Glycine-functionalized silica as sorbent for cobalt(II) and nickel(II) recovery

• We disclose that glycine functionalized silica particles (SiO2-Gly) are highly effective sorbents for the removal of Co(II) and Ni(II) ions from aqueous solution. SiO2-Gly can be prepared from commercial silica gel in a high yielding two step synthesis, and features a glycine concentration of 0.63 mmol.g(-1) (27 mmol.cm(-2)). This material can recover up to 2.81 mmol.g(-1) of Co(II) ions or 3.02 mmol.g(-1) of Ni(II) ions from aqueous solution, a capacity which is tenfold higher than unmodified silica and comparable to the best performing sorbents reported in the literature. These sorption capacities are superstoichiometric in relation to the concentration of glycine on the surface. Sorption of cobalt(II) was improved by addition of ammonia to leaching solutions to give rise to more readily absorbed cobalt amine complexes. Regeneration of sorbent was investigated by desorption of adsorbed metals under mildly acidic solutions, and efficient desorption was noted for both metals. To probe the mechanism of sorption, a thorough characterization campaign involving TGA, FTIR, nitrogen adsorption/desorption, SEM, solid state NMR, solid state UV-Vis-NIR, -COOH titration and pH(pzc) - pH drift methods was undertaken. Our mechanistic study indicated that adsorption was mediated by electrostatic interaction.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Adsorption

Wastewater treatment

Metal recovery

Surface functionalization

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