![]() ![]() Three series of pastes were prepared: the reference series, mixing water with Ordinary Portland Cement (OPC), and two series in which whether a styrene–butadiene rubber latex or a superplasticiser based on acrylic-modified polymer was added to the pastes. The role of polymeric additives on the hydration process of cement pastes admixed with a lead compound (Pb 3O 4) was investigated. The rate of leached Cu (II) ions from the matrix of hydrated C 3S was investigated by the application of diffusion equation derived for a plane source model. Most of the investigated samples showed high degree of immobilization of Cu (II) ions and the doped mixes showed better immobilization results than mixes hydrated in water containing wastes. Immobilization percentage of Cu (II) ions inside the C 3S hydrated matrix was examined by the determination of the leached copper by using atomic absorption spectroscopy. This is due to the precipitation of the less soluble Cu(OH) 2 which retards the precipitation of Ca(OH) 2 as a result of the reduction in pH. The results showed that the presence of Cu (II) ions retard the early hydration of C 3S. X-ray diffraction examination was performed for some selected samples. The chemically combined water and free Ca(OH) 2 contents were determined after 3, 6 h and 1, 3 and 7 days of hydration. Levels of Cu (II) used were 1 and 3 wt.% of C 3S. ![]() Copper ions here either doped inside C 3S during its preparation or present in the water of hydration. In the present work the stabilization of Cu (II) wastes by C 3S during its early hydration (from 3 h – 7 days) was studied. C 3S, tricalcium silicate, is one of the main phases in OPC and many of its properties were related to C 3S. The investigation showed that part of Cr 3+ was oxidized to Cr 6+ in the clinkering process and identified as the chromium compounds Ca 4Al 6O 12CrO 4 (3CaO♺l 2O 3♼aCrO 4), which resulted in the higher leaching of hydrated matrix of Cr-doped C 3A.Ĭement is the most adaptable binder currently available for the immobilization of heavy metals. To explain this, C 3A formation, chemical valence states of chromium in C 3A, hydration products and Cr distribution in the C 3A-gypsum hydrated matrixes were studied by XRD, XPS and FESEM-EDS. The results indicated that C 3A had a good solidifying effect on chromium using the clinkering process, however, the Cr leaching content of Cr-doped C 3A was higher than that of hydrated C 3A matrix in Cr(NO 3) 3 solution and was lower than that of the hydrated C 3A matrix in K 2CrO 4 solution, no matter the leachant was sulphuric acid & nitric acid or water. The immobilization rate of chromium in C 3A and the leaching characteristics of the C 3A hydrated matrixes containing chromium were investigated by ICP-AES. This work focus on the stabilization/solidification on chromium (III) wastes by C 3A and C 3A hydrated matrix. Hazardous wastes are usually used in the Portland cement production in order to save energy, costs and/or stabilize toxic substances and heavy metals inside the clinker. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |