碳纳米管-羟磷灰石对铅的吸附特性研究

采用多壁碳纳米管-羟磷灰石(MWCNT-HAP)复合材料,通过间歇试验研究了MWCNT-HAP对Pb(Ⅱ)的吸附特性.主要探讨了固液比、p H、离子强度、反应时间、Pb(Ⅱ)的初始质量浓度及温度等因素对吸附的影响.结果表明,固液比、p H与温度对于去除Pb(Ⅱ)的影响较大,离子强度影响较小.当温度为20℃,固液比为0.08 g·L-1,p H0为5.5,Pb(Ⅱ)的初始质量浓度为100 mg·L-1时,吸附量为716.13 mg·g-1.动力学试验结果表明,MWCNT-HAP吸附Pb(Ⅱ)为快速反应过程,在30 min时,吸附量可达最大吸附量的90%,60 min即可达平衡.伪二级动力学模型可较好地拟合动力学试验数据,可采用该模型描述MWCNT-HAP对Pb(Ⅱ)吸附的动力学过程.热力学试验结果表明,在不同温度下的自由能变均为负值,表明MWCNT-HAP对Pb(Ⅱ)的吸附为自发反应,升温有利于反应进行.Langmuir模型拟合不同温度下的等温试验结果得到可决定系数(R2为0.999 8~1.000 0),可采用该模型模拟MWCNT-HAP对Pb(Ⅱ)的等温吸附过程.MWCNT-HAP去除Pb(Ⅱ)的主要机制为MWCNT-HAP表面含氧官能团与Pb2+间的络合反应、HAP的分解-沉淀、Pb2+与Ca2+离子交换等.     

碱热-酸热法合成二氧化钛-钛酸纳米管复合纳米材料对Cd(Ⅱ)和苯酚的同步去除

以P25型Ti O2为原料,经碱热和酸热反应合成了Ti O2/TNTs复合纳米材料,该材料皆具钛酸纳米管(TNTs)和Ti O2晶相.Cd(Ⅱ)在Ti O2/TNTs上的吸附动力学过程很快,30 min即可达到吸附平衡,此外,Langmuir等温模型拟合所得最大吸附量达120.34 mg·g-1,其主要吸附机制为Cd2+与复合材料中TNTs层间Na+/H+的离子交换.Ti O2/TNTs对苯酚的吸附量较低(0.36 mg·g-1),因此光催化反应以实现苯酚的降解是必需的.构建的吸附-光催化系统可实现Cd(Ⅱ)和苯酚的同步有效去除,180 min时二者的去除率分别可达到99.6%和99.7%.Cd(Ⅱ)的去除源于暗室下复合材料中TNTs相的吸附,而苯酚的去除在于后续复合材料中Ti O2相的光催化.Cd(Ⅱ)的共存可提高苯酚的光催化降解效率,原因在于Cd(Ⅱ)吸附进入材料层间后有助于材料光催化性能的提升.共存Na+对Cd(Ⅱ)和苯酚在Ti O2/TNTs上的同步去除影响极小;而共存Ca2+由于竞争吸附和促进材料团聚的原因,会轻微抑制Cd(Ⅱ)在Ti O2/TNTs上的吸附,但对苯酚的光催化降解影响较小.此外,Ti O2/TNTs可有效循环利用,经HNO3解吸和Na OH再生后,3次循环后材料对Cd(Ⅱ)和苯酚的去除率依然可达91.7%和98.1%.该研究提供了一种合成皆具吸附和光催化性能的钛系材料的方法,对于应用纳米材料实现水体环境中重金属和有机物的同时去除具有一定的借鉴意义.     

Influence of the initial state of carbon nanotubes on their colloidal stability under natural conditions

The colloidal stability of dry and suspended carbon nanotubes (CNTs) in the presence of amphiphilic compounds (i.e. natural organic matter or surfactants) at environmentally realistic concentrations was investigated over several days. The suspensions were analyzed for CNT concentration (UV-vis spectroscopy), particle size (nanoparticle tracking analysis), and CNT length and dispersion quality (TEM). When added in dry form, around 1% of the added CNTs remained suspended. Pre-dispersion in organic solvent or anionic detergent stabilized up to 65% of the added CNTs after 20 days of mild shaking and 5 days of settling. The initial state of the CNTs (dry vs. suspended) and the medium composition hence are critical determinants for the partitioning of CNTs between sediment and the water column. TEM analysis revealed that single suspended CNTs were present in all suspensions and that shaking and settling resulted in a fractionation of the CNTs with shorter CNTs remaining predominantly in suspension.     

Removal of carbon nanotubes from aqueous environment with filter paper

The potential health and environmental hazards of carbon nanotubes (CNTs) have been a concerned issue. However, in contrast to the wide recognition of the toxicity of CNTs, little attention has been paid to the decontamination/remediation of CNT pollution. In this study, we report that CNTs can be removed from aqueous environment. In the presence of Ca²⁺, CNTs aggregate quickly to micron size and then enable easy and effective removal via normal filtration. After filtration, CNT suspension becomes colorless with the remnant CNT concentration less than 0.5 μg mL⁻¹, a safe dose based on the published data. The filtration approach also works well in the presence of typical surfactant and dissolved organic matter. The removal efficiency is Ca²⁺ concentration-dependent and regulated by the initial pH value and ionic strength. Our study is helpful for future decontamination of CNTs from aqueous environment.     

