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Comparison of Performance of Conventional Ozonation and Heterogeneous Catalytic Ozonation Processes in Phosphate- and Bicarbonate-Buffered Solutions
https://orcid.org/0000-0002-5087-3972
https://orcid.org/0000-0002-5411-3233
While many studies have demonstrated that both conventional ozonation and heterogeneous catalytic ozonation (HCO) processes possess at least some capacity to remove organic contaminants from solution, the mechanisms underlying these ozone-based technologies remain unclear due to the contradictory results that have often been presented. We hypothesize that part of the inconsistency among different studies may be due to the different buffering solutions used. In this work, we investigated the influence of two commonly applied buffers, phosphate and carbonate, on ozone decay as well as the rate and extent of degradation of particular target organic compounds (formate and oxalate) in both conventional ozonation and HCO processes. Our results reveal that the rate of ozone self-decay was considerably faster in phosphate buffer compared to carbonate buffer, with this effect resulting from the differing •OH scavenging capacities of the buffering ions. Interestingly, while the nature of the buffer used affected the rate of organic oxidation in conventional ozonation, there was minimal effect on the overall extent of oxidation of the target organic compounds. The results obtained also indicate that the carbonate radicals generated as a result of carbonate–•OH reaction are capable of oxidizing oxalate and formate, albeit slowly; however, the oxidation of these organics by phosphate radicals appears to be minimal. The presence of phosphate ions also affects the surface chemistry of the two Cu-based catalysts used in the HCO studies with phosphate inhibiting catalyst-mediated O3 decay and sorption of the target organic compounds on the catalyst surface. These results suggest that the influence of the buffering ions on the efficacy of organic oxidation is not only dependent on the nature of the organics but also on the mechanism of the catalytic ozonation process. Overall, caution should be exercised when selecting the buffer that will be used in investigations of the conventional ozonation and catalytic ozonation processes.
Comparison of Performance of Conventional Ozonation and Heterogeneous Catalytic Ozonation Processes in Phosphate- and Bicarbonate-Buffered Solutions
https://orcid.org/0000-0002-5087-3972
https://orcid.org/0000-0002-5411-3233
While many studies have demonstrated that both conventional ozonation and heterogeneous catalytic ozonation (HCO) processes possess at least some capacity to remove organic contaminants from solution, the mechanisms underlying these ozone-based technologies remain unclear due to the contradictory results that have often been presented. We hypothesize that part of the inconsistency among different studies may be due to the different buffering solutions used. In this work, we investigated the influence of two commonly applied buffers, phosphate and carbonate, on ozone decay as well as the rate and extent of degradation of particular target organic compounds (formate and oxalate) in both conventional ozonation and HCO processes. Our results reveal that the rate of ozone self-decay was considerably faster in phosphate buffer compared to carbonate buffer, with this effect resulting from the differing •OH scavenging capacities of the buffering ions. Interestingly, while the nature of the buffer used affected the rate of organic oxidation in conventional ozonation, there was minimal effect on the overall extent of oxidation of the target organic compounds. The results obtained also indicate that the carbonate radicals generated as a result of carbonate–•OH reaction are capable of oxidizing oxalate and formate, albeit slowly; however, the oxidation of these organics by phosphate radicals appears to be minimal. The presence of phosphate ions also affects the surface chemistry of the two Cu-based catalysts used in the HCO studies with phosphate inhibiting catalyst-mediated O3 decay and sorption of the target organic compounds on the catalyst surface. These results suggest that the influence of the buffering ions on the efficacy of organic oxidation is not only dependent on the nature of the organics but also on the mechanism of the catalytic ozonation process. Overall, caution should be exercised when selecting the buffer that will be used in investigations of the conventional ozonation and catalytic ozonation processes.
Comparison of Performance of Conventional Ozonation and Heterogeneous Catalytic Ozonation Processes in Phosphate- and Bicarbonate-Buffered Solutions
https://orcid.org/0000-0002-5087-3972
https://orcid.org/0000-0002-5411-3233
While many studies have demonstrated that both conventional ozonation and heterogeneous catalytic ozonation (HCO) processes possess at least some capacity to remove organic contaminants from solution, the mechanisms underlying these ozone-based technologies remain unclear due to the contradictory results that have often been presented. We hypothesize that part of the inconsistency among different studies may be due to the different buffering solutions used. In this work, we investigated the influence of two commonly applied buffers, phosphate and carbonate, on ozone decay as well as the rate and extent of degradation of particular target organic compounds (formate and oxalate) in both conventional ozonation and HCO processes. Our results reveal that the rate of ozone self-decay was considerably faster in phosphate buffer compared to carbonate buffer, with this effect resulting from the differing •OH scavenging capacities of the buffering ions. Interestingly, while the nature of the buffer used affected the rate of organic oxidation in conventional ozonation, there was minimal effect on the overall extent of oxidation of the target organic compounds. The results obtained also indicate that the carbonate radicals generated as a result of carbonate–•OH reaction are capable of oxidizing oxalate and formate, albeit slowly; however, the oxidation of these organics by phosphate radicals appears to be minimal. The presence of phosphate ions also affects the surface chemistry of the two Cu-based catalysts used in the HCO studies with phosphate inhibiting catalyst-mediated O3 decay and sorption of the target organic compounds on the catalyst surface. These results suggest that the influence of the buffering ions on the efficacy of organic oxidation is not only dependent on the nature of the organics but also on the mechanism of the catalytic ozonation process. Overall, caution should be exercised when selecting the buffer that will be used in investigations of the conventional ozonation and catalytic ozonation processes.
Comparison of Performance of Conventional Ozonation and Heterogeneous Catalytic Ozonation Processes in Phosphate- and Bicarbonate-Buffered Solutions
Yuan, Yuting (author) / Mortazavi, Mahshid (author) / Garg, Shikha (author) / Ma, Jinxing (author) / Waite, T. David (author)
ACS ES&T Engineering ; 2 ; 210-221
2022-02-11
Article (Journal)
Electronic Resource
English
| Taylor & Francis Verlag | 2012