Adsorption accumulation of proteins and dyes in foams of solutions and waste water

Abstract

We have previously derived equations that connect the main characteristics of foam accumulation and the separation of surfactants (accumulation ratio, liquid carry away, efficiency of surfactant extraction, degree of extraction and another) to properties of the surfactant solution (i.e. surfactant adsorption and surface tension) and the structural parameters of foam (expansion ratio, bubble size, film thickness). In these experiments we have applied these findings to investigations of proteins accumulation in foam at extraction from the waste water of heparin production, the accumulation of soap, made from the sulfate liquor of wood pulp manufacture, gelatin and dyes. Foam accumulation of protein substances from the waste water stream of heparin production was effected after dialysis in order to purify the solution from salts at pH 5 when the most stable foam was produced. For foam drainage under gravity the maximum accumulation ratio ( R max f ) was to 1.5 and R max f = 6 when the pressure difference was created in the liquid phase of foam. Accumulation of gelatin was carried on a stationary foam and in a moving foam at pH 4.8 (the isoelectric point) from a solution of gelatin and sodium dodecylsulfate mixture (at a gelatin/surfactant concentration ratio of 1.73 which corresponds to the formation of their complex). In dry foams R max f was 50 for the moving foam and R max f = 150 in the stationary foam. Separation of thymol blue shows that this dye forms the most stable foam in the acid region at pH 2.5 and in this region of pH dye is adsorbed on the foam bubble surfaces and the residual part of dye solution changes pH becoming more alkaline.