• Ettringite precipitation ( SAVMIN™) • Aluminum added to water to form ettringite (calcium aluminum sulfate, Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O • Reaction at pH 11 -13 • Feasible for SO 4 < ~ 1,800 mg/l (gypsum solubility) • Sulfate removal to ~ 10’s mg/l - 000’s mg/l SO 4 • Aluminum form can be:
Ettringite decomposition is the reverse of ettringite formation and forms the gibbsite for recycle. The solids formed in Reactor 1 are not separated and are transferred to the gypsum precipitation reactor, Reactor 2, where lime is added.
• Ettringite precipitation with Gibbsite recovery • Aluminum recovered from Ettringite sludge and recycled to front end of process • Recovered aluminum sludge sample 19 Mine Design, Operations, and Closure Conference: Short Course - Mine Water Treatment - Technologies, Case Studies, and Costs May 3, 2015 Elina Merta, VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, FI-02044 VTT, Finland, elina.merta(at)vtt.fi Chemical precipitation techniques can be used to solve a number of problems in mine water treatment. Precipitation and co-precipitation are applicable for the removal of metals as hydroxides, carbonates or sulphides. Precipitation techniques are available also for the removal Sulphate control by ettringite precipitation in textile industry wastewaters In the present study, ettringite precipitation was theoretically and experimentally evaluated as a means of sulphate removal. 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.
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). Figure 1: Removal of High-Concentration Sulfate Ions from the Sodium Alkali FGD Wastewater Using Ettringite Precipitation Method: Factor Assessment, Feasibility, and Prospect 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).
Ettringite formation can also provide a polishing effect, allowing precipitation of difficult-to-remove metals such as chromium, arsenic, selenium and cadmium, often below their respective analytical detection limits. Boron, fluoride and up to 30 percent of the chloride and nitrate in water have also been removed. The optimum pH for ettringite precipitation in all systems was found to be around 12.0.
5 Jan 2016 Conventional Rainfall; Orographic Rainfall; Frontal Precipitation Besides rain and snow, other forms of precipitation are sleet and hail (more
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 . For monosulfate, the data for the two series for 45 Ca agreed well, both resulting in a reconstruction time around 500 days.
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 ettringite precipitation stage, in comparison to the other two liquid reagents. Table 4 contains the test results for the solid reagents. It is surprising to find that products based on crystalline aluminium hydroxide (Hydrargillite), even at relatively high doses, are not appropriate for ettringite precipitation. The obvious 2020-08-01 · Ettringite precipitation was implemented as an alternative to lime precipitation to process sulfate-rich brine resulting from the NF operation.
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.
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Other constituents were in liquid phase, also gibbsite and portlandite.
Sulfate concentrations in water have come under increasing scrutiny from regulatory authorities over the past two decades. In contrast to contaminants such as nitrate, arsenic, and heavy metals, sulfate has no primary standard for drinking water or aquatic life. Continuous ettringite precipitation experiments for sulphate removal .
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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
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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ettringite stream gypsum Prior art date 2015-07-22 Application number PCT/ZA2016/050025 Other languages French (fr) Other versions WO2017015678A3 (en Inventor Martha Hendriette Kotze Original Assignee Mintek Priority date (The priority date is an assumption and is not a legal conclusion.
Often the most dangerous type of winter precipitation is freezing rain.
23 Nov 2018 Sulphate removal from mine water with precipitation as ettringite and further utilisation of the precipitate as arsenate sorbent was investigated in
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 . et al., 1996).
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. Ettringite formation can also provide a polishing effect, allowing precipitation of difficult-to-remove metals such as chromium, arsenic, selenium and cadmium, often below their respective analytical detection limits. Boron, fluoride and up to 30 percent of the chloride and nitrate in water have also been removed. The optimum pH for ettringite precipitation in all systems was found to be around 12.0. 2020-01-01 · In Portland cements, most of ettringite is formed by the hydration of tricalcium aluminate Ca 3 Al 2 O 6 (C 3 A in cementitious notation) with calcium sulfate that is the result of dissolution-precipitation processes. Solid reactants dissolve and hydrate compounds precipitate from the released ions.