Study of Cr(VI) adsorption onto nitrogen-enriched activated carbon from waste medium density fiberboard

Nitrogen-enriched activated carbons were prepared from waste medium density fiberboard waste by using NaOH, K₂CO₃ and KOH. The content of nitrogen in the activated carbon was 0.92, 0.74 and 1.33 % by analysis. The influence of contact time, pH, Cr(VI) initial concentration and the amount of activated carbon on the Cr(VI) adsorption capacity were investigated. The maximum adsorption capacity of Cr(VI) could reach 89.21 mg/g at pH 2 and a contact time of 9 h. The kinetics adsorption followed nicely the pseudo-second-order rate expression. In adsorption isotherm, the Langmuir model fitted better than the Freundlich model. Pure Poplar activated carbon was also prepared as the adsorbent for Cr(VI) removal as control sample. This study indicated that the nitrogen-enriched activated carbon prepared from waste medium density fiberboard can be used effectively for the removal of Cr(VI) compound from aqueous solutions.     

Characteristics of nitrogen-enriched activated carbon prepared from waste medium density fiberboard by potassium hydroxide

Most waste of medium density fiberboard (MDF) is burnt, which could release toxic gases and pollutants to the environment. So, the re-using waste of MDF is highly desired. The nitrogen atoms of waste medium density fiberboard originate from urea–formaldehyde resin adhesive used in the manufacturing process, so nitrogen-enriched activated carbons could prepared easily. Nitrogen-enriched activated carbons were prepared from waste MDF by potassium hydroxide. The activation temperature was ranged from 600 to 900 °C, and the chemical agent/waste MDF varied from 1 to 5. Iodine number was used to evaluate the adsorption ability of waste MDF activated carbons. The pore properties including surface area, pore volume and pore size distribution were determined by N₂ adsorption. The method of elemental analysis and XPS were used to estimate how nitrogen functional groups changed with different activation conditions. The results showed that the adsorption of iodine number of activated carbons was ranged from 661 to 1350 mg/g. The surface area of waste MDF activated carbons was different from 941 to 1876 m²/g and total pore volume was from 0.455 to 0.949 cm³/g. The pore size distribution indicated that waste MDF activated carbons included both micropores and mesopores, and the analysis of element implied that the contents of nitrogen varied from 0.41 to 2.31 %.     

利用低温竹炭制备竹活性炭初步研究

选用低温竹炭为原料、氢氧化钾为活化剂,制备不同炭碱比和不同活化时间的竹活性炭。运用傅立叶红外光谱议(FTIR)、比表面积测定仪(BET)等仪器对竹活性炭表面官能团、比表面积和孔径结构及比电容进行了测试和分析。结果表明,炭碱比1:4、活化温度700℃、活化时间3h条件下制备的竹活性炭,比表面积为2897.7m2/g,总孔容为1.340cm3/g,平均孔径为2.59nm,亚甲基蓝吸附值为27.7ml/0.1g,碘吸附值为1920mg/g,作为超级电容器(EDLC)的电极,其比电容为114.4F/g。     

热解活化法制备微孔发达椰壳活性炭及其吸附性能研究

以椰壳为原料,采用热解活化法制备微孔发达活性炭。研究了活化温度、活化时间对活性炭孔结构和吸附性能的影响。实验结果表明:活化温度为900℃,活化时间为4 h,可制得比表面积为994.42 m2/g的微孔发达活性炭,其碘吸附值为1 295 mg/g,亚甲基蓝吸附值为135 mg/g。N2吸附结果表明活性炭的平均孔径在2 nm左右,总孔容积为0.503 9 cm3/g,其中微孔容积为0.430 3 cm3/g,微孔率达85.39%。对该活性炭进行CO2动态吸附实验,CO2饱和吸附容量为56.61 mg/g,在热解活化法制备椰壳过程中,随着活化温度的升高和活化时间的延长,活性炭的得率有不同程度的降低。     

Pore structure and the properties of electric double layer capacitor electrode of bamboo-derived activated carbon prepared by superheated steam

