山杏壳制备活性炭的最佳工艺研究

以山杏壳为原料,用正交试验法,分别采用氯化锌、水蒸气活化法制备杏壳活性炭,并测定吸附能力,优选制备杏壳活性炭的最佳工艺参数,为杏壳活性炭的产业化生产提供技术依据。研究结果表明,以氯化锌为活化剂制备杏壳活性炭的最佳工艺参数为:氯化锌溶液浓度50%,料液比1∶1,活化温度500℃,活化时间90min;水蒸气活化法制备杏壳活性炭的最佳工艺参数为:水蒸气流量5mL/min,活化温度900℃,活化时间120min。在本试验确定的最佳工艺条件下,以氯化锌为活化法制备的活性炭得率为41.83%,碘吸附值为948.06mg/g,亚甲基蓝吸附值为133.42mg/g;以水蒸气活化法制备的杏壳活性炭得率为48.11%,碘吸附值为1001.67mg/g,亚甲基蓝吸附值为153.05mg/g,2种方法制备的杏壳活性炭均具有较强的吸附能力。     

低温磷酸活化棉秆制备活性炭的研究

以棉秆为原料,活化温度在300～450 ℃之间,研究了低温磷酸活化制备活性炭的可行性,并测定了活性炭的碘吸附值、亚甲基蓝吸附值和焦糖脱色率等吸附性能指标;根据氮气吸附等温线分析了活性炭的孔隙结构特征;采用Boehm 滴定方法分析了活性炭的各类表面官能团.结果表明:在磷酸的低温活化过程中,活化温度的升高显著促进了活性炭的比表面积及其对亚甲基蓝吸附值和焦糖脱色率等的吸附能力.在 350 ℃下的低温磷酸活化棉秆能够制备出比表面积达 1 244 m2/g,表面官能团含量高达 10.4 mmol/g,亚甲基蓝吸附值和焦糖脱色率分别达到 190 mL/g 和 100 % 的孔隙结构发达和极性较强的活性炭.     

水蒸气活化法制备松子壳活性炭的研究

以废弃的松子壳为原料,采用水蒸气活化法制备松子壳活性炭,系统研究了炭化温度、活化温度、活化时间、活化剂用量等关键工艺因素对活性炭产品性能的影响,分析其对碘吸附值和亚甲基蓝吸附性能的影响。结果显示,松子壳活性炭最佳工艺条件为:炭化温度为500℃、活化温度为860℃、活化时间为90 min、水蒸气流量为2.5 m L/min,此时松子壳活性炭得率为26.08%,碘吸附值为1 338 mg/g,亚甲基蓝吸附值为300 mg/g。松子壳活性炭孔径主要集中在3 nm左右,其平均孔径为2.396 nm,BET比表面积为105 2.68 m~2/g,总孔容积为0.630 6 cm~3/g,微孔容积为0.355 8 cm~3/g,占总孔容积的56.43%。     

高比表面积竹质活性炭的制备与性能研究

以竹子为原料、磷酸为活化剂,在不同条件下制备竹基活性炭,考察浸渍比、活化温度、活化时间、升温速率等因素对竹质活性炭产品吸附性能的影响,得到亚甲基蓝吸附值最高达200 mL/g、焦糖脱色率最高达120%的高吸附性能竹质活性炭。研究结果表明最佳工艺条件为:浸渍比3∶1(g∶g),活化温度400℃,升温速率10℃/m in,活化时间40 m in。对所制得的竹质活性炭产品进行扫描电镜(SEM)分析、N2吸附分析,结果表明所制得活性炭具有较高的BET比表面积(2 103 m2/g)和发达的孔结构。     

机械力辅助氯化锌活化法制备甘蔗渣活性炭

以甘蔗渣为原料,以氯化锌为活化剂,采用机械力化学方法制备具有较好吸附性能的活性炭,探讨工艺条件对活性炭碘吸附值和亚甲基蓝吸附值的影响.结果表明:在浸渍比为1∶1、活化温度为660℃、活化时间为120min、球磨时间为15 min的条件下,活性炭样品的碘吸附值、亚甲基蓝吸附值和比表面积分别为1 178.92 mg·g-1、270 mg·g-1和1 541.165 m2·g-1.     

