Effect of Ionic Strength and pH on the Sorption of Heavy Metals onto Polyaniline Copolymers in Aqueous Solutions

Polyaniline (PANI) and two copolymers, poly(aniline-co-o-toluidine) (PoTOL-50) and poly(aniline-co-o-anisidine) (PoANI-50) were synthesized with equal input ratios (1:1) to enhance PANI as sensing material for the sensing of various heavy metal analytes in aqueous solutions. The polymers were evaluated for both their sensitivity and selectivity toward four heavy metals (Ba²⁺, Cd²⁺, Cu²⁺, and Ni²⁺) and two common matrix interferents (Ca²⁺ and Mg²⁺) at 10 and 40 ppm. The effect of pH and ionic strength of the aqueous solutions on the sensitivity and selectivity was also evaluated. All three polymers showed high sensitivity and selectivity to Ba²⁺. Varying the pH and ionic strength of solutions did not show significant differences in either the selectivity or the sensitivity of the polymers.