Effect of pH and Dissolved Silicate on the Formation of Surface Passivation Layers for Reducing Pyrite Oxidation

Shengjia Zeng, Jun Li, Russell Schumann, Roger Smart

Levay& Co.; University of South Australia, Adelaide, South Australia, Australia.
Minerals and Materials Science & Technology, Mawson Institute.

DOI: 10.4236/cweee.2013.22B009                

Abstract

Acid mine drainage (AMD)and toxic metal release generated by oxidation of sulphide minerals, particularly pyrite, in mine wastes,are a critical environmental issue worldwide.Currently, there are many options to diminish sulphide oxidation including barrier methods that isolate pyrite from oxygen or water, chemical additives and inhibition of iron-oxidizing bacteria. This study focuses on understanding the rolethatsilicate and pH conditions play in the formation and stabilisation ofpyrite surface passivation layers found in lab and field studies.The results from pyrite dissolution tests under various conditions showed that the pyrite oxidation rate has been reduced by up to 60% under neutral pH with additional soluble silicate. Solution speciation calculation predicted that crystalline goethite is formed in the experiment without silicate additionbutan amorphous iron hydroxide surface layer is stabilizedby the addition of the silicate, inhibiting goethite formation and continuing pyrite oxidation.This coherent, continuous amorphous layer has been verified in SEM.

Keywords

Acid Mine Drainage; Pyrite; Passivation Coating; Silicate

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	J. Satur, N. Hiroyoshi, M. Tsunekawa, M. Ito and H. Okamoto, “Carrier-Microencapsulation for Pre-venting Pyrite Oxidation,” International Journal of Mineral Processing, Vol.83, No. 3–4, 2007, pp. 116-124. doi:10.1016/j.minpro.2007.06.003
[2]	E. Ahlberg and A. E. Broo, “Oxygen Reduction at Sulphide Minerals. 3. The Effect of Surface Pre-Treatment on the Oxygen Reduction at Pyrite,” International Journal of Mineral Processing, 1996, Vol. 47, No. 1–2, pp. 49-60. doi:10.1016/0301-7516(95)00100-X
[3]	N. Belzile, S. Maki, Y. W. Chen and D. Goldsack, “Inhibition of Pyrite Oxi-dation by Surface Treatment,” Science of The Total Environment, Vol. 196, No. 2, 1997, pp. 177-186. doi:10.1016/S0048-9697(96)05410-1
[4]	R. Cornell, R. Giovanoli and P. Schindler, “Effect of Silicate Species on the Transformation of Ferrihydrite into Goethite and Hematite in Alkaline Media,” Clays and Clay Minerals, Vol. 35, No. 1, 1987, pp. 21-28. doi:10.1346/CCMN.1987.0350103
[5]	D. B. Johnson and K. B. Hallberg, “Acid Mine Drainage Remediation Options: A Review,” Science of The Total Environment, Vol. 338, No. 1–2, 2005, pp. 3-14. doi:10.1016/j.scitotenv.2004.09.002
[6]	A. P. Chandra and A. R. Gerson, “The Mechanisms of Pyrite Oxidation and Leaching: A Fundamental Perspective,” Surface Science Reports, Vol. 65, No. 9, 2010, pp. 293-315. doi:10.1016/j.surfrep.2010.08.003
[7]	C. L. Caldeira, V. S. T. Ciminelli, A. Dias and K. Osseo-Asare, “Pyrite Oxidation in Alkaline Solutions: Nature of the Product Layer,” International Journal of Mineral Processing, Vol. 72, No. 1–4, 2003, pp. 373-386. doi:10.1016/S0301-7516(03)00112-1
[8]	V. P. Evange-lou, “Pyrite Microencapsulation Technologies: Principles and Potential Field Application,” Ecological Engineering, Vol.17, No. 2–3, 2001, pp. 165-178. doi:10.1016/S0925-8574(00)00156-7
[9]	Lalvani, S. B., B. A. DeNeve and A. Weston, “Passivation of Pyrite Due to Surface Treatment,” Fuel, Vol. 69, No. 12, 1990, pp. 1567-1569. doi:10.1016/0016-2361(90)90209-9
[10]	K. Nyavor, N. O. Egiebor and P. M. Fedorak, “Suppression of Microbial Pyrite Oxidation by Fatty Acid Amine Treatment, Science of The Total Environment, Vol. 182, No. 1–3, 1996, pp. 75-83. doi:10.1016/0048-9697(95)05052-3
[11]	C. L. Jiang, X. H. Wang and B. K. Parekh, “Effect of Sodium Oleate on Inhibiting Pyrite Oxidation,” International Journal of Mineral Processing, Vol. 58, No. 1–4, 2000, pp. 305-318. doi:10.1016/S0301-7516(99)00045-9
[12]	D. M. C. Huminicki and J. D. Rimstidt, “Iron Oxyhydroxide Coating of Pyrite for Acid Mine Drainage Control. Applied Geochemistry,” Vol. 24, No. 9, 2009, pp. 1626-1634. doi:10.1016/j.apgeochem.2009.04.032
[13]	R. S. C. Smart, S. D. Miller, W. S. Stewart, Y. Rusdinar, R. E. Schumann, N. Kawashima and J. Li, “In Situ Calcite Formation in Limestone-Saturated Water Leaching of Acid Rock Waste,” Science of The Total Environment, Vol. 408, No. 16, 2010, pp. 3392-3402. doi:10.1016/j.scitotenv.2010.04.028
[14]	S. Miller, R. Schumann, R. Smart and Y. Rusdinar, “Ard Control by Limestene Induced Armouring and Passivation of Pyrite Mineral Surfaces, in ICARD,” Skellefta Sweden, 2009, p. 11.
[15]	L. Dyer, P. D. Fawell, O. M. G. Newman and W. R. Richmond, “Synthesis and Characterisation of Ferrihydrite/Silica Co-Precipitates,” Journal of Colloid and Interface Science, Vol. 348, No. 1, 2010, pp. 65-70. doi:10.1016/j.jcis.2010.03.056
[16]	U. Schwertmann and R. M. Cornell, “Iron Oxides in the Laboratory: Preparation and Characterization, ” 1991, Weinheim: VCH.
[17]	S. Santomar-tino and J. A. Webb, “Estimating the Longevity of Limestone Drains in Treating Acid Mine Drainage Containing High Con-centrations of Iron,” Applied Geochemistry,Vol. 22, No. 11, 2007, pp. 2344-2361. doi:10.1016/j.apgeochem.2007.04.020
[18]	D. Mohapatra, P. Singh, W. Zhang and P. Pullammanappallil, “The Effect of Citrate, Oxalate, Acetate, Silicate and Phosphate on Stability of Synthetic Arsenic-Loaded Ferrihydrite and Al-Ferrihydrite, ” Journal of Hazardous Materials, Vol. 124, No. 1–3, 2005, pp. 95-100. doi:10.1016/j.jhazmat.2005.04.025
[19]	P. J. Swedlund, G. M. Miskelly and A. J. McQuillan, “An ATR-FTIR Study of Silicate Adsorption onto Ferrihydrite,” Geochimica et Cosmo-chimica Acta, Vol. 70, No. 18,(Supplement), 2006, pp. A632.