Effect of Ozonation and Hydroxyl Peroxide Oxidation on the structure of Humic Acids and their removal Introduction Pre-oxidation is a common practice nowadays for the removal of offensive smell and odour and control of DBPs precursors as organic pollution of source water has become a serious problem. Ozone and hydroxyl peroxide are the oxidants widely applied. One topic drawing attention is the effect of oxidation on the structure of natural organic matter which is the main DBPs precursor. In this study, the authors applied a pyrolysis-GC-MS technique to analyze the main functional groups before and after oxidation by ozone and/or hydroxyl peroxide. The effect of pre-oxidation was evaluated from the results of organic removal by oxidation itself and after subsequent coagulation and/or GAC adsorption Results Discussion Effect of oxidation on the structure of Ha TOC and UVas removal Figure 1 shows some of the pyrolysis-GC-Ms analysis results for raw Figure 2 shows pre-oxidation by ozone, H2O, and H2O, with catalysts can water, ozonated water and oxidized water by H2O2 with O3 as catalyst. It is more or less result in direct removal of organic matter. H2O2 can bring seen from this figure that the dominant functional groups detected from about certain removal of UV2s4 especially at higher doses but its effect of the raw water are cyclic hydrocarbons and aromatics, such as TOC removal is not apparent. As a low dosage of catalyst is applied, cyclohexanone, benzenetricarboxylic acid, significant improvement can be achieved in the removal of both UV254 and benzophenone etc, while after oxidation by ozone or H2O2 with ozone, Toc by H2O2, and O3 shows the best catalysing effect. It is also many of these cyclic hydrocarbons are no longer in existence and many noticeable that no matter which oxidant is applied, the removal of Uv2s4 is chain hydrocarbons and aliphatic acids with oxygenated groups such as much higher than that of TOC. The result implies that an important carboxyl, hydroxyl, ketone, ether, ester etc. are newly formed. Apparently function of the oxidants applied in this study is to alter the structure of the the organic functional groups undergo a significant change in thei organic molecules rather than to decompose them into inorganic matter structure, mostly from cyclic to chain hydrocarbons and/or from aromatics to aliphatics Figure 2 Direct Removal of TOC and Uv2s4 by Different Oxidant 40 Raw Water Effect of pre-oxidation on coagulation and GAC adsorption Figure 3 shows the effect of pre-oxidation on the overall removal of TOC as coagulation(aluminium sulphate as coagulant and at pH 5.0)or GAC adsorption is subsequently applied. Pre-oxidation can apparently improve the TOC removal, especially under the condition of pre-oxidation by ozone or H2O2 with ozone. Aliphatic groups such as carboxyl and hydroxy groups are believed to be more readily to react with alum to form Al-humic complexes which result in better coagulation. Because pre-oxidation MuiJa brings about an increase in the portion of aliphatic groups, the HA After Ozonation coagulant. For GAC adsorption, the molecular weight of the organic matter is an important factor. Larger organic matter can be broken into smaller ones by pre-oxidation. This makes the organic matter more favourable to be adsorbed by GAC. M此 Afer Oxdation by Hydroxyl Peroxide with Ozone as Catalyst Figure 3 Effect of pre-oxidation on coagulation and GAC Figure 1 Pyrolysis-GC-MS Analysis Results adsorption Conclusions Both ozone and H2O, with a small dose of zone as catalyst can bring about a decrease of cyclic hydrocarbons and aromatics and an increase of chain hydrocarbons and aliphatic acids. This is accompanied by a remarkable decrease of UV2s4 though an effective TOC removal may not be achieved. H2O2 itself is not effective for pre-oxidation unless certain chemicals, such as ozone, are used as catalysts. Pre-oxidation can improve the efficiency of overall organic removal by subsequent coagulation and/or GAC adsorption
Effect of Ozonation and Hydroxyl Peroxide Oxidation on the Structure of Humic Acids and their Removal Pre-oxidation is a common practice nowadays for the removal of offensive smell and odour and control of DBPs precursors as organic pollution of source water has become a serious problem. Ozone and hydroxyl peroxide are the oxidants widely applied. One topic drawing attention is the effect of oxidation on the structure of natural organic matter which is the main DBPs precursor. In this study, the authors applied a pyrolysis-GC-MS technique to analyze the main functional groups before and after oxidation by ozone and/or hydroxyl peroxide. The effect of pre-oxidation was evaluated from the results of organic removal by oxidation itself and after subsequent coagulation and/or GAC adsorption. Introduction Results & Discussion Conclusions