Leaching of Cr from wood ash: discussion based on different extraction procedures

• L.M. Ottosen ^[2] ; P.E. Jensen ^[2] ; G.M. Kirkelund ^[2] ; A. B. Ribeiro ^[1]
  1. [1] Universidade Nova de Lisboa

     Universidade Nova de Lisboa

     Socorro, Portugal

     
  2. [2] University of Denmark
• Localización: Wastes: solutions, treatments and opportunities III / Cândida Vilarinho (dir.), Fernando Castro (dir.), Margarida Gonçalves Neto (dir.), Ana Luísa Fernando (dir.), 2020, ISBN 9780367257774, págs. 408-413
• Idioma: inglés
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• Resumen

  • Experimental work with wood ash (WA) from incineration of virgin wood shows that about 45% of the initial 79 mg/kg Cr leaches out in water, and even after a three step washing process in water, the WA leaches Cr. The leaching is highest at highly alkaline conditions. Electrodialysis showed that the leached Cr was in anionic form, but at the present high pH, both Cr(III) and Cr(VI) can form anionic complexes, so the oxidation state cannot be determined from this investigation. Because the extraction of Cr is so dependent on pH under alkaline conditions, the use of acid in the first step of sequential extraction gave an error in assessing the Cr present in this step. More Cr is extracted from WA in water than in weak acid.