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topic 319

Dewatering sludge with reverse osmosis


I'm working on a master project at the University of Sherbrooke. This project is about dewatering sludge from wastewater treatment plant using electroosmosis. In our case, the cathode is a porous filter made of stainless steel. The anode is also made of stainless steel and is acting as a piston pushing on the sludge. Electroosmosis is the application of a voltage on an electrolyte. In my case, the electrolyte is the sludge. The voltage is 25 volts and the current is around 400 mA. Severe corrosion is occurring at the anode. Because of the reaction at the anode, the pH is very low at the anode (1 or 2). We had the idea of plating the anode with platinum but it is too expensive and the piece we want to plate is too big for the bath. Is there any kind of plating you know that could resist to that kind of corrosion? I know that platinum could resist but it is too expensive and also I would like to plate a big piece. For my tests, I did use stainless steel.

Do you know any kind of material we could use? The sludge is coming from a pulp and paper company. So there might be presence of chlorides in it.

Vincent Caron
University of Sherbrooke

Platinized titanium is probably the material of choice. For this reason it might be best to avoid introducing an extraneous variable (like hydrogen overvoltage differences) into your experiment by using a different material . Maybe one of the suppliers of platinized titanium will take pity on a graduate student, or want to encourage use of their material, and supply you some sample material.

Suppliers of platinized titanium include Intrepid Industries, Whitehouse Station, NJ; Electrode Products, Warren, NJ; Vincent Metals Corp., Hope Valley, RI; Technic, Pawtucket, RI.

Ted Mooney, Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


Depending on the chloride concentration you might want to consider a lead anode. You didn't mention any strength requirements, but you might have to back up a lead anode. There are precious metal oxide coated titanium anodes for oxygen service but at your apparent low electrolyte concentrations they probably wouldn't last long. Nevertheless I suggest you contact Heraeus Engelhard

Have you considered water removal through the cathode to another processable electrolyte that common anodes can operate in? Use of a membrane for the same purpose?

Hugh McCutchen

November 27, 2011

why don't you use a net of activated titanium (price more or less euros 700,00 per square metre)

ing. Carlo Falugi
- Parma, Italy

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