巯基改性生物炭对水中甲基汞的吸附

为探讨巯基改性生物炭对甲基汞的吸附特征及机理,以牛粪、污泥、竹屑为原料制备热解生物炭,并利用3-巯丙基三甲氧基硅烷分别对其改性,采用元素分析、电镜扫描和傅里叶变换红外光谱仪对改性前后的生物炭进行表征,结合等温吸附实验和吸附动力学实验,对比研究不同原料改性生物炭对甲基汞的吸附性能并探讨其吸附机理。结果表明:通过O—Si基团的成功引入证明巯基改性成功,巯基改性后的生物炭对甲基汞的吸附能力增强,主要归因于含硫基团(—SH、C—S)与甲基汞离子有较强的络合能力。改性后,3种生物炭对甲基汞的吸附符合准二级吸附动力学和Langmuir等温吸附方程。巯基改性生物炭对甲基汞的最大拟合吸附量达到526~1450ng·g^-1,显著高于未改性生物炭(331~533 ng·g^-1),改性组生物炭的吸附速率常数k₂(1.800~2.640)明显高于未改性组生物炭(0.014~0.156)。研究表明,巯基改性生物炭吸附甲基汞主要是通过其表面引入的—SH和C—S等官能团,与甲基汞形成—SHgCH₃和(CH₃Hg)₂S等络合物,从而有效去除水中甲基汞。     

活性炭对微污染水源中2,4-二氯苯酚的吸附研究

研究了振荡时间、温度、pH、腐殖酸添加量等因素对两种类型活性炭PJ-20、ZJ-15吸附微污染水源水中微量2,4-二氯苯酚效应的影响,同时对吸附等温进行Langmuir方程、Freundlich公式和BET公式曲线拟合.结果表明:PJ-20型活性炭对2,4-二氯苯酚的吸附效果稍好于ZJ-15型,温度有利于活性炭对2,4-二氯苯酚的吸附,pH值应控制在小于8的范围内,腐殖酸添加量对吸附效果也有一定的影响.     

植物塘+人工湿地+吸附池系统对灌溉水中痕量Cd的去除效果

为了降低灌溉水中Cd向农田输入,减轻农田土壤Cd污染,试验选取梭鱼草、狐尾藻、野茭白为材料,构建"植物塘+人工湿地+吸附池"系统,研究其对湖南典型矿区Cd超标灌溉水净化效果,并分析Cd在系统中的分布规律。结果表明:在2018年11月—2019年9月监测期间,进水全量Cd平均浓度为6.35μg·L~(-1),经系统净化后灌溉水中可溶态Cd、悬浮态Cd及悬浮颗粒物平均去除率分别为86.58%、90.37%和81.54%,构建的人工系统可有效降低灌溉水中Cd含量。进水口悬浮态Cd与悬浮颗粒物呈极显著正相关,悬浮颗粒物与进水流速呈显著正相关。灌溉水Cd输入总量为859.61 g,大气沉降Cd输入总量为95.34 g,处理系统拦截为865.52 g,各个单元拦截量从高到低依次为一级植物塘(544.64 g)三级人工湿地+吸附池(167.62 g)二级植物塘(156.26 g)。3种湿地植物对Cd均有较好的富集效果,富集浓度随水流方向下降。一、二级植物塘底泥最大Cd浓度分别为11.05、4.75 mg·kg~(-1),底泥中Cd弱酸可溶态比值较大,存在向水体解吸释放的风险。所构建的"植物塘+人工湿地+吸附池"净化系统可有效降低湖南典型矿区灌溉水中超标Cd含量,降低农田土壤Cd的灌溉输入通量。     

Electrons in finite-sized water cavities: hydration dynamics observed in real time

We directly observed the hydration dynamics of an excess electron in the finite-sized water clusters of (H2O)n- with n = 15, 20, 25, 30, and 35. We initiated the solvent motion by exciting the hydrated electron in the cluster. By resolving the binding energy of the excess electron in real time with femtosecond resolution, we captured the ultrafast dynamics of the electron in the presolvated ("wet") and hydrated states and obtained, as a function of cluster size, the subsequent relaxation times. The solvation time (300 femtoseconds) after the internal conversion [140 femtoseconds for (H2O)35-] was similar to that of bulk water, indicating the dominant role of the local water structure in the dynamics of hydration. In contrast, the relaxation in other nuclear coordinates was on a much longer time scale (2 to 10 picoseconds) and depended critically on cluster size.     

