Speciation of heavy metals in sediment by conventional, ultrasound and microwave assisted single extraction methods: a comparison with modified sequential extraction procedure

Sequential extraction procedure proposed by the European Standards, Measurements and Testing (SM&T) Program, formerly the Community Bureau of Reference (BCR), has been applied for the heavy metals (HMs) partitioning in fresh water lake sediment samples. The results obtained by conventional sequential extraction BCR method (SEB) for Cd, Cu, Cr, Ni, Pb and Zn were compared with those estimated from three alternative single extractions, conventional (CSE), ultrasonic (USE) and microwave assisted (MSE), using identical operating conditions applied in each individual BCR fraction and validated by the CRM BCR 701. Extractable HMs contents obtained by all compared methodologies were measured by atomic absorption spectrometery. With the use of compromised sonication and microwave conditions, steps 1-3 of the sequential extraction (excluding the hydrogen peroxide digestion in step 3) could be completed between 15-30 min using ultrasonic bath, while 60-120 s were required for MSE. The total extractable metal contents obtained by three single extractions ranged from 75.1% to 114.0% except Cr in first step, which was extracted (125.3%) by MSE method as compared to those obtained by SEB procedure. The precision of the proposed BCR single extraction methods (expressed as RSD%) was found in the range of (3.99-9.6%) for all metals.     

Heavy metal accumulation in different varieties of wheat (Triticum aestivum L.) grown in soil amended with domestic sewage sludge

The concentrations of heavy metals (HMs) in plants served to indicate the metal contamination status of the site, and also revealed the abilities of various plant species to take up and accumulate them from the soil dressed with sewage sludge. A study to comprehend the mobility and transport of HMs from soil and soil amended with untreated sewage sludge to different newly breaded varieties of wheat (Anmol, TJ-83, Abadgar and Mehran-89) in Pakistan. A pot-culture experiment was conducted to study the transfer of HMs to wheat grains, grown in soil (control) and soil amended with sewage sludge (test samples). The total and ethylenediaminetetraaceticacid (EDTA)-extractable HMs in agricultural soil and soil amended with domestic sewage sludge (SDWS) and wheat grains were analysed by flame atomic absorption spectrometer/electrothermal atomic absorption spectrometer, prior to microwave-assisted wet acid digestion method. The edible part of wheat plants (grains) from test samples presented high concentration of all HMs understudy (mgkg(-1)). Significant correlations were found between metals in exchangeable fractions of soil and SDWS, with total metals in control and test samples of wheat grains. The bio-concentration factors of all HMs were high in grains of two wheat varieties, TJ-83 and Mehran-89, as compared to other varieties, Anmol and Abadgar grown in the same agricultural plots.     

Ultrasonic extraction and field-portable anodic stripping voltammetric measurement of lead in dust wipe samples

Dust wipe samples were subjected to ultrasonic extraction (UE) in diluted nitric acid, and then analyzed for lead content using field-portable anodic stripping voltammetry (ASV). Recoveries of lead were determined from wipe materials which were spiked with certified reference materials (CRMs) containing known quantities of lead. Four different wipe materials and four different CRMs were tested, with and without filtration of aliquots of sample extract through 0.45 microm hydrophilic polytetrafluoroethylene filters. The CRMs consisted of paint, soil, particulate, and dust matrices. Wipe materials were chosen from those which have been found to meet the performance aspects of an ASTM standard specification. UE/ASV experiments were carried out in accordance with newly published ASTM procedures for on-site extraction and electroanalysis. Recoveries were found to vary for different wipe materials and CRMs. For several CRMs, quantitative (80--120%) recoveries for UE/ASV were observed for one wipe material whether filtration was used or not, while other wipe materials required filtration for quantitative recovery. In the case of one wipe material which contained detergents, quantitative recoveries could not be achieved whether filtration was used or not. The total analysis time for a sample set of 6--12 samples was 60--90 min, including extraction time and sample manipulation. The results of this work have provided information on the choice of wipe materials that can be used for quantitative lead measurements by UE/ASV in materials that are representative of sources of lead in surface dust.     

Hazardous impact of toxic metals on tobacco leaves grown in contaminated soil by ultrasonic assisted pseudo-digestion: multivariate study

Tobacco leaves (Nicotiana tabacum L.), agricultural soil and pollute irrigated lake water samples were collected during 2005–2006 and analyzed for Cd and Ni by electrothermal atomic absorption spectrometry (ETAAS). A simple and efficient procedure was investigated for the complete decomposition of tobacco leaves using ultrasonic assisted acid pseudo-digestion method (UPDM). A Plackett–Burman experimental design was used as a multivariate strategy for the evaluation of seven factors/variables at once, while central composite were used to found optimum values of significant variables. The accuracy of the proposed methods was assessed by analyzing certified reference (CRM); Virginia tobacco leaves (CTA-VTL-2). The results being compared with those obtained by conventional wet acid digestion method. The result obtained by optimized method showed good agreement with the certified values and sufficiently high recovery 97.8 and 98.7% for Cd and Ni, respectively. Under optimal conditions, the detection limits (3σ) were evaluated to be 0.019 μg g⁻¹ for Cd and 0.37 μg g⁻¹ for Ni. The proposed method was successfully applied to the determination of Cd and Ni in raw, processed tobacco and different branded cigarettes samples.     

Built-up edge reduction in drilling of AISI 1045 steel

In this study, a combined drilling method consists of ultrasonic-assisted drilling (UAD) under the presence of minimum quantity lubrication (MQL), is evaluated. Effect of this method on machinability factors is investigated by implementation of a dynamometer and a vision-measuring microscope. Then the results are compared with the values obtained in conventional drilling, and separately UAD and MQL-drilling. As a result, it was revealed that the output parameters were significantly improved when combined MQL–UAD method was exerted. In particular, built-up edge and drill skidding have almost been eliminated. Moreover, it was shown that increase of tool rake angle and producing broken chips caused thrust force and surface roughness to be reduced in UAD and UAD–MQL. In the combined strategy, burr-less hole has been achieved due to the formation of solid burr at the exit surface of drilled hole.     

Development of a high-pressure asher focused microwave system for sample preparation

The development of high-pressure Asher focused microwaves (HPA-FMs), a novel approach to microwave assisted digestion, is described. The system uses focused microwaves, at 2.45 GHz, to improve digestion capability with up to 650 W microwave power concentrated into six quartz pressure vessels containing samples and nitric acid. The device combines microwave heating with high-pressure vessel technology (reactions can be conducted at pressures and temperatures up to 130 bar and 320 °C, respectively). Methodology was developed using powdered biological reference material. The residual carbon content of digested bovine liver sample was determined by Coulometry after combustion in an oxygen stream to evaluate the effectiveness of the decomposition procedure. With this new decomposition device, organic material is totally oxidized with nitric acid in a single-step digestion.     

超声波辅助竹片染色工艺优化的研究

探讨了超声波辅助竹片染色在染液质量分数、pH值和染色温度一定的情况下,超声波功率、频率和超声波辅助染色时间等因素对竹片上染率的影响。在单因素实验的基础上,采用响应面法建立了二次回归模型,并对染色工艺进行了优化。研究结果表明:使用超声波辅助竹片染色能够提高上染率,当超声波功率为525 W、频率为30kHz、染色温度为70.0℃、染料质量分数为1.0%、染色时间为52min时,竹片的上染率可达到34.16%,比在相同工艺条件下未使用超声波辅助的提高了8.43%。     

Ultrasonic extraction followed by sonolysis-ozonolysis as a sample pretreatment method for determination of reactive arsenic toward sodium tetrahydroborate by flow injection-hydride generation AAS

A new sample pretreatment method based on ultrasonic extraction in HCI medium and subsequent oxidation of the extracts by sonozone (i.e., sonolysis-ozonolysis) has been developed for determination of reactive arsenic toward sodium tetrahydroborate [mainly As(III) + As(V)] by flow injection-hydride generation atomic absorption spectrometry. This method avoids the use of intensive treatments with concentrated and corrosive acids, high pressures, and temperatures that are inherent with traditional wet or dry ashing procedures and entails reduced waste production and reagent consumption. A sonozone process at room temperature was optimized to break the bond of As to proteins and macromolecular constituents which was an essential requirement for effective reduction by L-cysteine prior to arsine generation. Spiking experiments showed that As(III), As(V), MMA, and DMA were fully recovered from several matrixes on applying the above treatment. On the other hand, a nonreducible As species such as arsenobetaine that is predominant in some biological samples remained unchanged. Application of the method to sediment, soil, fly ash, and plant CRMs demonstrated that, in general, a good agreement existed between certified and found As contents, thereby indicating the absence of nonreducible As forms. Low As recoveries were observed for fish CRMs, as a result of the nondegradability of arsenobetaine by sonozone. The detection limit of As in the samples investigated was in the range 0.19-2.8 microg g(-1).     

