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Sustainable and Economically Profitable Reuse of Bauxite Mining Waste with Life Cycle Assessment
Published in Hossain Md Anawar, Vladimir Strezov, Abhilash, Sustainable and Economic Waste Management, 2019
Hossain Md Anawar, Vladimir Strezov, Tanveer M. Adyel, Golam Ahmed
To prepare gypsum waste mud is elutriated by sulphuric acid or by mixture of H2SO4, HNO3, KNO3, soil microorganisms (Deuteromyces) and water were combined in a weight ratio of 10:3:14:72, with pH value <1 and still mixed for 100–200 hours. A solid phase was created, after separation by filtration and drying, providing gypsum, while potassium aluminium sulphate was obtained from filtrate after crystallisation. After crystallisation it is possible to thicken the mother liquor by evaporation. Red pigment is obtained from solid amorphous phase with a majority share of hematite after drying, followed by calcination at the temperature of 600°C and treating particles size by ultrafine milling under 5 μm (Kusnierova et al., 2001).
Process Engineering
Published in Terry Jacobs, Andrew A. Signore, Good Design Practices for GMP Pharmaceutical Facilities, 2016
When the bed (cake) of solids is formed on the filter media, it is usually washed with cold, pure solvent to displace dissolved impurities in the still wet cake. Usually the wash liquor is collected in separate tanks from the initial (mother) liquor from the first filtration. Depending on the process, it may be economical to take the mother liquor and subject it to another evaporation or crystallization step to solidify additional product, which can be recovered in another filtration step. The wash liquor is generally considered waste. The product cake discharged from the filter or centrifuge is then vacuum dried. Without drying, the product cake presents many handling problems. For a large-volume product, the filter or centrifuge feeds the discharged cake directly into the dryer by gravity. This arrangement eliminates most of the handling problems associated with the wet cakes. However, most production plants are multiproduct facilities, and the filters and dryers are decoupled to increase flexibility, unless they are designed for highly potent compounds. If the filters are decoupled from the dryers, then the cake is discharged to a lined drum or an IBC. These are then staged until the drying step is scheduled. Getting the wet cake out of these containers frequently requires manual intervention.
Hydrometallurgy
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
In practice, polymolybdate is precipitated from solutions containing typically 280 to 300 g MoO3 per liter. For this, a preliminary concentration by evaporation is given if necessary. Neutralization is carefully carried out with hydrochloric acid by which the hydrolysis reaction, 4(NH4)2MoO4 + 5 H2O → (NH4)2O∙4 MoO3∙2 H2O + 6 NH4OH, takes place. The polymolybdate precipitates are obtained after centrifuging and washing with water. Most of the contaminants remain in the slightly acidic mother liquor. The solution is allowed to stand for a prolonged period of time, the pH is adjusted to 2.0, and amorphous polymolybdate precipitates are separated and returned to the purification stage. The residual mother liquors contain small amounts of molybdenum (1 g Mo per liter) which may be separated from them by sorption on ion-exchange resins (described in a later section of the chapter). The molybdate precipitates are also not of high purity. The presence of tungsten is inevitable since it coprecipitates with the polymolybdate. The precipitate also carries an increased amount of chloride ions (0.2 to 0.4%) which are not removed by water washing. Recrystallization of the polymolybdate is carried out to remove the chloride ions. The salt is dissolved in ammonia solution to yield a saturated solution (specific gravity 1.41 to 1.42). This solution is cooled, and about 50 to 60% of the molybdenum content is precipitated in the form of crystalline paramolybdate. The mother liquor is utilized for the successive recrystallization of polymolybdate precipitates. Impurities gradually build up in the mother liquor so that it needs purification. The precipitation of polymolybdates through neutralization as well as subsequent recrystallization from an ammoniacal solution yields ammonium paramolybdate of a higher degree of purity than that obtained by method 2 of Figure 2, involving evaporation and crystallization of paramolybdates.
Lithium Extraction from Spodumene by the Traditional Sulfuric Acid Process: A Review
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Javier Rioyo, Sergio Tuset, Ramón Grau
FC crystallizers can operate: (a) under vacuum or (b) at low super-atmospheric pressure (Gea 2012). A particle size lower that 0.5 mm is achievable using FC crystallizers (Mullin 2001). During the crystallization step, the crystals must be separated from the mother liquor. This can be achieved with a pusher centrifuge, if the crystal size is big enough, following pre-concentration in a thickener. Different brands specialize in providing centrifuges for this purpose (Andritz 2020; Riera Nadeu 2018).