The oxidation behavior of unactivated and mechanically activated sphalerite
- PDF / 185,965 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 67 Downloads / 217 Views
NTRODUCTION
EXTRACTION of nonferrous metals from sulfidic ores is a technically difficult and economically important task. The more chemically stable the sulfide is, the more difficult the extraction is. Thus, either drastic reaction conditions have to be applied or the chemical stability of sulfides has to be modified by a suitable chosen preleaching treatment. The mechanical activation of the ore by intensive grinding is an example of a pretreatment.[1] The best way to study mechanochemical transformation of the mechanical activation for ores is to analyze in situ the milled mixture using appropriate spectroscopic methods, since chemical handling can obscure the true nature of the initial products. Nowadays, common tools such as IR and X-ray diffractions (XRD) techniques normally allow the identification of the products.[2,3] Other techniques such as High Resolution Electron Microscopy (HREM), Extensive X-ray Fine Absorption Microscopy (EXFAM), X-ray Photoelectron Spectroscopy (XPS), and X-ray cyclotron resonance have been used to study the new surfaces of the milled products.[4] For example, Bala´z˘ et al.[5] investigated the changes produced in cinnabar by its mechanical activation in a planetary ball mill through XPS, BET, XRD, and DSC; and the DSC curves of mechanically activated cinnabars and unactivated cinnabar represent an association of endothermic effects, which differ from each other in shape and extreme temperature value. Because the differences of the oxidation behaviors between unactivated and mechanically activated sulfide ores were seldom studied using thermogravimetry (TG) and because sphalerite, an important part of sulfidic ores, belongs QIYUAN CHEN, ZHOULAN YIN, and PINGMIN ZHANG, Professors, HUIPING HU, Associate Professor, and LUSHENG YE, Undergraduate Student, are with the Institute of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, People’s Republic of China. Contact e-mail: [email protected] Manuscript submitted December 18, 2001. METALLURGICAL AND MATERIALS TRANSACTIONS B
to the group of substances exhibiting great sensitivity to mechanical stress,[6] the oxidation behavior of unactivated and mechanically activated sphalerite was studied with TG experiments for the first time. The difference in oxidation reactivity and the changes of surface structures of unactivated and mechanically activated sphalerites were examined and discussed. II. EXPERIMENTAL DETAILS Natural hand-sorted sphalerite ore was purchased from a domestic natural mine factory, and its chemical composition is summarized in Table I. It was found by XRD analysis that the sphalerite was predominantly cubic. Unactivated sphalerite was prepared by crushing the natural sphalerite in a jaw crusher to a particle size of ⱕ1 mm, and then stored for at least 6 months. The unactivated sphalerite (weighed charge in mill, 10 g) was added into a stainless steel vessel with 6 stainless steel balls of 18 mm in diameter and 12 balls of 8 mm in diameter. A vacuum with residue pressure ⱕ1 Pa was then pu
Data Loading...
