ELECTROWINNING AS A PART OF A TOTAL TREATMENT STRATEGY

Almost all electronic component manufacturers use a combination of treatment methods to maximize effluent quality. These methods can include, precipitation, ion exchange, micro/ultrafiltration, electrowinning, chemical reduction, etc. These methods when use optimally can reduce toatal metal output to less than 0.1 ppm. When not used correctly, operational costs accelerate rapidly and metal levels in the effluent rise to higher levels.

Electrowinning support for your batch treatment streams can dramatically reduce both cost and metal loadings on your primary treatment methodology. Electrowinning can rapidly recover hundreds of pounds of heavy metals, reduce chrome, oxidize cyanide, and destroy organics, all at minimal operational costs. Reducing the load on the primary treatment system allows the implimentation of a water reduction strategy without worries of becomming non-compliant.

The cost to electrowin is very low. A 3 phase 300 amp rectifier at 6 volts draws less than 10 amps. This will produce 24 pounds of copper per day. The cost at $ 0.11 per kwh is $6.36 per day. What does it cost you to make, filter, handle, and haul 24 pounds of Copper based sludge away? Our product is either a copper sheet (very high volume cells) or copper pellets.

Most copper in in the electronics industry is from batch dumps of microetches and dragouts. In the printed circuit board industry, much comes from electroless copper dumps. Note that all of these sources are concentrated sources, very suitable for electrowinning. If you took all of your concentrated sources and electrowinned them to recover the copper, how much would this reduce the load on you treatment system? A side benefit of electrowinning is that it oxidizes organics such as chelation compounds and formaldehyde. Add a touch of chlorine and cyanide is destroyed. There are many advantages to having an electrowinning system.

That big dumpster out back will go away for good as will big sacks of sludge. The labor and chemical cost reduction is very large when you switch to electrowinning. The cost in time and chemicals it takes to batch treat a load is very high because very few batch treatment operations are automated and the operator must determined how much of what to add with only a pH controller to guide him. It is much easier for an operator to just dump in a bunch of metal reducing agent (DTC, Sodium Borohydride, etc.) to drop the metal out than to adjust to the correct pH, measure, the add an exact amount of precipitant. The result is much higher treatment costs.

An electrowinning system needs little operator attention. Once started, it just runs until there is no more metal to plate out. Usually the visual appearance of the solution will tell you how close to finished you are. Once finished, the solution is pH adjusted if necessary and bled into an onstream treatment system directly.

Electrowinning, while simple in appearance, can also be simple in operation given some precautions are taken. The first thing to remember with all electrowinning systems is inherent in the system. The systems must conduct electricity so they have metal components. These metal components are subject to corrosion and due to the electrochemical nature of these systems, the corrosion can be very rapid. Proper maintance is very important. These systems must be maintained by using passive coatings to protect metal components. Wear or breaks in the coatings will result in eventual downtime and higher maintance.