In the metal and electroplating industries, acids are commonly used in the processes such as cleaning, etching, demoulding, etc. The acid stable NF membranes have the excellent acid permeability and high rejections to metal ions. Thus they could be applied to the recoveries of metal ions and acids.
NF membranes are extensively applied to separation and purification of food and biological products. Due to the organic fouling and bio-fouling, NF membrane surfaces are usually cleaned with acidic cleansing solution. The NF membrane should be acid stable and last for a longer period.
Some waste liquids from paper making industry, dyeing and printing industry contain acid. The acid stable NF membranes could be applied to treatments of such waste liquids and recoveries of inorganic acids.
Acid stable membranes could be applied to treatments of acid wastewater from soil washing, removing most COD.