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Electrolyte cleaning

Separation of metal hydroxides

EnviroFALK sets new standards for the separation of metal hydroxides using specially developed ultrafiltration units.

Electrochemical metal machining (ECM) involves the removal of metal ions from the workpiece. The ablated material, which settles as metal hydroxide sludge, needs to be filtered out of the electrolyte solution.

The conventional method: metal hydroxide through chamber filter press
The metal hydroxide sludge is passed through a chamber filter press.
However, the metal hydroxide sludge is so fine that no filter cake is formed in the chamber filter press, but rather a thin fluid mass, which requires intensive daily cleaning of the chamber filter press that takes about an hour. This cleaning needs to be carried out by additional staff or by the operator of the ECM machine and results in daily production downtime.

Our solution: separation of the metal hydroxides by ultrafiltration
The ultrafiltration system for electrolyte purification, specially developed by EnviroFALK, takes the contaminated electrolyte from the ECM system’s dirt tank and circulates it through the special capillary membranes of the ultrafiltration system, removing all of the impurities from the electrolyte. The treated electrolyte is then returned to the ECM system’s clean water tank.

By way of comparison: The ultrafiltration membrane used to clean the electrolyte solution has a pore size of 0.03 µm, whereas a sterile filter – as is frequently used in water treatment – has a pore size of 0.2 µm.

The ultrafiltration membrane is rinsed at regular intervals, depending on the process workload. The membrane is cleaned completely automatically, using only the electrolyte and compressed air, without using any chemicals for this special cleaning process. The advantage of this is that it rules out the possibility of the electrolyte being contaminated by other chemicals.

The metal hydroxide sludge produced during this membrane cleaning process is already highly concentrated by ultrafiltration before it is rinsed into a specially developed conical bottom tank for further sedimentation. The metal hydroxide sludge continues to thicken in the conical bottom tank and is then filtered out through the chamber filter press. The chamber filter press works in bypass mode, which means that the metal hydroxide sludge is slowly and continuously removed from the conical bottom tank. This operating mode increases the efficiency of the chamber filter press and leads to outstanding filtration results. The resulting filtrate is then returned to the ECM clean water tank in a closed circuit. The metal hydroxide sludge can be disposed of as a compact filter cake. It is normally only necessary to open the chamber filter press once a week.

An impressive success:
The ultrafiltration system guarantees consistently high electrolyte quality in the ECM process. All in all, this permits constant high utilization of the ECM machine. Another advantage is that the time required to clean the chamber filter press thoroughly each day is reduced to about 15 minutes a week, cutting unproductive downtime to a minimum, and the compact metal hydroxide filter cakes can be disposed of much more easily and economically.


For further information, visit: EnviroFALK ultrafiltration system for electrolyte processing