Historical Perspective of the Addition of Magnetic Nanoparticles Into Anaerobic Digesters (2014-2021)

Abstract

The addition of magnetic nanoparticles to batch anaerobic digestion was first reported in 2014. Afterwards, the number of works dealing with this subject has been increasing year by year. The discovery of the enhancement of anaerobic digestion by adding iron-based nanoparticles has created a multidisciplinary emerging research field. As a consequence, in the last years, great efforts have been made to understand the enhancement mechanisms by which magnetic nanoparticles (NPs) addition enhances the anaerobic digestion process of numerous organic wastes. Some hypotheses point to the dissolution of iron as essential iron for anaerobic digestion development, and the state of oxidation of iron NPs that can reduce organic matter to methane. The evolution and trends of this novel topic are discussed in this manuscript. Perspectives on the needed works on this topic are also presented.

Enhancement of Anaerobic Digestion with Nanomaterials: A Mini Review

“…Of course, these conclusions, within a research field clearly in expansion, can change over the following years [31].…”

“…(a) Among all the nanomaterials used, inorganic metallic NPs were, by far, the most used to enhance the process of anaerobic digestion. In the case of C-based NPs, practically all the works used graphene or graphene oxide; (b) Among all the inorganic metallic NPs used, those based on iron, zero-valent and oxide forms were the most frequently used, with specific reviews on this point [31,32]; (c) There existed a significant number of studies related to the use of a combination of metallic NPs, reporting better results than that of a single type of NP (Table 1).…”

“…However, the reader should consider that the number of conditions, concentrations of NPs, and modes of operation (i.e., continuous, semicontinuous or batch) is very large, which makes it difficult to interpret and compare results from different studies [31].…”