Determination of methylmercury and butyltin compounds in marine biota and sediments using microwave-assisted acid extraction,solid-phase microextraction,and gas chromatography with microwave-induced plasma atomic emission spectrometric detection

A method is described for the determination of methylmercury and butyltin compounds in marine sediment and tissue using microwave-assisted acid extraction or digestion and solid-phase microextraction (SPME) followed by analysis using gas chromatography with microwave-induced plasma atomic emission spectrometric detection (GC-MIP-AES). Using the SPME-GC-MIP-AES method, enrichment factors for methylmercury and butyltin compounds of 50-100 were achieved, as compared to the typical hexane extraction, and measurements in marine tissue and sediment matrixes were possible at 1-2 microg/kg (methylmercury) and 10-100 ng/kg (butyltins). The SPME-GC-MIP-AES method was validated using several marine sediment and tissue matrix certified reference materials (CRMs) with certified values for methylmercury and butyltin compounds. The SPME-GC-MIP-AES method was used to measure methylmercury in four marine tissue CRMs ranging from oyster tissue at 13.0 +/- 1.0 microg/kg to fish tissue at 397 +/- 13 microg/kg (as Hg dry mass). Results from the SPME-GC-MIP-AES method were used in conjunction with results from other techniques to assign certified values for methylmercury in oyster, mussel, and fish tissue CRMs. Mono-, di-, and tributyltin were measured in three sediment CRMs at concentration levels of (0.08 +/- 0.03)-(0.35 +/- 0.05) mg/kg (as Sn dry mass).     

Effect of acclimatization of microorganisms to heavy metals on the performance of activated sludge process

Although selected heavy metals (HMs) stimulate biological reactions at low concentrations, all HMs are toxic to microorganisms (MOs) at moderate concentrations and can cause inhibitory effects on the biological processes. Therefore, MOs must be acclimated to HMs or other toxic substances present in wastewaters (WWs) before they are used in an activated sludge process (ASP). In this study, combined effect of Cu(2+) and Zn(2+) ions in a synthetic WW on the efficiency of a laboratory-scale ASP without recycle was investigated using acclimated MOs at different extents.A synthetic feed solution of 1222 mg L(-1) proteose-peptone (corresponding to 1300 mg COD L(-1)) served as a source of carbon. Cu(2+) and Zn(2+) ions at different concentrations (1.5, 4.5 and 9, 27 mg L(-1), respectively) were introduced in the feed to a continuously stirred activated sludge reactor at different hydraulic residence times (2-40 h) keeping pH, temperature and stock feed composition constant. The combined effects of copper and zinc ions were determined by mixing these metallic ions at the specified combinations of concentrations such as "1.5 mg L(-1) of Cu(2+)+9 mg L(-1) of Zn(2+)" and "4.5 mg L(-1) of Cu(2+)+27 mg L(-1) of Zn(2+)". It was observed that using seed MOs acclimatized to two times of the combined threshold concentration of these HMs for an unduly long period of time (1-4 months) caused adverse effects on the ASP performance. Besides, it was found that usual inhibition effects of these HMs were enhanced with increasing period of acclimation. Substantially lower substrate removal efficiencies were obtained with acclimatized MOs than those obtained with non-acclimatized MOs. At the higher initial substrate concentration of 2500 mg COD L(-1), substrate-inhibition occurred causing a decrease in the specific growth rate constant (k); however, HM inhibition was suppressed, resulting to about 20% increase in treatment efficiency of the ASP. It can be concluded that the time period necessary for acclimatization of seed MOs must be adjusted carefully with concentrations of HMs lower than their threshold concentrations to achieve an optimal operation of an aerobic biological process.     

Effect of condensation product on electrodeposition of zinc on mild steel

Electrodeposition of zinc on steel was obtained from acid chloride bath containing condensation products (CP) of 3,4,5-trimethoxy benzaldehyde (TMB) and chitosan (CTN). The effect of bath constituents, pH, current density and temperature on the nature of deposit was studied by Hull cell experiments. The bath composition and operating parameters were optimized. The adhesion, ductility and corrosion resistance of the deposits were discussed. Throwing power and current efficiency values under different plating conditions were measured. SEM photomicrographs of the deposit were taken to study the surface morphology. The inclusion of addition agent in the deposit was investigated from IR spectrum of the scrapped deposit. The consumption of brightener in the lab scale is 10 mLL⁻¹ for 1000 amp-h.     

