木质纤维素接枝丙烯酸系吸附剂的合成技术研究

在离子液体中,以木质纤维素为基质,分别采用过硫酸铵和氧化--还原体系为引发剂,N,N′-亚甲基双丙烯酰胺为交联剂,与丙烯酸及丙烯酸丁酯反应,利用接枝聚合合成技术制备了纤维素改性吸附剂。用石蜡为分散相,经反相悬浮技术将接枝物球化。对产物进行了热重分析,并通过接枝率、接枝效率及金属离子吸附量对各个产物进行了对比,结果表明,氧化———还原引发下制得的共聚物吸附效果最佳,且对铜离子吸收最为敏感,最大吸附量可达218.3mg/g。     

微晶纤维素氰乙基化及其反应动力学研究

通过微晶纤维素的氰乙基化试验,研究了反应温度和反应时间对氰乙基化产物取代度(DS)的影响,表明在50℃以下,微晶纤维素的氰乙基化取代度随反应温度的升高和反应时间的延长而增加。傅里叶红外光谱分析显示微晶纤维素氰乙基化后羟基峰明显减弱,并形成了新的碳氮三键吸收峰,证明纤维素中的部分羟基氢被氰乙基所取代。X射线衍射分析显示微晶纤维素中原有的结晶结构被破坏。X4显微熔融温度测定仪、维卡软化点测定仪等的分析表明微晶纤维素氰乙基化产物的热塑性先随取代度的升高而提高,取代度超过1.43后,产物的热塑性又随取代度的升高而下降。确定了微晶纤维素氰乙基化在不同温度(30、35、40和45℃)下的反应速率常数(分别为1.30、1.61、1.94和2.26 s-1),计算出了微晶纤维素氰乙基化反应的表观活化能为29.8 kJ/mol。     

纤维素C_6位伯羟基的选择性氧化及用于双酚A的吸附研究

采用HNO3/H3PO4-NaNO2氧化体系制备了氧化纤维素,通过红外光谱、固体13C NMR对其结构进行表征,用酸碱中和滴定法测定了产物的羧基含量。同时以氧化纤维素为吸附剂,研究了对水中内分泌干扰物双酚A(BPA)的吸附性能。结果表明:该氧化体系能很好的选择性氧化纤维素的C6位伯羟基,含羧基为20%。在298 K时,氧化纤维素对双酚A最大吸附量为12.67 mg/g,吸附平衡时间为30 min,平衡吸附量随双酚A浓度增加而增加;溶液接近中性及低温条件有利于吸附的进行,溶液中存在电解质则不利于吸附的进行。双酚A的吸附过程属于单分子层吸附,以化学吸附为主,符合准二级动力学方程和Langmuir吸附等温模型。     

二醛基纤维素的制备及其对尿素的吸附性能

以微晶纤维素为原料,高碘酸钠作为氧化剂,制备二醛基纤维素(DAC),考察各影响因素对二醛基纤维素制备的影响,采用FTIR、元素分析、XRD以及化学官能团测定等手段对二醛基纤维素的结构进行表征;探讨二醛基纤维素的醛基含量与尿素吸附容量之间的关系,并研究二醛基纤维素对尿素的吸附平衡和吸附动力学。结果表明:高碘酸钠与微晶纤维素的质量比为2.4∶1、反应温度为35℃、反应时间为3.5 h、反应介质的pH为2时,制得二醛基纤维素的醛基含量最大为97.74%。二醛基纤维素对尿素的吸附容量随醛基含量的增加先增大后减小,最大吸附容量为59.23 mg.g-1,是包醛氧淀粉尿素吸附容量的10倍(6 mg.g-1),是包醛酶淀粉吸附容量的4倍(15 mg.g-1),吸附平衡时间为4 h。吸附等温线符合Freundich方程。     

端氨基超支化聚合物接枝双醛基纳米纤维素的 制备及其对Ni2+的吸附

通过聚合反应制得一种端氨基超支化聚合物(HBP-NH_2),并以桉木浆为原料,经超声波辅助-TEMPO氧化制得羧基化纳米纤维素(CNC)、再经高碘酸钠氧化制得双醛基纳米纤维素(DNC),最后利用HBP-NH_2对DNC进行氨基化改性,得到端氨基超支化聚合物接枝双醛基纳米纤维素(HBPN-DNC),并对反应条件进行优化,当10%的HBP-NH_2溶液加入量为10 mL,反应温度为70℃,反应时间为4 h时N元素质量分数最高,达到6.0%。采用多种方法对纳米纤维素的结构和性能进行了表征,结果表明:氨基成功地接枝到了纳米纤维素链上,使得分子链变长,HBPN-DNC的热稳定性提高。HBPN-DNC对Ni(II)的吸附性能研究表明:室温条件下,当HBPN-DNC吸附剂用量为0.1 g,溶液初始质量浓度为500 mg/L且pH值为5.0的条件下吸附3 h,吸附量为150.21 mg/g。吸附过程符合准二级动力学吸附模型和Langmuir等温吸附模型,说明其吸附过程主要为单分子层的化学吸附。     

