Waste Conversion and Resource Recovery from Wastewater by Ion Exchange Membranes: State-of-the-Art and Perspective

Wastewater treatment is in a dilemma: more energy and efforts have to be put forth to obtain an effluent with better quality, while a significant amount of sludge is generated and the treatment or disposal expenses are high. Even if the sludge is disposed of properly, the components can be released and pollute the environment again. Therefore, conversion and recovery of the contaminants to resources is the way out of the dilemma. An ion exchange membrane (IEM) is a special type of membrane, which allows charged solutes to pass through it while retaining uncharged components. Attributed to this character, IEMs are taking more important roles in separation and conversion processes recently. They act as key elements in many resource recovery systems, such as in separation and concentration, salt valorization, energy conversion, and even in microbial systems. This review summarizes the important processes for waste conversion and resource recovery from wastewaters by using IEMs. Drawbacks and perspectives are summarized in view of the development of the processes and the membranes.