Letter 39020

Remove calcium from Nickel Sulphate solution  

January 13, 2006

Please help us by suggesting a suitable way to remove Calcium from 10000 litres of Nickel Sulphate solution.
The Calcium present is about 1 gm per litre in the 10000 litres Nickel + Sodium Sulphate solution.

Can you please suggest a suitable method?

Abhishek Goel
Nickel India - India

Dear Abhishek,

A more effective procedure is to heat the solution to approx. 165 °F (73 °C) in a separate storage tank. This procedure should not be performed in the plating tank as tank walls, anode bags, and other associated equipment in the plating tank will be coated with insoluble calcium sulfate. (Although the calcium coating will redissolve when the temperature is lowered, the effectiveness of the treatment is reduced significantly.) The treatment procedure is as follows:

1. Pump the plating solution to a suitably lined storage tank fitted with heat and mixing capabilities.2. Heat the plating solution to 160 - 165 °F (71 - 73 °C) and agitate the solution.3. Maintain the temperature for at least 16 hours, preferably 24 hours, minimum.4. While still hot, filter the solution back to the previously cleaned plating tank.5. Clean the filter before re-using in the plating solution. Not performing this step will result in redissolving the calcium sulfate from the filter.

Kunjan Vaze
electroplaters - Mumbai, Maharashtra, India

Surely calcium sulphate is very insoluble, at least much less than 1g/l, so it should precipitate out by itself. I suspect you are using tap water to make up tour solutions; this is not a good idea and will cause problems, so use either DI or RO water

Trevor Crichton R&D practical scientist - UK

Hi,
I agree with the hot filtration at 73 deg cent. however, the filter cloth and paper used on the pressure filter must be suitable for fine filtration. Secondly, the Tank solution must be filtered for at least 3-4 hours in the same auxilliary Tank. Yes, change the filter papers, new cloth and then reuse in the main tank.
It should be checked if Calcium is being introduced in the main tank from precleaning of the plates / cathodes . If so, there are other processes to be used for pre cleaning.

Happy plating,

Rajiv Kulkarni
- Pune

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