Metal ions adsorption from ethanol solutions on ethylenediamine-modified poly(dimethylsiloxane) elastomeric network

An ethylenediamine-modified elastomeric network was obtained by the polycondensation reaction between poly(dimethylsiloxane), PDMS, with 2-aminoethyl-3-aminopropyltrimethoxysilane. The polymeric material was structurally characterized by its infrared spectrum and its solid state 13C and 29Si NMR. The 29Si NMR peaks at −70 and −61 ppm correspond to the Si environments in CSi(OSi)3 and CSi(OH)(OSi)2 units respectively, and a peak at −24 ppm is associated with C2Si(OSi)2. Thermogravimetric analysis of the product showed good thermal stability and differential scanning calorimetry showed a glass transition temperature from 150 to 160 K, with no evidence of crystallization. From the adsorption isotherms of Fe(III), Ni(II) and Cu(II), from an ethanol solution at 298 K, onto the polymeric network, the equilibrium constants were calculated for the adsorption reactions of these metal ions at the solid–solution interface. The following stability constants, β, and the adsorption capacities, tQ (in mmol of metal per gram of the adsorbent) were determined: (a) Cu(II): log β = 4.01 (0.03), tQ = 1.27 (0.02); (b) Fe(III): log β = 3.49 (0.03), tQ = 1.45 (0.05); (c) Ni(II): log β = 2.78 (0.06), tQ = 0.52 (0.05), where the numbers in parenthesis are the standard deviations.