Poly(dimethylsiloxane) (PDMS)-Schiff base, a new polymeric network and its adsorbent capability for copper ions from ethanol

Poly(dimethylsiloxane), PDMS, can be functionalized with a Schiff base-alkoxysilane precursor, giving rise to hybrid materials that are then used to adsorb metal ions from ethanol solutions. This study reports on the synthesis of the new hybrid materials based on three different Schiff bases with one, two and four amine groups into different-sized chains, supported onto PDMS (PDMS/amsal, PDMS/ensal and PDMS/diensal) which were then used to adsorb CuCl2 from ethanol. Two of the elastomeric networks obtained present specific sorption capacities (tQ) close to 1.0 mmol g−1 and stability constants (β) of the immobilized copper were: PDMS/amsal log β1 = 3.07 (0.74); PDMS/ensal log   β ( 2 ) 1 = 2.20 ( 0.05 ) / log   β ( 2 ) 2 = 5.09 ( 0.03 ) and PDMS/diensal log   β ( 2 ) 1 = 3.48 ( 0.05 ) / log   β ( 2 ) 2 = 5.57 ( 0.05 ) . It was observed that each Schiff base (SB) forms a different complex with the metal ions. For PDMS/amsal, in the adsorption of copper ions the predominant species are those formed when SB is linked by a bidentate chelate, for PDMS/ensal the predominant species are those formed when SB is linked by a tridentate chelate and for PDMS/diensal, two species coexists in the equilibrium, a tetradentate chelate and the complex obtained with two SB bidentate centers.