Separation of lead from high matrix electroless nickel plating waste solution using an ion-selective immobilized macrocycle system

Separation of trace levels of lead from concentrated-matrix electroless nickel plating (ENP) waste solutions is required to meet the increasingly stringent environmental regulations. A solid phase extraction (SPE) system using a molecular recognition technology (MRT) gel was used for the selective separation of trace levels of lead (Pb) from the waste discharge of ENP operations, followed by subsequent analysis with inductively coupled plasma optical emission spectrometry (ICP-OES). Two SPE-MRTs, AnaLig® Pb-01 and AnaLig® Pb-02, packed in 3 mL polypropylene cartridges were used to treat the synthetic metal-waste solutions that were used to simulate the typical metal mixture in ENP bath waste. The fortified solutions contained 100-1000 μg L^− 1 of Pb in an HNO₃ matrix with pre-added Ni, Cu and other interfering elements (1000 mg L^− 1). After the sample treatment, the SPE-MRT cartridges were washed with water and 0.1 M nitric acid, followed by elution with 0.03 M EDTA. The matrix elements (e.g., Ni, Cu) were completely removed at the washing step, while the ‘captured’ Pb was quantitatively eluted, as determined by ICP-OES measurements. The detection limit of the proposed method was 2.6 μg L^− 1. ‘Real’ samples from commercial ENP operations were used to assess the validity of this method, and almost quantitative Pb recovery was observed. The excellent Pb selectivity of the SPE-MRT system indicates the potential of the proposed technique for trace-level Pb separation from the Pb-containing high matrix aqueous waste discharge.     

Detection of lead ions in picomolar concentration range using underpotential deposition on silver nanoparticles-deposited glassy carbon electrodes

The efficacy of silver-deposited glassy carbon electrode for the determination of lead ions at the sub-nanomolar concentration ranges is investigated. The silver nanoparticles are electrodeposited on glassy carbon electrode using chronoamperometry and the electrode surface is characterized using SEM. Lead ions are detected in the region of underpotential deposition. The analysis is performed in square wave mode in the stripping voltammetry without the removal of oxygen. The detection limit of 10 pM has been obtained with a constant potential of −0.7 V during the electrodeposition step for a period of 50 s. The interference of surfactants in the detection of lead ions is also studied.     

Eu photoluminescence enhancement due to thermal energy transfer in Eu2O3-doped SiO2-B2O3-PbO2 glasses system

In this work, Eu³⁺-doped lead borosilicate glasses (SiO₂-B₂O₃-PbO₂) synthesized by fusion method had their optical properties investigated as a function of temperature. Atomic Force Microscopy images obtained for a glass matrix annealed at 350 and 500 °C show a precipitated crystalline phase with sizes 11 and 21 nm, respectively. Besides, as the temperature increases from 350 to 300 K a strong Eu³⁺ photoluminescence (PL) enhancement takes place. This anomalous feature is attributed to the thermally activated carrier transfer process from nanocrystals and charged intrinsic defects states to Eu³⁺ energy levels. In addition, the PL peaks in this temperature range were assigned to the Eu³⁺ transitions ⁵D₀→⁷F₂, at 612 nm, ⁵D₀→⁷F₁, at 595 nm, and ⁵D₀→⁷F₀, at 585 nm. It was also observed that the ⁵D₀→⁷F₃ and ⁵D₀→⁷F₄ PL bands at 655 and 700 nm, respectively, show a continuous decrease in intensity as the temperature increases.     

提前期需求为模糊随机条件下的连续库存补货策略

考虑提前期内需求为模糊随机变量且提前期为可缩短情形下,建立由购买商和供应商所组成的简单供应链连续库存补货策略优化模型,其中订单量、再订货点和提前期为决策变量.首先推导出模糊随机需求条件下购买商和供应链的成本函数,然后,进一步考虑总需求为三角模糊数,推导出供应商、购买商和供应链的模糊成本函数.在此基础上分别从购买商成本最小和供应链成本最小角度对模型进行求解,结合具体算例对模型进行应用分析和比较分析,结果表明模型具有有效性和实用性,并得出如下结论:从购买商本身角度考虑订购策略所产生的供应链成本总是大于从供应链整体角度考虑订货策略所产生的供应链成本,同时从购买商本身角度考虑订货策略所产生的最优订购量、购买商成本低于从供应链整体角度考虑订货策略所产生的最优订购量、购买商成本.     

Molecular-mediated crystal growth of PbTiO3 nanostructure on silicon substrate

A simple approach based on an organically modified sol-gel process has been developed to fabricate PbTiO₃ (PT) nanocrystals on Si (1 0 0) substrate, where the amorphous powder modified by acetylacetone (acac) was used as precursor. After dropping the amorphous powder precursor prepared by freeze-drying process, PT nanocrystals on Si (1 0 0) substrate were obtained after heat treatment at 720 °C for 30 min in air. PT nanocrystals have been detected by XRD to be tetragonal perovskite structure. With the increase of acac/Pb molar ratio, the relative (1 0 0)/(0 0 1) diffraction peak intensity gradually increases, which probably suggested an oriented growth of PT nanocrystal along [1 0 0] on Si (1 0 0) substrates. In addition, Atomic force microscopy (AFM) results indicated that the height and the average lateral size of PT nanocrystal increased and then decreased as the acac/Pb molar ratio increased. Piezoelectric force microscopy (PFM) results demonstrated that all the samples show obvious piezoelectric activity. These results implied that the acetylacetone molecular mediated the growth of PT nanocrystals on Si (1 0 0) substrates possibly by the acac/Pb molar ratio. This simple method has been suggested to be attractive for tailoring an oriented growth of the nanostructures of perovskite oxide systems on Si substrates.     

