High nickel in our wastewater

hello all!
I don't understand why high nickel in my wastewater. we reduce nickel by NaOH at pH = 9, Nickel about 40-60ppm
thank you very much!

Hi, Thang. I think you need to precipitate at a higher pH, say 10.5, but that may not be all that is wrong. Where does the nickel come from, electrolytic plating or electroless plating? You may need to do a chelate breaking process. Try to tell us more about your situation.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Thang. As Ted has mentioned, more information is required about the waste water stream to fully understand your problem. Is the nickel soluble or insoluble, is it a water /solids issue or a complexed metals issue, what are you currently using to treat, is the end result a clear supernate etc.

We have plated three nickel and a Chromium. We have a treatment wastewater. Solution with NiSO4+ small NiCl2 after treatment at pH = 9-11 is 5 ppm but if NiCl2 is high in solution, when treatment at pH=10-11, [Ni2+]=30 ppm. I tried to added NaOH but it doesn't reduce. When I added Ca(OH)2, It reduce much! What is this problem ?

Thanks!