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921.
Adsorption capacities and related characteristics of wood charcoals carbonized using a one-step or two-step process 总被引:2,自引:0,他引:2
Lilibeth Pulido-Novicio Toshimitsu Hata Yasuji Kurimoto Shuichi Doi Shigehisa Ishihara Yuji Imamura 《Journal of Wood Science》2001,47(1):48-57
Sugi (Cryptomeria japonlca D. Don) wood powder was carbonized at varying temperatures by a onestep process up to 1000C and a two-step process using wood charcoal as the raw material up to 1600C. This study was conducted to evaluate the adsorptive properties of wood charcoal and discuss the mechanism of its adsorptive function in relation to the physical and anatomical characteristics of wood after carbonization. Anatomical characteristics of carbonized wood materials were directly observed under heating using an environmental scanning electron microscope (ESEM); the cell wall structures were analyzed by high-resolution transmission electron microscope (HRTEM). The largest weight losses were observed at the highest temperatures, in both the one-step and twostep processes but leveled off above 800C. Shrinkages in the tangential, radial, and longitudinal directions increased with carbonization temperature, peaking at 1000C. Direct observations by ESEM showed distinct shrinkage at around 400C. The first trial observations by HRTEM on the changes in the ultrastructure of cell walls of wood charcoals were done, and it was assumed to affect the formation of micropores. Adsorption was found to follow the Langmuir isotherm model. With the one-step carbonization process, the iodine adsorption capacities of the carbonized wood powders increased with increasing carbonization temperature, peaking at 800C, but decreased at higher temperatures. The wood powder carbonized at 1000C with the two-step process showed the highest capacity, but further heating up to 1400C drastically decreased the adsorption. The shrinkage of cells was related to the increases and decreases in its specific surface area. Specific surface area and total pore volume were evidently related to the adsorptive properties.Part of this paper was presented at the Second International Wood Science Seminar, Indonesia, November 6–7, 1998 相似文献
922.
Lilibeth Pulido-Novicio Yasuji Kurimoto Masakazu Aoyama Kazuto Seki Shuichi Doi Toshimitsu Hata Shigehisa Ishihara Yuji Imamura 《Journal of Wood Science》2001,47(2):159-162
The ability of sugi wood carbonized at 1000°C to adsorb mercury was examined using aqueous solutions of mercuric chloride. Parameters studied include contact time, pH, adsorption temperature, and initial concentration of mercury in solution. Results showed that sugi wood carbonized at 1000°C could effectively remove mercury from aqueous solutions. The carbonized wood showed high adsorption ability for mercury at a wide pH range (pH 3–9), but its ability drastically decreased at pH 11. Adsorption decreased with increases in adsorption temperatures, indicating that the processes were exothermic in nature. Adsorption was found to follow the Freundlich isotherm model. The adsorption capacity of carbonized sugi wood was comparable to that of commercial activated carbon. 相似文献
923.
In order to understand the mechanism of destabilization occurring when wood is quenched, we applied chemical modifications,
and controlled the number of moisture adsorption sites in wood. The degree of destabilization was evaluated according to the
fluidity (1-E
t/E
0), increase in fluidity, and relative fluidity in relation to the nonmodified wood, and was discussed by comparing these quantities
with the hygroscopicity or swelling of wood. We found that destabilization of chemically modified wood was lower than that
in nonmodified wood, and the amount of adsorbed water controlled the magnitude of flow of wood. Moreover, according to the
analysis of water state by the Hailwood-Horrobin equation, it was shown that the function of dissolved water to the fluidity
is almost identical for both chemical modifications, whereas hydrated water has more effect on acetylated wood than on formaldehydetreated
wood. We speculate that the motion of water molecules due to quenching accompanied with the redistribution of energy resulting
from the exchange of their potential energy and movement to attain a new balance, and the introduced acetyl groups and cross-linking
restrict the water molecule movement.
An erratum to this article is available at . 相似文献
924.
文中对三通道刨花干燥机刨花干燥中被控对象的特性、过程控制的方法、检测仪表、调节控制器与调速系统进行了探索与研究。干燥机的热效率高、刨花终含水率均匀、形态好。 相似文献
925.
926.
