Interaction of functionalised surfaces on silica with dissolved metal cations in aqueous solutions

The study clearly shows that different metal cations were efficiently removed from water by employing coated silica particles with SO3H-terminated functionalized surfaces. Significant amounts of Fe, Mn, Ca, Mg, Na, and K could be removed from natural water samples with different concentrations varying from 0.075 mg/l for Mn up to 12 000 mg/l for Na by stirring the functionalized silica particles in the water samples for 1 h at room temperature. ICP-MS verify the removal of the elements and ToF-SIMS analyses clearly showed the presence of the elements on the particles after the treatment procedure. The removal of the metal cations is believed to be due to electrostatic attraction of the positively charged presumably hydrolysed metal cations to the negatively charged deprotonated SO3H-groups. However, from the current study it can not be excluded that chemisorption of the cations by the SO3H-group may be possible.