A simple,rapid and sensitive method based on modified multiwalled carbon nanotube for preconcentration and determination of lead ions in aqueous media in natural pHs

In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL^?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples.     

A generalized super AKNS hierarchy associated with orthosymplectic Lie superalgebra OSP(2,2) and its super bi-Hamiltonian structures

For the orthosymplectic Lie superalgebra $\text{◂⋅▸}OSP(2,2)$, we choose a set of basis matrices. A linear combination of those basis matrices presents a spatial spectral matrix. The compatible condition of the spatial part and the corresponding temporal parts of the spectral problem leads to a generalized super AKNS (GSAKNS) hierarchy. By making use of the supertrace identity, the obtained GSAKNS hierarchy can be written as the super bi-Hamiltonian structures.     

Breakthrough of 2- to 3-μm scale U–Pb zircon dating using Cameca IMS-1280HR SIMS

A zircon U–Pb dating method with a high spatial resolution of 2- to 3-μm was successfully implemented by using Cameca IMS-1280HR SIMS in this study. Homemade cathode and modified intermediate pole were used to improve the intrinsic performance of duoplasmatron ion source. An O⁻ primary beam with intensity of approximately 3 μA and stability of 0.68% over 40 minutes was achieved and could be used continuously for more than 240 hours under high current conditions. Under Gaussian illumination mode, a 2- to 3-μm O⁻ primary beam was obtained with an intensity of approximately 200 pA. Four standard zircons, namely, 91500, Temora, Plešovice, and Qinghu, were dated using the 2- to 3-μm high spatial resolution U–Pb isotopic analysis, yielding U–Pb ages consistent with their recommended values, within errors. Our work shows that zircon U–Pb dating with high accuracy and spatial resolution can be achieved, on the basis of a series of duoplasmatron modification and instrumental optimization.     

Single‐gap Microelectrode Functionalized with Single‐walled Carbon Nanotubes and Pbzyme for the Determination of Pb2+

Lead is a highly toxic metal, which can persist in the natural environment and enrich in biological bodies. It can cause many severe diseases in the human body even at extremely low concentration. Here, we developed a new biosensor using single‐walled carbon nanotubes (SWNTs) modified with a specific Pbzyme (Pbzyme/SWNTs/FET) to detect lead ion (Pb²⁺), which can monitor the lead pollution. This biosensor used 3‐aminopropyltriethoxysilane to immobilize SWNTs on the area between the source and the drain of single‐gap microelectrode (FET), and the duplex DNA (Pbzyme) consisted of DNAzyme (GR‐5) and complementary DNA (CS‐DNA) was functionalized with the SWNTs’ surface through a peptide bond. The use of GR‐5 DANzyme and Pb²⁺ to form a stable complex structure to cleave the CS‐DNA can change radically the Pbzyme's structure on the SWNTs’ surface, which will further affect the number of carriers in SNWTs and the conductivity of the Pbzyme/SWNTs/FET. The change in conductivity can be used to evaluate the Pb²⁺ concentration. Under the optimal conditions, the relative resistances presented a positive correlation with the Pb²⁺ concentrations, showing a good linear relationship in the range of 10 pM to 50 nM, where the linear regression equation was y=10.104log [C_Pb]+5.8656, and the detection limit was 7.4 pM. Finally, the biosensor was applied to measure the Pb²⁺ contents in the soil collected from the forest grass green belt and paint, and the results were compared with the results of atomic fluorescence spectrometry.     

The thermophysical properties of low‐temperature Pb plasma

The thermophysical properties of low‐temperature Pb plasma are calculated at temperatures 10–100 kK and densities below 0.2 of the solid‐state value. The thermodynamic values (pressure and internal energy) and transport coefficients (electrical conductivity, thermal conductivity, and thermal power) are considered. The plasma composition and thermodynamic parameters are obtained within the chemical approach, namely by means of the solution of the corresponding system of the coupled mass action law equations. Atom ionization up to +4 is taken into consideration. The electronic transport coefficients are calculated within the relaxation time approximation. The results obtained by means of the present model are compared with the available data of other models and experiments.     

