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Abstract

This study was undertaken to determine the effectiveness of biosurfactants - saponin, tannin and rhamnolipids JBR 515 and 425, for the removal of cadmium, zinc and copper from activated sludge immobilized in 1.5% sodium alginate with 0.5% polyvinyl alcohol. We also established the impact of pH value on biosorbent regeneration with the analyzed biosurfactants and determined the critical micelle concentration (CMC) in solutions containing the biosorbent and biosurfactant and in exact samples with heavy metals. Saponin exhibited the highest effectiveness of metals leaching at pH 1-5, and rhamnosides at pH 5-6. In addition, the study demonstrated a significant effect of the ratio of biosorbent mass to washing agent volume (m/V) on the effectiveness of metals leaching. Of the biosurfactants analyzed, saponin was ca. 100% effective in leaching zinc and copper. The effectiveness of the other biosurfactants was lower and depended on the metal being leached
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Abstract

The objective of this investigation was to test the effectiveness of the Acoustic Emission (AE) measurements in determining the critical stresses during four-point bending of mortar beams. Within the measuring procedure the parameter σcr/σ300 was calculated and analysed. Additionally, the influence of cement replacement by high calcium fly ash (HCFA) on the process of crack healing was discussed. Mortar beams with different content of HCFA and reinforced by steel microfibres were prepared for tests. After curing in standard conditions the beams were subjected to four-point bending test in order to introduce the pre-cracking. Thereafter the beams were cured in the lime water and loaded after 56 and 112 days in the same way as for the first time. Additionally the microstructure of mortars was studied in a stereo optical microscope as well in an electron scanning microscope including the Energy Dispersive X-ray analysis (EDX). The results of microstructural characterization of mortar containing HCFA from lignite combustion are presented. The applied load level slightly exceeded the critical stress, producing intense crack growth processes however did not significant affected the load capacity of the beams. During the consecutive loading the decreasing tendency of σcr/σ300 ratio was noted. The obtained results confirm that the latter parameter can be applied as a measure of the composite degradation level for the elements carrying the repeated loads of amplitude close to the critical stress of the structure and also that the cement replacement with HCFA influences the process of crack healing.
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