KOH活化高比表面积椰壳活性炭的制备及其性质研究

以椰壳炭化料为原料,通过KOH活化法制备高比表面积活性炭,并探索温度、时间和活化比对活性炭吸附性能的影响.通过单因素试验发现,活化温度800℃,活化时间60 min,活化比值为5的条件下活性炭的吸附性能最优.制备出的活性炭比表面积为3 360 m2/g,总孔孔容为1.798 cm3/g,平均孔径为2.140 nm,对碘的吸附性能为2809 mg/g,对亚甲基蓝溶液的吸附性能为675mg/g.     

微波辐照氯化锌法制备酸枣核壳活性炭工艺及其性能

采用微波辐照氯化锌法,对以酸枣核壳为原料制备活性炭开展了工艺及性能研究。通过正交试验法研究了不同因素:氯化锌浓度(A)、浸渍时间(B)、微波功率(C)、辐照时间(D)对酸枣核壳活性炭的得率、碘吸附值、亚甲基蓝吸附值的影响。结果表明:微波辐照氯化锌法制备酸枣核壳活性炭的最佳制备工艺条件为A3B1C3D2,即氯化锌浓度50%,浸渍时间14 h,微波功率700 W,辐射时间7 min;在此条件下,酸枣核壳活性炭的得率为60%,碘吸附值与亚甲基蓝脱色力分别为933.24 mg/g和111.92 m L/g;不同处理量的梯度试验表明,该工艺具备大规模处理酸枣核壳的能力。     

磷酸活化沙柳制备活性炭工艺

沙柳资源丰富且含有大量的纤维素和半纤维素,可作为制备活性炭的潜在原料。本研究以沙柳为原料、磷酸为活化剂,采用正交试验法确定沙柳基活性炭的制备工艺,探究浸渍比、活化温度和活化时间3个因素对沙柳基活性炭得率及亚甲基蓝吸附性能的影响。通过扫描电子显微镜(SEM)和X-射线衍射仪(XRD)对所制备活性炭的微观形貌和石墨层结构进行分析和表征,并利用氮气吸附和脱附曲线计算出BET比表面积、BJH孔径分布。试验结果表明:制备沙柳基活性炭的较理想工艺条件为,活化时间80 min,浸渍比3∶1(磷酸与原料的质量比),活化温度450℃;在此条件下制备的沙柳基活性炭平均得率为46.48%,亚甲基蓝吸附值为135.0 mg/g,BET比表面积为1 015.144 m2/g,孔径大小平均为4.23 nm。     

水蒸气活化法制备松籽壳活性炭工艺

研究了水蒸气法活化制备松籽壳活性炭的工艺条件,探讨了炭化温度、活化温度、活化时间和水蒸气用量对活化效果的影响。结果表明最佳工艺条件为:炭化温度500℃、活化温度950℃、活化时间120 min和水蒸气用量为炭化料的1.8倍,制备的活性炭碘值1144 mg/g,亚甲基蓝吸附值171 mL/g,产品得率15.6%。这些指标与木质活性炭相当,且投资少,能耗低,具有良好的社会效益与经济效益。     

微波辐射处理竹节废料制备活性炭研究

研究了以竹节及其炭化料为原料，采用微波辐射氯化锌法和水蒸气法制备活性炭的可行性。探讨了微波功率、活化时间、活化剂浓度及水蒸气流量对活性炭性能的影响。得到了微波辐射竹节废料制备活性炭的最佳工艺条件：水蒸气法的最佳条件为微波功率700W、活化时间7min、水蒸气流量3．1mL／min。用此工艺条件制得的活性炭碘吸附值1012．2mg／g、亚甲基蓝脱色率165mL／g、得率52．3％。该工艺所需活化时间为传统方法的l／45左右，得率为传统方法的2倍左右。氯化锌法的最佳条件为微波功率350w、活化时间5min、氯化锌质量分数40％。用此工艺条件制得的活性炭碘吸附值l088．4mg／g、亚甲基蓝脱色率220mL／g、得率39．2％。该工艺所需活化时间为传统方法的l／36，产品活性炭亚甲基蓝脱色率为国家一级标准的1．83倍(GB／T 12496．10-1999)。     

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.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.     

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.