Green synthesis and characterization of Tb-Fe-O-Cu ceramic nanocomposite and its application in simultaneous electrochemical sensing of zinc,cadmium and lead

In this work, a green technique for preparing TbFeO₃/CuO was reported by employing Crataegus and Lantana Camara leaves as fuel and alkalizing agents, respectively. The new sensor based on the perovskite-type nanocomposite was employed as a sensitive and selective platform to detect Pb(II), Zn(II) and Cd(II) simultaneously. TbFeO₃/CuO/Carbon paste electrode (CPE) exhibited a large specific surface area and great electrical conductivity, which enhanced electron transport in the electrochemical process considerably. Moreover, square wave anodic stripping voltammetry (SWASV) was used for the investigation of some factors influencing the sensor sensitivity like pH, modifier concentration, as well as accumulation time and potential. Therefore, the low detection limit (LOD) and a wide linear range were obtained at optimum conditions. In this study, a linear range between 0.9 and 110 µg/L for three ions and LOD of 0.48, 0.29 and 0.12 for zinc, cadmium and lead were achieved, respectively. Moreover, TbFeO₃/CuO/CPE was employed to detect zinc, cadmium and lead ions simultaneously in the real samples so that the results have shown consistency with a standard inductively coupled plasma (ICP).     

板栗内皮对水溶液中镉离子和铅离子的吸附

研究了板栗内皮对水溶液中金属离子(Cd²⁺,Pb²⁺)的吸附过程,以及吸附过程中不同条件对其吸附能力的影响。通过对反应时间、温度、pH、初始金属离子浓度等因素的控制,设计不同单一变量确定在不同条件下的吸附能力,利用红外光谱确定板栗内皮上参与反应的主要基团。结果表明,板栗内皮吸附Cd²⁺,Pb²⁺理论最佳吸附条件分别为pH 4.6和pH 5.0,吸附时间5.3 h和4.5 h,吸附温度53.80℃和43.09℃。在此吸附条件下,Cd²⁺和Pb²⁺的理论吸附率为98.91%与98.39%,实际吸附率为96.89%与97.84%。红外光谱分析表明其作用的主要基团为-C≡C-,C=O与C-H;通过动力学方程拟合,得出微观吸附过程符合准二级动力学模型。     

基体分离-电感耦合等离子体原子发射光谱法 测定精铋中10种杂质元素

试验采用电感耦合等离子体发射光谱法测定精铋中Cd、Co、Cu、Fe、Mg、Mn、Ni、Pb、Ti、Zn十种杂质元素,样品用优级纯硝酸溶解,往60℃左右的溶液中,滴加氨水(1+1),控制pH值在3.0~4.0。考察了温度、酸度、沉降时间对铋的去除率和对检测结果的影响。根据分析线的选择原则,结合待测元素的检测范围,选择无干扰、峰形对称、灵敏度适中的谱线作为分析线Cd 228.802nm、Co 237.862nm、Cu 324.754nm、Fe 259.940nm、Mg 279.553nm、Mn 257.610nm、Ni 231.604nm、Pb 182.205nm、Ti 323.452nm、Zn 213.856nm。各元素的质量浓度在一定范围内与其发射强度呈线性,校准曲线的线性相关系数均大于0.9997,方法中各元素检出限为0.002μg/g~0.253μg/g。?按照实验方法测定精铋实际样品,结果的相对标准偏差(RSD,n=9)为2.5%~9.8%,加标回收率为95.0%~102.2%,满足检测要求。     

基于Tessier-AAS法的华中大农区污染红土Pb赋存形态非生物转化机制研究

土壤重金属污染已成为人类面临的共同挑战,典型的重金属污染场地包括金属矿山、公路沿线、工业集中区、农业耕地等。对于事关农业安全生产的大农区,土壤超量重金属往往导致农产品品质下降甚至使用价值丧失,由此造成的经济损失不可估量。实际上,农作物体内累积重金属量与土壤"活性"重金属关系更加密切,这部分重金属主要以可交换态存在,在一定条件下能够与碳酸盐结合态、Fe-Mn氧化态、有机结合态和残渣态相互转换。因此,明确土壤条件对重金属有效性的作用规律,有望从源头上降低重金属对农作物的污染风险。基于前期研究成果,以华中大农区酸性网纹红土为检测对象,采用Tessier连续提取-原子吸收光谱法(AAS)揭示不同条件对红土Pb形态转化的非生物调控机制。结果表明:红土样品Pb总量为32.56mg·kg-1,低于《土壤环境质量标准》一级标准推荐值,但比全国土壤Pb平均含量要高。不同形态Pb含量分布为残渣态>Fe-Mn氧化态>有机结合态>碳酸盐结合态>可交换态,其中残渣态Pb占Pb总量的54.55%。红土pH值通过改变无机胶体和有机质表面电荷量来控制Pb的结合行为和可交换态含量;不同含水率导致红土氧化还原电位差异,进而影响Pb的形态转化行为。此外,秸秆加入量和老化时间也能改变Pb的形态分布,但残渣态Pb含量始终最高。红土Pb的Muller指数Igeo为0.302 5,表明土样采集区人为污染值得注意。Tessier连续提取-AAS法能有效表征红土Pb赋存形态的非生物转化机制。