REDUCTION OF FE(III) IN A HIGH-IRON SAPONITE - PILLARING OF THE REDUCED SAMPLES WITH AL-13 OLIGOMERS

A high-iron content saponite, of the variety griffithite, was reduced using sodium dithionite and hydrazonium sulphate solutions. An importa nt amount of Fe3+ was reduced during the treatments. When using sodium dithionite as reducing agent, the reduction was accompanied by the su bstitution of Ca2+ by Na+ as the exchangeable cation. When using hydra zonium sulphate, the reduction was accompanied by acid activation of t he clay, the protons being released in the oxidation reaction of the h ydrazonium cation. The charge balance in the clay layers is affected b y the reduction processes. These structural changes do not significant ly affect the pillaring ability of the clay, which is similar in the r educed solids and in the natural griffithite.