Part
1 Introduction
Part 2 Phase equilibrium
in liquid-liquid extraction
Part 3 Selection of solvents
for liquid-liquid extraction processes -methodology
Part 4 Selection of solvents
for liquid-liquid extraction processes (i)
organic systems
Part 5 Selection of solvents
for liquid-liquid extraction processes (ii)
metals and inorganic systems
Volume
SE III Part 1 Introduction.
This part gives an overview
of the volume and how to use it to best effect.
Volume
SE III Part 2 Phase equilibrium in liquid-liquid
extraction.
Liquid-liquid extraction
involves the treatment of a liquid mixture of two or
more components with a solvent which is immiscible with
the mixture but has a greater extractive power for one
of the components than the others. The successful application
of extraction depends on the mixture reaching or tending
to reach equilibrium. This part sets out and discusses
the various ways of representing equilibrium data for
binary, ternary and multicomponent systems. The various
methods used for determining phase equilibrium data
and measuring physical properties are described and
areas of research reviewed. The equations for correlating
equilibrium data and the ways in which they can be used
for prediction and for calculating the number of stages
for a separation process are discussed. The final chapter
reviews computer programs which can be used for evaluating
phase equilibrium data.
Volume
SE III Part 3 Selection of solvents for liquid-liquid
extraction processes - methodology.
This manual
part was written to supplement and update Parts 4 and
5 and to provide a general methodology for solvent selection
applicable to most extraction processes. Parts 4 and
5 deal respectively with the selection of solvents for
organic and inorganic (especially metals) systems: they
contain material which remains both valid and valuable,
and are retained.
Between
the publication of Parts 4 and 5 and the preparation
of Part 3 a significant diversification was apparent
in liquid-liquid extraction technology. Much of the
new literature focused not upon equilibrium systems
but reactive extractions, and the growth of biotechnology
led to novel techniques such as aqueous/aqueous and
micellar extraction. During the same period there was
also a significant growth in (mainly computer-aided)
techniques for equilibrium calculation and solvent selection.
These developments,
where not already covered in Part 2, are reviewed in
the context of a comprehensive method for solvent selection
presented as a series of decision trees. The user is
encouraged to develop an initial 'long-list' of feasible
solvents which is then cut down to provide a shortlist
for final selection. Shortlisting involves many practical
aspects of selection, such as the existence of suitable
equipment as well as product and solvent recovery strategies.
The selection
scheme is designed to be punctuated by laboratory and
pilot plant experimental work; but it may also be used,
in conjunction with other manual parts, for a rapid
'paper' study or evaluation of options.
Volume
SE III Part 4 Selection of solvents for liquid-liquid
extraction processes (i) organic systems.
In this report a procedure
is described for the selection of an appropriate solvent
for the extraction and purification of mixtures of organic
materials. The procedure describes the steps which need
to be followed in selecting a solvent for a particular
separation. The types of ternary system usually encountered
in liquid-liquid extraction are described, together
with the principles of selectivity. The effects of temperature,
solvent capacity and solubility on solvent selectivity
are described and a brief discussion of partition coefficients
is given. Experimental methods for determining equilibrium
data needed for design calculations are included. Methods
of solvent recovery are briefly reviewed and their influence
on overall process costs is discussed. A worked example
is given to demonstrate the solvent selection procedure.
Volume
SE III Part 5 Selection of solvents for liquid-liquid
extraction processes (ii) metals and inorganic systems.
This report describes a
procedure for the selection of solvents for the extraction
and purification of metals and inorganic materials.
It is concerned primarily with hydrometallurgical processes
but the procedures described can be applied equally
well to other inorganic materials such as wet process
phosphoric acid production and the recovery of salts
from brine. The procedure sets out the steps which have
to be followed to select a solvent, including the need
for a cost evaluation. Reagents are classified into
groups based on their mode and action. A brief discussion
of the extraction chemistry of these groupings is given.
The uses and properties of diluents and ways in which
their properties can be modified by small additions
of "modifiers" are described. The chemical
stability of the extraction and the effect on plant
performance of other properties, for example solubility,
viscosity and interfacial tension are discussed. The
steps which are used to derive a procedure for solvent
selection are used in a worked example.
