Chemisorption of copper ions in aqueous acidic solutions by modified chitosan

Abstract

Sorption of copper ions by composite sorbents based on cross-linked chitosan such as chitosan/colloid silicon dioxide, chitosan/polymethylsiloxane and chitosan/ polymethylsiloxane/gelatin have been studied. Sorption capacity of the sorbents is increased the pristine chitosan 1.5–3.85 times. Eliminating of Cu2+ is based on competing mechanism of salt formation between metal ions and amino-groups in a two-phase system “aqueous solution of acids and salts – chitosan”, which involve metal ions (M2+), protons (H+) and their carriers – anions (X−) on the amino-groups of composite sorbent with final formation of chelates of the following structure CS[(-NH2)2M(X)2] and CS[-NH3X]2.The role of pH on sorption of copper ions and protons is explained by competing mechanism of metal cations and protons for sorption sites. Sorption of protons is accompanies by transformation of amino-groups into inactive form, H-form, which is resulted in decreasing the capacity of sorbents for ions of heavy metals in aqueous acidic solutions.