Bamboo-derived activated carbon prepared by superheated steam (BAC) exhibited performance for utilization as an electric double layer capacitor (EDLC) electrode. Pore structure and EDLC performances were investigated by comparison with phenol resin-derived activated carbon (MSP-20), which is commercially available and often used for the purpose. The nitrogen adsorption isotherm showed that BAC had a large BET-specific surface area of 1268 g/m² with a developed pore structure, especially of the mesopore, in comparison with MSP-20. It is considered that inherent ash in bamboo promoted activation, in addition to physical activation by superheated steam. Capacitance per electrode volume (C_V) was 52 F/cm³ with BAC. Because the density of BAC is high (0.78 g/cm³) compared with that of MSP-20 (0.58 g/cm³), sufficient C_V for usage was obtained, although the capacitance per electrode mass (C_M) at 5 mA/cm² itself of BAC (67 F/g) was lower than that of MSP-20 (126 F/g). With IR drop, the resistance value of BAC (9.7 Ω) was lower than that of MSP-20 (10.5 Ω). Especially, the diffusion resistance of BAC disclosed to be smaller than that of MSP-20. These results indicated that BAC produced by steam activation is a promising material with a pore structure suitable for ion transfer in EDLC.     

Response surface methodology approach for methyl orange dye removal using optimized Acacia mangium wood activated carbon

The existing approach of response surface methodology was extended to study the adsorption of methyl orange dye on optimized Acacia mangium wood-based activated carbon with a Brunauer, Emmett and Teller surface area of 1,767 m²/g. The experiments were carried out in a batch system, and the optimal condition was determined by means of the face-centered central composite design of response surface methodology. The effect of activated carbon dose, temperature and contact time on the adsorption capacity and percentage removal of methyl orange dye molecules were optimized. The experimental results indicated that the optimal conditions for the maximum adsorption capacity were 0.515 g/L, 55.0 °C and 24 h for adsorbent dose, temperature and contact time, respectively. Under these conditions, the maximum adsorption capacity and percentage removal were found to be 181 mg/g and 90.5 %, respectively. At optimized conditions of methyl orange dye removal, studies of the kinetic and thermodynamic behavior of adsorption revealed that it followed the pseudo-second-order rate model and was spontaneously endothermic in nature.     

原料粒径与含水率对磷酸法活性炭性能的影响

以核桃壳和杏壳为原料,采用磷酸法制备活性炭,以亚甲基蓝吸附值、碘吸附值和得率为指标,研究了原料粒径和含水率对磷酸法活性炭性能的影响。结果表明:原料的粒径和含水率对活性炭的吸附性能有重要影响,在一定范围内减小原料粒径,对提高活性炭吸附性能有利,而原料含水率对活性炭吸附性能的影响因不同原料而异。增加原料含水率,对核桃壳活性炭吸附性能的提高有利,但会降低小粒径杏壳活性炭的吸附性能。以核桃壳为原料制备活性炭时,选择粒径0.5~0.7 mm、含水率11%的原料为佳,得率可达41%,亚甲基蓝吸附值230 mg/g,碘吸附值874 mg/g;以杏壳为原料制备活性炭时,选择粒径0.7~1.2 mm、烘干的原料为佳,得率可达42%,亚甲基蓝吸附值87 mg/g,碘吸附值734 mg/g。     

糯米灰浆粘结型富钙成型活性炭的制备及其性能

利用造纸白泥原位物理活化杉木屑制备富钙活性炭粉,考察了制备工艺条件对活性炭粉得率和吸附性能的影响。在富钙活性炭粉中加入糯米浆进行捏合并压制成型,制得糯米灰浆粘结型柱状成型活性炭。在白泥与杉木屑质量比3∶2,950℃活化1.5 h的优化条件下,可制备出比表面积为975 m~2/g、得率约24%的活性炭样品。经300℃热处理1 h后制得的糯米灰浆粘结型富钙成型活性炭,其抗压强度高达18 MPa,碘吸附值为410 mg/g,耐水浸泡性长达60 d以上。SEM和XRD分析结果显示:糯米灰浆粘结成型活性炭中各组分间胶结紧密,且糯米浆对成型活性炭试样中石灰组分的炭化结晶进程具有调控作用。     

