Two-dimensional images of dissolved sulfide and metals in anoxic sediments by a novel diffusive gradients in thin film probe and optical scanning techniques

A novel diffusive gradients in thin film probe developed comprises diffusive gel layer of silver iodide (AgI) and a back-up Microchelex resin gel layer. 2D high-resolution images of sulfide and trace metals were determined respectively on the AgI gel by densitometric analysis and on the Microchelex resin layer with laser-ablation-inductively-coupled plasma mass spectrometry (LA-ICP-MS).We investigated the validity of the analytical procedures used for the determination of sulfide and trace metals. We found low relative standard deviations on replicate measurements, linear trace-metal calibration curves between the LA-ICP-MS signal and the true trace-metal concentration in the resin gel, and a good agreement of the sulfide results obtained with the AgI resin gel and with other analytical methods. The method was applied on anoxic sediment pore waters in an estuarine and marine system. Simultaneous remobilization of sulfide and trace metals was observed in the marine sediment.

Hand-held voltammetric analyser for real-time monitoring of heavy metals in situ

This paper presents a novel hand-held instrument capable of real-time in situ detection and identification of heavy metals. The proposed system provides the facilities found in a traditional lab-based instrument in a hand held a design. In contrast to existing commercial systems, it can stand alone without the need of an associated computer. The electrochemical instrument uses anodic stripping voltammetry which is a precise and sensitive analytical method with excellent limits of detection. The sensors comprise disposable screen-printed (solid working) electrodes rather than the more common hanging mercury drop electrodes. The system is reliable, easy to use, safe, avoids expensive and time-consuming procedures and may be used in a variety of situations to help in the fields of environmental assessment and control.

Voltammetric in situ measurements of heavy metals in soil using a portable electrochemical instrument

This paper presents a portable electrochemical instrument capable of detecting and identifying heavy metals in soil, in situ. The instrument has been developed for use in a variety of situations to facilitate contaminated land surveys, avoiding expensive and time-consuming procedures. The system uses differential pulse anodic stripping voltammetry which is a precise and sensitive analytical method with excellent limits of detection. The identification of metals is based on a statistical microprocessor-based method. The instrument is capable of detecting six different toxic metals (lead, cadmium, zinc, nickel, mercury and copper) with good sensitivity

Acidity compensation of electrochemical measurements for on-site monitoring of heavy metals

This paper presents an electrochemical instrumentation system capable of real-time in situ detection of heavy metals. A practical approach to introduce acidity compensation against changes in amplitude of the peak currents is also presented. The compensated amplitudes can then be used to predict the concentration level of heavy metals. The system uses differential pulse anodic stripping voltammetry, which is a precise and sensitive analytical method with excellent limits of detection. The instrument is capable of detecting lead, cadmium, zinc, nickel and copper with good sensitivity and precision. The system avoids expensive and time-consuming procedures and may be used in a variety of situations to help environmental assessment and control. 

On-site monitoring and cartographical mapping of heavy metals

This paper presents a portable electrochemical instrument capable of real-time in situ detection and automatic identification of heavy metals. The instrument is equipped with an embedded Geographical Position System and is capable of storing the geographical position of the sample under test. Software has been developed to combine pollutant results with geographical position, in order to produce a cartographical presentation of the pollution of an area. The electrochemical instrument provides the facilities found in a traditional lab based instrument in a portable design for on-site measurements. The instrument is capable of detecting lead, cadmium, zinc, nickel, mercury, and copper with good sensitivity and precision. The system is reliable, easy to use, safe, and it may be used in a variety of situations to help environmental assessment and control.

Intelligent potentiostat for identification of heavy metals in situ

This article presents a low-cost portable electrochemical instrument capable of on-site identification of heavy metals. The instrument acquires metal-specific voltage and current signals by the application of differential pulse anodic stripping voltammetry. This technique enhances the analytical current and rejects the background current, resulting in a higher signal-to-noise ratio for a better detection limit. The identification of heavy metals is based on an intelligent machine-based method using a multilayer perceptron neural network consisting of three layers of neurons. The neural network is implemented using a 16 bit microcontroller. The system is developed for use in the field in order to avoid expensive and time-consuming procedures and can be used in a variety of situations to help environmental assessment and control. 

