Sonochemistry is the use of ultrasound to enhance or alter chemical reactions. Sonochemistry in the true sense of the term occurs when ultrasound induces “true” chemical effects on the reaction system, such as forming free radicals which accelerate the reaction. However, ultrasound may have other mechanical effects on the reaction, such as increasing the surface area between the reactants, accelerating dissolution, and/or renewing the surface of a solid reactant or catalyst. This comprehensive review summarizes several topics of study in the sonochemical literature, including bubble dynamics, factors affecting cavitation, the effects of ultrasound on a variety of chemical systems, modeling of kinetic and mass-transfer effects, the methods used to produce ultrasound, proposed cavitation reactors, and the problems of scaleup. The objective of this paper is to present a critical review of information available in the literature so as to facilitate and inspire future research in the field of sonochemistry.

This paper presents a critical review of the developments in the mathematical modeling of gas-solid noncatalytic reactions with particular emphasis on recent trends in the subject. A number of models proposed for analyzing this class of reactions have been reviewed with a fairly detailed discussion of the methods of incorporating structural changes which occur in the solid with the progress of reaction. The present status on the modeling of various types of complex gas-solid reactions is reviewed. Also the paper points out a number of areas in which future research may be needed. The review concludes with a critical discussion on the type of experimental data necessary for model verification and some comments on the choice of model for a given system. SCOPENoncatalytic gassolid reactions are encountered in a variety of chemical process industries. Tbe major applications are found in the fields of extractive metallurgy, control of gaseous pollutants, coal gasification processes, combustion of solid fuels, catalyst manufacture, etc. Tbe mathematical modeling of these systems is important in order to interpret laboratory data on these systems and in design and scaleup. The problem is complex since in addition to the interplay of heat and mass transfer, other considerations are necessary to account for the transient nature of the problem and the effects of changes in solid properties with the course of reaction. Some of the major developments in this area have been reviewed in a book by Szekely et .I. (1976) and in an edited monograph by Sohn and Wadsworth (1979) Since then considerable advances have taken place, and it is felt that there is a need for a comprehensive and critical review of the major recent developments in this area, and this review is written with this objective. Such a review also helps in evaluating some of the trends in research in this field. CONCLUSIONS AND SIGNIFICANCEIn this review the various models which are commonly used to describe gas-solid noncatalytic reactions have been discussed.The three common models which have been in use are the sharp interface model, the volume reaction model, and the particlepellet model. These models have been recently modified to take into account the effects of structural changes due to chemical reaction and sintering. AIso new models which take into account the basic porous nature of the solid and the pore size distribution have been proposed. The review covers all these major developments. Further, in each case the model parameters and their physical significance have been clearly indicated.Another important area of research is in the field of complex gas-solid noncatalytic reactions. A classification of the important reactions belonging to this class has been presented and the major developments in tbe modeling of these have been pointed out. The review also covers special characteristics of gasification and decomposition reactions and reactions showing significant nucleation effects. The information on the stability of noncatalytic gas-solid reactions ...

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Interest in pyruvic acid has been growing due to the increase in its potential areas of use and its importance in metabolic reactions. These reasons along with the limitations on recovery have prompted researchers to consider novel recovery techniques. Reactive extraction has been proposed as a promising approach to the recovery of carboxylic acids. In this study, equilibrium and kinetic data were obtained for reactive extraction of pyruvic acid using trioctylamine (TOA) or Alamine 336 in 1-octanol or oleyl alcohol. The results showed that, without pH adjustment in the aqueous phase, and without the use of an extractant, 1-octanol extracted more pyruvic acid than oleyl alcohol with a distribution coefficient (K D ) of 0.30. This trend remained the same when tertiary amines were used as an extractant. The K D values did not significantly differ with TOA or Alamine 336. The recovery of pyruvic acid was observed to increase as a function of TOA concentration and the stoichiometry of the reaction was mainly 1:1. As tertiary amines react only with undissociated acids, an increase in the initial pH of the aqueous phase lowered the K D values. When the pH was 4.0, the effect of TOA concentration on pyruvic acid extraction disappeared and for all concentration levels a distribution coefficient of 0.10 was obtained. Kinetic measurements showed that the reaction between pyruvic acid and TOA in 1-octanol is first order with respect to the two reactants with a rate constant of 0.94 L mol À1 s À1 . The enhancement factor was calculated as 25.