KOH微波活化法处理竹炭的研究

研究了以自制的快速裂解产物竹炭为原料,采用KOH-微波辐射活化法制备竹质活性炭.利用正交试验探讨了不同因素对竹质活性炭性质的影响.最佳工艺条件为KOH质量分数 25 %,浸渍时间 24 h,微波功率 800 W,活化时间 7 min,所制备的活性炭产品的碘吸附值为 1 239.08 mg/g,亚甲基蓝吸附值为 274.95 mg/g,比表面积为 1 394.16 m2/g,亚甲基蓝吸附值为国家一级品标准(GB/T 13803.2-1999)的2.04倍,同时测定了活化前后竹炭的红外光谱.结果表明,活化后竹炭表面结构有了较大的修饰,增加了较多的表面化学官能团,从而提高了竹炭的比表面积和吸附性能.     

磷酸氢二铵活化法制备活性炭的研究

以杉木屑为原料,采用磷酸氢二铵活化法制备活性炭。讨论了预处理温度、浸渍比和活化温度对活性炭碘吸附值的影响。结果表明,随着预处理温度、浸渍比和活化温度的升高,活性炭的碘吸附值均呈先升后降的趋势。在较佳生产工艺条件下:预处理温度160℃,浸渍比1.25:1,活化温度450℃,活性炭的碘吸附值达到930.2mg·g^-1。     

硼酸催化制备木屑活性炭工艺及孔结构特征

以木屑为原料,磷酸为活化剂,硼酸为催化剂制备活性炭。通过正交实验考察了活性炭制备过程中磷屑比、硼酸添加量,活化温度和活化时间等因素对活性炭性能的影响。实验结果表明:生产活性炭的最佳工艺条件为磷屑比为1.5∶1,硼酸的添加量为1%,活化温度是400℃,活化时间为60 min,此时活性炭的得率为33.5%,亚甲基蓝吸附值为225 mg/g,碘吸附值为855 mg/g。添加硼酸的制备方法要比传统的用磷酸制备时的条件更加温和,通过调整工艺条件,可以改变活性炭产品的孔隙结构,生产出用于不同环境的液相吸附专用活性炭。     

Removal of Cr(VI) from aqueous solutions by larch bark

The ability of larch (Larix leptolepis Gold.) bark to remove Cr(VI) from dilute aqueous solutions was investigated. The research parameters included the solution pH, contact time, temperature and initial concentration of Cr(VI) in solution. Of the parameters studied, the solution pH was found to be the most crucial. The Cr(VI) removal decreased steadily throughout the pH range studied (pH 2–6), while the Cr adsorption peaked at pH 3. Because the chemical reduction of Cr(VI) to trivalent state occurred to lesser extents even in strong acidic media, the Cr(VI) removal was mainly governed by physico-chemical adsorption. The positive value of the heat adsorption (ΔH ⁰) indicates the endothermic nature of the Cr(VI) adsorption. The relatively slow rate and irreversible nature of the adsorption as well as the order of the magnitude of the heat adsorption value suggest that the adsorption is of a chemical type. The adsorption data obtained from the equilibrium experiments were well fitted to both the Langmuir and Freundlich isotherms.     

Microbial conversion of bamboo hemicellulose hydrolysate to xylitol

A hemicellulose hydrolysate containing 19 g L^?1 xylose was prepared from the culm of bamboo (Phyllostachys pubescens) by hydrolysis with 3 % sulphuric acid with a liquor to solid ratio of 10 (g g^?1) at 121 °C for 1 h. After detoxification of the hydrolysate with a commercially available activated char followed by neutralisation with calcium carbonate, the resulting sugar solution was subjected to fermentation using the yeast, Candida magnoliae. The maximum xylitol production (10.5 g L^?1) and the maximum xylitol volumetric productivity (0.42 g L^?1 h^?1) were attained under agitation set at 400 min^?1 and aeration rate of 0.67 vvm (volume of air per volume of medium per minute). According to the results, a suitable control of the oxygen supply permits the xylitol formation from bamboo hemicellulose hydrolysate.     

