Arsenic removal in flue gas through anaerobic denitrification and sulfate reduction cocoupled arsenic oxidation.

Arsenic in flue gas from municipal solid waste incineration can damage to human health and ecological environment. A sulfate-nitrate-reducing bioreactor (SNRBR) for flue gas arsenic removal was investigated. Arsenic removal efficiency attained 89.4%. An integrated metagenomic and metaproteomic investigation showed that three nitrate reductases (NapA, NapB and NarG), three sulfate reductases (Sat, AprAB and DsrAB), and arsenite oxidase (ArxA) regulated nitrate reduction, sulfate reduction and bacterial As(III)-oxidation, respectively. Citrobacter and Desulfobulbus could synthetically regulate the expression of arsenite-oxidizing gene, nitrate reductases and sulfate reducatases, which involved in As(III) oxidation, nitrate and sulfate reduction. A bacterial consortium containing Citrobacter, UG_Enterobacteriaceas, Desulfobulbus and Desulfovibrio could capable of simultaneously arsenic oxidation, sulfate reduction and denitrification. Anaerobic denitrification and sulfate reduction were cocoupled to arsenic oxidation. The biofilm was characterized by FTIR, XPS, XRD, EEM, and SEM. XRD and XPS spectra verified the formation of aarsenic species (As(V)) from flue gas As(III) conversion. Arsenic speciation in biofilms of SNRBR consisted of 77% residual arsenic, 15.9% organic matter-bound arsenic, and 4.3% strongly absorbed arsenic. Flue gas arsenic was bio-stabilized in the form of Fe-As-S and As-EPS through biodeposition, biosorption and biocomplexation. This provides a new way of flue gas arsenic removal using the sulfate-nitrate-reducing bioreactor.

Noble Metal-Free Hierarchical ZrY Zeolite Efficient for Hydrogenation of Biomass-Derived Levulinic Acid.

Developing a low-cost and robust catalyst for efficient transformation of biomass-derived platform chemicals plays a crucial role in the synthesis of future transportation fuels. Herein, a post-synthetic strategy was employed to develop a noble metal-free and robust ZrY zeolite catalyst, which is efficient for the hydrogenation of biomass-derived levulinic acid (LA) into biofuel γ-valerolactone (GVL), whereas over 95% yield of GVL was achieved in 10 h at 220°C. The effects of acidic properties from ZrY catalysts and various reaction parameters on the catalytic performance were then discussed in detail. Subsequently, different characterization tools were used to compare the difference and relationship of structure activity between the fresh and spent ZrY catalysts. It was found that acidity and the metal-support interaction were important for the direct synthesis of GVL. This work provides a guideline to design a noble metal-free catalyst for high-value utilization of biomass-derived sources.