Diffusion of copper in wood cell walls following vacuum treatment
Diffusion of copper in wood cell walls following vacuum treatment
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作者：
P. Cooper
采用表达技术，对碱铜真空处理的红松（Pinus resinosa Ait.）和颤杨（Populus tremuloides Michx.）两种木材的木材结构中铜的再分配速率和程度进行了监测。铜进入细胞壁底物的扩散系数(D)由细胞腔内铜浓度的变化率确定，采用非定常菲克扩散的有限槽模型。D值在0.1-165 X 10 -10 cm 2 /s范围内，取决于木材种类和处理条件。这些D值大约是束缚水扩散的1/10到1/10,000。白杨树的平衡时间比红松长得多，部分原因是白杨树的平均扩散距离更大；然而，即使对不同扩散路径长度进行校正，杨木的估计D值也要低100倍以上。在平衡状态下，对细胞壁中铜的浓度没有明显的物种效应。根据溶液pH值的不同，细胞壁每克干木材保留2至4毫克铜，高pH值处理的保留率更高。扩散速率随温度的升高而增加，而木材含水率的影响不一致。初始pH相似的氨态和单乙醇胺铜溶液具有相似的铜扩散速率和平衡吸附速率。在氨态砷酸铜溶液中与铜配制的砷酸盐阴离子最初被排除在细胞壁底物之外，但最终渗透到细胞壁中，但渗透程度低于铜。
The rate and extent of copper redistribution in the wood structure of red pine ( Pinus resinosa Ait.) and trembling aspen ( Populus tremuloides Michx.) sapwood samples vacuum-treated with alkaline copper solutions were monitored using an expressing technique. Diffusion coefficients (D) for copper movement into the cell-wall substrate were determined from the rate of change of copper concentration in the cell lumens, using a finite bath model for unsteady state Fickian diffusion. D values were in the range of 0.1-165 X 10 -10 cm 2 /s, depending on the wood species and treating conditions. These D values are about 1/10 to 1/10,000 those for bound water diffusion. Equalization times were much longer for aspen than for red pine, partly as a result of the greater average diffusion distances in aspen; however, estimated D values were more than 100 times lower for aspen even with correction for the different diffusion path lengths. There was no significant species effect on the concentration of copper in the cell walls at equilibrium. Depending on the solution pH, the cell walls retained from 2 to 4 mg Cu per g dry wood with higher retentions for high pH treatments. The rate of diffusion increased with temperature, while wood moisture content had no consistent effect. Ammoniacal and monoethanol-amine copper solutions at similar initial pH had similar rates of copper diffusion and equilibrium adsorption. Arsenate anions formulated with copper in ammoniacal copper arsenate solutions were initially excluded from the cell-wall substrate but eventually penetrated into the cell wall, but to a lesser degree than copper.