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Removal of Insolubles

Removal of Insolubles. Sedimentation Precipitaion Cetrifugation Filtration Membrane separation *wastewater treatment –sedimentation * heavy metal(mercury) precipitation. Precipitation. Product precipitation example. Antibiotic . precipitation with water after ethanol extraction.

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Removal of Insolubles

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  1. Removal of Insolubles

  2. Sedimentation • Precipitaion • Cetrifugation • Filtration • Membrane separation *wastewater treatment –sedimentation * heavy metal(mercury) precipitation

  3. Precipitation Product precipitation example Antibiotic precipitation with water after ethanol extraction Protein precipitation using ammonium sulfate Precipitation with nonsolvent affects solubility thus leads to precipitation Protein (in buffer solution at its isoelectric pH) Solubility is minimum Antibiotic (in ethanol or acetone) • Method: • Water miscible organic solvent (ex. acetone, ethanol) • Water soluble polymer • (ex. Polyethylene glycol (PEG)) WATER Precipitate Precipitate Figure 1. Antibiotic precipitation. Figure 2. Protein precipitation.

  4. Heuristics of Precipitation • Precipitation at low temperature – increases yield and reduces denaturation • Precipitation at ionic strengths of 0.05 – 0.2M • At higher ionic strengths • requires excess solvent • more dilute solution • fine particle precipitate • High molecular weight solutes – requires less solvent • Solubility of one protein – decreased by the presence of another • Precipitated solute which will not redissolve is probably denatured. Experiments are needed to confirm heuristics.

  5. Centrifugation Natural separation, denser solids slowly settle under the influence of gravity Sedimentation Filtration When insolubles are dilute, large, and rigid Centrifugation • utilizes the density difference • use when filtration is not easy • effective for small solid particles • requires expensive equipment than filtration

  6. Settling of Solids Forces acting on solid particles Buoyant force Drag force Buoyant force acting on the spheres, FB where: d – sphere’s diameter ρs – density of the sphere ρ – density of the fluid a - acceleration

  7. Drag force, FD acting on a single sphere: (by Stokes’ Law) where: μ – viscosity υ – sphere’s velocity ,where Reynolds number, Sphere is small. When drag and buoyancy forces are equal. then Steady state (terminal velocity) of the sphere

  8. Two limits of terminal velocity equation: Settling: Acceleration is due to gravity Centrifugation: Acceleration is different where: ω – angular rotation in rad/sec r – radial distance

  9. Centrifuge Equipment Basket Unit Clarified Liquid Tubular Bowl Feed Solid Deposit Disc Type (most common) Feed Liquid Conical Discs – large sedimentation area Feed Solid Removal – intermittent – continuous

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