Ask the Expert Question-and-Answer Archive (Wastewater Treatment)
by Mike McGinness, EcoShield Environmental Systems, Inc.
Titanium Pickling Wastewater
Have you even come across a technology to selectively remove and possibly recycle Ti from pickling wastewater (HF and HNO3).
No, but I would be surprised if the big players in the titanium business, like titanium dioxide pigment makers for paint, or mining industry people don't know how to do it already. The Metal Finishing industry does not have a national EPA limit for discharge on titanium. Some of the dialysis or electrodialysis technologies may know how to do it.
HF could be removed as a calcium salt (CaF2 solid precipitant) but if you used Calcium hydroxide I would think the Titanium would drop out with the calcium, but most NO3 compounds are water soluble. Then you would need to separate the calcium from the titanium in the solids.