EDTA-nSiO2纳米颗粒对Cd2+的吸附

nSiO_2纳米颗粒是一种广泛应用的工程纳米材料,为增加其对水溶液中Cd~(2+)的吸附性能,采用接枝改性的方法制备出乙二胺四乙酸(EDTA)改性nSiO_2纳米颗粒(EDTA-nSiO_2),并用透射电镜、氮气吸附-解吸、红外光谱和差热分析等手段对其进行了结构表征,同时以其为吸附剂,通过批处理实验法探讨了体系pH、吸附时间、温度、离子强度等因素对Cd~(2+)吸附的影响,并结合X射线能谱(XPS)分析对其吸附机制进行了分析.结果表明,以EDTA为改性剂,可以成功制备出稳定性良好的EDTA-nSiO_2纳米颗粒,其对Cd~(2+)的吸附受体系p H控制;nSiO_2对Cd~(2+)的吸附量较小,EDTA改性可增加nSiO_2对Cd~(2+)的吸附作用,随着p H的升高,Cd~(2+)的吸附效果逐渐增强,在p H大于4.0后逐渐趋于稳定.EDTA-nSiO_2对Cd~(2+)的吸附速率较快,可在1 h内达到吸附平衡.EDTA-nSiO_2对Cd~(2+)的吸附为吸热的自发过程,吸附等温线可用Langmuir模型描述.NaCl浓度增加会导致Cd~(2+)的吸附量下降,当体系Na Cl浓度从0增加到100 mmol·L~(-1),Cd~(2+)的最大吸附量从0.433 mmol·g-1降低至0.294mmol·g-1.0.1 mol·L~(-1)HCl是较为合适的吸附剂再生液,Cd~(2+)洗脱率约94.36%.结合pH、温度、离子强度、再生和XPS分析结果,可以推测出EDTA-nSiO_2对Cd~(2+)的吸附是包含有简单的物理吸附和离子交换过程,并以化学络合为主的吸附过程.EDTA-nSiO_2是一种对水体Cd~(2+)具有较好吸附能力的工程纳米材料吸附剂.     

Characterizations of the Photocatalytically-Oxidized Cross-Linked Chitosan-Glutaraldehyde and its Application as a Sub-Layer in the TiO2/CS-GLA Bilayer Photocatalyst System

Photocatalytically-oxidized cross-linked chitosan-glutaraldehyde (CS-GLA) was obtained via irradiation of a simple assemblage of an immobilized layer-by-layer TiO₂/CS-GLA system on a glass plate with a 45-W fluorescent lamp. The oxidation process was observed to occur only in the presence of oxygen and TiO₂ within 5 cycles (10 h) of irradiation. Characterizations studies of the oxidized cross-linked polymer involving swelling index, pH-potentiometric titration and ionic conductivity measurements, as well as CHN, FTIR, ¹³C solid-state NMR,UV–Vis DRS and photoluminescence spectroscopy analyses generally indicated that the oxidation led to the formation of carbonyl groups, partial elimination of some un-reacted amino groups and change of visual color to be more brown without altering much of the whole molecular structure of the CS-GLA. This study also indicated that the photocatalytic performance of TiO₂/oxidized CS-GLA system was higher than both TiO₂/CS-GLA system and TiO₂ single layer for the removal of phenol. Moreover, the adsorption effect was extremely negligible and the photodegradation of phenol was mainly due to the photocatalytic process.     

Assessment of sunflower germplasm for phytoremediation of lead-polluted soil and production of seed oil and seed meal for human and animal consumption

Phytoremediation is a valuable technology for mitigating soil contamination in agricultural lands,but phytoremediation without economic revenue is unfeasible for land owners and farmers.The use of crops with high biomass and bioenergy for phytoremediation is a unique strategy to derive supplementary benefits along with remediation activities.Sunflower(Helianthus annuus L.) is a high-biomass crop that can be used for the phytoremediation of polluted lands with additional advantages(biomass and oi...     

Selective removal of some polyhydric phenols from aqueous solution by ferric antimonate

Ferric antimonate, a cation-exchanger, has been investigated as an adsorbent for the removal of phenol and polyhydric phenols from aqueous solution. It has been found that ferric antimonate in H+ form selectively adsorbs polyhydric phenols having hydroxyl groups on adjacent positions. While phenol, resorcinol, and quinol did not show any appreciable adsorption, catechol, pyrogallol, and gallic acid having hydroxyl groups on adjacent positions exhibited considerable adsorption on ferric antimonate. Batch equilibrium experiments were carried out to study the effect of contact time, initial concentration of phenolic compounds, and temperature on the adsorption of phenolic compounds on ferric antimonate. The equilibrium time was found to be 1.5 hours for gallic acid and pyrogallol and 2 hours for catechol and salicylic acid. The adsorption data of the phenols at temperatures of 30 degrees, 40 degrees, and 50 degrees C have been described by Langmuir and Freundlich isotherm models. The best fit was obtained with the Langmuir model in the whole range of concentrations studied at all temperatures, indicating a monolayer adsorption onto a homogeneous adsorption surface. On the basis of the Langmuir isotherm, the maximum adsorption capacity of ferric antimonate for gallic acid, pyrogallol, catechol, and salicylic acid was found to be 3.915, 3.734, 2.397, and 2.758 mg/g, respectively at 30 degrees C. The maximum sorption capacity of ferric antimonate for the phenolic compounds studied is in the following order: gallic acid > pyrogallol > salicylic acid > catechol. The adsorption of phenolic compounds was found to decrease with an increase in temperature. Thermodynamic parameters like free energy, enthalpy, and entropy changes were calculated and discussed. The adsorption of polyhydric phenols on ferric antimonate is exothermic and spontaneous in nature.     

