Fixation of Chromium in Wood from Trivalent Chromium Salt Solutions

Summary The aim of this study was to fix chromium chemically in wood from trivalent chromium solutions. Chromium(III) nitrate, chloride and sulphate salts were applied, both in aqueous and in methanolic solutions. To improve chromium fixation metallic zinc was used as a strong reductant to generate labile Cr(II) species from Cr(III), and base was added (NaOH for water and NaMeO for methanol). Aqueous solution reaction conditions were always acidic in spite of base addition, leading to unacceptable levels of wood degradation (e. g., weight loss), although relatively high chromium levels were attained in some cases. Methanolic solutions did not lead to wood degradation, and there was fixation of high levels of chromium. Although the addition of NaMeO seemed to improve chromium fixation, a chromium precipitate always formed, usually after a long reaction time (> 4h). Therefore the following experimental conditions for chromium fixation are suggested: alcoholic solution of Cr(III) chloride or nitrate, addition of metallic zinc, at reflux. To avoid using large amounts of zinc, Cr(III)-solutions can also be reduced electrochemically.

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