LI Zhongkui LI ZhiyongInstitute of Forestrv Policy Information Chinese Academy of Forestry. Beiiine. P.R. China 《中国林业科技(英文版)》2003,(4)
The current area of bamboo resource in China is 7.21 million ha, 4.21 million ha of which is the pure bamboo forest The stock value of the bamboo resource is 30.312 billion Renminbi (RMB) yuan, the present value of actual output from bamboo wood and shoot is 149.062 billion RMB yuan. The bamboo forest land is valuated as much as 8.133 billion RMB yuan. It is raised to improve the production and management conditions of the 2nd and 3rd type bamboo forests to raise production capacity of wood and shoot and output of processed products from bamboo. 相似文献
927.
928.
Yutaka Ishimaru Kazutoshi Arai Masato Mizutani Katsuhito Oshima Ikuho Iida 《Journal of Wood Science》2001,47(3):185-191
Some properties of wood (hinoki:Chamaecyparis obtusa) moisture-conditioned by an adsorption process from a dry state and by two desorption processes (from a water-saturated state and from a state with a moisture content slightly below the fiber saturation point) were investigated. The moisture contents of wood conditioned by the adsorption process and by the desorption process continued to approach to one another for the moisture-conditioning period of over 50 weeks. Accordingly, sorption hysteresis should be regarded as a transitional phenomenon that occurs during the process of approaching the true equilibrium, which requires a long time. The wood conditioned by the desorption process beginning from a water-saturated state showed slightly smaller dimensions than those conditioned by the adsorption process with the same moisture content; however, the wood conditioned by the desorption process from a moisture content below the fiber saturation point showed slightly larger dimensions than those conditioned by the adsorption process. The wood conditioned by the adsorption process from a dry state showed a higher modulus of elasticity and modulus of rupture than did the wood conditioned from a water-saturated state with the same moisture content. The mechanical properties of the wood also varied based on the states at which the desorption process was started. This is a notable characteristic of the relation between the drying condition and the mechanical properties of wood. 相似文献
929.
对4种不同栽培措施的日本落叶松、湿地松、马尾松和杉木等多种短周期工业材309株样木的材性进行了全面测试分析研究,结果表明.立地指数大,木材生长率和纤维宽度大.但纤维长度、纤维长宽比、木材基本密度、顺纹抗压强度和抗弯弹性模量减小;立地指数相差两级,木材的年龄宽度、纤维宽度、长度和微纤线角度的差异达到显著或极显著水平栽植密度小,木材的年轮宽度和干缩比增大但纤维长宽比及体积全干缩率减小;栽植密度增大,杉木和昭林6号杨木材的力学强度提高,但尾叶桉和I-69杨降低;不同栽植密度的木材pH值及酸碱总缓冲容量,都是心材大于边材,但木材的脲醛树脂胶凝速度,则是边材快于心材.与未间伐林分的木材比较,随着间伐强度的增大、年轮宽度增大.但纤维长宽比和微纤丝角度减小;间伐强度增大,针叶树村的力学强度降低,阔叶树树则提高.但将强度间伐材(间代40%)与未间伐材比较,结果完全相反;北京杨木材心材的pH值、酸碱缓冲容量及总容量,均随间伐强度的增大而增大,但边材却减小.施肥措施能够增大纤维直径,但将导致纤维长宽比、木材密度和力学强度的降低施肥可以使树木速生,但会降低木材密度和质量,在培育建筑结构材的林分应慎用. 相似文献
930.
We examined the abrasive wear properties and the effect of abrasive grain size on the rate of wear when sugi wood (Cryptomeria japonica D.Don), compressed to various densities, was rubbed with abrasive paper. The results showed that the wear resistance of compressed wood increased linearly with the increased compression ratio; and under the condition of a low compression ratio it tended to be higher in comparison with the strength of compressed wood. The critical grain size effect, which can be witnessed during the abrasive wear of metals and plastics, was seen when low pressure was applied to the abrasive material. At higher pressures, the wear rate of the compressed wood increased with grain size, but the critical grain size effect was not observed. The pressure required to create the critical grain size effect was found to be higher than that needed for other types of uncompressed wood with the same yield properties.Part of this report was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000 相似文献