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Oxidation of Sulfonamides in Aqueous Solution by UV-TiO2-Fe(VI).

Ma Y, Zhang K, Li C, Zhang T, Gao N - Biomed Res Int (2015)

Bottom Line: The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2.The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI).The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China ; Shanghai Urban Water Resources Development and Utilization National Engineering Center Co. Ltd., Shanghai 200082, China.

ABSTRACT
The photocatalytic degradation of sulfonamides in aqueous TiO2 suspension under UV irradiation has been investigated using potassium ferrate as electron acceptors. The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2. The experiments indicated that Fe(VI) could effectively scavenge the conduction band electrons from the surface of TiO2. The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI). The SD, SM, and SMX concentration was greatly reduced by 89.2%, 83.4%, and 82.0%, respectively, after 10 min with UV-TiO2-Fe(VI), comparing to 65.2%, 66.0%, and 71.9%, respectively, with Fe(VI) only in the dark and 71.3%, 72.7%, and 76.0%, respectively, with UV-TiO2. The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system. The degradation amount of sulfonamides after 10 min was a maximum at pH 7. The intermediate products of sulfonamides oxidation by UV-TiO2-Fe(VI) were analysed by LC-HESI-MS-MS and the results suggested that a majority of sulfonamides turned into large-molecule products without complete mineralization.

No MeSH data available.


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The protonation and deprotonation of sulfonamides ((a) sulfadiazine; (b) sulfamerazine; (c) sulfamethoxazole).
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fig5: The protonation and deprotonation of sulfonamides ((a) sulfadiazine; (b) sulfamerazine; (c) sulfamethoxazole).

Mentions: The experiments were performed in the pH range of 5–9. As shown in Figure 4, the removal of sulfonamides is much higher in UV-TiO2-Fe(VI) system than that resulting from ferrate oxidation alone in the pH range of 5–9, and the solution pH value significantly influenced the sulfonamides degradation. At pH 7, the removal of SD, SM, and SMX is the highest in the pH range of 5–9. The possible reason for the increased degradation is that this pH (7) is close to the pKa2 values of SD (6.5), SM (7.0), and SMX (5.7). At this pH, SD, SM, and SMX are dissociated (Figure 5). Previous studies found that the dissociation of the compound increases with increasing pH and deprotonated compounds are more readily oxidized by potassium ferrate and other oxidants such as •OH and hvb+ [15, 16]. Meanwhile, potassium ferrate had a much higher oxidation potential at acidic condition (E0 = 2.20 V) than that at basic conditions (E0 = 0.72 V) [17]. At pH <7, although oxidative ability of ferrate is high, the ferrate is highly unstable (Figure 1). Therefore, at pH 5, most Fe(VI) is decomposed to make the removal rate of sulfonamides low. In the UV-TiO2-Fe(VI) system, the ferrate oxidations of sulfonamides were enhanced most significantly at pH 9 due to the low oxidation ability of ferrate.


Oxidation of Sulfonamides in Aqueous Solution by UV-TiO2-Fe(VI).

Ma Y, Zhang K, Li C, Zhang T, Gao N - Biomed Res Int (2015)

The protonation and deprotonation of sulfonamides ((a) sulfadiazine; (b) sulfamerazine; (c) sulfamethoxazole).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4548100&req=5

fig5: The protonation and deprotonation of sulfonamides ((a) sulfadiazine; (b) sulfamerazine; (c) sulfamethoxazole).
Mentions: The experiments were performed in the pH range of 5–9. As shown in Figure 4, the removal of sulfonamides is much higher in UV-TiO2-Fe(VI) system than that resulting from ferrate oxidation alone in the pH range of 5–9, and the solution pH value significantly influenced the sulfonamides degradation. At pH 7, the removal of SD, SM, and SMX is the highest in the pH range of 5–9. The possible reason for the increased degradation is that this pH (7) is close to the pKa2 values of SD (6.5), SM (7.0), and SMX (5.7). At this pH, SD, SM, and SMX are dissociated (Figure 5). Previous studies found that the dissociation of the compound increases with increasing pH and deprotonated compounds are more readily oxidized by potassium ferrate and other oxidants such as •OH and hvb+ [15, 16]. Meanwhile, potassium ferrate had a much higher oxidation potential at acidic condition (E0 = 2.20 V) than that at basic conditions (E0 = 0.72 V) [17]. At pH <7, although oxidative ability of ferrate is high, the ferrate is highly unstable (Figure 1). Therefore, at pH 5, most Fe(VI) is decomposed to make the removal rate of sulfonamides low. In the UV-TiO2-Fe(VI) system, the ferrate oxidations of sulfonamides were enhanced most significantly at pH 9 due to the low oxidation ability of ferrate.

Bottom Line: The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2.The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI).The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China ; Shanghai Urban Water Resources Development and Utilization National Engineering Center Co. Ltd., Shanghai 200082, China.

ABSTRACT
The photocatalytic degradation of sulfonamides in aqueous TiO2 suspension under UV irradiation has been investigated using potassium ferrate as electron acceptors. The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2. The experiments indicated that Fe(VI) could effectively scavenge the conduction band electrons from the surface of TiO2. The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI). The SD, SM, and SMX concentration was greatly reduced by 89.2%, 83.4%, and 82.0%, respectively, after 10 min with UV-TiO2-Fe(VI), comparing to 65.2%, 66.0%, and 71.9%, respectively, with Fe(VI) only in the dark and 71.3%, 72.7%, and 76.0%, respectively, with UV-TiO2. The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system. The degradation amount of sulfonamides after 10 min was a maximum at pH 7. The intermediate products of sulfonamides oxidation by UV-TiO2-Fe(VI) were analysed by LC-HESI-MS-MS and the results suggested that a majority of sulfonamides turned into large-molecule products without complete mineralization.

No MeSH data available.


Related in: MedlinePlus