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Difference between revisions of "Crystallisation and precipitation"
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Crystallisation and precipitation (view source)
Revision as of 14:54, 21 February 2022
, 14:54, 21 February 2022→Process and technologies: moved paragraph to feedstock
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[[File:NaCl octahedra and part of crystal.svg|alt=Graphic showing NaCl (table salt) crystal consisting of sodium and chlorine atoms|thumb|200x200px|NaCl (table salt) crystal consisting of sodium and chlorine atoms]] | [[File:NaCl octahedra and part of crystal.svg|alt=Graphic showing NaCl (table salt) crystal consisting of sodium and chlorine atoms|thumb|200x200px|NaCl (table salt) crystal consisting of sodium and chlorine atoms]] | ||
=== Origin and composition === | === Origin and composition === | ||
The feedstock for crystallisation is a solution with crystallisable ingredients, e.g. minerals or organic molecules. | The feedstock for crystallisation is a solution with crystallisable ingredients, e.g. minerals or organic molecules. The majority of minerals and organic molecules crystallize easily, and the resulting crystals are generally of good quality, i.e. without visible defects. However, larger biochemical particles, like proteins, are often difficult to crystallize. The ease with which molecules will crystallize strongly depends on the intensity of either atomic forces (in the case of mineral substances), intermolecular forces (organic and biochemical substances) or intramolecular forces (biochemical substances). | ||
=== Pre-treatment === | === Pre-treatment === | ||
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==Process and technologies== | ==Process and technologies== | ||
Crystallization occurs in three major steps. The first is nucleation, the appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent. The second step is known as crystal growth, which is the increase in the size of particles and leads to a crystal state. An important feature of this step is that loose particles form layers at the crystal's surface and lodge themselves into open inconsistencies such as pores, cracks, etc. | Crystallization occurs in three major steps. The first is nucleation, the appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent. The second step is known as crystal growth, which is the increase in the size of particles and leads to a crystal state. An important feature of this step is that loose particles form layers at the crystal's surface and lodge themselves into open inconsistencies such as pores, cracks, etc. | ||
Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs. In chemical engineering, crystallization occurs in a crystallizer. Crystallization is therefore related to precipitation, although the result is not amorphous or disordered, but a crystal. | Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs. In chemical engineering, crystallization occurs in a crystallizer. Crystallization is therefore related to precipitation, although the result is not amorphous or disordered, but a crystal. | ||