Abstract In the present study, experiments were conducted to optimize sulfate removal efficiency with ettringite precipitation from landfill leachate using

The precipitation of boron in the form of an insoluble compound would be a very attractive method of treatment, but unfortunately, there is no known compound that quantitatively precipitates boron . The classical ettringite, having the chemical formula 6CaO·Al 2 O 3 ·3SO 3 ·32H 2 O [Ca 3 Al

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 ].

Ettringite precipitation

from the performed experimental tests with the tested mine waters that ettringite precipitation yielded in low residual concentrations in treated water. Ettringite precipitation can reduce the sulphate concentration to ca. 200 mg/l (concentrations < 100 mg/l have also been reported) and provides also simultaneous reduction of calcium. Ettringite formation can also provide a polishing effect, allowing precipitation of metals and metalloids such as Ni, Cd, Cu, Zn, Cr, As, Se, and Cd. Sulphate precipitation as ettringite is a modification of high pH lime precipitation (Geldenhuys et al., 2003, Tolonen et al., 2015). With precipitation as ettringite, mine water sulphate concentration can be reduced to less than 200 mg/L. This is less than the drinking water guideline in Finland, which is 250 mg/L sulphate (Directive 98/83/EC).

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19 Aug 1999 added after standard lime treatment to precipitate a compound called ettringite, which can be removed using a clarifier and filter press. Sulfate

Sulfate others like calcium hydroxide and ettringite can precipitate in the water phase. 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.

2016-10-01 · Sulphate precipitation as ettringite is a modification of high pH lime precipitation (Geldenhuys et al., 2003, Tolonen et al., 2015). With precipitation as ettringite, mine water sulphate concentration can be reduced to less than 200 mg/L. This is less than the drinking water guideline in Finland, which is 250 mg/L sulphate (Directive 98/83/EC).

The precipitation conditions Chemical, physical and biological technologies for removal of sulphate from mine tailings pond water (8 g SO 4 2-/L) were investigated. Sulphate concentrations of approximately 1,400, 700, 350 and 20 mg/L were obtained using gypsum precipitation, and ettringite precipitation, biological sulphate reduction or reverse osmosis (RO) after gypsum pre-treatment, respectively. Figure 1: Removal of High-Concentration Sulfate Ions from the Sodium Alkali FGD Wastewater Using Ettringite Precipitation Method: Factor Assessment, Feasibility, and Prospect ettringite precipitation. The pilot plant was supplied by G.U.N.T.

Alumin- 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. Solution analyses quantified contaminant removal, and the collected solid was characterized using bulk and microprobe X-ray diffraction coupled with pair distribution function and microprobe X-ray Chemical, physical and biological technologies for removal of sulphate from mine tailings pond water (8 g SO 4 2-/L) were investigated. Sulphate concentrations of approximately 1,400, 700, 350 and 20 mg/L were obtained using gypsum precipitation, and ettringite precipitation, biological sulphate reduction or reverse osmosis (RO) after gypsum pre-treatment, respectively. 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 2021-04-20 · Even though these components may be available, thermodynamic favorability and concentration of limiting reagents control the precipitation of ettringite and thaumasite (3). Although several calcium-aluminum-sulfate hydrates can form during stabilization, only mono-sulfate hydrate and tri-sulfate hydrate forms are stable in solution (18).
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• Softening and pH adjustment by re-carbonation. Figure 1 shows a schematic process flow diagram.

It is a colorless to yellow mineral crystallizing in the trigonal system. The prismatic crystals are typically colorless, turning white on partial dehydration. It is part of the ettringite-group which includes other sulfates such as thaumasite and bentorite.
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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

With increasing ettringite content during hydration, the effect on the flow behavior becomes much larger. WO2017015678A2 PCT/ZA2016/050025 ZA2016050025W WO2017015678A2 WO 2017015678 A2 WO2017015678 A2 WO 2017015678A2 ZA 2016050025 W ZA2016050025 W ZA 2016050025W WO 2017015678 A2 WO2017015678 A2 WO 2017015678A2 Authority WO WIPO (PCT) Prior art keywords sulphate calcium ettringite stream gypsum Prior art date 2015-07-22 Application number … Ettringite precipitation Introduction.

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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. Solution analyses quantified contaminant removal, and the collected solid was characterized using bulk and microprobe X-ray diffraction coupled with pair distribution function and microprobe X-ray

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. Solution analyses quantified contaminant removal, and the collected solid was characterized using bulk and microprobe X-ray diffraction coupled with pair distribution function and microprobe X-ray The optimum pH for ettringite precipitation in all systems was found to be around 12.0. By the application of the method, 0.06 M initial sulphate concentration was reduced down to 60 mg/L for (2016). Sulphate control by ettringite precipitation in textile industry wastewaters. Environmental Technology: Vol. 37, 9TH IWA SYMPOSIUM ON WASTE MANAGEMENT PROBLEMS IN AGRO-INDUSTRIES-AGRO’2014, pp.

Ettringite precipitation was implemented as an alternative to lime precipitation to process sulfate-rich brine resulting from the NF operation. More than 93% of the sulfate ions were removed by ettringite precipitation, whereas lime precipitation removed less than 28% under the same conditions due to the difference in their solubility.

The pilot plant was supplied by G.U.N.T. 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.

et al., 1996). This precipitation process is well-understood, reliable and can be easily controlled. The SAVMIN process is similar to the One of the main challenges in industrial wastewater treatment and recovery is the removal of sulfate, which usually coexists with Ca2+ and Mg2+. The effect of Mg2+ on sulfate removal by ettringite precipitation was investigated, and the process was optimized in the absence and presence of Mg2+. 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 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. The determined reconstruction time for ettringite lay within 1.2-4 years, which resulted in a dissolution-precipitation rate of 10 À 12.2 to 10 À 11.5 mol m À 2 days À 1.