Evaluation of Mass Transfer Mechanisms During Osmotic Treatment of Plant Materials

2000 ◽  
Vol 65 (6) ◽  
pp. 1016-1019 ◽  
Author(s):  
N.K. Rastogi ◽  
A. Angersbach ◽  
D. Knorr
Author(s):  
Venkatasubramanian Sivakumar

Background: In the growing environmental concern use of natural products, efficient processes and devices are necessary. Solid-Liquid extraction of active Ingredients from Plant materials is one of the important unit operations in Chemical Engineering and need to be enhanced. Objectives: Since, these active ingredients are firmly bound to the plant cell wall membrane, which pose mass-transfer resistance and need to get detached through the use of suitable process intensification tools such as ultrasound and suitable devices. Therefore, detailed analysis and review is essential on development made in this area through Publications and Patents. Hence, the present paper illustrates the development of ultrasound assisted device for solid-liquid extraction are presented in this paper. Methods: Advantages such as % Yield, Reduction in extraction time, use of ambient conditions, better process control, avoidance or minimizing multi stage extraction could be achieved due to the use of ultrasound in extraction as compared to conventional processes. Conclusions: Use of ultrasound to provide significant improvements in the extraction of Vegetable tannins, Natural dyes for application in Leather processing has been demonstrated and reported earlier. These enhancement could be possible through various effects of ultrasound such as better flow of solvents through micro-jet formation, mass transfer enhancement due to rupture of plant cell wall membranes through acoustic cavitation, better leaching due to micro-mixing and acoustic streaming effects. This approach would minimize material wastage; thereby, leading to eco-conservation of plant materials, which is very much essential for better environment. Hence, various methods and design for application of ultrasound assisted solid-liquid extractor device are necessary.


AIChE Journal ◽  
2016 ◽  
Vol 63 (6) ◽  
pp. 2394-2408 ◽  
Author(s):  
Matthieu Roudet ◽  
Anne‐Marie Billet ◽  
Sébastien Cazin ◽  
Frédéric Risso ◽  
Véronique Roig

Author(s):  
Irina V. Alexandrova ◽  
Dmitri V. Alexandrov ◽  
Eugenya V. Makoveeva

The Ostwald ripening stage of a phase transformation process with allowance for synchronous operation of various mass transfer mechanisms (volume diffusion and diffusion along the block boundaries and dislocations) and the initial condition for the particle-radius distribution function is theoretically studied. The initial condition is taken from the analytical solution describing the intermediate stage of a phase transition process. The present theory focuses on relaxation dynamics from the beginning of the ripening process to its final asymptotic state, which is described by the previously constructed theories (Slezov VV. et al. 1978 J. Phys. Chem. Solids 39 , 705–709. ( doi:10.1016/0022-3697(78)90002-1 ) and Alexandrov & Alexandrova 2020 Phil. Trans. R. Soc. A 378 , 20190247. ( doi:10.1098/rsta.2019.0247 )). An evolutionary behaviour of particle growth rates dependent on various mass transfer mechanisms and time is analytically described. The boundaries of the transition layer, which surround the blocking point, are found. The fundamental and relaxation contributions to the particle-radius distribution function are derived for the simultaneous occurrence of various mass transfer mechanisms. The left branch of this function is shifted to smaller particle radii whereas its right branch extends to the right of the blocking point as compared with the asymptotic universal distribution function. The theory under consideration well agrees with experimental data. This article is part of the theme issue ‘Transport phenomena in complex systems (part 1)’.


1985 ◽  
Vol 17 (8) ◽  
pp. 1469-1471
Author(s):  
H. Siegrist ◽  
W. Gujer

The diffusion coefficient of three different chemical species in naturally grown, heterotrophic biofilms have been measured. The mechanical structure of the biofilm matrix reduces the molecular diffusion to about 50 to 60 % of the value in pure water. Depending on the roughness of the biofilm surface and the flow conditions eddy diffusion increased the mass transfer into the biofilm near the surface. The influence of the diffusion potential and the donnan potential on the ions have been evaluated by comparing the diffusion coefficients of a positively and negatively charged ion and a neutral molecule in experiments with different background electrolyte concentrations. Mass transfer effects by electrostatic forces are negligible at the ionic strength of waste water and tap water.


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