酸法合成α-FeO(OH)反应动力学研究

本文对酸法合成α-FeO(OH)反应的动力学过程进行了研究, 考察了初始浓度、反应温度、pH值、氧分压、空气流量及搅拌强度对Fe(OH)_2悬浮液氧化速率的影响, 确定对Fe(Ⅱ)在晶核生成阶段为零级反应, 在晶体生长阶段近似为0.5级反应, 对氧分压均呈一级反应, 并分别求出反应活化能.提出了在晶核生成阶段存在溶解-氧化的动态平衡过程, 以解释零级反应及pH-时间曲线的平稳区。物理扩散为该多相反应的控制步骤. α-FeO(OH)生成动力学的研究将为工业反应器的研制、工程放大及过程优化控制提供基本依据。

KINETICS OF α-FeO(OH) FORMATION IN WEAK ACIDIC MEDIUM

The kinetics of a-FeO(OH) formation in weak acidic medium was studied. The effects of initial concentration, temperature, pH value, partial presure of oxygen, air flow rate and agitating intensity on the oxidation rate of Fe(OH)_2 suspensions have been investigated. It is confirmed that reaction order for Fe(Ⅱ) is zero at the stage of a-FeO(OH) seeds formation, and around 0.5 at the stage of the seeds growth, and in both processes of the partial pressure of oxygen appears to be first order. The activation energy is determined respectively. Dissolution-oxidation equilibrium existing in the process of seeds formation has been assumed, by which the zero order reaction for Fe(II) and plateau in the pH-t curve may be explained. Physical process is the rate-determining step of the heterogeneous reaction. The studies of the dinetics of α-FeO(OH) formation may provide some fundamental information for the reactor design, the engineering scale-up and the optimizing control for the industrial process.