ChemInform Abstract: Interactions of Nickel and Manganese Carbonyls with Oxide Surfaces: Formation of Reduced, Oxidized, and Zerovalent Metal Species.

ChemInform ◽  
1989 ◽  
Vol 20 (28) ◽  
Author(s):  
M. P. KEYES ◽  
L. U. GRON ◽  
K. L. WATTERS
Keyword(s):  
Metal Species ◽  
Oxide Surfaces ◽  
Manganese Carbonyls

Production and STEM examination of controlled-size silver clusters

1983 ◽  
Vol 41 ◽  
pp. 338-339
Author(s):  
M. A. Listvan ◽  
R. P. Andres
Keyword(s):  
Cluster Size ◽  
Metal Clusters ◽  
Experimental Parameter ◽  
Carbon Films ◽  
Metal Species ◽  
Silver Clusters ◽  
Free Jet ◽  
Size Dependent ◽  
Cluster Properties ◽  
Controllable Size

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.

The Nature of Oxide Surfaces: Topographic and Electronic Structure

1993 ◽  
Vol 51 ◽  
pp. 966-967
Author(s):  
Dawn A. Bonnell ◽  
Yong Liang
Keyword(s):  
Transition Metal Oxides ◽  
Electronic Structures ◽  
Recent Progress ◽  
Spatial Localization ◽  
Level Of Detail ◽  
Scanning Tunneling ◽  
Oxide Surfaces ◽  
Tunneling Microscopy ◽  
Considerable Effort ◽  
Complete Understanding

Recent progress in the application of scanning tunneling microscopy (STM) and tunneling spectroscopy (STS) to oxide surfaces has allowed issues of image formation mechanism and spatial resolution limitations to be addressed. As the STM analyses of oxide surfaces continues, it is becoming clear that the geometric and electronic structures of these surfaces are intrinsically complex. Since STM requires conductivity, the oxides in question are transition metal oxides that accommodate aliovalent dopants or nonstoichiometry to produce mobile carriers. To date, considerable effort has been directed toward probing the structures and reactivities of ZnO polar and nonpolar surfaces, TiO2 (110) and (001) surfaces and the SrTiO3 (001) surface, with a view towards integrating these results with the vast amount of previous surface analysis (LEED and photoemission) to build a more complete understanding of these surfaces. However, the spatial localization of the STM/STS provides a level of detail that leads to conclusions somewhat different from those made earlier.

Effects of NTA on the Fate of Heavy Metals in Sediments

1993 ◽  
Vol 28 (8-9) ◽  
pp. 191-194 ◽  
Author(s):  
S. L. Lo ◽  
L. J. Huang
Keyword(s):  
Heavy Metals ◽  
Sodium Tripolyphosphate ◽  
Equilibrium Concentration ◽  
Chelating Agent ◽  
Metal Species ◽  
Pollution Problem ◽  
Trisodium Salt ◽  
Major Factors ◽  
Apparent Equilibrium ◽  
Degradation Time

Sodium tripolyphosphate (STPP), which is widely used as a builder in synthetic detergents, was found as one of the major factors of eutrophication in rivers and lakes. Many countries have used nitrilotriacetate (NTA) in detergents to replace STPP, but it induced another pollution problem. Because NTA is an effective chelating agent, it will dissolve heavy metals from the sediments and affect the fate of metal species in rivers. The purpose of this study is to investigate the effect of the mobilization of heavy metals from sediments by NTA. The experimental results indicated that NTA increases the mobilization of heavy metals as the shaking time increases and reaches an apparent equilibrium concentration after 24–48 hours. Typical results show that using 20mg/l of NTA and shaking time of 6 days, the fraction mobilized is about 8 to 15% for Cu, 1 to 7% for Zn, 7 to 10% for Pb, and 7 to 30% for Cd. Hardness of the water affects the formation of heavy metal-NTA complexes significantly. Biodegradation of the trisodium salt of NTA starts after 6–9 days with degradation time of the metal-NTA complexes decreasing in the order of Cu > Cd > Zn > Pb > Ca.

Metal and phosphate speciation during anaerobic digestion of phosphorus rich sludge

1997 ◽  
Vol 36 (6-7) ◽  
pp. 191-200 ◽  
Author(s):  
C. M. Carliell ◽  
A. D. Wheatley
Keyword(s):  
Anaerobic Digestion ◽  
Metal Speciation ◽  
Extraction Methods ◽  
Phosphate Removal ◽  
Metal Species ◽  
Chemical Extraction ◽  
Inorganic P ◽  
Similar Work ◽  
Extractable P ◽  
Phosphate Speciation

Chemical extraction methods are used to investigate metal and phosphate speciation during anaerobic digestion of phosphorus-rich sludge. Tests were performed using model compounds to evaluate the efficacy of the reagents in the extraction sequences and these results compared with similar work by other researchers. The metal speciation method was found to be suitable for identifying shifts in metal distribution but was unrepresentative of actual metal species. The phosphate speciation method did give adequate separation of the phosphate compounds tested. Full-scale digesters treating chemical and biological phosphate removal (CPR and BPR) sludge were analysed according to the methods developed. Results show that digestion of CPR sludge did not increase the soluble P concentration in the digester and that most of the precipitated phosphorus appeared to be retained in the sludge as inorganic P. The digester treating BPR sludge showed increased soluble and water-extractable P, in comparison to the control digester. Trace metal speciation profiles were found to be affected by addition of CPR sludge.

Modelling heavy metal mobilisation in solid waste deposits - a predictive tool for environmental risk assessment

1999 ◽  
Vol 39 (10-11) ◽  
pp. 193-196
Author(s):  
J. Petersen ◽  
J. G. Petrie
Keyword(s):  
Heavy Metal ◽  
Solid Waste ◽  
Environmental Risk ◽  
Mechanistic Model ◽  
Small Sample ◽  
Waste Material ◽  
Metal Species ◽  
Model Parameters ◽  
Assessment Methodology ◽  
Predictive Tool

The release of heavy metal species from deposits of solid waste materials originating from minerals processing operations poses a serious environmental risk should such species migrate beyond the boundaries of the deposit into the surrounding environment. Legislation increasingly places the liability for wastes with the operators of the process that generates them. The costs for long-term monitoring and clean-up following a potential critical leakage have to be factored in the overall project plan from the outset. Thus assessment of the potential for a particular waste material to generate a harmful leachate is directly relevant for estimating the environmental risk associated with the planned disposal operation. A rigorous mechanistic model is proposed, which allows prediction of the time-dependent generation of a leachate from a solid mineral waste deposit. Model parameters are obtained from a suitably designed laboratory waste assessment methodology on a relatively small sample of the prospective waste material. The parameters are not specific to the laboratory environment in which they were obtained but are valid also for full-scale heap modelling. In this way the model, combined with the assessment methodology, becomes a powerful tool for meaningful assessment of the risks associated with solid waste disposal strategies.

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