Utilization of milk protein as an environmental material: accumulation of metal ions using a protein–inorganic hybrid material

Abstract

A casein–inorganic hybrid material was prepared by mixing casein, one of phosphoproteins, and a silane coupling reagent. This casein–inorganic hybrid material was stable in an aqueous solution owing to the electrostatic interactions between the phosphate group in casein and the amino group in the silane coupling reagent. The hybrid materials could selectively accumulate heavy and light metal ions and did not interact with the rare-earth metal ions. In addition, the metal ion-accumulated hybrid materials could be recycled by washing with an aqueous EDTA solution or hydrochloric acid.