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After partial sulphate removal, a smaller dosage of the more expensive aluminium chemical is required for the ettringite precipitation step. DOI: 10.1590/0104-6632.20180353S20170528 Corpus ID: 104463417. STATISTICAL OPTIMIZATION OF ETTRINGITE PRECIPITATION IN LANDFILL LEACHATE @article{Aygun2018STATISTICALOO, title={STATISTICAL OPTIMIZATION OF ETTRINGITE PRECIPITATION IN LANDFILL LEACHATE}, author={A. Aygun and S. Dogan and M. E. Argun}, journal={Brazilian Journal of Chemical Engineering}, year={2018}, volume={35}, pages={969-976} } 2000-02-28 · ettringite could reduce the protection the air void system affords against freeze-thaw damage (see discussion of freeze-thaw resistance below).

The presence of AFt and AH 3 was verified by XRD and FTIR characterization of the 2-d pastes, which exhibited some minor carbonation in the form of calcite (see Figure 3 ), observed to increase in intensity over time. In this study, the principles of chemical precipitation of sulfate which is based on the formation of ettringite, a double salt with the formula Ca3Al2O6.3CaSO(4).32H(2)O are evaluated. When ettringite precipitation is used for waters with high sulphate concentration (>3000 mg/L), it may be economical to use traditional lime precipitation as a pre-treatment to remove some of the sulphate. After partial sulphate removal, a smaller dosage of the more expensive aluminium chemical is required for the ettringite precipitation step. The aim of this research was to investigate sulphate removal from mine water by precipitation as ettringite (Ca6Al2(SO4)3(OH)12·26H2O) and the utilisation of the precipitate as a sorbent for arsenate removal. The mine water sulphate concentration was reduced by 85-90% from the initial 1400 mg/L during ettringite precipitation depending on the treatment method. Ettringite was precipitated in the presence of TcO 4 –, IO 3 –, and/or CrO 4 2–, known contaminants of concern to nuclear waste treatment, over pre-determined precipitation periods.

Ettringite is a calcium sulfoaluminate hydrate with a composition of C 6ASS 3H 32: As such, the penetrating sulfates need to ﬁnd a source of aluminium and calcium with which to react. Alumin- Regarding the phase development during hydration, ettringite precipitation was identified as the dominant reaction in the first two hours.

22) measured the dissolutionprecipitation reaction rate between the solid ettringite and the aqueous Abstract In the present study, experiments were conducted to optimize sulfate removal efficiency with ettringite precipitation from landfill leachate using ettringite precipitation Source. OnePetro (1) Date. 2020 (1) to. Go SPE Disciplines.

The first step of reaction is the dissolution of sulphate and alkali constituents, Sulphate concentrations of approximately 1,400, 700, 350 and 20 mg/L were obtained using gypsum precipitation, and ettringite precipitation, biological The evaluation of chemical precipitation for sulfate removal such as gypsum and ettringite formation as well as the use of membrane filtration and the decision ettringite mentioned in (a) is formed in the hydration of portland cement, ferro- precipitation from the solution phase, i . e., ions of calcium, aluminate, and precipitation of expansive phases (ettringite and gypsum) in the pore network are of the ettringite precipitation may be more relevant than the total quantity of The immobilization mechanism mainly involves co-precipitation with ettringite and hydrocalumite, the marginal formation of insoluble Ca salts, and occlusion in from the performed experimental tests with the tested mine waters that ettringite precipitation yielded in low residual concentrations in treated water. Ettringite precipitation can be considered as responsible for these expansions. The experimental study of the CaO-SiO2-Al2O 3-SO3-H2O system clarified the of sulfate ions as minerals like gypsum and ettringite via calcium/ aluminum Keywords: Sulfate Reduction, Industrial Wastewater, Chemical Precipitation, Sulfate-induced heaving in soils is primarily attributed to ettringite formation from the reactions between calcium of a lime or cement stabilizer, reactive alumina Selective sulphate removal by ettringite precipitation. • Softening and pH adjustment by re-carbonation. Figure 1 shows a schematic process flow diagram.
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Description of the technology.

In the absence of Mg2+, the optimum conditions with sulfate removal of 99.7% were obtained at calcium-to-sulfate ratio of 3.20, aluminum-to-sulfate ratio of 1.25 and pH of 11.3 using response surface precipitation as ettringite (Ca6Al2(SO4)3(OH)12·26H2O) and the utilisation of the precipitate as a sorbent for arsenate removal.
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ETTRINGITE. Portland Cement: Clinker Compounds: -C3A. -C3S. -C2S. -C4AF. - Gypsum (CSH2) is added to the clinker.

Namely, under these conditions, the supersaturation level is the highest for ettringite which is then the more stable phase. Ettringite precipitates according to the reaction : 3Ca 2+ + 2Al 3+ + 12OH-+ 3Ca 2+ + 3SO 4 2-+ 26H 2O Ca 6Al 2(SO 4)3(OH) 12,26H 2O (III) Due to the precipitation of these salts in the hardened matrix , the process was intensified in the 90-d material by the slight decline in ettringite content (Figure 9b). The products identified were similar to the ones found when PC, attacked by sulfates, cracks in response to their formation [ 42 , 43 ]. Precipitation of ettringite The most common image of sulfate attack is associated with the precipitation of ettringite, leading to expansion and cracking. Ettringite is a calcium sulfoaluminate hydrate with a composition of C 6ASS 3H 32: As such, the penetrating sulfates need to ﬁnd a source of aluminium and calcium with which to react.

The results showed that ettringite precipitation is an effective and reliable method for sulphate removal. When ettringite precipitation is used for waters with high sulphate concentration (>3000 mg/L), it may be economical to use traditional lime precipitation as a pre-treatment to remove some of the sulphate. After partial sulphate removal, a smaller dosage of the more expensive aluminium chemical is required for the ettringite precipitation step. Ettringite •Ettringite is a complex hydrated calcium aluminum sulfate compound with this overall formula in nature: Ca 6 Al 2 (SO 4) 3 (OH) 12 ·26H 2 O •Theoretically, a precipitation process forming ettringite can drop dissolved sulfate levels to 50 mg/L or less under the right conditions In this study, the principles of chemical precipitation of sulfate which is based on the formation of ettringite, a double salt with the formula Ca3Al2O6.3CaSO(4).32H(2)O are evaluated. The aim of this research was to investigate sulphate removal from mine water by precipitation as ettringite (Ca6Al2(SO4)3(OH)12·26H2O) and the utilisation of the precipitate as a sorbent for arsenate removal.