Use of X-ray diffraction in a study of ammonia leaching of multimetal sulfides
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INTRODUCTION
SIGNIFICANT literature exists regarding the effective utilization of low-grade complex sulfide ores to recover base metals and precious metals. These ores are found in large quantities in Australia, Canada, Japan, Norway, Portugal, and Spain. In India, they occur as isolated and scattered deposits. The mineralogical compositions of complex sulfides vary widely. Optical microscopy and electron microscopy are commonly used to obtain useful mineralogical data. The relative quantities of minerals, mineral associations, mineral and particle sizes, and degree of liberation of the minerals in particles can be quantitatively estimated by the use of computer-controlled scanning electron microscopes and electron microprobes. Successful aqueous processing of complex sulfide ores depends on the composition and mineralogy of raw materials and on their leaching behavior. Surprisingly, studies on the mineralogical characterization of process residues have not received due attention in the literature. Most of the available information is from conventional chemical analysis, which has some limitations. Many elements occur in a variety of minerals that respond differently to the leaching process. In such cases, microscopic studies supported by X-ray diffractometry (XRD) and chemical analysis are more useful for identification of the various mineral phases of leach residues and for qualification of the leaching reaction mechanism. Recently, the authors I~l have discussed the importance of using an integrated approach in a simultaneous study of the mineralogical characteristics and reactivity of a Cu-Zn-Pb bulk concentrate during oxidative ammonia K. SARVESWARA RAO, Assistant Director, R.P. DAS. Deputy Director, and H.S. RAY, Director, are with Regional Research Laboratory (CS/R), Bhubaneswar-751013, Orissa. India. P.G. MUKUNDA, Professor, is with the Department of Metallurgical Engineering, Indian Institute of Technology, Kharagpur-721302, India. Manuscript submitted January 28, 1991. METALLURGICAL TRANSACTIONS B
leaching and during roasting. Optical microscopy, chemical analysis, XRD and thermal analysis techniques were used to study the original complex sulfide ore, different concentrates before and after roasting, and leach residues and leach liquors. The combined application of these techniques provided useful information on the characterization and leaching of bulk concentrates. A typical example of the use of quantitative XRD analysis was given for the dissolution of sphalerite in ammoniaammonium sulfate at 115 ~ It appears that the shift in the d-spacing of a sulfide mineral in the residue can be related to leaching kinetics. 123m Klug and Alexander 15} have discussed various quantitative XRD techniques for estimation of mineral species in homogeneous inixtures. The application of the line pair integrated intensity ratio (direct comparison) method in physical metallurgy is well established. 15"671 For example, the austenite phase retained in steel can be estimated using the coexisting martensite phase as an
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