Hazardous impact and translocation of vanadium (V) species from soil to different vegetables and grasses grown in the vicinity of thermal power plant

The distribution of vanadium (V) species in soil (test soil), vegetables and grasses, collected from the vicinity of a thermal power plant has been studied. For comparison purpose soil (control soil), same vegetable and grass samples were collected from agricultural land devoid of any industrial area. A simple and efficient ultrasonic assisted extraction method has been developed for the extraction of V(5+) species from soil, vegetable and grass samples using Na(2)CO(3) in the range of 0.1-0.5 mol/L. For comparison purpose same sub samples were also extracted by conventional heating method. The total and V species were determined by electrothermal atomic absorption spectrometry using different modifiers. The validity of V(5+) and V(4+) determination had been confirmed by the spike recovery and total amount of V by the analysis of CRM 1570 (spinach leave) and sub samples of agricultural soil. The concentration of total V was found in the range of 90-215 and 11.4-42.3 μg/g in test and control soil samples, respectively. The contents of V(5+) and total V in vegetables and grasses grown around the thermal power plant were found in the range of 2.9-5.25 and 8.74-14.9 μg/g, respectively, which were significantly higher than those values obtained from vegetables and fodders grown in non exposed agricultural site (P<0.01). Statistical evaluations indicate that the sum of concentrations of V(5+) and V(4+) species was not significantly different from total concentration of V in same sub samples of vegetable, grass and soil of both origins, at 95% level of confidence.     

Quantitative analysis of metal impurities in carbon nanotubes: efficacy of different pretreatment protocols for ICPMS spectroscopy

Metal impurities in carbon nanotubes (CNTs) are undesirable for their uses in diverse applications, for instance, they may potentially have a negative health impact when using in biomedical fields. However, so far there is a lack of analysis methods able to quantify metallic impurities in CNTs. In this paper, using the neutron activation analysis (NAA) technique as a nondestructive standard quantification method and inductively coupled plasma mass spectrometry (ICPMS) as a practical approach, we established an analytical method for quantitative determination of metallic impurities in CNTs. ICPMS, one of the most sensitive analytical techniques used for coincident multielement measurements, has become a common tool in many laboratory, and thus it is easily available and a good selection for determining the metal impurities in CNTs. However, because of their extremely stable structure and the encapsulated metals in the defect structure, CNTs must undergo special pretreatments before ICPMS. We investigated different sample pretreatment procedures for ICPMS analysis, including dry ashing coupled with acid extraction, wet digestion, and a combination of dry ashing with acid digestion. With the reference data from the nondestructive analytical method of NAA, we found that the quantitative determination of metal impurities in CNTs is highly dependent on the sample pretreatment in which the conditions are largely different from those used for conventional biological samples or environmental materials. This paper not only provides the practical method and analysis conditions for quantifying the metal impurities of CNTs but also the first protocol for pretreatment processes of CNT samples.     

Optimization of microwave assisted digestion procedure for the determination of zinc, copper and nickel in tea samples employing flame atomic absorption spectrometry

The present paper describes the development of a microwave assisted digestion procedure for the determination of zinc, copper and nickel in tea samples employing flame atomic absorption spectrometry (FAAS). The optimization step was performed using a full factorial design (2(3)) involving the factors: composition of the acid mixture (CMA), microwave power (MP) and radiation time (RT). The experiments of this factorial were carried out using a certified reference material of tea GBW 07605 furnished by National Research Centre for Certified Reference Materials, China, being the metal recoveries considered as response. The relative standard deviations of the method were found below 8% for the three elements. The procedure proposed was used for the determination of copper, zinc and nickel in several samples of tea from Turkey. For 10 tea samples analyzed, the concentration achieved for copper, zinc and nickel varied at 6.4-13.1, 7.0-16.5 and 3.1-5.7 (microg g(-1)), respectively.     

超声波对锡铈合金镀液性能的影响

为弄清超声波对锡铈合金镀液性能的影响,了解影响镀液稳定的因素,采用正交试验法研究了镀液配方对镀液稳定性的影响,得出影响镀液稳定性的主次顺序为:硫酸高铈、添加剂、硫酸亚锡和硫酸,并总结出最稳定镀液配方;在此基础上,测试了超声波对镀液的稳定性、阴极电流效率和沉积速度等性能的影响.结果显示,随着超声波功率的增加,镀液的稳定性略有降低,这是由超声波的能量效应和热效应引起的,但相对来说影响甚微;而超声波能显著提高阴极电流效率和沉积速度,则是由于超声波降低了极化程度,加快了电极过程的缘故.     

