Selective Cu 2+ adsorption and recovery from contaminated water using mesoporous hybrid silica bio-adsorbents

Abstract

Metallothioneins (MTs) are low-molecular weight proteins (1–10 kDa), which are known to bind selectively metal ions such as Zn or Cd in metal–thiolate clusters. The present work describes the preparation of copper–metallothionein (Cu–MT) and its immobilization by covalent grafting on mesoporous silica for the selective uptake and recovery of Cu 2+ from water. The mesoporous silica used (SiDav) features 10 nm pore size suitable to accommodate Cu–MT (6 nm size) and 200 μm particle size adequate for flow processes. For the covalent coupling, SiDav was first functionalized with aminopropyl (SiDav–NH 2) or glycidoxypropyl (SiDav–Gly) functions before to react with Cu–MT. After decomplexation of Cu, the resulting MT–SiDav–NH 2 and MT–SiDav–Gly materials were used to adsorb Cu 2+ from aqueous solutions in the presence of various competing cations. The adsorption capacity of the hybrid biocomplexant silica materials was studied in batch and in column for flow process. Starting from a solution containing 2 mM of four cations, the maximum adsorption capacity under flow (1 mL/min, pH 6) was obtained for MT–SiDav–NH 2 with a high selectivity for Cu 2+: Cu 2+ (0.210 mmol g −1) ≫ Cd 2+ (0.009 mmol g −1) > Zn 2+ (0.005 mmol g −1) > Pb 2+ (0.003 mmol g −1). Furthermore, adsorbed Cu 2+ ions were quantitatively recovered by simply eluting the column with HCl. This column was also successfully used to preconcentrate Cu 2+ contained in different water samples as tap or mineral waters for an easier analysis of Cu traces.