纤维素基吸附材料除污工艺及吸附模型研究进展

纤维素基吸附材料因其具有原料种类丰富、来源广泛、价格低廉和可循环再生等优点,在重金属和有机废水处理领域中越来越受到广泛的关注。本文以纤维素基吸附材料为对象,重点从吸附工艺及吸附模型等方面综述了其在重金属和有机污染物去除方面的研究进展,揭示了吸附工艺、吸附模型、吸附机理、吸附性能之间的内在逻辑关系。最后,总结了纤维素基吸附材料在重金属和有机废水处理领域存在的一些问题并对其应用作出了展望。     

Granular convection observed by magnetic resonance imaging

Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here.     

水土环境中微塑料对磷的吸附行为

为了探究微塑料在水体和土壤环境中对磷的吸附特性及不同因素对磷等生源物质在微塑料及土壤中赋存的影响,采用聚丙烯(PP)、聚苯乙烯(PS)这两种常见的微塑料进行吸附试验。结果表明:疏松多孔的PP拥有比PS更强的吸附性能和更大的吸附容量;两种微塑料的Zeta电位随pH的增加而降低,并且PS和PP的零电荷点(pH_(PZC))分别在pH为5.92和6.45时达到;PP、PS对磷的吸附以单层饱和吸附为主,吸附方式主要为物理吸附,并且吸附过程为放热和熵减的自发反应;微塑料对磷的单位吸附量随pH的增大呈现出先降低后升高的"U型"趋势,且温度的升高不利于PP、PS这两种微塑料对磷的吸附;随土壤中微塑料质量添加比的增加,土壤-微塑料体系对磷的吸附量增大幅度有限。研究表明,不同类型的微塑料其吸附能力存在差异,且环境因素能够对其吸附磷造成明显影响,微塑料的持续性积累对土壤-微塑料体系吸附磷的促进作用十分有限,并且这个促进作用也不会因微塑料的种类不同而产生较大差异。     

The rubble-pile asteroid Itokawa as observed by Hayabusa

During the interval from September through early December 2005, the Hayabusa spacecraft was in close proximity to near-Earth asteroid 25143 Itokawa, and a variety of data were taken on its shape, mass, and surface topography as well as its mineralogic and elemental abundances. The asteroid's orthogonal axes are 535, 294, and 209 meters, the mass is 3.51 x 10(10) kilograms, and the estimated bulk density is 1.9 +/- 0.13 grams per cubic centimeter. The correspondence between the smooth areas on the surface (Muses Sea and Sagamihara) and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting. Itokawa is considered to be a rubble-pile body because of its low bulk density, high porosity, boulder-rich appearance, and shape. The existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re-agglomeration into a rubble-pile object.     

Light flashes observed by astronauts on skylab 4

Two dedicated light flash observing sessions were conducted by one of the crewmen during the Skylab 4 mission. Analyses of his observations reveal a strong correlation between flash frequency and primary cosmic-ray flux, and an even stronger correlation between flash frequency and the South Atlantic Anomaly (SAA) region of the inner belt trapped radiation. Calculations indicate that an all-proton inner belt probably cannot produce the observed SAA flash rate, and they suggest that there may exist a previously unobserved inner belt flux of multiply charged nuclei.     

Single molecules observed by near-field scanning optical microscopy

Individual carbocyanine dye molecules in a sub-monolayer spread have been imaged with near-field scanning optical microscopy. Molecules can be repeatedly detected and spatially localized (to approximately lambda/50 where lambda is the wavelength of light) with a sensitivity of at least 0.005 molecules/(Hz)(1/2) and the orientation of each molecular dipole can be determined. This information is exploited to map the electric field distribution in the near-field aperture with molecular spatial resolution.     

Asymmetric adsorption of alanine by quartz

Radioactive D- and L-alanine hydrochloride in 10(-5) molar dimethylformamide solution was adsorbed by d- and 1-quartz to the extent of 20 to 30 percent, as shown by radioactivity loss. d-Quartz preferentially adsorbs D-alanine and 1-quartz adsorbs L-alanine. The extent of asymmetric preferential adsorption is about 1.0 to 1.8 percent, at the 99.9 percent confidence level.     

