Macroporous Cryogel-Based Systems for Water Treatment Applications and Safety: Nanocomposite-Based Cryogels and Bacteria-Based Bioreactors

Providing clean water to everyone is one of the current global challenges highlighted by the United Nations. Continuous industrial development, agricultural expansion, and population growth place high demands on water supply and create new problems associated with the emergence of new pollutants from human activities. Wastewater treatment is essential to protect the environment and reduce health risks. Modern wastewater treatment methods cannot always provide safe treatment to address current pollution problems, and there is a need to develop new advanced technologies to meet current demand. This chapter discusses new technologies based on the efficient utilization of cryogels with immobilized nanoparticles (NPs) and bacteria for water purification. Methods for the preparation of nanocomposite cryogels and cryogels based on bacteria are summarized with examples of recently published studies. The cryogel nanocomposites have shown good efficiency in removing heavy metals, dyes, nitro, and chlorophenols using adsorption and catalytic processes. The remediation efficiency depended on the nanoparticle nature and loading, immobilization method, cryogel composition, and operating mode. In addition, methods for assessing the safety of nanocomposite devices and current legislation are critically reviewed. It emphasizes the need to collect more data on NP toxicity and to develop more reliable protocols for assessing the toxicity of nanocomposites. The preparation and use of cryogels with immobilized bacteria are discussed with the provision of recent examples producing bacteria-based bioreactors by direct cross-linking of bacteria with a minimum amount of polymer. Bacterial bioreactors have shown promise for removing phenolic compounds. Finally, further challenges associated with the use of cryogels for water purification are discussed.