薄皮核桃壳基活性炭的制备及表征

【目的】以农林废弃物薄皮核桃壳为原料,通过化学活化-高温炭化法制备多孔活性炭材料,优化制备工艺过程,表征吸附性能机理,为薄皮核桃壳的开发利用提供技术指导。【方法】以碘吸附值和亚基甲蓝吸附值为考察指标,进行活化剂的筛选,并进一步考察原料粒度、料液比、活化时间、炭化温度和炭化时间对制备出的活性炭的吸附性能的影响。采用N2吸附-脱附等温线、元素分析仪和FTIR测定了活性炭的孔隙结构、主要元素组成和表面官能团,扫描电镜分析形貌结构,XRD和TG分析活性炭的结晶度和热稳定性。【结果】选用磷酸为最佳活化剂,薄皮核桃壳活性炭的最佳制备工艺条件为:核桃壳粉100目、料液比1:4、活化时间120 min、炭化温度500℃、炭化时间60 min,此工艺条件下制备出的活性炭的碘吸附值为657.42±3.16 mg/g、亚甲基蓝吸附值为248.55±1.94 mg/g。制备出的活性炭的表面积为449.80 m2/g,具有丰富的孔隙结构,孔容积为1.11 m2/g,平均孔径为7.87 nm。碳元素含量为65.56%,结晶度不高,为无定型结构,活性炭在400℃左右发生热降解,主要含有羧基、酚基、醇羟基等活性官能团。【结论】采用磷酸活化法制备出的薄皮核桃壳活性炭的孔隙结构发达,具有良好的吸附性能,碘吸附值和亚甲基蓝吸附值均高于国家标准,具有将废弃物资源循环利用的价值和前景。     

Curing kinetics study of melamine–urea–formaldehyde resin/liquefied wood

The objective of this research was to investigate the effect of liquefied wood (LW) on the cure kinetics and network properties of melamine–urea–formaldehyde (MUF) resins by differential scanning calorimetry. The MUF/LW compounds exhibited two distinct cross-linking processes. It can be assumed that there did not appear to be a coreaction of the MUF with the LW. The overall apparent activation energies (E _a) of the curing reactions were calculated using the Kissinger equation. An nth-order kinetic model was used to describe the cross-linking of MUF/LW compounds, of various compositions, cured at different heating rates. The E _a values for the cross-linking process of the MUF/LW compounds predominantly tended to be approximately 80 and 71 kJ mol^?1 for MUF and LW, respectively. The apparent reaction orders of the MUF cross-linking process of the MUF/LW compounds were in the range 1–2, whereas the n values of the LW were approximately unity or less, which hints to there being a more complex mechanism of this process.     

微波辐射竹节磷酸法制备活性炭的研究

研究了以竹节废料为原料，采用微波辐射磷酸法制备活性炭的可行性。探讨了微波功率、活化时间及磷酸浓度对产品活性炭各项指标的影响。得到了微波辐射磷酸法制备活性炭的最佳工艺：微波功率560W、活化时间9min、磷酸质量分数40％。用此工艺条件制得的活性炭碘吸附值889．0mg/g、亚甲基蓝脱色率178mL／g、得率31．0％。该工艺所需活化时间为传统方法的1／45，产品活性炭亚甲基蓝脱色率为国家一级品标准(GB／T 12496．10-1999)的1．48倍。本工艺方法为竹节废料的综合开发利用找到了新的途径。     

Mode I interlaminar fracture property of moso bamboo (Phyllostachys pubescens)

Bamboo is a unidirectional fiber-reinforced bio-composite. Once having cracks, the delaminating propagation is not controlled by the strength but by the interlaminar fracture toughness. In this paper, the behaviors of Mode I (crack opening mode) interlaminar fracture parallel to grain of moso bamboo (Phyllostachys pubescens) were studied. Based on energy theory, the Mode I interlaminar fracture toughness, G _IC, was measured using the double cantilever beam specimens, and the fracture surfaces were examined under scanning electron microscope. The results show that: (1) the interlaminar fracture toughness of Mode I is the basic characteristic of bamboo material. The mean value of G _IC = 358 J/m² (coefficient of variation = 16.88%) represents the resistance arresting crack propagation. No significant difference was found for G _IC among the specimens located at different heights of the bamboo. (2) Due to the low G _IC of bamboo, the crack propagation parallel to grain developed easily. The crack was a self-similar fracture without fiber-bridging. On the fracture surfaces, smooth fibers and plane ground tissue were found at the extended area of Mode I fracture along the longitudinal direction. Under scanning electron microscope, it could be seen that the crack propagation developed along the longitudinal interface between fibers or ground tissue. It indicates that the longitudinal interface strength was weak among bamboo cells.     

