An Example of Economic Plating Waste Treatment by Reverse

The large volumes of water used in rinsing operations in the plating industry may 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).