Sep 19, 2019 The ettringite precipitation is a modification of high pH lime precipitation (Tolonen et al. 2016), and judging from the lower solubility of ettringite,
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.
Known processes for sulphate removal with ettringite precipitation contain the main unit Development stage. Known 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).
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 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 Source. OnePetro (1) Date. 2020 (1) to. Go SPE Disciplines. Highlight matches. Any in SPE Disciplines (1) Conference. Abu Dhabi International Petroleum Exhibition & Conference (1) Publisher. Society of Petroleum Engineers (1) Theme. OnePetro (1) Author. Bonnier, Nicolas (1)
The mine water sulphate concentration was reduced by 85-90% from the initial 1400 mg/L during ettringite precipitation depending on the treatment method. 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.
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,
Tim Ledbetter, PNNL. Sarah Saslow, a chemist at Pacific Northwest National Laboratory, led the team that explored ettringite’s ability to immobilize the contaminant pertechnetate. Ettringite precipitation Stage 3 is the heart of the Ettringite process and involves the addition of aluminium hydroxide to the saturated gypsum solution from stage 2. This results in the formation of the Stage 3 Solids (gypsum) Mine water Heavy metals Lime Lime Stage 1 … Rather, the water for ettringite precipitation would be sourced from the excess water in the amorphous AH x forming.
Effects of solid to liquid ratios, pH and temperature on ettringite dissolution, Al recovery and transformation of precipitates were investigated by batch experiments. The optimum condition for Al recovery is pH =3.0, suspended solid of 9.8 g/L and
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.
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Iodate Leach Behavior from Ettringite and Implications for Iodine Retention in Previous studies using ettringite precipitation to remove aqueous IO3- have Nov 5, 2019 The diffusion-precipitation mechanism is translated by a rough chemical model. The resulting local volume fraction of ettringite is estimated by a.
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).
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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 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. All these outcomes together have not been observed in the current most used processes of sulphate precipitation, i.e.
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The immobilization mechanism mainly involves co-precipitation with ettringite and hydrocalumite, the marginal formation of insoluble Ca salts, and occlusion in
Tim Ledbetter, PNNL. Sarah Saslow, a chemist at Pacific Northwest National Laboratory, led the team that explored ettringite’s ability to immobilize the contaminant pertechnetate.
Chemical precipitation. Sulphide precipitation; Precipitation with barium salts; Ettringite precipitation; Iron co-precipitation; Ion exchange; Membrane processes; Sulphate reduction in reactors; Treatment/disposal of water treatment residues; Passive treatment technologies. Aerobic constructed wetlands; Anaerobic constructed compost wetlands
Description of the technology.
Other constituents were in liquid phase, also gibbsite and portlandite. Final pH was lower than with the experiments.