活性氧化铝对饮用水中氟离子的吸附行为

研究了WZ和KHD两种活性氧化铝对饮用水中氟离子的吸附平衡及其吸附动力学 ,利用传质理论模型对试验数据进行了处理。吸附平衡试验结果表明 ,Langmuir方程能够很好地描述WZ和KHD对氟离子的吸附平衡 ,WZ和KHD的静态饱和吸附容量分别达到 9 4 7和 6 38mg·g-1。动力学研究表明 ,氟离子在WZ和KHD上的吸附均为颗粒内孔扩散控制 ,颗粒内孔扩散过程是决定吸附速度的控制步骤 ,颗粒内孔扩散速率常数分别为 3 35×10 -2 和 2 36× 10 -2 min-1/ 2 。     

柚子皮对水中Pb(Ⅱ)吸附性能的试验研究

对柚子皮吸附去除水中Pb(Ⅱ)的模拟试验研究结果表明,pH、吸附时间、柚皮粉用量和Pb(Ⅱ)初始浓度、温度等因素对柚皮粉吸附水中Pb(Ⅱ)有显著影响.适宜的吸附条件为:pH 5.3～6.0,吸附时间1.5 h,柚皮粉用量8 g/L,Pb(Ⅱ)初始浓度50 mg/L,温度30℃.在该条件下,Pb(Ⅱ)的去除率可达到90％以上.柚皮粉对水中Pb(Ⅱ)的吸附符合动力学二级反应,等温吸附规律可用Freundlich、Langmuir和Temkin模式较好地描述.     

膨润土改性及对水中Cr(Ⅵ)吸附性能的研究

目的 提高膨润土对水中Cr（Ⅵ）的吸附性能。方法 采用氢氧化钠和壳聚糖对膨润土进行改性,分别得到碱改性膨润土（B-NaOH）、壳化膨润土（B-CS）和壳化碱改性膨润土（B-NaOH-CS）。以钠基膨润土（B）为对照,利用红外光谱仪、扫描电镜和比表面积分析仪表征3种改性膨润土的理化性质,研究其对Cr（Ⅵ）的吸附性能。结果 B-NaOH-CS中出现了强N—H吸收峰以及增强的C—H对称弯曲峰,同时B-NaOH-CS表面片状结构卷曲分散,层间孔隙增多,比表面积是其他膨润土的1.2倍以上。当Cr（Ⅵ）质量浓度为50 mg·L^-1时,B-NaOH-CS对Cr（Ⅵ）的平衡吸附量为1.03 mg·g^-1,分别是B-CS、B-NaOH的1.26、1.84倍。描述膨润土吸附Cr（Ⅵ）的动力学过程,准二级动力学模型优于准一级动力学模型;描述膨润土吸附Cr（Ⅵ）的热力学过程,Langmuir等温模型优于Freundlich等温模型。热力学参数△H>0、△G<0、△S>0,表明膨润土吸附Cr（Ⅵ）为吸热、自发、无序反应。B-NaOH在pH=7.0时对Cr（Ⅵ）的吸附量最大,B-CS、B-NaOH-CS在pH = 3.0时对Cr（Ⅵ）的吸附量最大。结论 B-NaOH-CS对Cr（Ⅵ）的吸附效果最好,改性膨润土对去除Cr（Ⅵ）污染有重要作用。     

Regulated fast nucleocytoplasmic shuttling observed by reversible protein highlighting

The observation of the regulation of fast protein dynamics in a cellular context requires the development of reliable technologies. Here, a signal regulation cascade reliant on the stimulus-dependent acceleration of the bidirectional flow of mitogen-activated protein kinase (extracellular signal-regulated kinase) across the nuclear envelope was visualized by reversible protein highlighting. Light-induced conversion between the bright and dark states of a monomeric fluorescent protein engineered from a novel coral protein was employed. Because of its photochromic properties, the protein could be highlighted, erased, and highlighted again in a nondestructive manner, allowing direct observation of regulated fast nucleocytoplasmic shuttling of key signaling molecules.     

蒙脱石-壳聚糖复合物对磷吸附性能的研究

为探究蒙脱石-壳聚糖复合物对水体中磷(P)的吸附性能和应用前景,将壳聚糖加载于蒙脱石,通过X射线衍射仪和傅立叶变换红外光谱表征该复合物结构,并通过静态吸附实验研究其对磷的吸附行为。结果表明,饱和吸附的壳聚糖能插层蒙脱石层间形成复合物;随pH从2增加到6,P在复合物上的吸附量增加,并在pH 6时达到最大吸附量16.15 mg·g~(-1),随着pH继续增加至9,吸附量减少至9.05 mg·g~(-1);P在复合物上约3 h达到吸附平衡,动力学吸附结果拟合准二阶方程较好,说明化学吸附为速率控制阶段;复合物对P的吸附为自发放热反应,在20~40℃范围内随温度上升,吸附量减少;等温吸附拟合Langmuir方程最佳,拟合最大吸附量为16.36 mg·g~(-1),pH 6条件下,复合物对P的吸附为均质吸附。该研究结果说明蒙脱石-壳聚糖复合物具有吸附P的应用价值。     

