Poly(sodium acrylate) hydrogels as potential pH-sensitive sorbents for the removal of model organic and inorganic pollutants from water

Anionic poly(sodium acrylate), PANa, hydrogels bearing negatively charged –COO- groups were
used as sorbents for the removal of colored organic or inorganic model pollutants, namely Crystal
Violet and Cu2+, from water. It was found that PANa hydrogels adsorb stronger Cu2+ions than Crystal
Violet, as a consequence of the formation of coordination complexes between the hydrogel and the
metal ions, while just electrostatic interactions are the major driving forces for Crystal Violet.
Furthermore, the influence of pH, i.e. the neutralization degree i of the hydrogel, on its adsorption
efficiency was investigated. It is shown that the adsorption of Cu2+ ions follows stoichiometry, namely
one metal ion per two carboxylate anions. On the contrary, the adsorption of Crystal Violet is much
lower than the charged stoichiometry.