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 %.     

Thermal treatment of sawdust and coal-tar pitch mixture to produce porous carbon materials by chemical activation

In this work, different activated carbons were prepared from composites based on birch sawdust and coal-tar pitch by chemical activation with zinc chloride, phosphoric acid, and potassium hydroxide followed by carbonization. The influence of different chemical agents (ZnCl₂, KOH, and H₃PO₄), final temperature of carbonization and media on yield and structural properties of the carbonic product was studied. It was shown that chemical agents allow increasing yield of carbonic residue. Composite modification by H₃PO₄ or ZnCl₂ facilitates the formation of molded porous carbonic residue during the carbonization process. However, addition of KOH to the composite leads to formation of powder-like carbonic residue having a specific surface area of 1,600 m² g^?1 at 800 °C. It was established that all samples aged in air medium at 800 °C have higher values of specific surface area in comparison with the same samples aged in argon medium at similar conditions.     

Electromagnetic shielding wood-based composite from electroless plating corrosion-resistant Ni–Cu–P coatings on Fraxinus mandshurica veneer

A novel and simple electroless Ni–Cu–P plating process was used for preparing corrosion-resistant and electromagnetic interference shielding wood-based composite. The effects of CuSO₄·5H₂O concentration, pH value in the plating solution and operation temperature on the metal deposition, surface resistivity, chemical composition, corrosion resistance and surface morphology of the composite were investigated. The surface morphologies were observed by using scanning electron microscopy and the chemical compositions were analyzed by X-ray energy dispersive spectrometer. The electromagnetic shielding effectiveness (ESE) was measured by spectrum analyzer. The corrosion resistance was evaluated by potentiodynamic corrosion measurement. The results show that metal deposition increases with pH value and temperature increase; however, it decreases with CuSO₄·5H₂O concentration increase. The corrosion resistance of the plated Ni–Cu–P coatings obviously depends on the total content of Cu and P in the coating. Higher total content of Cu and P leads to higher corrosion resistance. The optimum conditions are as follows: CuSO₄·5H₂O concentration of 1.0 g/L, pH value of 9.5, and operation temperature of 90 °C. The obtained coating contains 77.41 % Ni, 8.96 % Cu, and 13.63 % P. The wood-based composite exhibits higher corrosion resistance and ESE of around 60 dB in frequencies ranging from 9 kHz to 1.5 GHz. In this paper, a promising process for corrosion-resistant and electromagnetic shielding wood-based composites was developed.     

Study of Cr(VI) adsorption onto nitrogen-containing activated carbon preparation from bamboo processing residues

Nitrogen-containing bamboo charcoals were prepared using bamboo processing residues, and modified by melamine or urea. The iodine value of the products we obtained was analyzed, and two samples were chosen for the Cr(VI) adsorption. The experimental results show that under the KOH and carbon ratio of 3:1 (w₁/w₂), activation temperature 800 °C and activation time 1 h, the activated carbons modified by melamine boasted the iodine value of 1144 mg/g and the activated carbons modified by urea boasted the iodine value of 1263 mg/g. In addition, the equilibrium adsorption capacity is 95.3 mg/g for the activated carbons modified by melamine with the adsorbent dosage of 1.0 g/L at an initial pH 2 in the presence of 100 mg/L K₂Cr₂O₇ at 30 °C for 180 min and it is 94.2 mg/g for the activated carbons modified by urea in the same reaction condition. The pseudo-second-order kinetic model can better reflect the two kinds of nitrogen-containing activated carbons adsorption kinetic process of Cr(VI). The adsorption process conforms to the Langmuir model, indicating that the process is single molecular layer adsorption.     

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.     

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.     

Seasonal dynamics and impact factors of urban forest CO<Subscript>2</Subscript> concentration in Harbin,China

CO₂ concentrations in different plant communities (larch, birch, lilac, and grassland) were measured during the growing season in the Heilongjiang Forest Botanical Garden to study diurnal variation, seasonal and annual dynamics and factors that impact CO₂ concentration in different spaces. CO₂ concentration in different communities in green lands had an obvious diurnal variation, chronically decreasing, and temperature influenced the lilac area and the grassland. Seasonally, CO₂ was lowest in the larch green land (344.03 ± 23.03 μmol/mol) and highest in the grassland (360.13 ± 22.43 μmol/mol). The overall trend in CO₂ concentration was autumn > spring > summer; temperature is the main factor controlling variation in CO₂ concentrations during the growing season; the CO₂ concentration at the larch, birch, lilac, and grassland types of sites was negatively correlated with land surface temperature and air temperature, and the CO₂ concentration at the larch and birch sites was positively correlated with atmospheric pressure. Without any obvious annual change law, further study and observation are needed.     

