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Title of Thesis

Reaction Kinetics And Mass Transfer Studies In Selective Leaching Of Low-grade Calcareous Phosphate Rock

Author(s)

Muhammad Ashraf

Institute/University/Department Details
Department Of Chemistry / Bahauddin Zakariya University, Multan
Session
2010
Subject
Chemistry
Number of Pages
194
Keywords (Extracted from title, table of contents and abstract of thesis)
Adjustable, Investigate, Reaction, Parameters, Systems, Kinetics, Selective, Calculated, Leaching, Phosphate, Particles, Calcareous, Solutions, Transfer, Lowgrade, Studies, Mass

Abstract
In the present thesis, the dilute solutions of succinic acid have been used to investigate the selective leaching of calcareous material in low-grade phosphate rock.The effective parameters on the dissolution rate are reaction temperature, particle size, acid concentration and liquid-solid ratio. The results indicate that succinic acid can be used to selectively dissolve the calcareous material in low-grade phosphate rock as it improves the P2O5 content of the rock and makes it viable as a feed to an acidulation plant.
Using the known size particles of the sample, acid concentration and liquid-solid ratio, the influence of different reaction temperatures has been studied in order to elucidate the leaching kinetics of calcareous material in the rock.The results show that the leaching rate of calcareous material increases with increasing temperature. A kinetic model has been suggested to describe the selective leaching process of calcareous material analyzing the kinetic data.The selective leaching curves have been evaluated in order to check the validity of shrinking core models for liquid-solid systems.The experimental data have been tested by graphical and statistical methods and it is found that the leaching of calcareous material in the rock is controlled by the chemical reaction i.e. 1 (1 x)1/ 3 1.47 106e64.92 / RT t .The apparent activation energy of the dissolution process has been found to be 64.92 kJ mol-1 over the reaction temperature range from 313 to 353 K. Such a value of activation energy indicates that the process is a chemically controlled reaction and agrees with the values obtained in the similar research of fluidsolid reaction systems.The agreement between the experimental conversion and the values calculated from the suggested empirical equation has been tested, and which is found to be very good.
For a comparison study, lactic acid has also been used to study the selective leaching kinetics of calcareous phosphate rock.The effect of acid concentration, liquid/solid ratio, particle size and temperature has been studied in order to expound the leaching kinetics of calcareous material in the rock. It has been found that the leaching rate of calcareous material increases with increasing the acid concentration, liquid/solid ratio and temperature and decreasing particle size. A semi-empirical model has been suggested to illustrate the selective dissolution of calcareous material analyzing the experimental data. The selective leaching curves have been evaluated to test the validity of kinetic models for liquid-solid systems. The kinetic data are analyzed by graphical and statistical methods and it has been found that the dissolution of calcareous material in the rock is controlled by chemical reaction i.e.
1  (1   )1 / 3  19 .1 C 1 .753 ( L / S )1 .627 D  0.737 e  42954 .62 / RT t .
The analysis of the obtained results reveals that the applicability of the suggested model is good and it can work within a certain range for the choice of adjustable parameter values depending on the degree of selective leaching. The results show that the controlling step of the overall process of the heterogeneous reaction is a chemical change. According to the analyzed results, it is recommended that the parameter values for the optimum selective leaching rate are C = 8% v/v, L/S = 7 cm3g-1, T = 318 K, SS = 350 min-1 and D = 0.1255 mm.

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1,008 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 CONTENTS

 

6
10 KB
2

1

INTRODUCTION

1.1 Flotation Method
1.2 Other Flotation Separation Techniques
1.3 Magnetic separation Techniques
1.4 Calcination Method
1.5 Electrostatic Upgrading
1.6 Bioleaching of phosphate ores
1.7 Partial Acidulation of phosphate ores
1.8 Direct Application of Phosphate Rock
1.9 Dissolution and Selective Leaching

17
78 KB
3 2 CHEMISTRY OF THE LEACHING PROCESS

 

47
24 KB
4 3 RESEARCH METHODOLOGY

3.1 Sample Collection
3.2 Size reduction and sieving
3.3 Sample Preparation for Analysis
3.4 Selective Leaching with Lactic Acid
3.5 Experimental Procedure
3.6 Chamicals Used
3.7 Instrumental Techniques Used for Analysis
3.8 Scanning Electron Microscopy

52
677 KB
5 4 RESULTS AND DISCUSSION

4.1 Effect of Reaction Time on the Leaching Process at Different Temperatures
4.2 Effect of Reaction Temperature on Dissolution
4.3 Effect of Acid Concentration on P2O5 and CO2 Contents
4.4 Effect of Liquid/Solid Ratio on P2O5 and CO2 Contents
4.5 Leaching with Lactic acid
4.6 Kinetic Analysis

86
149 KB
6 5 RECOVERY OF SPENT ACID AND ECONOMY OF PROCESS

 

163
35 KB
7

6

REFERENCES AND APPENDIX

 

172
47 KB