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,

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

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 effect of Mg 2+ on sulfate removal by ettringite precipitation was investigated, and the process was optimized in the absence and presence of Mg 2+. In the absence of Mg 2+ , 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 methodology.

Other constituents were in liquid phase, also gibbsite and portlandite. Final pH was lower than with the experiments. The simulation result for the solids mass was larger than the final experimental value. 2020-08-01 2017-07-01 2016-10-01 Chemical precipitation. Elina Merta, VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, FI-02044 VTT, Finland, elina.merta (at)vtt.fi.

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 aluminium precipitation with the simultaneous formation of ettringite was chosen for laboratory testing as it is appropriate when the concentrations of sulphates have to be reduced-up to 300

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. Alumin- Regarding the phase development during hydration, ettringite precipitation was identified as the dominant reaction in the first two hours.

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 results showed that ettringite precipitation is an effective and reliable method for sulphate removal. 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. 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 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).
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For monosulfate, the data for the two series for 45 Ca agreed well, both resulting in a reconstruction time around 500 days.

Effects of solid to liquid ratios, pH and temperature on ettringite dissolution, Al recovery and transformation of precipitates were investigated by batch experiments.
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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. Known processes for sulphate removal with ettringite precipitation contain the main unit Development stage. Known

Any in SPE Disciplines (1) Conference. Abu Dhabi International Petroleum Exhibition & Conference (1) Publisher. Society of Petroleum Engineers (1) Theme.