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Evaluation of Selected Phosphate Sources for the Control of Acid

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Evaluation of Selected Phosphate Sources for the Control of Acid Evaluation of selected phosphate sources for the control of acid production from pyritic coal overburden by Edward Spotts A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Land Rehabilitation Montana State University © Copyright by Edward Spotts (1990) Abstract: Acid Mine Drainage (AMD) is a serious and pervasive threat to surface and groundwater quality in the eastern Appalachian coal regions and at surface area coal mines in the western United States. Recent research has indicated that the use of phosphate materials can be an effective treatment for the amelioration of AMD. Phosphate is effective at immobilizing iron and inhibiting the production of acid associated with the oxidation of FeS2. A preliminary simulated weathering study was performed to evaluate the potential of several regional phosphate sources for controlling the production of acid from pyritic coal overburden. Sources deemed most effective were tested further for application rate determination utilizing a replicated soxhlet leaching technique described by Renton et al (1988a). Phosphate sources tested in this part of the study included two apatite ores (Cominco ore and Texas Gulf ore) at an application rate of 3% by weight apatite and two byproducts of the phosphate industry (Cominco waste and Stauffer sludge) at rates of 1%, 3% and 5% apatite by weight. Results of leachate analyses indicate that all sources at all rates of application resulted in significant decreases in titratable acidity versus a control. Acidity reductions ranged from a low of 7% for samples treated with Cominco waste (1%) to a high of 67% for Texas Gulf ore-treated samples. Texas Gulf ore, Stauffer sludge (1%, 3% and 5%) and Cominco waste (1%, 3% and 5%) significantly reduced dissolved total iron (Fe) concentrations in leachate, with Stauffer sludge (5%) and Texas Gulf ore producing the most notable diminutions (62% and 63%, respectively). Maximum decreases in sulfate (SO42-) concentrations of 26%, 20% and 25% were achieved by applications of Texas Gulf ore and Stauffer sludge (3% and 5%), respectively. The more effective overall performance of the Stauffer sludge and Texas Gulf ore can be attributed to the considerably greater relative surface area and P solubility of these amendments. Results of a scanning electron microscope examination of amendments corroborate these findings. EVALUATION OF SELECTED PHOSPHATE SOURCES FOR THE CONTROL OF ACID PRODUCTION FROM PYRITIC COAL OVERBURDEN by Edward Spotts A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Land Rehabilitation MONTANA STATE UNIVERSITY Bozeman, Montana March 1990 ii APPROVAL of a thesis submitted by Edward Spotts This thesis has been read by each member of the thesis committee and has been found to be satisfactory regarding content, English usage, format, citations, bibliographic style, and consistency, and is ready for submission to the College of Graduate Studies. f j Date Chairperson, Graduate Committee Approved for the Major Department ---------- O CL Date Head, Major Department Approved for the College of Graduate Studies Date Graduate Dean iii STATEMENT OF PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a master’s degree at Montana State University, I agree that the Library shall make it available to borrowers under the rules of the Library. Brief quotations from this thesis are allowable without special permission, the provided that accurate acknowledgement of source is made. Permissinri for extensive quotation from or reproduction of this thesis may be granted by my major professor, or in his absence, by the Dean of Libraries when, in the opinion of either, the proposed use of the material is for scholarly purposes. Any copying or use of the material in this thesis for financial gain shall not be allowed without my written permission. Signature iv ACKNOWLEDGEMENTS The author would like to thank Dr. Douglas J. Dollhopf for his assistance with this project and for his thoughtful review of this manuscript. Gratitude is also extended to Dr. William Inskeep for his helpful suggestions and insights into the chemistry involved in this study and to Dr. Frank Munshower for his patience and administrative guidance. Mr. Dennis Neuman contributed many useful suggestions pertaining to laboratory procedures. Ms. Rosie Wallander provided valuable laboratory assistance and an uncommon amount of patience. Sincere appreciation is also extended to Dr. William Schafer for the generous donation of both his time and resources. Finally, the author wishes to express his most genuine gratitude to his parents, Mr. and Mrs. Edward Spotts, for their unquestioning love and enduring support throughout this and all of my endeavors. TABLE OF CONTENTS Page ACKNOWLEDGEMENTS .........................................................................................iv TABLE OF CONTENTS ........................................................ v LIST OF TABLES ..............................'. ..................................................................vii LIST OF FIGURES ................................................................... ix ABSTRACT ................................................................................................................. x INTRODUCTION.............................................................................................. I LITERATURE REVIEW ......................................................................................... 3 Pyrite Genesis and Morphology........................................... 3 Chemistry of AMD ..................................................... 4 Role of Bacteria............................................................ 5 , Hydrolysis of Ferric I ro n ..................................................................... 6 Oxidation, of FeS2 by ferric iron . ..................................... .. 7 Treatment of AMD ........................................................ 8 Isolation Approaches .......................................................................... 9 Neutralization ...................................................................................... 9 Bactericides . ....................................................... 10 W etlands.............................................................................................. H Control of AMD Using Phosphates ............................... 13 STUDY OBJECTIVES ......................................................................... 17 MATERIALS AND M ETHODS................................................ 18 Experimental Design ..................................................................... 18 Phase I .............................................................. 18 Phase II ................................................. .. • ................................... 18 Acid Producing Overburden Sample . .................................................... • 19 Amendment Materials .................................................................................. 20 Phosphate Source Location . ............................................ 21 Experimental Procedure....................................... ................................ • • 22 Amendment Evaluation............................................................... ■ 22 Phosphate Source Rate Determination....................................... 23 Leachate Analysis................................................... 25 Phosphorous and Sulfur Solubility Determination.......................... 27 vi . TABLE OF CONTENTS-Continued Page RESULTS AND DISCUSSION ....................................... 28 Amendment Selection.......................................................... ............... 28 Overburden Characterization . ................................................................... 29 Leachate C hem istry................. 31 Cumulative Response to Amendments ............................. 31 Cychc Response to Amendments .............................................................. 38 Cycle I ....................... 38 Cycle 2 ....................... 39 Cycle 3 .............. 43 Cycle 4 ............'. ........................................... ..................... .. 45 Cycle 5 ............ 46 Summary of Cyclic Trends ........................................................................ 47 Amendment Solubility and Surface Area Determination ........................ 48 Phosphorous Solubility .................................................... 49 Sulfur Solubility ................................ 52 SEM - EDAX Analyses of Amendments . ................................... 53 Post-Leaching Sulfur Fractionation...................... 59 Stoichiometric Balance of FeS2 Oxidation........................ 61 Iron ............ 63 Sulfate ....................... 65 Acidity ................................................. 65 Operative Mechanisms of FeS2 O xidation............................................... 67 Economic Considerations ........................................................... 70 SUMMARY AND CONCLUSIONS................................................................... 72 LITERATURE CITED ......................................................................................... 74 APPENDICES ........................................................................................................ 80 Appendix A ..................................................................................................
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