Solid-Liquid Extraction (( Leaching

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Chapter (10) Solid-Liquid Extraction (( Leaching )) Leaching : is the separation of a solute from solid mixture by dissolving it in a liquid phase. Leaching occurs in two steps: 1. Contacting solvent and solid to effect a transfer of a solute ( Leaching ). 2. The separation of the solution from the remaining solid (washing). Factors influencing the rate of Extraction : There are four important factors to be considered: 1. Particle size. 2. Solvent. 3. Temperature. 4. Agitation of the fluid. Mass Transfer Third Year Assist. Prof. Dr. Ahmed Daham 2 Batch Leaching Mass transfer rates within the porous residue are difficult to assess because it is impossible to define the shape of the channels through which transfer must take place.

water in a counter-current. The residue from each stage containing 0.25 kg water per kg insoluble solid. Find the number of stages such that the sand from the final stage contains 10% salt when dried. Solution: B = (0.625) (1.6) = 1 kg/s S 0 = 1.6 – 1 = 0.6 kg/s V N+1 = 0.5 kg/s L N+1 = 0 (Pure solvent)

  Residues, Insoluble