Protein nutrition in red deer (Cervus elaphus)

Red deer can adjust to seasonal change of forage quality to maintain a relatively constant crude protein level (21.1±4.0, 14.7±1.0, 11.1±1.1 and 6.5±0.8 in spring, summer, fall and winter, respectively). Apparent protein digestibility is variable from −99.9% to 97.5% depending upon season and forage type. True protein digestibility is 99%. Digestion of protein is significantly influenced by phenolics in diets. Minimum digestible energy intake of 153.5 kcal/kg^0.75/day is necessary to maintain a positive nitrogen balance. Red deer recycles 18–85% of the urea produced and urea kinetic parameters (urea pool size urea entry rate and urea excretion rate) are correlated to plasma urea concentration. Rumen NH₃-N production changes with season, but seasonal changes in other NH₃-N kinetic parameters (NH₃-N concentration, NH₃-N pool size and NH₃-N outflow rate) are in dispute. Protein metabolism may be promoted in response to cold stress. Endogenous urinary nitrogen is 0.09 (red deer) and 0.16 g N/kg^0.75·day (elk). and metabolic fecal nitrogen is 5.58 g N/kg dry-matter intake. Protein requirements ranges from 100 g/kg DM to 170 g/kg DM for red deer of various ages and physiological stages. In conclusion, the knowledge of protein nutrition of red deer is limited. Much work is urgently needed in metabolism and requirements of protein before the appropriate feeding standard of red deer is coming.     

竹节制备提金活性炭及其表征

以竹节为原料,采用水蒸气活化法制备提金活性炭,研究温度、保温时间、水蒸气流量等因素对活性炭性能的影响,并对其孔隙结构进行表征.结果表明:随着温度和保温时间的增大,活性炭的吸附性能总体呈上升趋势;随着水蒸气流量的增加,活性炭的吸附性能呈先升后降的趋势;N_2吸附等温线的分析表明,竹节活性炭具有发达的微孔、中孔、大孔结构.在较佳的试验条件下,活性炭的强度、亚甲基蓝吸附值、碘吸附值、比表面积、总孔容积和微孔容积分别为97.5%,262 mg·g~(-1),1 072.7 mg·g~(-1),1 334.2 m~2·g~(-1),0.671 mL·g~(-1)和0.574 mL·g~(-1).     

磷酸法活性炭的三聚氰胺表面改性及其电化学性能研究

为了考察磷酸法活性炭作为双电层电容器电极材料的可行性,通过浸渍三聚氰胺后在500、700、900℃下热处理的方法对活性炭进行了表面改性,分别得到改性活性炭AC-N-500、AC-N-700、AC-N-900,考察不同热处理温度对活性炭表面氮元素结合状态的影响,及其对磷酸法活性炭作为双电层电容器电极材料的电化学性能的影响。采用氮气吸附、元素分析、X射线光电子能谱及电化学测试等方法分析表征活性炭的孔隙结构、元素组成、表面官能团存在形式以及电化学性能。结果表明:随着热处理温度的升高,改性活性炭氮元素含量逐渐下降,由AC-N-500的8.49%下降为AC-N-900的4.16%;三聚氰胺改性活性炭比表面积和总孔容明显降低。改性活性炭中氮元素主要以N-6(吡啶型)、N-5(吡咯型)、N-Q(季氮型)、N-X(氮氧型)4种形式存在;随着热处理温度的升高,N-6和N-5型官能团的比例略微减少并部分转变为N-Q。改性活性炭AC-N-700可制备出比电容达203 F/g(扫描电压1 m V/s)的活性炭电极材料,减小电极与电解液间的阻力有利于离子的渗入和电荷的传导,表明磷酸法活性炭具有作为双电层电容器电极材料的潜力。