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The metal activating sulfite system has attracted widespread attention as a novel advanced oxidation process recently. In this study, a silica-supported highly dispersed cobalt catalyst was prepared using Co ammine complex as precursor, characterized by transmission electron microscope, X-ray diffraction, Brunauer–Emmett–Teller surface area, X-ray photoelectron spectroscopy and so forth, and used to activate sulfite for the removal of organic pollutants. The as-prepared catalyst displayed a durable and remarkable catalytic activation of sulfite for organic degradation in sequential experiments. The mechanistic study corroborated the dual roles of sulfite as a complexing ligand on catalyst surface and a precursor of oxysulfur radicals. The surface-bound and free SO 4 •− were found to be the dominating radicals responsible for organic degradation. The steady-state approximation of SO 4 •− were examined and the apparent reaction rate constant of SO 4 •− generation was 0.60 ± 0.07 M−1 s−1 at 0.25 g L−1 catalyst. The influencing factors and operating parameters, including catalyst dosage, sulfite/contaminant ratio, pH, temperature, anions and natural organic matter were investigated and optimized systematically. As conclusion, the as-prepared catalyst to efficient activation of sulfite can be proposed as a promising advanced oxidation process based on oxysulfur radicals for the treatment of wastewater. Image 1 • The silica-supported cobalt catalyst is synthesized via a complexation process. • CoASi shows an effective performance in sulfite activation for organic degradation. • Sulfite acts as a complexing ligand and a radical precursor in activation process. • Surface-bound and free sulfate radicals are responsible for dye degradation. • The optimal operating conditions are obtained for further application. [ABSTRACT FROM AUTHOR]

Crawfish shell wastes (CSW) are abundant with valuable substrates, which possess great resource potentials. This work has revealed the feasibility of CSW reutilization for effective volatile fatty acids (VFAs) generation with waste active sludge (WAS) via anaerobic fermentation. The maximum VFAs generation reached 17963 mg COD/L when the CSW/WAS mass ratio was 3.25:1, while it was 784 mg COD/L in the control reactor. Meanwhile, each gram of CSW could be transformed into 264 mg COD equivalent VFAs. The feed of CSW brought in massive organic substrates, which significantly promoted the solubilization, hydrolysis and acidification processes in the CSW/WAS co-fermentation systems simultaneously. The metabolism of carbohydrates took priority over proteins in contributing to the VFAs promotion. More importantly, the functional anaerobes (i.e. , Paludicola sp. and Macellibacteroides sp.), which participated in the main substrates decomposition with the VFAs as the primary metabolites, were evidently enriched in the presence of CSW. The critical hydrolases and acid-forming enzymes relevant to VFAs biosynthesis were all enhanced. Moreover, the key genes encoding for the main substrates metabolisms (i.e., chitin) and VFAs production were remarkably up-regulated. The evident promotion of microbial activities and metabolic functions was mainly ascribed to the favorable fermentation conditions (i.e., pH, ORP and C/N) induced by CSW conditioning. This study proposed an innovative strategy to recover high-value products from CSW, and in-depth insights of microbial traits and genetic functions in CSW/WAS co-fermentation systems. [Display omitted] • Each gram of CSW can be transformed into 264 mg COD equivalent VFAs. • The solubilization, hydrolysis and acidification steps are synchronously promoted. • The VFAs promotion is mainly attributed to the carbohydrates metabolism. • The functional anaerobes involved in VFAs generation are enriched. • The critical metabolic activities (i.e. enzymes and genes) are enhanced. [ABSTRACT FROM AUTHOR]

In this study, the approach of stimulating the production of volatile fatty acids (VFAs) during food wastes (FW) fermentation by linear alkylbenzene sulphonates (LAS) is proposed and the underlying mechanisms from a metagenomic perspective are analyzed. The results show that with an appropriate level of LAS (50 mg/L), VFA production is greatly enhanced (11854 versus 1825 mg COD/L) with the increased proportions of high-value long-chain ones. Mechanistic explorations indicate that LAS contributes to the solubilization/hydrolysis of the main organic components in FW (i.e., carbohydrates, proteins and lipids) due to the amphipathic features. Besides, LAS would interact with the cell membranes and increase the cell permeability to promote the membrane transport of substrates into the functional microorganisms for further metabolisms. The metagenomic analysis demonstrates that the critical genes involved in hydrolase secretion (i.e., bglX, pepD and lip), ABC transporter (i.e., rfbA and lolD), main substrate metabolism (especially the proteins and lipids, i.e., glsA and glpK) and fatty acid biosynthesis (i.e., accA , accC and accD) all highly expressed in LAS-conditioned reactors. The upregulation of these encoding genes stimulates microbial metabolic activities and improves the production rates of VFAs. Besides, the distribution of functional microbial populations and their associations with genetic expressions in different reactors were investigated. This study provides profound information on the stimulating effects of LAS on FW fermentation for VFA production from genetic and functional perspectives. [Display omitted] • Linear alkylbenzene sulphonates (LAS) enhanced volatile fatty acids (VFAs) production. • The organics solubilization/hydrolysis and membrane transport process were improved. • LAS mainly upregulated the genetic expressions of proteins and lipids metabolism. • The encoding genes involved in VFAs biosynthesis were enriched. • The microbial structure and its association with genetic expressions were analyzed. [ABSTRACT FROM AUTHOR]