Figure 1 shows some of the pyrolysis-GC-MS analysis results for raw water, ozonated water and oxidized water by H2O2 with O3 as catalyst. It is seen from this figure that the dominant functional groups detected from the raw water are cyclic hydrocarbons and aromatics, such as benzoaldehyde, cyclohexanone, benzenetricarboxylic acid, benzophenone etc, while after oxidation by ozone or H2O2 with ozone, many of these cyclic hydrocarbons are no longer in existence and many chain hydrocarbons and aliphatic acids with oxygenated groups such as carboxyl, hydroxyl, ketone, ether, ester etc. are newly formed. Apparently the organic functional groups undergo a significant change in their structure, mostly from cyclic to chain hydrocarbons and/or from aromatics to aliphatics. Figure 1 Pyrolysis –GC-MS Analysis Results Both ozone and H2O2 with a small dose of zone as catalyst can bring about a decrease of cyclic hydrocarbons and aromatics and an increase of chain hydrocarbons and aliphatic acids. This is accompanied by a remarkable decrease of UV254 though an effective TOC removal may not be achieved. H2O2 itself is not effective for pre-oxidation unless certain chemicals, such as ozone, are used as catalysts. Pre-oxidation can improve the efficiency of overall organic removal by subsequent coagulation and/or GAC adsorption. Effect of oxidation on the structure of HA TOC and UV254 removal Figure 2 shows pre-oxidation by ozone, H2O2 and H2O2 with catalysts can more or less result in direct removal of organic matter. H2O2 can bring about certain removal of UV254 especially at higher doses but its effect of TOC removal is not apparent. As a low dosage of catalyst is applied, significant improvement can be achieved in the removal of both UV254 and TOC by H2O2 , and O3 shows the best catalysing effect. It is also noticeable that no matter which oxidant is applied, the removal of UV254 is much higher than that of TOC. The result implies that an important function of the oxidants applied in this study is to alter the structure of the organic molecules rather than to decompose them into inorganic matter. Figure 3 shows the effect of pre-oxidation on the overall removal of TOC as coagulation (aluminium sulphate as coagulant and at pH 5.0) or GAC adsorption is subsequently applied. Pre-oxidation can apparently improve the TOC removal, especially under the condition of pre-oxidation by ozone or H2O2 with ozone. Aliphatic groups such as carboxyl and hydroxyl groups are believed to be more readily to react with alum to form Al-humic complexes which result in better coagulation. Because pre-oxidation brings about an increase in the portion of aliphatic groups, the HA molecules in the solution become more coagulable with aluminium coagulant. For GAC adsorption, the molecular weight of the organic matter is an important factor. Larger organic matter can be broken into smaller ones by pre-oxidation. This makes the organic matter more favourable to be adsorbed by GAC. Effect of pre-oxidation on coagulation and GAC adsorption Figure 2 Direct Removal of TOC and UV254 by Different Oxidant Figure 3 Effect of pre-oxidation on coagulation and GAC adsorption 0 0.1 0.2 0.3 0.4 0.5 0 2 0 4 0 6 0 8 0 O x idant Dos e(m g/L) UV254(cm-1 ) H2O2+ O3 (0.5mg/L) H2O2+Fe2 +(2.8mg/L) H2O2+Cu2 +(3.2mg/L) H2O2+Mn2 +(2.8mg/L) H2O2 only O3 only 0 2 4 6 8 1 0 TOC(mg/L) H2O2+ O3 (0.5mg/L) H2O2+Fe2 +(2.8mg/L) H2O2+Cu2 +(3.2mg/L) H2O2+Mn2 +(2.8mg/L) H2O2 only O3 only 0 0.1 0.2 0.3 0.4 0.5 0 2 0 4 0 6 0 8 0 O x idant Dos e(m g/L) UV254(cm-1 ) H2O2+ O3 (0.5mg/L) H2O2+Fe2 +(2.8mg/L) H2O2+Cu2 +(3.2mg/L) H2O2+Mn2 +(2.8mg/L) H2O2 only O3 only 0 2 4 6 8 1 0 TOC(mg/L) H2O2+ O3 (0.5mg/L) H2O2+Fe2 +(2.8mg/L) H2O2+Cu2 +(3.2mg/L) H2O2+Mn2 +(2.8mg/L) H2O2 only O3 only 10 20 30 40 50 60 70 Relative Abundance 0 10 20 30 Acetic Acid Propanioc Acid Ethanol,2-butoxy- Oleyl Alcohol 2-Propenoic Acid,Butyl Ester 4-acetamido-1-pentanol Phenol Dodecane Fluorene 9-Octadecenoic acid(2)-,methyl Ester Benzophenone Tetradecanoic Acid Squalane After Oxidation by Hydroxyl Peroxide with Ozone as Catalyst Benzaldehyde Bis(2-ethylhexyl)ph thalate 2,4bis(1,1-dimethylethyl)-phenol Cyclohexanone Phenethylamine Indene 1,2,4-benzenetricarboxylic acid Thiourea Glycine Benzophenone Bis(2-ethylhexyl)phthalate Squalane 0 10 20 30 10 20 30 40 50 60 70 Epinephrine Raw Water Relative Abundance 0 10 20 30 Squalane Tetradecanoic Acid Benzophenone Diethyl Phthalate Fluorene Octanoic Acid Phenol 2-Propenoic Acid,Butyl Ester Oleyl Alcohol Hexanoic Acid Amyl Nitrate Ethanol,2-butoxy- Propanioc Acid Acetic Acid After Ozonation Relative Abundance Octanoic Acid Diethyl Phthalate 1-Tetradecanol 0 0.2 0.4 0.6 0.8 1 TOC Removal H O2 2+Fe2+ H O2 2 H O2 2+Cu2+ H O2 2+Mn2+ H O2 2+O3 O3 None Coagulation 0 0.2 0.4 0.6 0.8 1 TOC Removal H O2 2+Fe2+ H O2 2 H O2 2+Cu2+ H O2 2+Mn2+ H O2 2+O3 O3 None
