Laboratoire des Sciences et Technologie de l'Environnement, Université de Mentouri-Constantine, Algeria.
Ultrason Sonochem. 2011 Sep;18(5):1107-12. doi: 10.1016/j.ultsonch.2011.03.008. Epub 2011 Mar 21.
The degradation of the phenylurea monolinuron (MLN) by ultrasound irradiation alone and in the presence of TiO(2) was investigated in aqueous solution. The experiments were carried out at low and high frequency (20 and 800 kHz) in complete darkness. The degradation of MLN by ultrasounds occurred mainly by a radical pathway, as shown the inhibitory effect of adding tert-butanol and bicarbonate ions to scavenge hydroxyl radicals. However, CO(3)(-) radicals were formed with bicarbonate and reacted in turn with MLN. In this study, the degradation rate of MLN and the rate constant of H(2)O(2) formation were used to evaluate the oxidative sonochemical efficiency. It was shown that ultrasound efficiency was improved in the presence of nanoparticles of TiO(2) and SiO(2) only at 20 kHz. These particles provide nucleation sites for cavitation bubbles at their surface, leading to an increase in the number of bubbles when the liquid is irradiated by ultrasound, thereby enhancing sonochemical reaction yield. In the case of TiO(2), sonochemical efficiency was found to be greater than with SiO(2) for the same mass introduced. In addition to the increase in the number of cavitation bubbles, activated species may be formed at the TiO(2) surface that promote the formation of H(2)O(2) and the decomposition of MLN.
单独使用超声辐射和在 TiO(2)存在下研究了水中苯基脲类除草剂单氰胺（MLN）的降解。实验在低频（20 kHz）和高频（800 kHz）下完全黑暗中进行。超声降解 MLN 主要通过自由基途径进行，如添加叔丁醇和碳酸氢根离子以清除羟基自由基的抑制作用所示。然而，碳酸氢根离子形成了 CO(3)(-)自由基，并与 MLN 依次反应。在这项研究中，使用 MLN 的降解速率和 H(2)O(2)形成的速率常数来评估氧化声化学效率。结果表明，仅在 20 kHz 下，纳米 TiO(2)和 SiO(2)的存在提高了超声效率。这些颗粒在其表面提供了空化泡的成核位点，当液体被超声辐射时，导致气泡数量增加，从而提高了声化学反应产率。在 TiO(2)的情况下，发现相同质量引入时的声化学效率大于 SiO(2)。除了增加空化泡的数量外，可能在 TiO(2)表面形成了活性物质，促进了 H(2)O(2 的形成和 MLN 的分解。