Effect of multipurpose tree species on soil fertility and CO2 efflux under hilly ecosystems of Northeast India

A 26 years old agroforestry plantation consisting of four multipurpose tree species (MPTs) (Michelia oblonga Wall, Parkia roxburghii G. Don, Alnus nepalensis D. Don, and Pinus kesiya Royle ex-Gordon) maintained at ICAR Research Complex, Umiam, Meghalaya, India were compared with a control plot (without tree plantation) for soil fertility status and CO₂ efflux. The presence of trees improved all the physico-chemical and microbial biomass parameters studied in this experiment. Relative to control, soils under MPTs showed significant increases of 17 % soil organic carbon, 26 % available nitrogen (AN), 28 % phosphorus (AP), 50 % potassium (AK), 65 % mean weight diameter (MWD) of aggregates, 21 % moisture and 34 % soil microbial biomass carbon (MBC) while reducing the mean bulk density (7 %). However, these parameters significantly differed among the tree species i.e., soils under A. nepalensis and M. oblonga had higher values of these attributes except bulk density, than under other species. Irrespective of treatments, the values of all these attributes were higher in surface soils while bulk density was highest in subsurface (60–75 cm). Cumulative CO₂ efflux under MPTs was significantly higher (15 %) and ranged from 1.71 g 100 g^?1 (M. oblonga) to 2.01 g 100 g^?1 (A. nepalensis) compared to control at 150 days of incubation. In all the treatments, increment in temperature increased the oxidation of soil organic matter, thereby increased the cumulative CO₂ efflux from soils. Of the tree species, with increment in temperature, A. nepalensis recorded more CO₂ efflux (2.50 g 100 g^?1) than other MPTs but the per cent increase was more in control plot. P. kesiya and A. nepalensis recorded highest activation energy (59.1 and 39 kJ mol^?1, respectively). Net organic carbon sequestered in soil was highest under A. nepalensis (25.7 g kg^?1) followed by M. oblonga (19.3 g kg^?1), whereas control showed the lowest values. Amount of net carbon stored in the soil had significant and positive correlation with MBC (r = 0.706**), MWD (r = 0.636*), and AN (r = 0.825**).     

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.     

Soil properties and microbial functional structure in the rhizosphere of Pinus densiflora (S. and Z.) exposed to elevated atmospheric temperature and carbon dioxide

Rhizosphere-induced changes of Pinus densiflora (S. and Z.) grown at elevated atmospheric temperature and carbon dioxide are presented based on experiments carried out in a two-compartment rhizobag system filled with forest soil in an environmentally controlled walk-in chamber with four treatment combinations: control (25°C, 500 μmol mol^?1 CO₂), T2 (30°C, 500 μmol mol^?1 CO₂), T3 (25°C, 800 μmol mol^?1 CO₂), and T4 (30°C, 800 μmol mol^?1 CO₂). Elevated temperature and atmospheric carbon dioxide resulted in higher concentration of sugars and dissolved organic carbon in soil solution, especially at the later period of plant growth. Soil solution pH from the rhizosphere became less acidic than the bulk soil regardless of treatment, while the electrical conductivity of soil solution from the rhizosphere was increased by elevated carbon dioxide treatment. Biolog EcoPlate? data showed that the rhizosphere had higher average well color development, Shannon–Weaver index, and richness of carbon utilization compared with bulk soil, indicating that microbial activity in the rhizosphere was higher and more diverse than in bulk soil. Subsequent principal component analysis indicated separation of soil microbial community functional structures in the rhizosphere by treatment. The principal components extracted were correlated to plant-induced changes of substrate quality and quantity in the rhizosphere as plants’ response to varying temperature and atmospheric carbon dioxide.     

氢氧化钠活化杉木屑制备活性炭的研究

采用杉木屑为原料,氢氧化钠为活化剂制备木质活性炭产品,探讨活化时间、活化温度、氢氧化钠浓度等工艺参数对木质活性炭的得率和吸附性能的影响.结果 表明,随活化温度、氢氧化钠浓度和活化时间的增大,木质活性炭的得率呈不断下降的趋势,木质活性炭的吸附性能呈先上升后下降的趋势.较优的工艺条件为:活化温度850℃、活化时间1.0h、...     

