Metal analysis sample slurries

A development in the 1960s was that of on-line elemental analysis of slurries using x-ray fluorescence. These have become the industry standard. Both in-stream probes and centralized analyzers are available. The latter is used in large-scale operations. The success of the analyzer depends on how representative the sample is and how accurate the caUbration standards are. Neutron activation analyzers are also available (45,51). These are especially suitable for light element analysis. On-stream analyzers are used extensively in base metal flotation plants as well as in coal plants for ash analysis. Although elemental analysis provides important data, it does not provide information on mineral composition which is most cmcial for all separation processes. Devices that can give mineral composition are under development. 

A useful method of analysis of cmde and wear metals is the sample slurry method. It is well known that cmde and wear oils contain soluble, suspended and insoluble metal particulates and analysis of oils containing the soluble and suspended metals can be successfully carried out using a slurry method, provided that they are less than 4.0 pm in size and at a concentration that can be detected. An internal standard can be added to the oil sample slurry and nebulised along with the sample for matrix correction. 

Samples for trace metal analysis by A AS or ICP-OES must be presented to these instruments in liquid form. However, in some cases, samples are submitted as powders or solids (chippings, residues, etc.) requiring chemical decomposition prior to metal analysis that can lead to systematic errors in accuracy and precision of measurements. There have been many attempts to introduce samples as a slurry suspension and these were found to be successful for a limited number of samples provided that the particle sizes are suitably small. In most cases the nebulisation of the majority of samples analysed this way has shown that very low sample-introduction efficiency caused by variable particle sizes is in some cases difficult to dissociate, owing to the short residence times in the plasma. The availability of standards for this type of analysis is non-existent or difficult to obtain. 

After 1 h on an orbital shaker, pH is recorded and 5 mL aliquots of each thin slurry are filtered for ICP analysis. Over powders, Pt adsorption is complete within minutes [19,23], and 1 h contact is sufficient to ensure equilibration. Samples of the parent solution (before contact) are also filtered and analyzed with ICP, which can be used to determine not only metal uptake, but also dissolution of the support. The metal uptake, in terms of surface density (mol/m2), is calculated by dividing the concentration difference by the SL ... 

Activated carbon Activated carbon will remove a broad-spectrum of chemicals (e.g., organics, metal) from solution. Although nonselectivity of activated carbon is a limitation (and toxicants cannot typically be recovered) it can be useful in cases where toxicity is not removed by any of the other Phase I treatments, or when combined with chemical analysis before and after treatment. Samples are passed through a column (or mixed as a slurry) containing carbon and then tested for toxicity. 

The iron content of the catalyst samples was determined by chemical analysis after dissolution of the zeolite in concentrated sulfuric acid. Before this measurement, the metal complex made by the ion-exchange method was slurried for 1 hour in a saturated NaCl (aq) solution in an effort to reexchange uncomplexed iron. 

Preparation and Characterization of Lanthanide and Actinide Solids. Standard crystalline lanthanide and actinide phosphates were prepared by literature procedures (16-18) and characterized by X-ray powder diffraction, FTIR spectroscopy, and thermogravimetric analysis (TGA). Europium was used as an analogue of the trivalent actinides. Metal-phytate solids were generated by mixing Eu(III), U(VI), or Th(IV) nitrate solutions with 0.1 M phytic acid at pH 5 and metal.phytate ratios of 1 1 2 1, and 4 1. The metal phytates precipitated immediately. The resulting slurries were stirred at 85 °C for 30 days and sampled periodically for analysis of the solids by TGA, X-ray powder diffraction, and FTIR. The rate of phosphate release to the solution was monitored colorimetrically. 

Results. The slurry method of analysis of wear oils can give reproducible results when compared with the bomb combustion method (Table 5.19). The random selected metals analysed for this sample were used to show that this method could be used as an alternative provided that the particle sizes of insoluble suspensions in the oil are suitably small. This method may be an alternative to sample preparation by tedious destructive methods. 

The data in Table V were obtained by sequential treatment of the initial sample with sodium iodide and lithium chloride. Complexation with sodium iodide was done in a heptane-benzene slurry. The sparingly soluble sodium iodide chelate was isolated by filtering the mixture. The remaining solution was concentrated, and the residue obtained was contacted with lithium chloride in pentane. After stirring this heterogeneous mixture, a solid lithium chloride chelate complex was isolated by filtration. Decomposition of the alkali-metal salt complexes followed by recovery and analysis of the polyamine components showed that the sodium iodide complex contained 82.6% n-HMTP while the LiCl complex contained 94.8% N,N -c-PMPP. Table V shows that the initial polyamine sample contained 48.8 and 11.4% of these ligands, respectively. 

Once the sample has been polished to 3 pm, a final step (fine polishing) usually involving either an alumina slurry or colloidal silica slurry is used. The size of particles in these aqueous slurries can be as small as 0.02 pm. Once finished with this step, the sample is ready for etching. If elemental analysis of the polished sample is to be performed using SEM/EDS or other X-ray techniques, extra care should be taken. Often times artifact silicon or aluminum peaks can be introduced by accumulation of polishing abrasives in cracks and pores, and sometimes, depending on the metal hardness, by intrusion into the sample surface. 

A single multielement calibration standard is used to establish a relative sensitivity factor (R.) for each analyte (i) to be determined in the multielement analysis. For solution analysis, this multielement standard is usually prepared from high-purity metal salts dissolved in deionized water, with sufficient nitric acid added to stabilize their concentrations (pH 2 or less). Because this is only a semiquantitative analysis, matrix matching of the calibration standard to the matrix of the sample is not required. When using solid analysis techniques (i.e., slurry nebulization, laser ablation, etc.), an appropriate solid phase multielement calibration standard is most desirable however, novel approaches for the use of a solution standard have been used with some methods. 

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