Mechanism and kinetics of autoxidation of calcium sulfite slurries

Pasiuk-Bronikowska, W.; Bronikowski, Tadeusz; Ulejczyk, Marek

doi:10.1021/es00034a015

Cited by 33 publications

(9 citation statements)

References 5 publications

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“…Moreover, it has been reported that deprotonated complexes (Co(II)−OH), which is more reactive toward SO 3 2− compared to HSO 3 − would be formed at alkaline pH values (R1) leading to the formation of a Co(II)−SO 3 complex [27]. Co(II)−SO 3 could be oxidized to Co(III)−SO 3 + complex in the presence of dissolved oxygen as reported in different works (R2 and R3) [38]. SO 3 − could be generated during the redox reaction between the Co(III)-SO 3 + complex and SO 3 2− (R4).…”

Section: Effect Of Initial Ph On Paracetamol Degradationmentioning

confidence: 97%

Rapid oxidation of paracetamol by Cobalt(II) catalyzed sulfite at alkaline pH

Yuan

Zhao

et al. 2018

Catalysis Today

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In this study we have investigated the efficiency Cobalt (II) (Co(II)) for the activation of sulfite ions following the oxidation of paracetamol used as model contaminants.Physico-chemical parameters that can impact the paracetamol degradation (pH, initial paracetamol concentration, Co(II)/S(IV) molar ratio, oxygen concentration) and contribution of various radicals were investigated in order to elucidate the chemical mechanism. Main results show that the pH is a key factor controlling the efficiency in the system Co(II)/Sulfite. Higher efficiency is observed for pH between 9.0 and 10.0.Increasing S(IV) concentrations, until 1 mM, slightly promoted the degradation of paracetamol. In fact, an excess of sulfite ions inhibits the reaction through the scavenging of SO 4 − and SO 5 − . Moreover, degradation efficiency drastically decreases from ~ 85% to less than 5% in absence of oxygen. SO 4 − was confirmed to be the main oxidant responsible for the paracetamol degradation. For the first time we determined the second order rate constant between SO 4 − and paracetamol (1.33 ± 0.79 × 10 9 M −1 s −1 (at pH 5) and 6.14 ± 0.99 × 10 8 M −1 s −1 (at pH 11.0)). Moreover, radical-scavenging experiments also suggest the possible implication of SO 5 − . Hence, this work provides a precise understanding of the overall mechanism and a new 2 promising strategy by using sulfite and transition metal such as Co(II) to promote organic compounds degradation in water under neutral and alkaline pH conditions.

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Section: Effect Of Initial Ph On Paracetamol Degradationmentioning

confidence: 97%

Rapid oxidation of paracetamol by Cobalt(II) catalyzed sulfite at alkaline pH

Yuan

Zhao

et al. 2018

Catalysis Today

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“…Compared of Mg 2+ with 2S 2 2P 6 outmost electron configurations, the Co 2+ with 3d 7 electron configurations could accommodate the electron delocalized away from SO 3 2– , resulting a electron hole in SO 3 2– . Thus the free radicals of ·SO 3 – are produced that initiate the chain reaction as follows. , .25ex2ex chain initiation SO 3 2 − + Co 2 + → • SO 3 − + Co + (1) chain propagation • SO 3 − + normalO 2 → • SO 5 − (2) • SO 5 − + SO 3 2 − → SO 5 2 − + • SO 3 − (3) product formation SO 5 2 − + SO 3 2 − → 2 SO 4 2 − (4) chain termination • SO …”

Section: Discussionmentioning

confidence: 99%

Oxidation Rate of Magnesium Sulfite Catalyzed by Cobalt Ions

Wang

Zhao

et al. 2014

Environ. Sci. Technol.

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Oxidation of magnesium sulfite is important for recycle of byproduct in the magnesium desulfurization. The oxidation rate of magnesium sulfite, prepared by vacuum evaporation method, was investigated in a bubbling tank in presence of transition metal catalysts, which shows cobalt is the most effective. The general reaction orders with respect to cobalt, magnesium sulfite, and oxygen are 0.44, 0, and 0.46, respectively, and the apparent activity energy is 17.43 KJ·mol. The catalytic performance of cobalt compared with other metals was also analyzed employing the ion potential theory. Integrated with the three-phase reaction model, we inferred that the general oxidation rate of magnesium sulfite is controlled by mass transfer of oxygen. Further, the intrinsic kinetics was predicted, indicating that the reaction orders with respect to cobalt and oxygen are 1.0 and 0, respectively. The results are helpful for the recycle of magnesium sulfite in magnesia desulfurization.

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“…In this paper, we assumed that eq was the slowest step, and eq is also slow, which was considered by Ba̅ckstro̅m in his well-known mechanism of this chain reaction. − Thus, the production rate of •SO 3 – is expressed as k 1 × [HSO 3 – ] × [O 2 ], where k 3 × [•SO 5 – ] × [SO 3 2– ] is much less and neglected. Hence, the extinction rate of •SO 3 – is expressed as k 5 × [C 2 H 5 OH] × [•SO 3 – ] 2 , where k 2 × [•SO 3 – ] × [O 2 ] is much less and neglected.…”

Section: Discussionmentioning

confidence: 99%

Discussion on the Kinetics of Sulfite Oxidation Inhibited by Ethanol: A Reply to “Comments on ‘Mechanism and Kinetics of Sulfite Oxidation in the Presence of Ethanol’”

Wang

Hao

et al. 2012

Ind. Eng. Chem. Res.

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Sir: Sulfite oxidation is an important step in the wet flue gas desulfurization process. The published literature has shown that the reaction rate of sulfite oxidation is greatly affected by additives, including catalysts and inhibitors. However, most of the previous reports are limited to revealing the categories of possible inhibitors, and lacked systematic research on the prohibited oxidation kinetics in both depth and extent.We compared the effects of four inhibitors on the intrinsic oxidation of sulfite in literature, 1 in which ethanol is considered to be the best for application in wet desulfurization. The intrinsic oxidation kinetics of sulfite in the presence of ethanol was studied in a batch apparatus. The reaction orders, with respect to all the reagents, were achieved, as well as the activation energy. Hence, the results were used to discuss the oxidation kinetics of calcium sulfite in the literature. 2 In addition, we put forward a mechanism for the intrinsic reaction based on a steady-state assumption that agrees well with the experimental data.Dr. Rockstraw recently proposed some comments on the mechanism and experimental data. The present work aims to discuss these questions and share with the colleagues.

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Mechanism and kinetics of autoxidation of calcium sulfite slurries

Cited by 33 publications

References 5 publications

Rapid oxidation of paracetamol by Cobalt(II) catalyzed sulfite at alkaline pH

Rapid oxidation of paracetamol by Cobalt(II) catalyzed sulfite at alkaline pH

Oxidation Rate of Magnesium Sulfite Catalyzed by Cobalt Ions

Discussion on the Kinetics of Sulfite Oxidation Inhibited by Ethanol: A Reply to “Comments on ‘Mechanism and Kinetics of Sulfite Oxidation in the Presence of Ethanol’”

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