KOH活化木材苯酚液化物炭纤维的制备与孔结构分析

为了考察碱／炭比、炭化温度以及活化温度对活性炭纤维孔结构的影响,以木粉为原料经液化、纺丝、固化、炭化及KOH活化工艺过程制备了木材苯酚液化物活性炭纤维;采用正交实验方法优化了活性炭纤维制备工艺。结果表明：诸因素中的显著性依次为活化温度〉炭化温度〉碱／炭比;优化组活性炭纤维的比表面积为1546m^2／g;400℃炭化温度下制备的活性炭纤维具有较高的中孔比率。     

Response of soil respiration to a severe drought in Chinese <Emphasis Type="Italic">Eucalyptus</Emphasis> plantations

Extreme droughts can adversely affect the dynamics of soil respiration in tree plantations. We used a severe drought in southwestern China as a case study to estimate the effects of drought on temporal variations in soil respiration in a plantation of Eucalyptus globulus. We documented a clear seasonal pattern in soil respiration with the highest values (100.9 mg C–CO₂ m^?2 h^?1) recorded in June and the lowest values (28.7 mg C–CO₂ m^?2 h^?1) in January. The variation in soil respiration was closely associated with the dynamics of soil water driven by the drought. Soil respiration was nearly twice as great in the wet seasons as in the dry seasons. Soil water content accounted for 83–91% of variation in soil respiration, while a combined soil water and soil temperature model explained 90–99% of the variation in soil respiration. Soil water had pronounced effects on soil respiration at the moisture threshold of 6–10%. Soil water was strongly related to changes in soil parameters (i.e., bulk density, pH, soil organic carbon, and available nitrogen). These strongly influenced seasonal variation in soil respiration. We found that soil respiration was strongly suppressed by severe drought. Drought resulted in a shortage of soil water which reduced formation of soil organic carbon, impacted soil acid–base properties and soil texture, and affected soil nutrient availability.     

Potassium acetate-catalyzed acetylation of wood: reaction rates at low temperatures

Spruce wood blocks were acetylated in the presence of potassium acetate (KAc) at 20, 40, 60, 80 and 120°C. At 20°C, the weight percent gain (WPG) due to the KAc-catalyzed acetylation reached 20% in 18 days, whereas that due to pyridine-catalyzed acetylation did not exceed 8%. The hygroscopicity and dimensional stability of the KAc-acetylated wood were the same as those of conventionally acetylated wood at the same WPG, irrespective of reaction temperature. These facts suggest that the KAc enables simplified acetylation of wood at room temperature. The activation energy (E _a) of the KAc-acetylation in the lower temperature range (20–40°C, 121–131 kJ/mol) was comparable to that of the acetylation of wood meal (140–146 kJ/mol). It was speculated that diffusion became a minor factor at reduced reaction rates in the lower temperature range, thus requiring a greater E _a.     

Soil organic carbon stocks and fractions in different orchards of eastern plateau and hill region of India

Soil organic carbon (SOC) plays an important role in soil fertility and productivity. It occurs in soil in labile and non-labile forms that help in maintaining the soil health. An investigation was undertaken to evaluate the dynamics of total soil organic carbon (C _tot), oxidisable organic carbon (C _oc), very labile carbon (C frac ₁), labile carbon (C frac ₂), less labile carbon (C frac ₃), non-labile carbon (C frac ₄), microbial biomass carbon (C _mic) and SOC sequestration in a 6-year-old fruit orchards. The mango, guava and litchi orchards caused an enrichment of C _tot by 17.2, 12.6 and 11 %, respectively, over the control. The mango orchard registered highest significant increase of 20.7, 13.5 and 17.4 % in C frac ₁, C frac ₂ and C frac ₄, respectively, over control. There is greater accumulation of all the C fractions in the surface soil (0–0.30 m). The maximum total active carbon pool was 36.2 Mg C ha^?1 in mango orchard and resulted in 1.2 times higher than control. The passive pool of carbon constituted about 42.4 % of C _tot and registered maximum in the mango orchard. The maximum C _mic was 370 mg C kg^?1 in guava orchard and constituted 4.2 % of C _tot. The carbon management index registered 1.2 (mango orchard)- and 1.13 (guava and litchi orchard)-fold increase over control. The mango orchard registered highest carbon build rate of 1.53 Mg C ha^?1 year^?1 and resulted in 17.3 % carbon build-up over control. Among the carbon fractions, C frac ₁ was highly correlated (r = 0.567**) with C _mic.     

