engleski

The Effect of Zn^2+ -ion Saturated Zeolite in Hydration Processes in its Solidification in Portland Cement Composites

The zeolite and environmentally hazard waste remaining after ion exchange in the treatment of waste water saturated with Zn^2+- ions must be stabilized and permanently taken care of. One of possible methods is solidification by hydration in cement composites, which has been applied in this work. The reaction system used consisted of industrial Portland cement PC-45B with different additions, wZ(0-50%), of clinoptilolite type zeolite saturated by Zn^2+-ions and polymer admixture of a plasticizer-water reducing agent in the amount of wA(0, 3%) relative to the mass of the solid (cement + zeolite). Microcalorimetrical measurements have determined the values of hydration heat for the samples examined and their reaction degrees (alpha) ; curves of heat effects recorded have been analyzed to determine the effect of the zeolite addition on location and size of such recorded effects relative to hydration duration during stabilization and solidification. Determination of specific conductivity relative to the content of Zn^2+ -ion saturated zeolite and analysis of the results obtained have shown that samples with increased zeolite addition content have lower specific conductivity for all hydration times. The Zn^2+ -ion content in elutes formed by rinsing the solidified cement pastes has been determined by means of UV/Vis spectrophotometric analysis. The analysis results indicate that the Zn2+ -ion content in elutes, after rinsing with distilled water, for different periods of time (1, 2, and 24 hours) and solidification for 1, 3, 7, and 28 days, is very low and not readily recorded at all. Elutes obtained by rinsing with 0, 5 M HAc as the aqueous electrolyte of the same solidified cement samples contain some Zn^2+ -ion content, which is lower the longer the stabilization by solidification lasts and the shorter the rinsing time. Samples with lower content of the zeolite addition have lower values of Zn^2+ -ions in elutes. The examinations made confirm that the content of Zn^2+ - ion saturated zeolite in cement composite pastes affects both the development and the processes of hydration. Stabilization of such harmful wastes can be successfully realized by solidification in cement composites.

cement composite; cement hydration; stabilization/solidification; hazardous waste

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