Ozonation Of Humic Substances Research Articles

Monitoring changes in the structure and properties of humic substances following ozonation using UV–Vis, FTIR and 1H NMR techniques

The main objective of this work is to conduct a comprehensive structural characterization of humic substances using the following experimental techniques: FTIR, 1H NMR and several UV–Vis parameters (Specific UV Absorbance at 254nm or SUVA254, SUVA280, A400, the absorbance ratios A210/254, A250/365, A254/203, A254/436, A265/465, A270/400, A280/350, A465/665, the Absorbance Slope Index (ASI), the spectral slopes S275–295, S350–400 and the slope ratio SR). These UV–Vis parameters have also been correlated with key properties of humic substances such as aromaticity, molecular weight (MW) and trihalomethane formation potential (THMFP). An additional objective of this work is also to evaluate the usefulness of these techniques to monitor structural changes in humic substances produced by the ozonation treatment. Four humic substances were studied in this work: three of them were provided by the International Humic Substances Society (Suwannee River Fulvic Acid Standard: SRFA, Suwannee River Humic Acid Standard: SRHA and Nordic Reservoir Fulvic Acid Reference: NLFA) and the other one was a terrestrial humic acid widely used as a surrogate for aquatic humic substances in various studies (Aldrich Humic Acid: AHA). The UV–Vis parameters showing the best correlations with aromaticity in this study were SUVA254, SUVA280, A280/A350 ratio and A250/A364 ratio. The best correlations with molecular weight were for SUVA254, SUVA280 and A280/A350 ratio. Finally, in the case of the THMFP it was STHMFP-per mol HS the parameter showing good correlations with most of the UV–Vis parameters studied (especially with A280/A350 ratio, A265/A465 ratio and A270/A400 ratio) whereas STHMFP-per mg C showed poor correlations in most cases. On the whole, the UV–Vis parameter showing the best results was A280/A350 ratio as it showed excellent correlations for the three properties studied (aromaticity, MW and THMFP). A decrease in aromaticity following ozonation of humic substances can be readily monitored by 1H NMR and FTIR; the latter technique also allows to monitor an increase in carboxylic acidity with ozone dosage. This organic matter originated following ozonation (more aliphatic in character and more polar) is expected to be recalcitrant to further oxidation. The terrestrial humic acid (AHA) showed some structural differences with the aquatic humic substances and its behavior upon ozonation also differed in some extent from that shown by them.

Flavouring Group Evaluation 15, Revision 1 (FGE.15Rev1) - Aryl-substituted saturated and unsaturated primary alcohol/aldehyde/acid/ester derivatives from chemical group 22 - Opinion of the Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in contact with Food (AFC).

Flavouring Group Evaluation 15, Revision 1 (FGE.15Rev1) - Aryl-substituted saturated and unsaturated primary alcohol/aldehyde/acid/ester derivatives from chemical group 22 - Opinion of the Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in contact with Food (AFC).

Behavior Of Glyoxal During Granular Activated Carbon Treatment

Glyoxal, which was the strong mutagen formed by ozonation of humic substances, was treated with granular activated carbon (GAC) and the behavior of glyoxal was investigated. Glyoxal itself was adsorbed well on GAC at pH 5–7. But, glyoxal increased by GAC treatment of ozonated humic substances when the ozone dose was insufficient to decolorize the humic substances. The precursors of glyoxal may be among other ozonated products which may be changed to glyoxal on GAC.

Generation of mutagenicity by ozonation of humic substances' components

Components of humic substances, such as vanillin, syringaldehyde, vanillic acid and di- n-butylphtalate, were ozonated and subjected to the mutagenicity assay using Salmonella typhimurium TA 98 and 100 with and without S9 mix. The strong mutagenic activity was found on all components except di- n-butylphtalate by strain TA 100 with and without S9 mix. Substances with strong mutagenic activity in ozonated vanillin were water-soluble and were slightly extracted with benzene, dichloromethane and ethyl acetate. Following gel chromatography on Sephadex G-10, the strong mutagens generated by ozonation were found with molecular weights > 300.

Mutagenicity from ozonation of humic substances

Eight structural components of humic substances were ozonated. Mutagenic activity was found using TA100 with and without S9 mix for all ozonated components. p-Hydroxybenzaldehyde was chosen as an important component and ozonation products were determined by gas chromatography-mass spectrometry (GC-MS). Aldehydes, ketones and carboxylic acids were identified as the ozonation products. Among these products, acetaldehyde, formaldehyde, glyoxal, methylglyoxal and glyoxylic acid were recognized to be mutagenic. Furthermore, p-hydroxybenzaldehyde was first ozonated and then chlorinated. A great variety of chlorinated organic compounds, many of which are known mutagens, have been identified by GC-MS in the ether extract. The same compounds have previously been reported as chlorination products of humic substances. Aldehydic products by ozonation were identified from ozonation followed by chlorination of humic substances and p-hydroxybenzaldehyde.

Aldehydes as mutagens formed by ozonation of humic substances

Humic substances and p-hydroxybenzaldehyde, one of their components, were ozonated and quantitative analysis of the mutagenic aldehydes (formaldehyde, acetaldehyde, glyoxal, glyoxylic acid and methylglyoxal) was performed. Glyoxal and glyoxylic acid were the main mutagenic compounds. The ozone-treated solutions were flowed through a granular activated carbon (GAC) column and the KMnO 4 consumed of the effluent decreased to about 40–50%. Most of the aldehydes formed by ozonation reduced, but glyoxal increased.

Effect of Humic Substances on the Flotation Response of Coal

Abstract This study investigated the generation of humic substances from the coal and the coal surface, and evaluated the effect of humic substances on the surface property of coal. The humic substances in aqueous solution were readily adsorbed on the surface of a fresh coal. The adsorption affects the surface hydrophobicity of the coal and, hence, the flotation recovery of coal. The adsorption of humic substances is maximum at neutral pH and diminishes toward both the alkaline pH and the acid pH. This effect is reflected in the flotation reponses of the fresh coal. Solutions of humic substances were oxidized with oxygen gas and ozone. The oxidation of humic substances in solution resulted in an adsorption that greatly enhanced the hydrophilicity of the coal and thus impaired the flotability of the coal. On the other hand, the ozonation of humic substances in solution resulted in the decomposition of humic substances and an improvement in the flotation response of the coal. Direct oxidation and ozonation of coal surface decreased the hydrophobicity of the coal, which resulted in a decrease in the flotation response.

Ozonation of Humic Substances: Effects on Molecular Weight Distributions of Organic Carbon and Trihalomethane Formation Potential

Abstract Four different sources of humic substances were studied to determine the effects of ozonation on molecular weight-distributions, based on dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP). Solutions of two soil-derived fulvic acids and a one soil-derived humic acid, as well as dissolved organic matter (DOM) associated with a natural water source were studied. Both gel permeation chromatography (GPC) and ultrafiltration (UF) were employed to define apparent molecular weight (AMW). Applied ozone doses ranged from 2.0 to 2.5 mg O3/mg DOC. Overall samples of untreated and ozonated waters, as well as individual molecular weight fractions, were characterized according to DOC, UV absorbance, and THMFP. Ozonation resulted in a significant disappearance of higher AMW material with a corresponding increase in lower AMW material. Although little overall reduction in DOC concentration was observed, significant overall reductions in UV absorbance and THMFP levels were observed.