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ABSTRACT. Milled aspen wood was thermochemically modified with citric acid for the purpose of improving the copper (Cu 2+ ) ion sorption capacity of the wood when tested in 24-hour equilibrium batch tests. The wood-citric acid adducts provided additional carboxyl groups to those in the native wood and substantially increased Cu 2+ ion uptake of the modified wood compared with that of the unmodified wood. Sorption capacity (q e ) measured with an unbuffered standard solution increased to a maximum of 7.9 mg Cu 2+ ion/g of wood (treated) from 1.3 mg Cu 2+ ion/ g wood (untreated). When measured with a buffered standard solution, the q e increased to a maximum of 13.8 mg Cu 2+ ion/g of wood (treated) from 4.1 mg Cu 2+ ion/g wood (untreated). The treatment necessary for maximum q e was 2 hours at 130°C. Modification treatments included three time periods (2, 4, 6 hours) and three temperature regimes (110, 120, 130°C). To further evaluate the efficacy of modification treatments, weight change after treatment was monitored as an indirect measure of bound citric acid. It was found that increases to the original mass of greater than about 30% were associated with no further increase or a decline in q e . The contribution of citric acid ester linkages to increasing mass at longer reaction times was monitored with ATR/FTIR.

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Heat treatment of wood fibers in a closed press for 4 and 8 minutes and pressed into fiberboards greatly reduces moisture regain and increases dimensional stability of the boards. Part of the hemicellulose sugars are lost during the steam treatment and furan intermediates were detected. Mannose, galactose, xylose, arabinose and rhamnose were partially lost during the steaming process. The steam treated boards have lower strength as compared to adhesive added boards but they do not fall apart when placed in water.