Summary for phosphoric acid recovery Discussion
Nanofiltration for phosphoric acid recovery is discussed as a possible alternative to decanting in electropolishing, but the answer is conditional. Willie Alexander says rising phosphate costs make the idea worth exploring, especially with a Koch MP-34 membrane. Lyle Kirman cautions that the key factor is acid concentration: above 25%, none of the acid purification technologies work very well. Below that level, both nanofiltration and acid retardation may be viable. He also warns that the operating pressure required to overcome osmotic pressure may be much higher than expected, which could affect cost effectiveness. The thread does not give a definitive yes or no, but it suggests nanofiltration may only be practical at lower phosphoric acid concentrations and should be evaluated carefully against pressure and operating costs.
March 26, 2013
Q. We are currently using phosphoric acid to electropolish stainless steel. Increased production and rising costs of phosphate warrant looking at nanofiltration. The Koch MP-34 membrane seems to be a possibility.
We would like to find out if nanofiltration is a cost effective alternative to decanting.
Willie Alexander
Metal Finishing Manager – Colorado Springs, Colorado, USA
A. The answer to your question depends partly on the acid concentration. At concentrations above 25%, none of the acid purification technologies work very well. Below this concentration, both nanofiltration and acid retardation may work. That being said, the operating pressure needed to overcome the osmotic pressure may be much higher than you expect.
Lyle Kirman
consultant – Cleveland Heights, Ohio
April 1, 2013
April 3, 2013
Thanks for the input Lyle. The concentration is above 25%, and we are aware the pressure needed is 600 psi +. We’ll keep plugging away at it.
Willie Alexander
– Colorado Springs, Colorado