 Industrial
water equipment limited's approach to waste metal reduction
is to recover process metals from effluent to reuse. For
example materials used in metal finishing processes can
be effectively recovered using techniques such as;
- Dragout
- Evaporation
- Reverse osmosis
- Electro dialysis
- Electrolytic recovery
The more commonly used metal recovery processes are;
Gold recovery
Silver recovery
Copper recovery
Cyanide
recovery
Chromium recovery
Zinc recovery
Nickel recover
Lead recovery
Cobalt recovery
Manganese recovery
Mercury
recovery
Palladium recovery
Tin recovery
however there
are many more metal that can be removed with our recovery
processes.
Dragout recovery explained;
Dragout recovery is a simple technology used by metal
finishers to recover plating chemicals. It involves a
process using drain boards, drip tanks, fog spray tanks
or drag out tanks separately or in combination, to capture
plating chemicals dragged out of plating tanks from parts
being plated. Drain boards are widely used throughout
the industry to capture plating solutions. Boards are
suspended between process tanks and are usually constructed
of plastic or Teflon coated steel. Solutions simply drip
off the coated parts and back into their retrospective
tanks. Drip tanks recover process chemicals by collecting
dragout into an empty tank, from which it is usually returned
to the process as required. Fog spray tanks recover plating
chemicals clinging to parts by washing them with a fine
water mist. The solution collected in the bottom of the
tank is returned to the process tank as required. The
added water can help to offset evaporative losses from
the process tank. Dragout tanks are essentially rinse
tanks.Dragout chemicals are captured in a water solution,
which is returned to the process tank as required.
Evaporative recovery explained;
Evaporative recovery or evaporation is a widely used
metal salt recovery technique. In the evaporation process,
plating chemicals are concentrated by evaporating water
from the solution. Evaporators may use heat or natural
evaporation to remove water. There are essentially two
types of evaporators; those that operate at atmospheric
pressure and those that operate under a vacuum. Atmospheric
evaporators are the most commonly used units. They are
open systems used to process heat and warm air to evaporate
water. These evaporators are relatively inexpensive, require
low maintenance and are self-operating. Under the right
conditions they can evaporate water from virtually any
plating bath or rinse. Vacuum evaporators are closed systems
that use steam heat to evaporate water under a vacuum.
Like atmospheric evaporators they require low maintenance
and are self-operating.
Reverse osmosis explained;
Reverse osmosis or r/o recovers plating chemicals from
rinse water by removing water molecules with a semi permeable
membrane. The membrane allows water molecules to pass
through, but blocks metals and other additives. A reverse
osmosis system will work on most plating lines or baths.
Diluted or concentrated solutions are circulated through
the membrane at pressures greater than aqueous osmotic
pressure. This action results in the separation of water
and metals or chemicals. Please view our reverse osmosis
link for more information. Electro dialysis explained;
Electro dialysis units recover plating chemicals differently
from the other recovery units listed. In electro dialysis
electromotive forces selectively drive metal ions through
an ion selective membrane. The membranes are constructed
from plastic and have either anionic or cationic characteristics.
Electro dialysis units are constructed from plate and
frame technology very similar to filter presses.
Alternative layers of anionic and cationic membranes are
placed between two electrodes. The plating or rinse solution
to be recovered known as electrolyte circulates past the
units electrodes. This produces hydrogen and oxygen. Positive
ions travel to the negative terminal and negative ions
travel to the positive terminal.
The electrolyte also provides the overall conductivity
to the cell.
In some more advanced units the polarity of the unit is
reverse occasionally to protect the membrane from fouling.
The electro dialysis technology is compatible with most
plating baths and the design of the unit is dependent
upon the rinse water flow rate and concentration.
Electrolytic recovery systems explained;
Electrolytic recovery or er is the oldest method of metal
recovery. Metal ions are plated out of solution electrochemically
by reduction at the cathode. The are basically two types
of cathodes used for this process. Metal cathode known
as electro winning and high surface area cathodes known
as hsac. Both of these technologies are very successful
on plating metals such as gold, zinc, cadmium, copper
and nickel. Electrolytic metal recovery can be used with
most plating baths. The amount of metal to be plated per
square meter of cathode determines the electrolytic recovery
units design capacity With this in mind the volume and
concentration of plating dragout greatly influences system
design and size.
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