Recovery and separation of organic acids by membrane-based solvent extraction and pertraction An overview with a case study on recovery of MPCA

Hollow fiber solvent extraction: Performances and design

Solvent extraction is a common industrially used equilibrium-based separation process. In such a process, a solute (or solutes) in a solution, aqueous or organic, is extracted into an immiscible solvent, organic or aqueous, by dispersing one of the immiscible phases as drops in the other phase. This creates a large interfacial area and increases the extraction rate considerably. After the extraction is over, the phases are separated and the dispersed phase coalesced. There are two general categories of equipment for solvent extraction. A mixer-settler arrangement provides a single equilibrium stage; a number of them connected together provide multistage extraction. Continuous countercurrent contacting equipment whether in the form of columns or centrifugal devices can generate the equivalent of many stages in one device (Treybal 1963).

Membrane-Based Solvent Extraction

In conventional gas absorption, gas is dispersed in the absorbent liquid as bubbles in a vessel acting as a single stage or in a multistage column with the gas and the liquid in countercurrent flow. The dispersion of the gas increases the gas/liquid contact area and increases the mass transfer rate of the species to be absorbed in the liquid. After contacting is over, the gas bubbles coalesce as they leave the liquid phase except when foaming tendencies appear. Con-ventional gas absorption is also carried out with liquid dispersed as drops or thin films in the gas flowing countercurrently as in spray towers, packed towers, venturi scrubbers, etc. (Treybal 1980). Current gas stripping processes operate in an identical manner and in the devices used for gas absorption except that species are transferred from the liquid to the gas phase.

Other New Membrane Processes

A sample holder for use in infrared spectrophotometric analysis The holder comprises a microporous sheet and is particularly useful for analysis of solutions, colloids, small particle solids, flowable solids, solvents, and viscous fluids The microporous sheet preferably has a low absorbance (high spectral transmittance) in infrared wavelengths The sample holder is especially useful for the analysis of aqueous based samples Also, a method for using such sample holders for infrared spectrophotometric analysis

Spectroscopic sample holder and method for using same

Nondispersive solvent extraction using microporous membranes.

We have studied the transfer coefficients for O2 transport to and CO2 removal from a model cell-free system using microporous hydrophobic hollow fibers axially placed along a tubular bioreactor for ethanol production with immobilized yeast in the shell. In this locally integrated bioreactor, O2 and CO2 transfer rates depend strongly on the shell side liquid flow rate; O2 flow rate in the fiber bore influences O2 transport only at very low flow rates. Diffusion of CO2 does not affect O2 transport. Local and overall O2 and CO2 transfer coefficients have been determined for a wide range of Reynolds Numbers. The efficiency of such transfers has been demonstrated for alcohol fermentation.

G. T. Frank

Papers

Nondispersive solvent extraction using microporous membranes.

Evaluation of O2 and CO2 transfer coefficients in a locally integrated tubular hollow fiber bioreactor