tailieunhanh - Phsicochemical Treatment of Hazardous Wastes - Chapter 11

Các hiệu ứng sonochemical sản xuất bởi sonolysis là do hiện tượng sủi bọt, đó là mầm của các bong bóng trong một chất lỏng dưới ảnh hưởng của siêu âm. Sonolysis là dựa trên các khái niệm cơ bản và lý thuyết liên quan đến trong sonochemistry, quan điểm lịch sử của sonochemistry trong Bảng cung cấp một cái nhìn sâu sắc vào sự phát hiện và hiểu biết về các quá trình cơ bản trong sonolysis. Khi một chất lỏng có áp suất hơi tương đối cao và độ bền kéo năng động (chẳng hạn như nước). | 11_ Sonolysis Introduction The sonochemical effects produced by sonolysis are due to the phenomenon of cavitation which is the nucleation of bubbles in a liquid under the influence of ultrasound. Sonolysis is based on the fundamental concepts and theory involved in sonochemistry the historical perspective of sonochemistry in Table provides an insight into the discovery and understanding of fundamental processes in sonolysis. When a liquid of relatively high vapor pressure and dynamic tensile strength such as water is exposed to high-frequency ultrasonic waves a few to several hundred kilohertz acoustic cavitation in the liquid will occur. The cavitation process includes the formation growth and implosive collapse of small gas bubbles. Cavitation by ultrasound is accompanied by high temperature 2000 to 2500 K and high pressure hundreds of atmospheres which are responsible for the degradation of organic pollutants. Therefore sonolysis can degrade organic pollutants to CO2 and H2O or convert them to compounds that are less harmful than the original compounds. The degradation of organic pollutants may result from combustion supercritical water oxidation and oxidation by radicals such as hydroxyl radicals and hydrogen radicals. Sonolysis was found to be efficient and economical to decontaminate industrial organics before they are discharged into aquatic ecosystems. Therefore the applications of ultrasound to destroy organic pollutants have increased significantly in the past decade. Fundamental Processes in Sonochemistry Physical Processes Sonochemistry is defined as the chemical effects produced by ultrasonic waves. Ultrasound with frequencies roughly between 15 kHz and 10 MHz has a drastic effect on chemical reactions. It is the most important 2004 by CRC Press LLC TABLE Historical Perspective of Sonochemistry Year Historical Event 1867 Early observations of cavitation by Tomlinson and Gernez 1880 Discovery .