碳纳米管对偏二甲肼的吸附性能分析

利用NaOH和H₂O₂对碳纳米管进行表面处理，用于去除低浓度偏二甲肼废液，用分光光度法进行测定。扫描电镜和红外谱图观测表明，原产品管子较长，分散性差，NaOH处理的分散性好，H₂O₂处理的管子被截断并且表面引入了—OH、 >CO和—COOH。碳纳米管对偏二甲肼的吸附性能研究表明，H₂O₂浸泡氧化方法改性的碳纳米管吸附去除偏二甲肼效能最佳，NaOH处理的次之，原产品稍差。通过对吸附数据的拟合,发现在温度为298 K和40～190 mg/L的浓度范围内，吸附等温线均符合Freundlich和Langmuir吸附等温式。     

Interaction of engineered nanoparticles with various components of the environment and possible strategies for their risk assessment

Nanoparticles are the materials with at least two dimensions between 1 and 100 nm. Mostly these nanoparticles are natural products but their tremendous commercial use has boosted the artificial synthesis of these particles (engineered nanoparticles). Accelerated production and use of these engineered nanoparticles may cause their release in the environment and facilitate the frequent interactions with biotic and abiotic components of the ecosystems. Despite remarkable commercial benefits, their presence in the nature may cause hazardous biological effects. Therefore, detail understanding of their sources, release interaction with environment, and possible risk assessment would provide a basis for safer use of engineered nanoparticles with minimal or no hazardous impact on environment. Keeping all these points in mind the present review provides updated information on various aspects, e.g. sources, different types, synthesis, interaction with environment, possible strategies for risk management of engineered nanoparticles.     

Electrochemical analysis of trifluralin using a nanostructuring electrode with multi-walled carbon nanotubes

The electroanalytical behaviors of the endocrine-disrupting chemical trifluralin have been studied at a nanostructuring electrode. The nanostructuring electrode was fabricated by coating a uniform multi-wall carbon nanotubes/dihexadecyl hydrogen phosphate (MWNTs/DHP) film on glassy carbon electrode (GCE). The reduction peak currents of trifluralin increased remarkably and the reduction peak potential shifted positively at the nanostructuring electrode, compared with that at a bare GCE. The results showed that this nanostructuring electrode exhibited excellent enhancement effects on the electrochemical reduction of trifluralin. Consequently, a simple and sensitive electroanalytical method was developed for the determination of trifluralin. Under optimal conditions, a linear response of trifluralin was obtained in the range from 5.0 × 10⁻⁹ to 6.0 × 10⁻⁶ mol L⁻¹ (r = 0.998) and with a limit of detect (LOD) of 2.0 × 10⁻⁹ mol L⁻¹. The proposed procedure was successfully applied to determine trifluralin in soil samples with satisfactory results.     

碳纳米管/羟基磷灰石复合材料对水体F-的去除研究

以碳纳米管（CNT）和羟基磷灰石（HAP）为原料,通过原位合成法制备碳纳米管/羟基磷灰石（CdH）复合材料.利用XRD、FTIR、SEM与氮气吸附-脱附等表征其结构形貌,并通过静态吸附实验考察CdH对氟离子（F^-）的吸附性能.结果表明,室温下,CdH对F^-的吸附容量为11.05mg/g,明显高于HAP（5.02mg/g）.吸附动力学模型、Weber-Morris方程、Langmuir和Freundlich方程拟合结果表明,F^-在CdH表面进行Langmuir单分子层吸附,其吸附过程符合准二级动力学方程,并且颗粒内部扩散起主要作用.pH值为6时有利于CdH对F^-的去除.此外,结合反应前后固样XPS分析可知CdH对F^-的吸附机制主要为离子交换作用.     

邻苯二甲酸酯及邻苯二甲酸在碳管上的吸附

以邻苯二甲酸（PA）和邻苯二甲酸二乙酯（DEP）为目标污染物,碳纳米管（CNTs）为吸附剂,通过不同pH值条件下单、双溶质的吸附实验,结合能量分布理论,分析PA对DEP在CNTs上的竞争和取代吸附.结果表明,在同一pH值下,DEP在CNTs上的吸附性强于PA.对于DEP,pH值改变导致的CNTs分散稳定性的变化是影响其吸附的决定因素.对于PA,溶液pH值会影响CNTs的表面电荷及PA的解离程度,两者均会产生影响.双溶质体系下,PA对DEP在CNTs上的吸附存在竞争和取代效应.在不同pH值条件下,PA对DEP在CNTs上的竞争和取代的程度与CNTs的分散稳定性和PA的解离程度有关.基于能量分布的分析表明,虽然PA的加入导致DEP在CNTs上可利用的高能吸附位点数量显著下降,但是其可利用的低能吸附位点数量增加.