Sorption and precipitation of iron on kaolinite. IV. Further characteristics of sorption From 0.15 M solutions

Abstract

Sorption and desorption of small amounts of iron(III) on kaolinite suspended in 0.15M sodium perchlorate solutions was measured at various times over a range of pH values and temperatures. In addition, the effects of transferring these systems from one temperature to another was investigated. The results showed that some of the sorbed iron was strongly bound to the clay, whilst the remainder re-equilibrated relatively rapidly following changes of solution concentration or temperature. The reactions could be regarded as consecutive, the amount of iron sorbed during the first (reversible) stage being one of the factors controlling the amount of strongly bound iron. The extent of both reactions was increased by increasing temperature. The effects of various competing ions introduced at the same time as iron confirmed that the reversible reaction was not a simple electrostatic process but rather specific sorption of hydrolysed ionic species. Extraction of sorbed iron by several reagents endorsed the strong affinity between some of the sorbed iron and the clay. Attempts to define the location of sorbed iron by the use of reagents capable of reacting with either the basal surfaces or the edges of kaolinite particles failed to give conclusive results because of unavoidable secondary reactions.