REDUCTION OF THE CATION-EXCHANGE CAPACITY OF MONTMORILLONITE BY TAKE-UP OF HYDROXY-A1 POLYMERS 1

Abstract- The cation-exchange capacity (CEC) of Na-A1- and Ca-Al-montmorillonite aft r neutralization with NaOH or Ca(OH)2 was studied at three A1 levels: I0, 25, and 50 % of the CEC. Hydroxy-A1 polymers were effective in reducing the CEC of Na-montmorillonite (bymore than 46%), the exact effectiveness being dependent on the hydroxy-A1 content. The hyclroxy-A1 polymers were less effective in reducing the CEC of Ca-montmorinonite (less than 26%). The CEC reduction was equal to or larger than the amount of the untitrated A1. The electrostatic charges of the clay which were blocked by the hydroxy-A1 polymers were compensated forby both the positive charge of the hydroxy-A1 polymers and the trapped cations on the clay surfaces. These cations remained on the clay even after extensive washing with 0.1 M KC1. Key Words--Cation-exchange capacity, Hydroxy-A1 polymer, Interlayer, Montmorillonite, Smectite.