Determination of thorium and uranium in ultrapure lead by inductively coupled plasma mass spectrometry

A method for the determination of U and Th at sub-ppt levels in high-purity Pb samples using extraction chromatography with ICPMS detection is described. Following acid digestion, uranium and thorium are separated from the lead matrix using UTEVA resin. Sorption and elution procedures were optimized, the potential reusability of the chromatographic resin was evaluated, and a performance comparison between prepacked and freshly prepared UTEVA column was made. Uranium could be eluted with 0.025 M HCl and Th then recovered using 0.5% oxalic acid. Recovery yields for U exceed 80% whereas those for Th were typically 60%. Procedural detection limits of 0.5 and 1.5 pg g(-)(1) were obtained for U and Th, respectively. For purposes of comparison, GD-MS analysis of samples was also performed, yielding results consistent with those generated by ICPMS but with inferior detection power.     

One-step synthesis of CdS sensitized TiO₂ photoanodes for quantum dot-sensitized solar cells by microwave assisted chemical bath deposition method

Sensitized-type solar cells based on TiO? photoanodes and CdS quantum dots (QDs) as sensitizers have been studied. CdS QDs are grown on TiO? films, utilizing one-step microwave assisted chemical bath deposition (MACBD) method. This method allows a facile and rapid deposition and integration between CdS QDs and TiO? films. The photovoltaic performances of the cells fabricated using CdS precursor solutions with different concentrations are investigated. The results show that the cell based on MACBD deposited TiO?/CdS electrode achieves a maximum short circuit current density of 7.20 mAcm?2 and power conversion efficiency of 1.18 % at one sun (AM 1.5G, 100 mW cm?2), which is comparable to the ones prepared using conventional techniques.     

超声空化作用于水中天然有机质特性研究

利用超声空化作用去除水中天然有机质(Natural Organic Matter,简称NOM)不会产生消毒副产物.研究了采用低频高功耗率的超声处理富里酸溶液,结果表明:由于超声空化的热解及氧化作用,随着声功率及富里酸溶液浓度的增加,溶液的pH、ORP逐渐减小,溶液的温度、浊度逐渐增加,体系中加入盐酸后能够放大超声作用.作为水中NOM浓度的替代参数,UV<,254>在超声作用下缓慢增加,而总有机碳(TOC)的超声降解符合准一级反应规律,在20min超声作用之后,TOC去除率由21.2%增至31.6%,加入盐酸后,由24.7%增至34.8%.该研究可为超声协同其他工艺进行水处理提供放大设计依据.     

超声波-双水相萃取印楝素工艺的研究

采用超声波耦合乙醇-硫酸钠双水相提取印楝素,将超声功率密度,超声时间,超声辐射方式作为其影响因素,并分别进行单因素实验和正交实验对其进行研究,最终确定了超声波双水相提取印楝素的最佳工艺。最佳工艺条件为:功率密度为2.4 w/cm2,时间为30 min,辐射方式为7s/10s。并且影响印楝素超声提取率的主次因素为功率密度辐射方式超声时间,最优条件下印楝素的提取率为0.3200%。     

Ionic liquid ultrasound assisted dispersive liquid-liquid microextraction method for preconcentration of trace amounts of rhodium prior to flame atomic absorption spectrometry determination

In this article, we consider ionic liquid based ultrasound-assisted dispersive liquid-liquid microextraction of trace amounts of rhodium from aqueous samples and show that this is a fast and reliable sample pre-treatment for the determination of rhodium ions by flame atomic absorption spectrometry. The Rh(III) was transferred into its complex with 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol as a chelating agent, and an ultrasonic bath with the ionic liquid, 1-octyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide at room temperature was used to extract the analyte. The centrifuged rhodium complex was then enriched in the form of ionic liquid droplets and prior to its analysis by flame atomic absorption spectrometry, 300 μL ethanol was added to the ionic liquid-rich phase. Finally, the influence of various parameters on the recovery of Rh(III) was optimized. Under optimum conditions, the calibration graph was linear in the range of 4.0-500.0 ng mL(-1), the detection limit was 0.37 ng mL(-1) (3S(b)/m, n = 7) and the relative standard deviation was ±1.63% (n = 7, C = 200 ng mL(-1)). The results show that ionic liquid based ultrasound assisted dispersive liquid-liquid microextraction, combined with flame atomic absorption spectrometry, is a rapid, simple, sensitive and efficient analytical method for the separation and determination of trace amounts of Rh(III) ions with minimum organic solvent consumption.