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Precipitation
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Charge solubility
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Antisolvent, supersaturation, temperature, pH change
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Low cost, selective removal possible, high yeild, can remove dissolved solids
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Impurities, co-precipitates
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Sedimentation or decantation
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Density gradient, Settling velocity
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Size, density, tank depth, residence time
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Effective at removing dense particles, cheap to implement
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Requires large space, must be designed based on maximum volume, cannot remove dissolved solids
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Centrifugation
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Settling velocity
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Centrifugal force, Size, density, angular speed, the ratio of centrifugal to gravitational force, and settling distance
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Effective at removing low-density and colloidal particles in a shorter time frame than sedimentation
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Energy-intensive, cannot remove dissolved solids, generates high heat, poses a safety hazard when processing volatile solvents
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Distillation
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Relative volatility
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Relative volatility >1.05, Heat of vaporization and energy requirements
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Designed for a large variety of flow rates, it can separate a homogeneous fluid mixture
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Energy-intensive, difficult to separate azeotropes unless a modification is made
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Membranes
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Particle/molecular size/permeability Sorption/Diffusion Pressure
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Pore size, Mol. wt. cut-off, average flux, Pressure gradient, type of membranes – M.F., U.F., N.F., and R.O.
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Lower energy requirement than distillation, highly selective with products, break azeotropes
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Fouling, cannot operate at high temperature, may not be compatible with all solvents
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Pervaporation
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Sorption/Diffusion
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Partial pressure, heat of vaporization, chemical potential gradient, pressure gradient, average flux, membrane selectivity
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Can break azeotropes, separate close-boiling point mixture, lower energy requirement than distillation
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Low-permeate flow rate, reduced membrane stability
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Liquid–liquid extraction
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Selective partitioning of solutes
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Partition coefficient, the solubility of solutes, low solubility of the added solvent in water
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Extracts dissolved solids from solvents, high selectivity, separates azeotrope mixture, does not require high temperature
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Solvent-intensive, limited by solubility
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Aqueous Two-Phase Extraction
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Partitioning of solute, bioselectivity
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Solubility, the composition of two phases, molecular weight
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Highly practical with separating bioproducts
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Macromolecule partition differently than smaller molecules
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