal efficiency [10][11][12][13]. They can also react with chlorine during drinking water treatment processes to produce potentially carcinogenic such as trihalomethanes and haloacetic acids [14][15][16][17]. Activated carbon adsorption, coagulation, electro-coagulation, and biosorption have been widely used for the removal of HA [18][19][20][21].…”