Obtenção e caracterização de filtros de profundidade de crisotilas brasileiras

AUTOR(ES)
DATA DE PUBLICAÇÃO

1989

RESUMO

Chrysotile asbestos has been used in the manufacture of deep filtration filters since longo, owing to its high specific surface area and its positive surface charge. However, as in the case of other natural materials, the performance of the filters depends very strongly on the chrysotile origin. Filters obtained from brazilian asbestos have considerabily poorer performance than those imported. This work describes procedures developed to purify, to remove iron compounds, to maximaze surface area and saturation of comercial chrysotiles, yielding filters with proper perfor-mance. Comercial chrysotile type 5RL was dispersed in aqueou solutions cationic, anionic and non-ionic surfactants, and sodium of hexametha- phosphate; the dispersions were either shaked in a thermostatic bath, or mechanically agitated, or ultra-sonified, and then washed in tap water over a Tyler 250 sieve. In any case, (38 ± 1)% material was removed. The average value found for the iron content in the commercial chrysotile 5RL was 2,2 mg Fe/g chrysotile, and in the purified chrysotile was 1.3 mg Fe/g chrysotile. The deep filters developed are built up of chrysotile type 5RL and cellulose. The ratio chrysotile/cellulose, and the cellulose type (pinus or eucalipt) were varied. The porosity of the different filters was calculated; values obtained are between 0,76 and 0,81, which are typical values for deep filters. Permeability was determined mesuring the pressure drop in an air flow through the filters. The values obtained showed a certain dependen- ce on the cellulose type. The filters of composition chrysotile-cellulose (pinus) have higher permeabilities, campared with the permeabilities of the filters of chrysotile-cellulose(eucalipt). Saturation degree was determined by filtration of a methylene blue solution; this essay was applied to filters with variations in the ratio chrysotile-cellulose; the results showed that the filters of chrysotile-cellulose(eucalipt) are more efficient concerning to the retained mol number/g chysotile and filtrate volume of the methylene blue solution, compared with the filters of composition chrysotile-cellulose (pinus). The filters were also tested for the retention of isodisperse latex particles of polystyrene, 0,109/mm in diameter, typically, 97% retention was found after filtration of 50 ml of 6,5 FTU dispersion.

ASSUNTO(S)

filtros e filtrações crisotila

ACESSO AO ARTIGO

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