Acid Nickel Recovery

Q: I’m searching for a qualified supplier of an acid nickel recovery system for our plating rinse water. I prefer to have the system with membrane separation process to recover the metal and water from the rinse water. If it does really work, we may need several units for our electroplating zone. Please tell me if you know of someone who has this technology. Thanks! N.H.

A: I am unable to recommend specific suppliers; however, if you look under “Filtration Equipment, Solution” in the PRODUCTS FINISHING DIRECTORY AND TECHNOLOGY GUIDE, you will find a number of reputable suppliers of membrane technology.
Certainly, membrane technologies have proven themselves in the recovery of metals from electroplating rinse waters. Because these technologies concentrate not only the valuable metals but also contaminants, great care and evaluation is needed for successful implementation.

One likely source of contamination is your water supply; salts in your potable water, including iron, calcium, magnesium, chlorides, sulfates, phosphates, silicates, etc, can ruin your plating baths if allowed to build in excessive concentrations. Very high--quality water is one of the keys to successful recovery of nickel or any other plating metal.

The two most common technologies used for treatment of water are ion exchange and reverse osmosis. If one is a high water user and the incoming water has total dissolved solids greater than 500 ppm, it may be more economically advantageous to use reverse osmosis alone or as a “roughing” filter in front of ion exchange. If your potable water is hard due to excessive calcium, you may need to place a water softener in front of a reverse osmosis unit so as to prevent scaling inside the membrane, which would likely ruin the membrane. For small volumes of water, usually ion exchange is least costly, especially if you can utilize a nearby firm that will exchange the ion exchange columns (aka “bottles”), regenerate them off-site, and return fresh columns back to you.

Another source of contamination is the breakdown of the brighteners and wetting agents in your plating bath. Since membrane technologies will capture these organics along with your target metals, additional activated carbon treatment of your nickel plating bath or the addition of an activated carbon filter in front of the membrane technology may be needed to remove these contaminants.

Another key action when preparing to recover metals from plating rinse water is to determine the least possible rinse water flow rate than can be achieved without adversely impacting product quality. Actions you can take to accomplish this include

Converting parallel rinses to counterflow rinses,
Adding one or two additional counterflow rinses (this may reduce rinse water flow rate by 10 times or more)
Operate process tank at minimum chemical concentrations (less plating bath in dragout, less rinse water needed),
Orient parts to maximize drainage,
Make small design changes to parts to minimize cupping and maximize drainage,
Allow sufficient time above plating tank for drainage to occur, and
Utilize low-drag out barrels.

The suppliers that you find in the DIRECTORY AND TECHNOLOGY GUIDE should be able to provide you with much further detailed guidance for a successful application of their specific technology.