ABSTRACT
Liquid membranes were invented by Li in 1968 and have been proposed as solutions to a number of waste disposal problems. There are two major types of liquid membrane systems: a water-immiscible emulsion dispersed in water and an oil-immiscible emulsion dispersed in oil. Metal anions and complex anions are removed by the proper choice of liquid ion-exchange and stripping agents. Chromate removal from wastewater is a serious problem both in the US and elsewhere. Chromates are extracted from aqueous systems by employing either tertiary amines or quaternary ammonium salts. Mohan and Li reported a novel use of biological enzyme systems to trap nitrates and nitrites in liquid membrane formulations. This process has promise for large-scale continuous operations of secondary and tertiary waste water treatment. The Takuma Company of Japan has evaluated liquid membrane processes for heavy metals removal in a continuous, two-stage counter-current pilot plant and reported the results in two publications.