A multi-capability sensor for hydrocarbons, synthetic-based fluids and heavy metals:Applications for environmental monitoring during removal of drill cuttings piles

As part of any drilling cuttings pile removal process the requirement for monitoring the release of contaminants into the marine environment will be critical. Traditional methods for such monitoring involve taking samples for laboratory analysis. This process is time consuming and only provides data on spot samples taken from a limited number of locations and time frames. Such processes, therefore, offer very restricted information. The need for improved marine sensors for monitoring contaminants is established. We report here the development and application of a multi-capability optical sensor for the real-time in situ monitoring of three key marine environmental and offshore/oil parameters: hydrocarbons, synthetic-based fluids and heavy metal concentrations. The use of these sensors will be a useful tool for real-time in situ environmental monitoring during the process of decommissioning offshore structures. Multi-capability array sensors could also provide information on the dispersion of contamination from drill cuttings piles either while they are in situ or during their removal.

NO Oxidation on Platinum Group Metals Oxides:First Principles Calculations Combined with Microkinetic Analysis

By combining density functional theory calculation and microkinetic analysis, NO oxidation on the platinum group metal oxides (PtO(2), IrO(2), OsO(2)) is investigated, aiming at shedding light on the activities of metal oxides and exploring the activity variations of metal oxides compared to their corresponding metals. A microkinetic model, taking into account the possible low diffusion of surface species on metal oxide surfaces, is proposed for NO oxidation. The resultant turnover frequencies of NO oxidation show that under the typical experimental condition, T = 600 K, p(O2) = 0.1 atm, p(NO) = 3 x 10(-4) atm, p(NO2) = 1.7 x 10(-4) atm; (i) IrO(2)(110) exhibits higher activity than PtO(2)(110) and OsO(2)(110), and (ii) compared to the corresponding metallic Pt, Ir, and Os, the activity of PtO(2) to catalyze NO oxidation is lower, but interestingly IrO(2) and OsO(2) exhibit higher activities. The reasons for the activity differences between the metals and oxides are addressed. Moreover, other possible reaction pathways of NO oxidation on PtO(2)(110), involving O(2) molecule (NO + O(2) -> OONO) and lattice bridge-O(2c), are also found to give low activities. The origin of the Pt catalyst deactivation is also discussed.

Insights into the Staggered Nature of Hydrogenation Reactivity over the 4d Transition Metals

Hydrogenation reactions at transition metal surfaces comprise a key set of reactions in heterogeneous catalysis. In this paper, density functional theory methods are employed to take an in-depth look at this fundamental reaction type. The energetics of hydrogenation of atomic C, N, and O have been studied in some detail over low index Zr, Nb, Mo, Tc, Ru, Rh, and Pd surfaces. Detailed bonding analysis has also been employed to track carefully the chemical changes taking place during reaction. A number of interesting horizontal and vertical trends have been uncovered relating to reactant valency and metal d-band filling. A general correlation has also been found between the reaction barriers and the reaction potential energies. Moreover, when each reaction is considered independently, correlation has been found to improve with decreasing reactant valency. Bonding analysis has pointed to this being related to the relative position of the transition state along the reaction coordinate and has shown that as reactant valency decreases, the transition states become progressively later.

Ionic liquid solvents of perhalide type for metals for extraction radioactive metals from mineral ores.

The invention relates to a process for dissolving metals (e.g., Al, Cu, Fe, Cr, Sb, Ti, and W) in perhalide contg. ionic liqs. having the formula (I), and to the extn. of metals from mineral ores; the remediation of materials contaminated with heavy, toxic, or radioactive metals; and to the removal of heavy and toxic metals from hydrocarbon streams. In the formula (I), [X] comprises at least one perhalide anion selected from [I3]-, [BrI2]-, [Br2I]-, [ClI2]-, [ClBr2]-, [BrCl2]-, or [ICl2]-, [ClI3]-. The (Cat+) is a cationic species selected from: ammonium, azaannulenium, azathiazolium, benzimidazolium, benzofuranium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, diazabicyclo- undecenium, dithiazolium, furanium, guanidinium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, iso-oxazolium, oxathiazolium, pentazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, isoquinolinium, quinoxalinium, selenozolium, sulfonium, tetrazolium, iso-thiadiazolium, thiazinium, thiazolium, thiophenium, thiuronium, triazadecenium, triazinium, triazolium, iso-triazolium, and uronium. [on SciFinder(R)]

Process for removing metals from hydrocarbons.

This invention relates to a process for removing metals, particularly mercury, from hydrocarbon streams by use of an ionic liq., where in the metal-contg. hydrocarbon stream is contacted with an ionic liq. to produce a product hydrocarbon stream having reduced mercury content. [on SciFinder(R)]