Effects of nanoscale zero valent iron (nZVI) concentration on the biochemical conversion of gaseous carbon dioxide (CO2) into methane (CH4)

Methanogenesis Inhibition in Anaerobic Granular Sludge for the Generation of Volatile Fatty Acids from CO2 and Zero Valent Iron

“…Recently, Vyrides et al (2018) using anaerobic granular sludge pointed out that CO 2 (as a sole carbon source) can be utilized to CH 4 by addition of zero valent iron (ZVI) in anaerobic granular sludge under aquatic ambient conditions. Dong et al (2019) using nano-ZVI, found similar results. ZVI (Fe 0 ) can be oxidized under abiotic aquatic carbonate anaerobic conditions, generating H 2 and siderite as shown in the (Equation 1) (Palacios et al, 2019).…”

Sustained effect of zero-valent iron nanoparticles under semi-continuous anaerobic digestion of sewage sludge: Evolution of nanoparticles and microbial community dynamics

“…In this sense, it should be interesting to study the effect of higher doses in a continuous operation mode using an acclimated microbial consortium having in mind the possible changes that higher doses can have on microbial communities. Indeed, Dong et al (2019), using 25 g L −1 of nZVI reported the promotion of homoacetogenesis, with acetic acid production instead of conversion of CO 2 to CH 4 , and inhibition of the methanogenesis, which is a dose significantly higher than the employed in this work.…”

“…After the addition of these two punctual doses, the results suggested that a minimum of freshly synthetized nZVI should remain in the reactor to enhance biogas composition. The loss of the effect could be attributed to changes in nZVI once in contact with the anaerobic medium, possibly related to their role as an electron donor (Dong et al, 2019) and possible oxidation.…”

“…The positive results of nZVI addition have been related both, to the enhancement of enzyme activities in hydrolysis and acidification steps (Zhang et al, 2020) even during the removal of persistent organic substances in waste activated sludge (Zhou et al, 2020) and antibiotics ; and the growth of H 2 -utilizing microorganisms including homoacetogens and hydrogenotrophic methanogens by providing electrons directly or producing hydrogen through the iron anaerobic oxidation (Zhen et al, 2015;Xu et al, 2019). However, adverse effects on the methanogenesis were also reported at high doses (Dong et al, 2019). Some references using powder and scrap Fe in AD experiments have shown positive effects in biogas yield.…”

Impact of metallic nanoparticles on anaerobic digestion: A systematic review

“…The bio-hydrogen produced from the AD fermentation phase is catalysed by hydrolysis-acidification microorganisms via a redox reaction of proton transfer (Bharathiraja et al, 2016;Ding et al, 2010;Hallenbeck, 2009), which is immediately used by methanogens to form methane in the one-stage AD system. Whilst in the two-stage AD system, the harvested bio-hydrogen can either be used directly as a clean energy source or combined with carbon dioxide to form methane (Dong et al, 2019). Furthermore, the effluent from this process can also be used as feedstock for methane generation for a two-stage AD system (Bharathiraja et al, 2016).…”