Mass transfer effects on biodegradation of methylene blue by immobilized cell in a packed bed bioreactor

Additive manufacturing of hollow connected networks for solar photo-Fenton-like catalysis

A 3D-printing approach is used to fabricate green bodies/precursor microarchitectures that, upon annealing, allow the fabrication of hierarchical 3D hollow microarchitectures (3DHMs). The 3DHMs are composed mainly of TiO2 and inorganic stabilizers that enable the production of inorganic cellular units upon thermal annealing at 650 °C. Morphological inspection reveals that the 3D architecture beams comprise TiO2 nanoparticles (NPs). The inner and outer diameters of the hollow beams are ∼80 μm and ∼150 μm, retained throughout the 3D hollow network. A proof-of-concept photo-Fenton reaction is assessed. The 3DHMs are impregnated with α-Fe2O3 NPs to evaluate solar photo-Fenton degradation of organic compounds, such as MB used as control and acetaminophen, an organic pollutant. The optical, structural, and chemical environment characteristics, alongside scavenger analysis, generate insights into the proposed solar photo-Fenton degradation reaction over TiO2 3DHMs loaded with α-Fe2O3. Our work demonstrates newly hollow printed microarchitecture with interconnected networks, which can help direct catalytic reactions.

New application of gelatin and starch as biocarriers for the biodegradation of reactive blue azo dye using immobilized mixed cells

Reactive azo dyes, if discharged in unmonitored manner to natural water bodies, can cause remarkable irreversible damage. The current study is centered on the decolorization and biodegradation of reactive blue (RB4) azo dye in an integrated sequential anaerobic-aerobic batch mode process. The biodegradation of reactive blue (RB4) was accomplished using alternatively both starch and gelatin-immobilized mixed cells. Activated sludge freshly collected from a sewage treatment plant was used as the biocatalyst. Complete decolorization of 10 mg/L RB4 under anaerobic conditions observed within 30 h by using individually mixed bacterial cells immobilized with; (1) starch cross-linked with polyvinyl alcohol (PVA-St beads), and (2) gelatin cross-linked with polyvinyl alcohol (PVA-Ge beads). The results revealed that maximum removal efficiencies of chemical oxygen demand (COD) under aerobic conditions were 89, 88, and 86%, using PVA-St beads, whereby they were 90, 85, 84% using PVA-Ge beads occurred within 70, 90 and 100 h at detected concentrations of 10, 20, and 40 mg/L, respectively. The effect of biocarrier has been proven to be negligible as the results were comparable using both bio-carriers.