Effects of Hot Water Posttreatment on Accelerating Copper Fixation in ACQ-D-Treated Chinese FIR

The effects of hot water posttreatments on accelerating copper fixation in alkaline copper quat-type D (ACQ-D) -treated Chinese fir [C. lanceolata (Lamb.) Hook] were evaluated. The rate and extent of copper fixation in treated wood posttreated at 60, 80, and 100°C were monitored by analyzing the copper content in the expressed solution over time. The fixation qualities of copper in treated wood after different hot water posttreatments were evaluated by the AWPA E11-06 leaching test. The valence conversion of copper in treated wood was investigated by UV/visible spectroscopy. The expressing results showed that copper stabilized much faster during hot water posttreatments, especially at 80 and 100°C; more than 90% of copper could be fixed in treated wood in less than 2 h. The valence conversion of copper was highly dependent on the temperature and duration of the treatment. After a 100°C hot water bath of 6 h, more than 40% of cupric copper was reduced to cuprous forms. Based on the results of leaching tests of ACQ-D-treated wood, the best copper leaching resistance was obtained at 100°C; the percentage of copper leaching was reduced to about 12% when posttreated for 9 h. The compressive strength of treated wood was not impaired significantly in that condition