机械力化学法制备氯化锌法活性炭及其性能表征

研究利用机械力化学技术制备了性能良好的活性炭。采用Central Composite Design中心复合设计和响应面分析,对影响活性炭碘吸附值的主要影响因素进行多项回归模型建立和参数优化,并通过低温液氮(N2/77 K)吸附测定较优条件下制备的活性炭的比表面积、孔容及孔径分布。结果表明,利用氯化锌为活化剂的机械力化学技术制备活性炭的较优工艺条件为:氯化锌与绝干木屑的质量之比(锌屑比)值3.00,研磨时间10 min,活化温度584℃,活化时间2.5 h,此条件下制备的活性炭碘吸附值为1 262.47 mg/g。     

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。     

Carbon dioxide fluxes across the Sierra de Guadarrama, Spain

Understanding the spatial and temporal variation in soil respiration within small geographic areas is essential to accurately assess the carbon budget on a global scale. In this study, we investigated the factors controlling soil respiration in an altitudinal gradient in a southern Mediterranean mixed pine–oak forest ecosystem in the north face of the Sierra de Guadarrama in Spain. Soil respiration was measured in five Pinus sylvestris L. plots over a period of 1 year by means of a closed dynamic system (LI-COR 6400). Soil temperature and water content were measured at the same time as soil respiration. Other soil physico-chemical and microbiological properties were measured during the study. Measured soil respiration ranged from 6.8 to 1.4 μmol m^?2 s^?1, showing the highest values at plots situated at higher elevation. Q ₁₀ values ranged between 1.30 and 2.04, while R ₁₀ values ranged between 2.0 and 3.6. The results indicate that the seasonal variation of soil respiration was mainly controlled by soil temperature and moisture. Among sites, soil carbon and nitrogen stocks regulate soil respiration in addition to soil temperature and moisture. Our results suggest that application of standard models to estimate soil respiration for small geographic areas may not be adequate unless other factors are considered in addition to soil temperature.     

Nutrients leaching from green leaves of three potential agroforestry tree species

Nutrient (NH₄, PO₄ and K) leaching from oven dried green leaves of Emblica officinalis Gaerten, Sesbania grandiflora (L.) Pers. and Moringa oleifera Lam.were investigated in laboratory condition. Oven-dried green leaves were immersed in demineralized distilled water for 8 days. Electrical conductivity (EC), Total dissolved solids (TDS) and nutrients (NH₄, PO₄ and K) of leaching water samples were measured at 0.25, 0.5, 1, 2, 3, 4, 6, 8, 12, 24, 48, 72, 96, 144, and 192 h of intervals. All these species showed an increasing trend for EC and TDS in leachate and comparatively higher EC and TDS were observed in E. officinalis, which is followed, by S. grandiflora and M. oleifera. Significantly high amount (P < 0.05) of NH₄ was leached from S. grandiflora and PO₄ from M. oleifera. But, both S. grandiflora and M. oleifera leached significantly higher (P < 0.05) K than E. officinalis. Within the first 0.25 h, 100 % and 82 % of NH₄ and 68 % and 74 % of K were leached from leaves of S. grandiflora and M. oleifera respectively. S. grandiflora and M. oleifera leached 100 % of PO₄ within 6 h. The concentrtions of NH₄, PO₄ and K in the leachate from E. officinalis, S. grandiflora and M. oleifera were not significantly different (P > 0.05). The green leaves of S. grandiflora and M.oleifera can be a potential source of NH₄, PO₄ and K for a quick nutrient supplement to the agricultural crops in agroforestry practices.     

The impact of the environmental factors on the photosynthetic activity of common pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis>) in spring and in autumn in the region of Eastern Siberia

The taiga coniferous forests of the Siberian region are the main carbon sinks in the forest ecosystems. Quantitatively, the size of the carbon accumulation is determined by the photosynthetic productivity, which is strongly influenced by environmental factors. As a result, an assessment of the relationship between environmental factors and photosynthetic productivity makes it possible to calculate and even predict carbon sinks in coniferous forests at the regional level. However, at various stages of the vegetative period, the force of the connection between environmental conditions and the productivity of photosynthesis may change. In this research, correlations between the photosynthetic activity of Scots pine (Pinus sylvestris L.) with the environmental conditions were compared in spring and in autumn. In spring, close positive correlation of the maximum daily net photosynthesis was identified with only one environmental factor. For different years, correlations were for soil temperature (r_s = 0.655, p = 0.00315) or available soil water supply (r_s = 0.892, p = 0.0068). In autumn within different years, significant correlation was shown with two (temperature of air and soil; r_s = 0.789 and 0.896, p = 0.00045 and 0.000006, respectively) and four factors: temperature of air (r_s = 0.749, p = 0.00129) and soil (r_s = 0.84, p = 0.00000), available soil water supply (r_s = 0.846, p = 0.00013) and irradiance (r_s = 0.826, p = 0.000001). Photosynthetic activity has a weaker connection with changes in environmental factors in the spring, as compared to autumn. This is explained by the multidirectional influence of environmental conditions on photosynthesis in this period and by the necessity of earlier photosynthesis onset, despite the unfavorable conditions. This data may be useful for predicting the flow of carbon in dependence on environmental factors in this region in spring and in autumn.