Particulate pyrite in aqueous solution: Synthesis, ferrous bisulfide complexation, and semiconductor electrochemistry.

摘要

Microsize particles of pyrite were synthesized in aqueous solution at room temperature using ferric chloride and sodium hydrosulfide as starting materials. The pyrite sample obtained by Fe(III)/S(II) reaction was further purified by solvent extraction to remove elemental sulfur. The purified pyrite contained 99.46% FeS{dollar}sb2{dollar}. The particles of pyrite had an average diameter of 1.5 {dollar}mu{dollar}m, and a specific surface area of 4.1 m{dollar}sp2{dollar}/g. The isoelectric point (iep) for the purified pyrite particles was at pH 2.3.; The formation of the iron sulfide complex as an initial product from the reaction of ferrous ions with sulfide was studied using a stopped-flow spectrophotometric technique. A complex of the form the Fe(HS){dollar}sp+{dollar} was identified from the stoichiometric experiments. The rate law for the formation of Fe(HS){dollar}sp+{dollar} complex was determined to be d (Fe(HS){dollar}sp+{dollar}) /dt = 10{dollar}sp{lcub}3.81{rcub}{dollar} (Fe{dollar}sp{lcub}2+{rcub}rbrack lbrack{lcub}rm HS{rcub}sp-{dollar}). A formation constant of 10{dollar}sp{lcub}4.34 pm 0.15{rcub}{dollar} at 25{dollar}spcirc{dollar}C and I = 0 was obtained.; Electrochemical experiments showed that illumination on pyrite microelectrodes increases the anodic dissolution rate, but does not affect the cathodic process. This indicates that the pyrite synthesized in this study is an n-type semiconductor, and the anodic dissolution of this material involves hole reactions. Pyrite dissolution in acidic solution was found to involve both electrochemical oxidation and chemical decomposition. The mechanism for chemical decomposition of pyrite in acidic solution may involve surface complexation of hydrogen ions. Anodic current on pyrite microelectrodes was of negligible magnitude in non-aqueous solution relative to that in aqueous solution. This indicates that direct reaction of the holes with S{dollar}sb2sp{lcub}2-{rcub}{dollar} in the pyrite lattice is not significant, and dissolution of pyrite requires the presence of water. The dissolution products of pyrite included elemental sulfur, which was detected by X-ray diffraction.