Ferron逐时络合比色法测定Fe(Ⅲ)溶液聚合物的形态

DETERMINATION OF POLYMERIC Fe(Ⅲ) SPECIES BY FERRON-COMPLEXATION TIMED SPECTROPHOTOMETRIC METHOD

本文研究用Ferron逐时络合比色测定法把Fe(Ⅲ)区分为Fe(a),Fe(b)和Fe(c)三种不同聚合程度的形态.Fe(a)为单核铁化合物,瞬间可与Ferron反应;Fe(b)为过渡性低聚物,可逐渐与Ferron反应;Fe(c)为较稳定的高聚物,基本不与Ferron反应. 实验结果表明Fe(Ⅲ)的水解和聚合较之Al(Ⅲ)快得多.熟化两周后,溶液接近准平衡,Fe(b)转化为Fe(c)后消失,Fe(a)略有降低,而Fe(a)/Fe(c)趋近于一常数.当OH/Fe升高时,Fe(a)降低,而Fe(b)显著增加,熟化后,处于准平衡的Fe(a)/Fe(c)也降低. Ferron络合定时测定法是一种简便而有效的区分Fe(Ⅲ)聚合物形态的方法.

A ferron-eomplexation timed spectrophotometric method was used to classify the aqueous species of Fe(Ⅲ) into three categories which represented their different extents of hydrolysis and polymerization, respectively. Fe(a) included the simple monomeric and oligomeric species which reacted almost instantly with ferron. Fe(b) appeared to include the transitional low polymeric species which reacted with ferron gradually. Fe(c)consisted of more stable high polymeric species which did not react with ferron basically.Experiments showed that Fe(Ⅲ) hydrolyzed and polymerized more rapidly than Al(Ⅲ) . After two weeks aging, solution approached to a pseudo-equilibrium condition. Fe(b) transformed into Fe(c) and disappered, Fe(a) remained its Initial portion, and Fe(a)/Fe(c) ratio tended to a fixed value. When the OH/Fe ratio was raised, the Fe(a) decreased and the Fe(b) increased significantly, then the Fe(a)/Fe(c) ratio at pseudo-equilibrium after aging time also decreased.