Electroplating rinse waters

The raffinate from the process is thus a chromate-depleted solution, which can be recycled to the rinse baths, and a concentrated sodium chromate solution, from which the chromate can be recovered. Similar schemes have been proposed for copper, zinc, mercury and nickel rinse waters. 2S 26 66-70 

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Eisenmann, J. L. May 1979. "Membrane Processes for Metal Recovery from Electroplating Rinse Waters." Proceedings of the 2nd Conference on Advanced Pollution Control for the Metal Finishing Industry. USEPA/American Electroplaters Society. Cincinnati OH. EPA-600/8-79-014. 

Point-of-Source Recovery - in certain circumstances, it is possible to utilize reverse osmosis to effect a "zero discharge" electroplating rinse water recovery system. The rinse water from the first rinse is pumped to a reverse osmosis system that concentrates the salts and directs them back to the plating bath. The purified rinse water (permeate) is directed to the last rinse, and neither solute nor solvent is lost. in the united States there are approximately 150 reverse osmosis systems operating in this manner on nickel baths and 12 on acid copper. There are also a few installations operating on copper cyanide, hexavalant chrome, and acid zinc. 

The two water desalination applications described above represent the majority of the market for electrodialysis separation systems. A small application exists in softening water, and recently a market has grown in the food industry to desalt whey and to remove tannic acid from wine and citric acid from fruit juice. A number of other applications exist in wastewater treatment, particularly regeneration of waste acids used in metal pickling operations and removal of heavy metals from electroplating rinse waters [11]. These applications rely on the ability of electrodialysis membranes to separate electrolytes from nonelectrolytes and to separate multivalent from univalent ions. 

Removal of chromate ions from electroplating rinsing water (Experiment 115)... 

Chiapello and Gal [93] studied the recovery of cyanide electroplating rinse waters by electrodialysis. The transfer rates of the ionic species present in a copper or zinc cyanide rinse bath was limited by the high resistance of the anion exchange membrane used. The presence of highly charged cyano complexes of copper increased the resistance of the anion exchange membrane. The transfer of zinc was easier at higher... 

Desalination of seawater and brackish water Electroplating rinse water Etch bath rinse water... 

Recycling Nickel Electroplating Rinse Waters by Low Temperature Evaporation and Reverse Osmosis... 

Typical applications of ultrafiltration processes are the treatment of electroplating rinse water, the treatment of cheese whey, and the treatment of waste-water from the pulp and paper industry. 

Tests with Bacillus megaterium isolated from sedimentation contaminated with mercury, lead, strontium, and cesium have been conducted on laboratory solutions and electroplating rinse waters. The rinse water pH was adjusted with HCl, and the solution was filtered. Spores were added to give a 0.10 weight ratio (wet) of spores to rinse water, and the mixture was incubated for 24 hours. 

The metallic substrate, clean and rinsed, is immersed wet in the plating cell. The base metals which are usually plated present an essentially metallic surface to the electrolyte, and the slight corrosive action of the rinse water in preventing the formation of any substantial oxide film is important. A critical balance of corrosion processes in the initial stages is vital to successful electroplating, and for this reason there is a severe restriction on the composition of the electroplating bath which may be used for a particular substrate. This will be discussed later. The substrate is made the cathode of the cell it may be immersed without applied potential ( dead entry) or may be already part of a circuit which is completed as soon as the substrate touches the electrolyte ( live entry). Live entry reduces the tendency for the plating electrolyte to corrode the substrate in the period before the surface... 

Water reuse is practiced at several plants in this industry. Water that may be reused for such purposes as rinse water, makeup water, and cleanup water includes air conditioning water, acid treatment rinsewater, and noncontact cooling water. Reuse of acid rinsewater in alkaline rinses has been demonstrated at many electroplating plants. 

Spent plating solutions and rinse waters containing copper, nickel, tin, lead, gold, and cyanide result from electroplating operations. 

Metals from spent process solutions and rinse waters can also be recovered in many of the same ways as are employed for electroplating and other surface treatment wastes. These are discussed under "Recycling" in Section 7.4. 

Because printed circuit products require higher quality rinse waters than typical electroplated products, demineralized water is often used, and there is economic justification for recovery of this more expensive water. 

Figure 5.27 Flow scheme showing the use of a reverse osmosis system to control nickel loss from rinse water produced in a countercurrent electroplating rinse tank...

W.C. Babcock, R.W. Baker, M.G. Conrod and K.L. Smith, Coupled Transport Membranes for Removal of Chromium from Electroplating Rinse Solutions, in Chemistry in Water Reuse, Ann Arbor Science Publishers, Ann Arbor, MI (1981). 

A nickel electroplating line uses a dip-rinse tank to remove excess plating metals from the parts. Currently, a single tank is used that requires R gal/h of fresh rinse water to clean F parts/h (see Figure 107). Assume the cleaning is governed by the following equilibrium relation ... 

Provide usable water where none available Brackish water desalination Seawater desalination Pure water production Industrial rinse waters Food industry Electroplating Power plant boiler feed Beverage production Medical... 

Transport Membranes for Removal of Chromium from Electroplating Rinse Solutions" in Chemistry in Water Reuse, Ann Arbor Science Ann Arbor, Ml (1981). 

Fig.7 Point-Source Treatment of Electroplating Rinses 1- direction of plating work flow, 2- pre-plating, 3- plating bath, 4- static or drag-out rinse tank, 5- first running rinse, 6- second running rinse, 7- process water input, 8- electrolytic recovery cell, 9-discharge to sewer or waste treatment...

Electroplating Spent plating bath Waste rinse waters Metals, cyanide, sulfate... 

Electroplatings including spent and contaminated baths, static rinses (drag-outs) and rinse waters,... 

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