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.
Gerätebau GmbH. A photograph of the plant in use with NaAlO 2 and lime and a close-up of the ettringite precipitates can be seen in Figures 1 and 2. The plant consists essentially of a raw water tank, a reactor tank followed by a consumed by ettringite precipitation. 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).
Sulfate-resistant cements are manufactured in the absence or with very low proportions of C 3 A (0–5% in CEM I-SR []) to prevent the detrimental precipitation of ettringite (3CaO∙Al 2 O 3 ∙3CaSO 4 ∙32H 2 O). Ettringite precipitation Introduction.
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.
The statistical analysis of the results showed that the operating parameters such as molar rates of Ca/ SO4 and Al/SO4, and pH had a significant effect on sulfate removal efficiency. Ettringite was precipitated in the presence of TcO4-, IO3-, and/or CrO42-, known contaminants of concern to nuclear waste treatment, over pre-determined precipitation periods. Solution analyses quantified contaminant removal and the collected solid was characterized using bulk and microprobe XRD coupled with PDF and microprobe XRF more » analyses. 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.
Under conditions of extreme deterioration, and repeated wetting and drying, ettringite crystals can appear to completely fill voids
1.Introduction. Sulfate-resistant cements are manufactured in the absence or with very low proportions of C 3 A (0–5% in CEM I-SR []) to prevent the detrimental precipitation of ettringite (3CaO∙Al 2 O 3 ∙3CaSO 4 ∙32H 2 O).
Ettringite precipitation Introduction.
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A photograph of the plant in use with NaAlO 2 and lime and a close-up of the ettringite precipitates can be seen in Figures 1 and 2. The plant consists essentially of a raw water tank, a reactor tank followed by a consumed by ettringite precipitation. 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 stirring rate, with a bar magnet, was taken equal to 400 rpm. A novel sulfate removal process via ettringite precipitation was developed by dissolving ettringite and recycling Al 3+ under low pH condition. Effects of solid to liquid ratios, pH and temperature on ettringite dissolution, Al recovery and transformation of precipitates were investigated by batch experiments. ettringite precipitation is a well-known process and can be described as a standard method for sulphate removal from industrial wastewater at relatively small flow (S. CHUSTER .
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Effects of solid to liquid ratios, pH and temperature on ettringite dissolution, Al recovery and transformation of precipitates were investigated by batch experiments. Ettringite crystals in air voids and cracks are typically 2 to 4 micrometers in cross-section and 20 to 30 micrometers long. Under conditions of extreme deterioration, and repeated wetting and drying, ettringite crystals can appear to completely fill voids 1.Introduction. Sulfate-resistant cements are manufactured in the absence or with very low proportions of C 3 A (0–5% in CEM I-SR []) to prevent the detrimental precipitation of ettringite (3CaO∙Al 2 O 3 ∙3CaSO 4 ∙32H 2 O). Ettringite precipitation Introduction. Ettringite precipitation (addition of lime and Al (OH) 3) can be used to remove sulphate and heavy metals. Description of the technology.
The following equation shows the basic chemical reaction to form ettringite Eq (1):) 1 (
Ettringite and its chromium analogs were synthesized and their solubilities measured via dissolution and precipitation experiments over a range of temperatures between 5 and 75ºC and pH values between 10 and 13. Environmental Technology In the present study, ettringite precipitation was theoretically and experimentally evaluated as a means of sulphate removal.
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CHUSTER . et al., 1996). This precipitation process is well-understood, reliable and can be easily controlled.