Al-Ferron逐时络合比色光度法测定聚合铝溶液中Ala,Alb和Alc三种铝形态的时间界限研究

Al-Ferron逐时络合比色法是研究聚合铝溶液中铝的形态分布及其转化规律的基本方法。但在具体操作过程中，由于Ala，Alb和Alc三种铝形态时间界限划分的随意性和武断性，使得许多实验结果难以重复。造成这种差别的原因主要是因为这三种铝形态的具体组分与Ferron反应时具有不同的反应机理和动力学，同时也由于不同OH／Al摩尔比的Alb具体形态之间与Ferron反应时的动力学反应速率存在差异。章应用ExpAssoc分布对Al-Ferron逐时络合动力学曲线进行了定量模拟，用外推法求得了实验手工操作中难以获取的1min单核铝测定值Ala，以实验曲线达到水平平台作为Alb和Alc的时间界限，用微波消解技术快速测定了聚合铝的总铝Alr浓度。借助于这些方法，我们可以方便地定量计算单核铝Ala聚合铝Alb和凝胶Alc含量，从而为克服以往测定三种铝形态的随意性、武断性以及Ala和Alb的重叠计算等问题提供了一种新方法。

Assay of Three Kinds of Aluminum Fractions (Ala, Alb and Alc) in Polynuclear Aluminum Solutions by Al-Ferron Timed Spectrophotometry and Demarcation of Their Time Limits

Al-Ferron timed spectrophotometry assay is a basic method in the study on the formation of polynuclear hydroxyl aluminum species and their transformation laws in aqueous systems. In actual working process, this methodology has some dogmatism and arbitrariness in the time limits demarcation of the three kinds of aluminum fractions (Al_a, Al_b and Al_c) in polynuclear aluminum solutions, which makes this kind of classification rougher, and the experimental results non-reproducible. The reason for this difference is that the specific species within Al_a, Al_b and Al_c have different reaction mechanism and dynamics, and that specific species of Al_b having different OH/Al ratios have different reaction rates with ferron. In this paper, the ExpAssoc distribution was applied to quantitatively fit the Al-Ferron reaction dynamics curve, and the extrapolation method was used to survey the 1 min measured value Al_a] of monomeric Al, which is hard to obtain in manual manipulation. The time demarcation between Al_b and Al_c should reach the point of the experimental data curve up to horizontal platform. The microwave-radiated technology was used to fast assay the total aluminum concentration Al_T]. With these methods, the contents of monomeric Al_a, polynuclear Al_b and gel Al_c can be conveniently and quantitatively measured. It offers a novel method for surmounting the arbitrariness in the measurement of the three kinds of aluminum fractions and the repetitive calculation of Al_a and Al_b.