What is liquid-solid extraction?

Answer 1

Leaching is one of many solid-fluid separation processes that are carried out in

the chemical, mineral and related industries. In fact, it is one of the oldest unit

operations in the chemical industries. The fundamental principle behind leaching

is the removal of a soluble material from an insoluble, permeable solid phase. The

soluble fraction, solid or liquid, may exist mechanically in the pore structure of

the insoluble material or chemically combined with that material. This soluble

material is removed through dissolution in a dissolving solvent. The most familiar

example of leaching is the extraction of tea and coffee, and most importantly

mineral recovery.

The rate of leaching (extraction) is affected by many physical and chemical phenomena. Mass transfer and equilibriumphenomena obviously playmajor roles. The process of leaching consists of the following steps: (i) The solvent diffuses into the solid phase; (ii) The diffused solvent dissolves the solutes (i.e. transfer the solute to the liquid phase). Leaching is always followed by solvent recovery, which involves another mass transfer operation; such as filtration.