DIFFERENCES IN RECOVERY PERCENTS BETWEEN THE CALCIUM ION (II) AND MAGNESIUM ION (II) WITH ACTIVATED AND INACTIVATED BENTONITE BY ION-EXCHANGE CHROMATOGRAPHY

This study aims at determining the optimum pH for the separation of calcium (II) and magnesium (II) and knowing differences in recovery percents between calcium (II) and magnesium (II) using activated and inactivated bentonite. The method used in this research was ion-exchange chromatography in which the bentonite was used as the stationary phase. The research procedures conducted were the sample preparation, stationary-phases making, the cation-exchange capacity determination, the determination of mobile-phase pH influences on the separation of calcium ions (II), and the determination of mobile-phase pH influences on the separation of magnesium ions (II). Preparation of the stationary phase was performed in two models which were activated stationary phase and inactivated stationary phase. Preparation of the stationary phase was activated by chemically activating bentonite by immersion using HCl of 1 M and physically by calcining at 400°C. Determination of the cation-exchange capacity was done by interacting the stationary phase with saturated Na CI and then titrated with Na OH of 0.05 N. Determination of mobile-phase pH influences on the result of the calcium ion (II) separation was conducted by varying the pH of the mobile phase when the process of the ion-exchange chromatography separation. The absorbance was measured using atomic absorption spectrophotometer at a wavelength of 422.7 nm while for the magnesium ion (II) absorbance was measured at a wavelength of 285.2 nm. The results showed an optimum pH producing the greatest recovery percent at both metals with activated and inactivated bentonite occurred at pH 3. There were significant differences between the recovery percents of calcium ions (II) by activated and inactivated bentonite. There was no significant difference between the recovery percents of magnesium ions (II) by activated and not activated bentonite. There was no significant difference between the recovery percents of both metals with activated and inactivated bentonite