Department of Environmental Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea.
Department of Environmental Engineering, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea; Department of Energy Engineering Convergence, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea.
Ultrason Sonochem. 2023 Jul;97:106452. doi: 10.1016/j.ultsonch.2023.106452. Epub 2023 May 22.
Dissolved gases have a substantial influence on acoustic cavitation and sonochemical oxidation reactions. Little research on the changes in dissolved gases and the resultant changes in sonochemical oxidation has been reported, and most studies have focused only on the initial dissolved gas conditions. In this study, the dissolved oxygen (DO) concentration was measured continuously during ultrasonic irradiation using an optical sensor in different gas modes (saturation/open, saturation/closed, and sparging/closed modes). Simultaneously, the resulting changes in sonochemical oxidation were quantified using KI dosimetry. In the saturation/open mode using five gas conditions of Ar and O, the DO concentration decreased rapidly when O was present because of active gas exchange with the atmosphere, and the DO concentration increased when 100% Ar was used. As a result, the order of the zero-order reaction constant for the first 10 min (k) decreased in the order Ar:O (75:25) > 100% Ar ≈ Ar:O (50:50) > Ar:O (25:75) > 100% O, whereas that during the last 10 min (k) when the DO concentration was relatively stable, decreased in the order 100% Ar > Ar:O (75:25) > Ar:O (50:50) ≈ Ar:O (20:75) > 100% O. In the saturation/closed mode, the DO concentration decreased to approximately 70-80% of the initial level because of ultrasonic degassing, and there was no influence of gases other than Ar and O. Consequently, k and k decreased in the order Ar:O (75:25) > Ar:O (50:50) > Ar:O (25:75) > 100% Ar > 100% O. In the sparging/closed mode, the DO concentration was maintained at approximately 90% of the initial level because of the more active gas adsorption induced by gas sparging, and the values of k and k were almost the same as those in the saturation/closed mode. In the saturation/open and sparging/closed modes, the Ar:O (75:25) condition was most favorable for enhancing sonochemical oxidation. However, a comparison of k and k indicated that there would be an optimal dissolved gas condition that was different from the initial gas condition. In addition, the mass-transfer and ultrasonic-degassing coefficients were calculated using changes in the DO concentration in the three modes.
溶解气体对声空化和超声化学氧化反应有很大的影响。关于溶解气体的变化及其对超声化学氧化的影响的研究很少，大多数研究仅关注初始溶解气体条件。在这项研究中，使用光学传感器在不同的气体模式（饱和/开放、饱和/关闭和曝气/关闭模式）下连续测量超声辐照过程中的溶解氧（DO）浓度。同时，使用 KI 剂量法定量测量超声化学氧化的变化。在使用 Ar 和 O 五种气体条件的饱和/开放模式下，由于与大气的活性气体交换，当存在 O 时，DO 浓度迅速下降，而当使用 100% Ar 时，DO 浓度增加。结果，前 10 分钟的零级反应常数（k）的顺序按 Ar:O（75:25）>100% Ar≈Ar:O（50:50）>Ar:O（25:75）>100% O 的顺序降低，而当 DO 浓度相对稳定时的最后 10 分钟（k）的顺序按 100% Ar>Ar:O（75:25）>Ar:O（50:50）≈Ar:O（20:75）>100% O 的顺序降低。在饱和/关闭模式下，由于超声脱气，DO 浓度降低到初始水平的约 70-80%，除 Ar 和 O 以外的气体没有影响。因此，k 和 k 的顺序按 Ar:O（75:25）>Ar:O（50:50）>Ar:O（25:75）>100% Ar>100% O 的顺序降低。在曝气/关闭模式下，由于曝气引起的气体吸附更活跃，DO 浓度保持在初始水平的约 90%，k 和 k 的值几乎与饱和/关闭模式相同。在饱和/开放和曝气/关闭模式下，Ar:O（75:25）条件最有利于增强超声化学氧化。然而，k 和 k 的比较表明，存在一个与初始气体条件不同的最佳溶解气体条件。此外，使用三种模式下 DO 浓度的变化计算了传质和超声脱气系数。