纸浆纤维素苄基化及其反应动力学

通过纸浆纤维素的苄基化试验,研究反应温度和反应时间对苄基化产物取代度的影响,证明适当延长反应时间、提高反应温度有利于提高产物的取代度。傅里叶红外光谱仪、差示扫描量热仪、X射线衍射仪等对纸浆纤维素苄基化产物的分析表明:原料中的部分羟基被苄基取代,原有的结晶结构被破坏,产物热稳定性略有下降。维卡软化点和熔融温度测试显示产物的热塑性随取代度的增加而增加。本文还确定纸浆纤维素苄基化在4个不同温度下的反应速度常数,计算出纸浆苄基化反应的表观活化能为46.1kJ·mol-1。     

对伞花烃及其裂解产物甲苯的间接电解氧化反应研究

在无隔膜电解槽中,Pb-Sb合金为阳阴电极,Mn2 电解氧化成Mn3 的理想条件为:极板面积比(A /A-)为5:1,硫酸浓度为5 mol/L,阳极电流密度为80 mA/cm2,Mn2 浓度为1 mol/L左右,温度在25～35 ℃,电量比值为1.20.此时电解电流效率在60%左右,Mn3 得率超过70%.Mn3 氧化对伞花烃得到的主要产物为对甲基苯乙酮和枯茗醛,Mn3 与对伞花烃摩尔比为4:1时,氧化产物中枯茗醛的选择性相对较高,对甲基苯乙酮和枯茗醛的得率分别为55.19%和31.64%.Mn3 氧化甲苯得到的主要产物为苯甲醛,合适的氧化条件是Mn3 与甲苯摩尔比为1:6,苯甲醛的得率为73.67%.电解液经正己烷萃取和活性炭吸附可再生循环使用8次以上.     

利用FTIR对苯基异氰酸酯与不同含水率纤维素反应的研究

通过FTIR红外光谱对苯基异氰酸酯与醇、水、不同含水率纤维素反应产物的研究 ,确定了产物的红外光谱吸收峰的归属。研究发现 :异氰酸酯与绝干纤维素羟基反应产物是氨基甲酸酯 ,随着纤维素含水率的增加 ,异氰酸酯与纤维素的反应越来越低 ,与水反应的比例越来越高 ;当纤维素含水率为 9 78%时 ,异氰酸酯绝大部分与水反应生成取代脲     

端氨基纳米纤维素的制备及对Pb(Ⅱ)的吸附性能研究

以桉木浆为原料,经TEMPO氧化制得羧基化纳米纤维素(CNC)、再经高碘酸钠氧化制得双醛基纳米纤维素(DANC),最后利用二乙烯三胺(DETA)通过席夫碱反应对其进行氨基化改性,得到端氨基纳米纤维素(ANCC)。采用多种方法对纳米纤维素的结构和性能进行了表征,结果表明:DANC含醛基为2.95 mmol/g,ANCC含氨基为1.7 mmol/g,DETA上的氨基成功地接枝到了纳米纤维素链上,使得分子链变长,ANCC的热稳定性提高。ANCC对Pb(Ⅱ)的吸附性能研究表明:室温条件下,当ANCC吸附剂用量为0.1 g,溶液初始质量浓度为400 mg/L且p H值为5.0的条件下吸附3 h,吸附量为210.15 mg/g。吸附过程符合准二级动力学吸附模型和Langmuir等温吸附模型,说明其吸附过程主要为单分子层的化学吸附。     

甘蔗渣基离子吸附剂的研究

以甘蔗渣为原料,用丙烯腈和盐酸羟胺对其进行改性,在甘蔗渣分子中引入胺肟基团,提高其对金属离子的吸附能力.讨论了羟胺化反应条件如温度、时间、羟胺质量浓度对胺肟基团含量的影响.用红外光谱表征了产物的结构,用元素分析法测试了产物中氮元素的含量.在反应温度90℃、反应时间180min、羟胺质量浓度100g/L时,改性甘蔗渣中最大含氮元素为13.4%,最大含胺肟基团为3.38mmol/g,并对改性产物进行了铜离子的吸附研究,其最大铜离子吸附量为54.0mg/g.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Boron in forest trees and forest ecosystems

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.     

Survival and Growth of Picea abies Regeneration after Shelterwood Removal with Single- and Double-grip Harvester Systems

Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m³ shelterwood with 200 stems ha^-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth.     

Development of Pinus sylvestris Main Stems Following Three Different Precommercial Thinning Methods in a Mixed Stand

Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.