Patent ID: 7160526

Claim:
A process for the detoxification of CCA-treated wood, said process comprising the steps of: (a) liquefying CCA-treated wood in the presence of a liquefying reagent comprising an acid and a hydroxyl-containing substance wherein said hydroxyl-containing-substance is an aliphatic hydroxyl-containing substance or an aromatic hydroxyl-containing substance and wherein said acid is selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, oxalic acid, toluene sulfonic acid, phenol sulfonic acid and mixtures thereof, said acid being from about 0.1% to about 20% by weight based on the dry weight of CCA-treated wood at a temperature and for a, time sufficient to form liquefied CCA-treated wood; (b) diluting the liquefied CCA-treated wood with water or an aqueous solution of an organic solvent to form an aqueous solution of liquefied CCA-treated wood; (c) adding to said aqueous solution of liquefied CCA-treated wood at least one heavy metal precipitating or complexing agent, thereby precipitating from said aqueous solution of liquefied CCA-treated wood insoluble heavy metal precipitates or complexes and forming a solution of detoxified CCA-treated wood; (d) separating the insoluble heavy metal precipitates or complexes from the solution of detoxified CCA-treated wood; and (e) isolating chromated copper arsenate from said insoluble heavy metal precipitates or complexes of step (d).