金属矿物的反应动力学与地球化学意义

REACTION KINETICS OF METAL MINERALS AND ITS GEOCHEMICAL SIGNIFICANCE

概述了动力学实验的技术方法和金属矿物的反应动力学研究进展。动力学实验使用的三种基本化学反应装置是间歇反应器（ＢＲ）、活塞流反应器（ＰＦＲ）和混合流反应器（ＭＦＲ），确定速率定律的数学方法包括积分法、微分法和混合法，以微分法中的初始速率法应用最广。目前主要研究了水溶液中黄铁矿氧化、黄铁矿和黄铜矿形成、晶质铀矿和磁铁矿溶解的速率定律和反应机理，发现：（１）酸性溶液中黄铁矿的氧化速率对Ｆｅ３＋和Ｏ２浓度呈分数依赖并受表面反应的控制；（２）低于３００℃时黄铁矿不能从溶液中直接成核，而需初始地通过ＦｅＳ先驱物的硫化生成，ＦｅＳ与Ｈ２Ｓ反应形成黄铁矿的速率方程为二级；（３）磁黄铁矿或黄铁矿与Ｃｕ２＋反应均可形成黄铜矿，前者经历了一系列准稳的ＣｕＦｅ硫化物的中间物，后者的速率方程为表观一级并受表面反应的控制；（４）酸性ｐＨ时磁铁矿的非线性溶解行为可采用表面反应扩散输运耦合的收缩核模型（ＳＣＭ）来描述。有关动力学实验成果完善和深化了对矿床中黄铁矿、黄铜矿的形成机理和风化壳中磁铁矿的稳定性等方面的认识。将来的实验研究将向更多的金属矿物和高温高压领域发展。

The techniques and methods of kinetic experiments and the research advance of reaction kinetics of metal minerals are outlined in this paper The three fundamental types of chemical reactors used in kinetic experiments are batch reactor(BR),plug flow reactor(PFR),and mixed flow reactor(MFR) The mathematical methods to determine rate law include the integration methods,the differential methods,and the hybrid methods,and the initial rate method of differential methods is the most widely applied one At present,the rate laws and reaction mechanisms of pyrite oxidation,pyrite and chalcopyrite formation,uraninite and magnetite dissolution in aqueous solutions are mainly studied,and it is discovered that (1)oxidation rate of pyrite controlled by surface reaction assume fractional dependence on Fe 3+ and O 2 molalities in acid solutions; (2)Pyrite cannot nucleate directly from solutions below 300 ℃,it can only form initially through sulfidation of a FeS precursor The rate equation of reaction between FeS and H 2S to form pyrite is of the second order; (3)Chalcopyrite is formed by reactions of pyrrhotite or pyrite with Cu 2+ ,the former proceeds via a series of mediate metastable phases of Cu Fe sulfide,whereas the rate equation of the latter is apparently of the first order which is controlled by surface reaction; (4)The nonlinear behavior of magnetite dissolution at acid pH can be represented by a shrinking core model (SCM) coupling with surface reaction and diffusion transport These kinetic experimental results improve and deepen the knowledge of formation mechanisms of pyrite and chalcopyrite in deposits and stability of magnetite in weathering crust,etc The researches in future will be carried on with more metal minerals under high temperature and pressure conditions