Copper inclusion in cellulose using sodium D-gluconate complexes

Copper containing cellulose material is of growing interest, e.g. offering alternative in the field of antimicrobials. Solutions of copper D-gluconate complexes (Cu2+-DGL) were used to introduce copper ions into a swollen cellulosic matrix. A ligand exchange mechanism forms the chemical basis of the sorption process. Copper sorption in cellulose was studied in the range between pH 6 and 13. An estimate for the complex stabilities of the Cu-cellulose system could be derived from the calculated species distribution of the different Cu2+-DGL complexes present. Spectrophotometry and cyclic voltammetry of Cu2+-DGL complex solution were used to confirm the presence of different species participating in the ligand exchange reaction. The pH dependent uptake of Cu2+ ions in the cellulose matrix can be explained on the basis of the relative stabilities of Cu2+-DGL complex vs. Cu2+-cellulose complexes. In comparison to pH 10, higher copper content was observed at pH 6 and 13. Copper content was limited by carboxyl content of cellulosic materials, thus in analogy to the structure of Cu2+-DGL complexes participation of the carboxyl group as complex forming site is proposed. At high Cu2+-concentration and longer time of immersion in the copper complex solutions formation of solid deposits was observed on the surface of the treated fibres. (C) 2012 Elsevier Ltd. All rights reserved.