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The addition of magnetite nanoparticles (MNPs), reduced graphene oxide (rGO), and reduced graphene oxide decorated with magnetite nanoparticles (rGO-MNPs) was evaluated during biomethane enrichment process. rGO-MNPs presented the highest beneficial impact on the hydrogenotrophic assays with an improvement of 47 % in CH 4 production. The improvement was linked to the increase of the electron shuttling capacity (ESC) by rGO-MNPs addition, which boosted the hydrogenotrophic activity of microorganisms, to the rGO and rGO-MNPs, which served as reservoirs of hydrogen, improving H⁠ 2 transport from the gas to the liquid phase, and to the iron ions released, which acted as a dietary supply for microorganisms. Raman and XRD confirmed a greater disorder and lower crystallinity of rGO-MNPs after the hydrogenotrophic assays, with a lower effect at a nanoparticle concentration of 50 mg/L. Moreover, FTIR analysis indicated that rGO-MNPs were oxidized during the hydrogenotrophic tests. This study highlights the advantages of adding rGO-MNPs as a magnetic nanocomposite. Furthermore, rGO-MNPs can be easily recovered, minimizing their release to the environment., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

An innovative biofiltration technology based on anoxic biodegradation was proposed in this work for the treatment of inert VOC-laden emissions from the petrochemical industry. Anoxic biofiltration does not require conventional O2 supply to mineralize VOCs, which increases process safety and allows for the reuse of the residual gas for inertization purposes in plant. The potential of this technology was evaluated in a biotrickling filter using toluene as a model VOC at loads of 3, 5, 12 and 34 g m(-3)h(-1) (corresponding to empty bed residence times of 16, 8, 4 and 1.3 min) with a maximum elimination capacity of ∼3 g m(-3)h(-1). However, significant differences in the nature and number of metabolites accumulated at each toluene load tested were observed, o- and p-cresol being detected only at 34 g m(-3)h(-1), while benzyl alcohol, benzaldehyde and phenol were detected at lower loads. A complete toluene removal was maintained after increasing the inlet toluene concentration from 0.5 to 1 g m(-3) (which entailed a loading rate increase from 3 to 6 g m(-3)h(-1)), indicating that the system was limited by mass transfer rather than by biological activity. A high bacterial diversity was observed, the predominant phyla being Actinobacteria and Proteobacteria., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The effect of liquid and solid transfer vectors (silicone oil and Desmopan, respectively) on the gaseous interfacial area (a(g)) was evaluated in a two-phase partitioning bioreactor (TPPB) using fresh mineral salt medium and the cultivation broth of a toluene degradation culture (Pseudomonas putida DOT-T1E cultures continuously cultivated with and without silicone oil at low toluene loading rates). Higher values of a(g) were recorded in the presence of both silicone oil and Desmopan compared to the values obtained in the absence of a vector, regardless of the aqueous medium tested (1.6 and 3 times higher, respectively, using fresh mineral salt medium). These improvements in a(g) were well correlated to the oxygen mass transfer enhancements supported by the vectors (1.3 and 2.5 for liquid and solid vectors, respectively, using fresh medium). In this context, oxygen transfer rates of 2.5 g O(2)L(-1)h(-1) and 1.3 g O(2)L(-1)h(-1) were recorded in the presence of Desmopan and silicone oil, respectively, which are in agreement with previously reported values in literature. These results suggest that mass transfer enhancements in TPPBs might correspond to an increase in a(g) rather than to the establishment of a high-performance gas/vector/water transfer pathway., ((c) 2009 Elsevier B.V. All rights reserved.)