Spectroscopic studies on Pb3O4-ZnO-P2O5 glasses doped with transition metal ions

Optical absorption, Electron Paramagnetic Resonance (EPR) studies are carried out on lead zinc phosphate glass systems doped with Cr³⁺ and VO²⁺. From optical absorption investigations the crystal-field parameters Dq, B and C are evaluated. EPR measurements on Cr³⁺ systems indicate that Cr³⁺ ions are located at sites with low symmetry. EPR spectra of vanadyl doped system revealed the characteristic nature of vanadyl ion. Spin-Hamiltonian and hyperfine values are evaluated for both the systems. Optical absorption spectra of vanadyl doped system revealed three bands that are characteristic of VO(II) ion in tetragonally distorted octahedral site. By correlating both EPR and optical data, the dipolar coupling constant (P) and Fermi-constant coupling parameter (κ) and molecular orbital coefficients β^?2, e_π^?2 are evaluated. Electron Paramagnetic Resonance and optical absorption studies showed that the chemical bonds of Cr³⁺ ions and VO²⁺ ions with the ligands have more covalent nature. From these studies it is also observed that lead spinals are playing major key role in sustaining the covalent nature of bonding.     

火焰原子吸收光谱法测定海木耳中3种重金属

采用火焰原子吸收光谱法(FAAS)测定了海木耳中3种重金属(铜、铅和镉)。将海木耳样品去柄后剪碎并在烘箱中烘干至恒重,称取干燥样品1.0000g,分次用硝酸-高氯酸(9+1)混合酸10mL消解至溶解完全,定容至10mL,用FAAS按选定的仪器工作条件测定其中的铜、铅和镉量。对同一样品的上述3元素作5次平行测定,测定值的相对标准偏差依次为2.0%,3.2%及2.5%。用标准加入法测得方法的回收率为95.4%(铜),95.3%(铅)及103.0%(镉)。在测定结果中除铜量外,铅量及镉量均分别超过国家标准规定允许量的34.3倍和13.9倍。     

5,10,15-三苯基-20-吡啶基卟啉荧光猝灭法测定痕量铅

:试验制备了一种荧光试剂5,10,15-三苯基-20-吡啶基卟啉(TPPyP),该试剂激发光谱(λ_(ex))为420nm时,在650nm波长处有发射光谱(λ_(em))峰。当试剂与铅(Ⅱ)反应时产生荧光猝灭现象。提出了以此试剂为荧光探针测定痕量铅(Ⅱ)的荧光光度法。在邻苯二甲酸盐-盐酸缓冲溶液中,一定量的十六烷基三甲基溴化铵(CTMAB)存在下,通过测定样品溶液和空白溶液在发射波长650nm的荧光强度,计算得反应液荧光强度的降低程度△F;结果表明:△F值与铅(Ⅱ)的质量浓度在1.0×10~(-4)～1.5×10~(-3)mg·L~(-1)范围内呈线性关系,方法的检出限(3s/k)为4.0×10~(-5)mg·L~(-1)。此方法用于膨化食品中铅(Ⅱ)的测定,回收率在95.0%～107.0%之间,相对标准偏差(n=6)小于3%。     

胞外生物高聚物的制备及其对铅离子的吸附性能研究

采用Pseudomonas sp.的胞外生物高聚物对Pb(Ⅱ)进行吸附试验。分别用扫描电子显微镜、X射线能谱仪(SEM-EDX)和傅里叶变换红外光谱(FTIR)对吸附铅前后的胞外生物高聚物进行表征分析,研究了Pb(Ⅱ)在胞外生物高聚物上的吸附行为。结果表明,Pb(Ⅱ)的最佳吸附pH值为6.0,其吸附行为符合Langmuir吸附等温模型,最大单分子层吸附容量为34.48mg/g。FTIR及EDX实验结果表明,胞外生物高聚物对Pb(Ⅱ)的吸附被认为是高聚物表面的活性基团对Pb(Ⅱ)的络合作用和离子交换机制共同发挥作用。被吸附的Pb(Ⅱ)可用1mol/L的硝酸定量洗脱。方法检出限为3.6ng/mL,相对标准偏差为2.7%[Pb(II):0.05μg/mL,n=9]。在优化的实验条件下,实测了环境水样中痕量Pb的含量,结果满意。     

火焰原子吸收光谱法测定四大怀药中10种元素

对四大怀药(即怀山药、怀地黄、怀菊花及怀牛膝)中的8项微量元素(铜、铁、锌、锰、镍、钴、铬和铅)、2种常量元素钾及钙,用火焰原子吸收光谱法做了测定。比较了水煎酸化和硝酸-高氯酸(4+1)混合酸直接消解两种溶样方法,结果表明:用后一种溶样方法可使上述10种元素从药材中更完全地提取。在所述的最优分析条件下,上述10种元素的质量浓度与其相应吸光度在一定范围内呈线性关系。对方法的回收率和精密度做了试验,测得回收率在97.0%～105.0%之间,相对标准偏差(n=5)均小于5%。