Microaggregations of oceanic plankton observed by towed video microscopy

Oceanic plankton have been hypothesized to occur in micropatches (<10 meters) that can have a large impact on marine ecosystem dynamics. Towed video microscopy was used to unobtrusively determine distributions of oceanic plankton over a continuum of scales from microns to hundreds of meters. Distinct, taxa-specific aggregations measuring less than 20 centimeters were found for copepods but not for nonmotile (cyanobacterial colonies) or asexual (doliolid phorozooids) forms, which suggests that these small patches are related to mating. Significant patchiness was also found on larger scales and was correlated among taxa, indicating physical control. These video observations provide new insights into basic plankton ecology by allowing quantitative assessment of individual plankton in their natural, undisturbed state.     

改性柚皮吸附剂的制备及其去除水中六价铬效果分析

[目的]研究改性柚皮吸附剂制备工艺及其对水中六价铬[Cr(VI)]的去除效果,为实现果皮类废弃物资源化利用提供参考依据.[方法]以柚皮为原料,采用磷酸活化改性并经挤压成型制备柚皮炭基颗粒吸附剂(PP-H3PO4),通过红外光谱(IR)、扫描电镜(SEM)和热重—差热(DSC/TG)检测分析柚皮活化改性前后的组成、结构和性质变化,并考察PP-H3PO4投加量、pH、处理时间和盐浓度等因素对含100 mg/L Cr(VI)污水去除效果的影响.[结果]正交试验获得柚皮粉最优磷酸改性制备工艺为:柚皮粉与磷酸质量比1:1.2、活化温度130℃、活化时间45 min,所得产物碘值达1036.79 mg/g;经IR、SEM和DSC/TG检测分析证实,改性吸附剂的-OH、-NH2和-C=O活性基团增多,内部孔道更丰富、结构变粗糙.PP-H3PO4对含100 mg/L Cr(VI)污水处理的最佳条件为:吸附剂投加量3.0 g/L、温度25℃、pH 2.0,处理120 min可达吸附平衡,Cr(VI)去除率在99.50%以上,且0~3.0 mol/L的氯化钠盐物质对Cr(VI)去除率影响较小.[结论]采用磷酸活化改性并经挤压成型制备的柚皮炭基颗粒吸附剂(PP-H3PO4)对Cr(VI)有很强的吸附能力,可用于去除污水中Cr(VI).     

氧化铁/水界面Cd吸附研究:CD-MUSIC模型模拟

以针铁矿和赤铁矿为研究对象,研究p H、Cd浓度等对不同类型氧化铁Cd吸附行为的影响,构建氧化铁Cd吸附的CD-MUSIC模型,并分析氧化铁表面Cd的形态分布特征。结果表明:氧化铁表面Cd吸附量和吸附密度均随p H升高、Cd浓度增大而增大。针铁矿对Cd的吸附量和吸附密度显著高于赤铁矿。CD-MUSIC模型能准确模拟Cd在氧化铁/水界面的吸附特征,拟合结果表明Cd主要以(Fe OH)2Cd+1、(Fe OH)2Cd OH0两种形态吸附在氧化铁表面,其在针铁矿和赤铁矿表面亲和常数(lg KCd)分别是7.3、12.8和6.1、11.0。Cd的形态分布受p H的影响显著,但几乎不受Cd浓度的影响。p H 5.0和7.0时,针铁矿的Cd形态分布与赤铁矿相似,(Fe OH)2Cd+1是主要吸附形态。p H 9.0时,针铁矿上超过80%的Cd以(Fe OH)2Cd OH0形态存在。赤铁矿上,Cd浓度较低时,(Fe OH)2Cd+1是主要吸附形态;随Cd浓度增大,(Fe OH)2Cd+1和(Fe OH)2Cd OH0所占比例均逐渐接近50%。     

Dynamic instability of sheared microtubules observed by quasi-elastic light scattering

The kinetics of microtubule reassembly was studied in vitro by quasi-elastic light scattering (QELS). When microtubules assembled in the absence of microtubule-associated proteins (MAPs) were sheared, they rapidly depolymerized, recovered, and reassembled. The mean length of the recovered microtubules was the same as that observed just before shearing, implying that on average one fragment per original microtubule survived the fragmentation and recovery. When microtubules that contained 25 percent brain MAP were sheared, the fragments did not depolymerize extensively and the average length of the fragments decreased by a factor of 3 relative to the unsheared sample. The results support the dynamic instability model, which predicts that cellular microtubules are latently unstable structures protected on their ends by stabilizing caps.