Wet Chemical Extraction Research Articles

Seasonal cycling of Fe in saltmarsh sediments

This study combines an analysis of porewater chemistry with new, solid phase wet chemical extractions to examine the seasonal cycling of Fe in vegetated and unvegetated (cyanobacterial mat) saltmarsh sediments. Saltmarsh sediments are shown to contain more solid phase reactive Fe than other marine sediments studied so far. From the partitioning and speciation of solid Fe, and solid/soluble reduced S analysis in 10 sediment cores, we have observed that a majority of solid Fe in these sediments is cycled rapidly and completely between oxidized reactive Fe and reduced Fe as pyrite. Vegetated porewaters showed a lower pH and much higher Fe(II) concentrations on average than unvegetated porewaters in the top 10 cm, whereas sulfate, alkalinity, and sulfide concentrations were similar in the two environments. The amorphous Fe(III) oxide fraction showed a high negative correlation to solid and soluble reduced S (r2 = −0.86 and −0.71, respectively) in surface vegetated sediments whereas the crystalline Fe(III) oxide fraction showed a high negative correlation (r2 = −0.96) to sulfide only at depth. Though reactive Fe was observed in unvegetated sediments, no seasonal trend was apparent and the speciation of solid Fe revealed that most of it was reduced. Solid phase and porewater chemistry support the dominant role of the biota (Spartina alterniflora and bacteria) in controlling the reactivity of Fe and suggest that the current definition of solid phase, reactive Fe should be expanded to include crystalline Fe(III) minerals which are available for pyrite formation in saltmarsh sediments. In support of previous saltmarsh studies, we present evidence that the redox cycle of solid Fe is controlled by sulfate reduction and sediment oxidation which respond to both annual cycles (light, temperature) and to short-term, episodic effects such as weather and tides.

Surface-Enhanced Raman Vapor Dosimeter

This paper describes a new direct-reading personal dosimeter designed to detect vapors of organic chemicals. The device employs the surface-enhanced Raman scattering (SERS) technique for direct measurement of the amount of analyte collected on the dosimeter, requiring no sample desorption or wet-chemical extraction procedure. The time-weighted average exposure to the chemical vapors can be determined on the dosimeter substrate. The results with benzoic acid used as the model compound illustrate the usefulness of this SERS-based dosimeter.

A simple wet chemical extraction procedure to characterize soil organic matter (SOM). I. application and recovery rate

Abstract The knowledge of soil organic matter (SOM) composition is important for research in soil science. This is why two classical wet chemical extraction procedures were tested and combined to characterize SOM. Twenty‐five samples from typical forest and arable soils in Schleswig‐Holstein, Northwest Germany, were investigated in the laboratory. Lipids were extracted using a pre‐step method. Several polysaccharide fractions were extracted sucessively with inorganic acids in a litter compound analysis (LCA). Proteins and lignins were determined in the bulk soil sample. In a humic compound analysis (HCA), fulvic and humic acids were extracted in the classical way with NaOH, and the non‐humic substances were removed with the aid of the “Sulfacetolysis” from the residues (= usually “humins)‐ The combination of these two wet chemical extraction proce dures (LCA and HCA) permitted quantitative estimations of the SOM composition in several soil horizons. The LCA method produced a better recovery rate (104%±4%...

MgO-supported CO hydrogenation catalysts derived from [H 3ReOs 3(CO) 13

Magnesia-supported catalysts were prepared from [Os 3(CO) 12], [H 3Re 3(CO) 12], a combination of the two, and [H 3ReOs 3(CO) 13]. The catalysts were tested for hydrogenation of CO in a flow reactor, the surface structures were characterized by infrared spectroscopy and wet chemical extraction (cation metathesis), and the used catalysts were investigated with transmission electron microscopy and energy dispersive X-ray spectroscopy. The catalysts all lost activity during operation; the catalyst made from the triosmium cluster lost activity as a result of being converted into the inactive [OS 10C(CO) 24] 2−, as observed previously. The catalyst made from the bimetallic cluster lost activity less rapidly than the others, and the IR spectra indicate that formation of the decaosmium cluster had been prevented by Re, which was present near the Os particles in the used catalyst. In contrast, when [Os 3(CO) 12] and [H 3Re 3(CO) 12] were used in combination, the formation Of [Os 10C(CO) 24] 2− took place, the deactivation was relatively rapid, and there was negligible Re in the immediate neighborhood of the Os particles. Evidently, Re remote from the Os exerted no stabilizing effect. These results indicate an advantage of having the two metals initially bonded to each other in the catalyst precursor.

Von der Schadstoffquelle zur Schadstoffsenke – neue Konzepte der Müllverbrennung

AbstractFrom pollutant source to pollutant sink – Novel concepts of solid incineration. Until a few years ago, solid waste incineration plants were considered to be major sources of pollutant emission. Meanwhile, by enhancing the effectiveness of combustion and by integration of modern flue gas cleaning techniques, solid waste incineration now leads with regard to emission reducing engineering measures. Harmful effects on the environment no longer originate in the stacks of these plants. Recently, pollutants enriched in flue gas cleaning products have caused disposal problems. These problems can be solved by concentrating the harmful inorganic constituents, above all mercury and cadmium, to a still higher level through wet chemical extraction and removal of the resulting concentrate from the process. Organic pollutants can be conveniently destroyed by thermal treatment. Despite all the objections there are good chances of using solid waste incineration as a pollutant sink and hence as a tool helping to protect our environment.

Determination of chromium speciation in environmental particles. Multitechnique study of ferrochrome smelter dust

The chemical speciation of particulate Cr has a significant influence on its environmental impact, with Cr/sup 6 +/ compounds of greatest current concern. A novel analytical regimen was evaluated for the determination of the concentration, speciation, and potential bioavailability of environmental Cr by using the example of ferrochrome smelter dust. Various wet chemical extractions were compared for possible use in the routine environmental monitoring of bioavailable Cr and Cr/sup 6 +/. Roughly half of the total Cr in the primary smelter dust was extractable by routine acid/base leaching (bioavailable), of which about 40% was Cr/sup 6 +/. The Cr/sup 6 +/ exists as Cr/sub 2/O/sub 7//sup 2 -/ or CrO/sub 4//sup 2 -/ and predominates in submicron particles probably formed during smelting. The remainder of the Cr is primarily insoluble Cr/sub 2/O/sub 3/ which is located in large particles similar to the original chromite ore.