AN EXAMPLE OF ECONOMIC PLATING
WASTE TREATMENT BY
REVERSE OSMOSIS
A. GOLOMB
Department of Physical Chemistry, Ontario Research Foundation,
Sheridan Park, Ontario, Canada
INTRODUCTION
The large volumes of water used in rinsing operations in the plating industry m?y
contain cyanides, chromium, nickel, and zinc, resulting in a substantial loss of valuable
plating chemicals. From an economic viewpoint, particular consideration should be given
to measures that will permit recovery of chemicals and water for reuse.
In view of the wide variety of conditions found in plating practice, treatment processes
have to be tailored to each installation (Barnes, 1968). A simple approach to conservation
of water and chemicals is the use of counter-current rinsing. Ideally, if a sufficiently large
number of stages can be installed, rinse water from the first stage can be returned to the
plating bath as make-up to balance the volumetric rate of evaporative loss. However, in an
existing plant, where it is impractical to install a sufficiently large number of rinse tanks,
some alternative method of reclamation must be sought. For instance, evaporative and
ion exchange recovery systems have been incorporated in many plants.
In the last few years, growing interest has been expressed in a relatively new chemical
engineering separation technique for water purification, Reverse Osmosis (RO), which
received much of its impetus from the work of Loeb and Sourirajan (1964). The various
types of commercially available RO modular units have been critically reviewed by
Golomb and Besik (1970).
LABORATORY TESTS ON WATTS NICKEL RINSES
Details of the laboratory test unit used to evaluate the RO performance characteristics
of Loeb-Sourirajan type cellulose acetate membranes for nickel rinse waters have been
previously reported by Golomb (1970). Eastman Kodak cellulose acetate membranes
(type RO-97), a grade with very high rejection for inorganic salts, received most attention
in these experiments.
Simulated nickel rinse waters were prepared by dilution with distilled water of a Watts
bath formulation having the following composition:
NiSO 4 .6H 2 0
337.5 g/1 (45 oz/gal)
NiCl 2 .6H 2 0
75.0 g/1 (10 oz/gal)
H3BO3
37.5 g/1 (10 oz/gal)
pH4.0
A series of exploratory reverse osmosis tests was performed on diluted Watts bath
solutions (no organic addition agents) at levels of 100 ppm Ni
++
; 1, 10, 25 and 50 per cent
of bath concentration.
The membranes from these experiments were subsequently stored in the
corresponding test solution and re-tested at intervals of several weeks to obtain an
567
WASTE TREATMENT BY
REVERSE OSMOSIS
A. GOLOMB
Department of Physical Chemistry, Ontario Research Foundation,
Sheridan Park, Ontario, Canada
INTRODUCTION
The large volumes of water used in rinsing operations in the plating industry m?y
contain cyanides, chromium, nickel, and zinc, resulting in a substantial loss of valuable
plating chemicals. From an economic viewpoint, particular consideration should be given
to measures that will permit recovery of chemicals and water for reuse.
In view of the wide variety of conditions found in plating practice, treatment processes
have to be tailored to each installation (Barnes, 1968). A simple approach to conservation
of water and chemicals is the use of counter-current rinsing. Ideally, if a sufficiently large
number of stages can be installed, rinse water from the first stage can be returned to the
plating bath as make-up to balance the volumetric rate of evaporative loss. However, in an
existing plant, where it is impractical to install a sufficiently large number of rinse tanks,
some alternative method of reclamation must be sought. For instance, evaporative and
ion exchange recovery systems have been incorporated in many plants.
In the last few years, growing interest has been expressed in a relatively new chemical
engineering separation technique for water purification, Reverse Osmosis (RO), which
received much of its impetus from the work of Loeb and Sourirajan (1964). The various
types of commercially available RO modular units have been critically reviewed by
Golomb and Besik (1970).
LABORATORY TESTS ON WATTS NICKEL RINSES
Details of the laboratory test unit used to evaluate the RO performance characteristics
of Loeb-Sourirajan type cellulose acetate membranes for nickel rinse waters have been
previously reported by Golomb (1970). Eastman Kodak cellulose acetate membranes
(type RO-97), a grade with very high rejection for inorganic salts, received most attention
in these experiments.
Simulated nickel rinse waters were prepared by dilution with distilled water of a Watts
bath formulation having the following composition:
NiSO 4 .6H 2 0
337.5 g/1 (45 oz/gal)
NiCl 2 .6H 2 0
75.0 g/1 (10 oz/gal)
H3BO3
37.5 g/1 (10 oz/gal)
pH4.0
A series of exploratory reverse osmosis tests was performed on diluted Watts bath
solutions (no organic addition agents) at levels of 100 ppm Ni
++
; 1, 10, 25 and 50 per cent
of bath concentration.
The membranes from these experiments were subsequently stored in the
corresponding test solution and re-tested at intervals of several weeks to obtain an
567