Aim: The aim of this publication is to experimentally identify the components of foaming agents that may have an impact on reducing the absorbency of rigid polyurethane foam waste in relation to post-foaming waste. This will allow to determine the mechanism behind the process which limits the sorbent’s effectiveness in rescue operations.
Methodology: The research methods used were a modified Westinghouse test and a proprietary method of analysis of results taking into account the loss of mass following the evaporation of sorbate from the sorbent space. The tests used rigid polyurethane foam in the form of a solid powder. The tests examined selected combinations of ingredients that concentrate foaming agents, including sodium dodecyl sulphate, 2-butanol, 1-undecanol.
Results: The dependence of the mass of sorbate solution absorbed in the pores of the sorbent as a function of dripping time and the maximum theoretical mass was determined for all tested systems by extrapolation of evaporation line to the OY axis. The determination of the influence of chosen ingredients of foaming agents on sorption was related to water sorption. To this end, the average maximum theoretical masses obtained for individual systems with different concentrations were compared and their compatibility with the average value obtained for water was examined. For this purpose, the comparative criterion was used at the level of significance a = 0.1.
Conclusions: During the preliminary tests, the sorptivity of rigid polyurethane foam was noticeably lower in the presence of foaming agents, as compared to water. The tests clearly show that the factor responsible for the deterioration of pumice absorption properties is the presence of 1-undecanol in the foam concentrate, which is used as a foam stabiliser. This is of course synergistic with sodium dodecyl sulphate. While sodium dedecyl sulphate alone caused a small change in the absorbed mass of sorbate (about 2%), the addition of undecan-1-ol caused as much as 43% change. The addition of a solvent (2-butanol), in turn, caused only a slight change in absorptive properties, with the absorbency being slightly increased irrespective of the combination. The obtained results indicate that the factor responsible for the drop in sorptivity may be the low value of surface tension, which is typical of foaming agents solutions containing anionic surfactants. The decrease in surface tension causes a reduction in the capillary force and, as a result, facilitates the leakage of liquid from sorbent pores. The results indicate some limitations in the use of rigid polyurethane foam in rescue operations aimed at removing residuals of foaming agent solutions or water solutions containing traces of such agents.
Keywords: firefighting foam waste, rescue operations, contamination removal, post-fire sewage, sorbent sorptivity
Type of article: original scientific article