Glass filters, elemental content

A number of investigators have reported proximate analyses and elemental composition of textile mill dusts and trash. Only two of these involve studies of dusts collected with an elutri-ator sampler (20,31). Samples from both of these studies were collected in a model card room at North Carolina State University (42). In one of these, glass fiber filters were used and the dusts were analyzed for average ash contents (see Table IV). The total ash content was about 20%. The average ash content of area samples also collected on glass filters was found to be slightly lower. 

Another problem encountered was the impurity content of the filter paper used in the high volume samplers to collect the particulate samples. The conventional filter material used by EPA was glass fiber filter media. However, this was not compatible with INAA because of its high and varied impurity content. Discussions with K. Rahn of the Ford Reactor at the University of Michigan revealed that Whatman-41 filter paper was the most desirable medium for use with INAA (see Ref. 2). Our analyses showed Whatman-41 to be very low in impurities with consistent impurity levels from batch to batch. Average impurity levels, based on 12 batch analyses, are shown in Table III. Although the levels for calcium, chlorine, sodium, aluminum, and iron appear large, they rarely affected elemental levels found in filtered particulates. Impurity levels did not vary more than 25% from the mean. 

These ceramic membranes are relatively easy to operate for filtering particulates. The pressure drop across the thickness of a membrane element and the gas flow rate follows a linear or nearly linear relationship. It has been found, however, that not all inorganic membranes are suitable for clean room air filtration. Glass membranes, for example, suffer from the problem of particle shedding under mechanical shock conditions [Jensen and Goldsmith, 1987]. Sometimes high moisture content in the filtered air can be a problem. Some chemical treatments to ceramic membranes prior to their utilization as... 

This is the typical Italian grape-based pomace distillate. Produced and kept with a higher alcohol content, before sale it is diluted with water to a content of between 38% and 60% alcohol by volume (usually 42-43%) and filtered. As a consequence of water dilution, haze and turbidity of the product may occur. The elemental composition of grappa is related in particular to the stability of the product -mainly caused by Cu, Fe and related colour changes, and Ca and Mg precipitations with sulphates - and the presence of heavy metals eventually leached by distillation apparatus, tanks and pumps, wooden casks, filter pads and glass bottles. A survey of limpid and apparently stabile 58 grappa samples produced in northern Italy, some processed by very small distilleries, is shown in Table 8.10. The data show that the maximum values of several elements are clearly due to the cited leaching phenomena. 

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