Optimized processing power and trainability of neural network in numerical modeling of Al Matrix nano composites

In this research, an experimental study of reinforcing alumina nano-particles into the aluminum alloy matrix was implemented to verify the accuracy of modeling results obtained by feed forward neural networks. Artificial neural network combined with numerical technique were used to predict the various parameters of mechanical properties such as hardness, tensile and compressive yield stress, UTS and elongation percentage. Much experimentation were taken to discover a suitable number of hidden neurons, avoid detraction from the trainability and enable feed forward neural networks to solve more complex problems. The predictions were found to be consistent with experimental measurements.     

全球价值链视角下中国农产品贸易隐含氮、磷、钾研究

基于GTAP数据库提供的多区域投入产出表,采用全球价值链方法测算中国农产品贸易中隐含的化肥转移,并按照农产品最终消费的地理位置将其分解为四部分。研究发现：（1）中国农产品进口为国内节约640万t化肥（占我国化肥用量的13%）,同时引起全球化肥用量节约285万t,为缓解全球资源和环境压力做出贡献;（2）中国农产品贸易深度参与全球价值链,进口农产品中隐含的化肥有12%会再次出口到全球,意味着农产品贸易背后隐含的资源到达中国后会再次出口,形成多次跨境转移。建议在全球价值链视角下更为客观地估算农产品贸易隐含的化肥及其他资源环境问题,倡导共同承担贸易引致的资源环境问题。     

Adsorption of Disperse Blue SBL dye by synthesized poorly crystalline hydroxyapatite

The present study has been undertaken to evaluate the adsorption in batch mode of a disperse dye (Disperse Blue SBL) by poorly crystalline hydroxyapatite synthesized by coprecipitation between Ca(NO_3)_2 and (NH_4)_2HPO4 reagents in aqueous solution at room temperature. The adsorption experiments were carried out to investigate the factors that influence the dye uptake by the adsorbent, such as the contact time under agitation, adsorbent dosage, initial dye concentration, solution temperature, and pH. The e...     

黄土丘陵区林草退耕年限对土壤团聚体特征的影响

随着国家退耕还林还草战略的实施、植被覆盖的变化,林、草地植被恢复进程中土壤团聚体特征的变化受到广泛关注.本研究以黄土丘陵区西部的官山林场退耕后栽植的刺槐林地、撂荒草地为对象,选取退耕年限为10、25 a的林、草地,采用湿筛法测定各样地0~30 cm土壤的水稳性团聚体组成,比较退耕还林、还草和退耕年限(10、25 a)对土壤水稳性团聚体平均质量直径(MWD)和分形维数(D)的影响.结果表明:退耕10 a的林地0~30 cm土层水稳性大团聚体含量(R0.25)、MWD和D分别为57.60%、1.91 mm和2.73;退耕25 a的林地分别为60.17%、1.88 mm和2.74;退耕10 a的草地分别为59.89%、1.82 mm和2.74;退耕25 a的草地分别为72.69%、2.71 mm和2.61.进一步分析证明,随着退耕年限的增加,土壤团聚性增强;但林草地的变化存在差异:恢复10 a阶段,土壤团聚性林地尚优于草地,25 a后草地优于林地.各样地土壤的SOC含量与R0.25呈显著正相关关系(p0.01),与D呈显著负相关关系(p0.05).退耕类型和退耕年限对土壤团聚性有显著影响.     

Compositing climate change vulnerability of a Mediterranean region using spatiotemporally dynamic proxies for ecological and socioeconomic impacts and stabilities

The study presents a new methodology to quantify spatiotemporal dynamics of climate change vulnerability at a regional scale adopting a new conceptual model of vulnerability as a function of climate change impacts, ecological stability, and socioeconomic stability. Spatiotemporal trends of equally weighted proxy variables for the three vulnerability components were generated to develop a composite climate change vulnerability index (CCVI) for a Mediterranean region of Turkey combining Landsat time series data, digital elevation model (DEM)-derived data, ordinary kriging, and geographical information system. Climate change impact was based on spatiotemporal trends of August land surface temperature (LST) between 1987 and 2016. Ecological stability was based on DEM, slope, aspect, and spatiotemporal trends of normalized difference vegetation index (NDVI), while socioeconomic stability was quantified as a function of spatiotemporal trends of land cover, population density, per capita gross domestic product, and illiteracy. The zones ranked on the five classes of no-to-extreme vulnerability were identified where highly and moderately vulnerable lands covered 0.02% (12 km²) and 11.8% (6374 km²) of the study region, respectively, mostly occurring in the interior central part. The adoption of this composite CCVI approach is expected to lead to spatiotemporally dynamic policy recommendations towards sustainability and tailor preventive and mitigative measures to locally specific characteristics of coupled ecological–socioeconomic systems.     

The role of land use change on the sustainability of groundwater resources in the eastern plains of Kurdistan,Iran

In this study, land use change and its effects on level and volume of groundwater were investigated. Using satellite images and field measurements, change in land uses was determined from 1998 to 2007. By analyzing the observation wells data and preparing the zoning maps in GIS, groundwater level fluctuations were assessed. Considering the area corresponding to these fluctuations, changes in aquifers volume were calculated. The rain gauge and synoptic stations data were used to calculate meteorological parameters and evapotranspiration. The water requirement of the main crops was determined by CROPWAT software. Results showed an increase in average rainfall and crops water requirement. The classification of satellite images showed that 11,800 ha was increased in lands under irrigated crops cultivation, while 27,655 ha of rangeland was declined in the region. Groundwater levels dropped an average of 7 m, equal to 63.4 MCM reductions in volume of water in the aquifer.