QUANTITATIVE MONITORING OF SIDE PRODUCTS DURING HIGH LOADING OF ZEOLITES BY HEAVY-METALS VIA PH MEASUREMENTS

Zeolites of types A, X, and Y were modified by cation exchange in salt solutions of heavy metals. Because of the alkaline reaction of these zeolites in aqueous solutions, heavy metal hydroxides of low solubilit y precipitated. pH measurement during the exchange process enabled the direct monitoring of the consecutive reactions of precipitation and d issolution of hydroxides and the calculation of the amount of precipit ated hydroxide. Sulfidation of heavy metal ion-exchanged zeolites prod uced semiconductor particle-loaded zeolites of which the light absorpt ion behavior was sensitive to the extent of the side reaction of hydro xide precipitation prior to the sulfide formation.