Phenol and its chloro-derivatives contribute significantly to environmental pollution hazards due to their high degree of toxicity as well as improper disposal methods. Cavitation can be used successfully for degradation of phenolic compounds and the rates of degradation are dependent on the type of the primary pollutant in the system. In the present work, a theoretical explanation has been provided to explain the observed degradation trends of phenol and chlorophenols on the basis of concentration of the pollutant at the cavitation bubble/solution interface. Chemical stability of these compounds towards radical attack in the liquid phase has been discussed. It has been observed that chloro-derivates degrade much faster as compared to the parent compound due to higher hydrophobicity of chloro-derivates.

No abstract

in Wiley InterScience (www.interscience.wiley.com).Generating hydrodynamic/ acoustic cavitation (Gogate et al.) for a useful purpose encompasses the following energy transformation steps: (1) Burning fuel in boiler. (2) Expanding the steam in a turbine generator. (3) Using electrical output from the generator to: (a) Pump water through a mechanical constriction (hydrodynamic cavitation), or (b) Operate ultrasonic transducer (acoustic cavitation). The combined loss, which is the mathematical product of each of the above step efficiencies, lowers the overall efficiency. An energy efficient method for generating useful cavitation is presented here. It suggests direct injection of steam (I) into sub-cooled water to produce cavitation, thereby eliminating the inefficiencies of the remaining steps (II and III). Cavitation produced by this technique was experimentally and numerically shown to produce collapse conditions similar to hydrodynamic/acoustic cavitation. Direct steam injection cavitation coupled with acoustic cavitation, exhibited 4-16 times greater energy efficiency as compared to acoustic cavitation alone. Similar effects have been numerically speculated for hydrodynamic cavitation.

No abstract