Silica-supported ionic liquid for efficient gaseous arsenic oxide removal through hydrogen bonding.

The emission of highly-toxic gaseous As2O3 (As2O3 (g)) from nonferrous metal smelting poses environmental concerns. In this study, we prepared an adsorbent (SMIL-X) by loading an ionic liquid (IL) ([HOEtMI]NTf2) into MCM-41 through an impregnation-evaporation process and then applied it to adsorb As2O3 (g). SMIL-20% exhibited an As2O3 (g) adsorption capacity of 35.48 mg/g at 400 °C, which was 490% times higher than that of neat MCM-41. Characterization of SMIL-X indicated that the IL was mainly supported on MCM-41 through O-H…O bonds formed between the hydroxyl groups (-OH) and the silanol groups (Si-OH) and the O-H…F bonds formed between the C-F groups and the Si-OH groups. The hydrogen bonds significantly contributed to the adsorption of As2O3 (g), with -NH and -OH groups forming hydrogen bonds with As-O species (i.e., N-H…O and O-H…O). This showed superior performance to traditional adsorbents that rely on van der Waals forces and chemisorption. Moreover, after exposure to high concentrations of SO2, the adsorption capacities remained at 76% of their initial values, demonstrating some sulfur resistance. This study presents an excellent adsorbent for the purification of As2O3 (g) and shows promising application potential for treating flue gas emitted by nonferrous metal smelting processes.

Characteristics variations of size-fractionated anammox granules and identification of the potential effects on these evolutions.

Anaerobic ammonium oxidation (anammox) granulation which contributed to system stabilization and performance improvement has great potential in the field of wastewater nitrogen removal. The researchers fractionated anammox granules into small-size (0.5-0.9 mm), medium-size (1.8-2.2 mm), and large-size (2.8-3.5 mm) categories to examine their properties and mechanisms. Various analyses, including high-throughput sequencing, determination of inorganic elements and extracellular polymeric substances (EPS), and microbial function prediction, were conducted to characterize these granules and understand their impact. The results revealed distinct characteristics among the different-sized granules. Medium-size granules exhibited the highest sphericity, EPS content, and anammox abundance. In contrast, large-size granules had the highest specific surface area, heme c content, specific anammox activity, biodiversity, and abundance of filamentous bacteria. Furthermore, the precipitates within the granules were identified as CaCO3 and MgCO3, with the highest inorganic element content found in the large-size granules. Microbial community and function annotation also varied with granule size. Based on systematic analysis, the researchers concluded that cell growth, chemical precipitation, EPS secretion, and interspecies interaction all played a role in granulation. Small-size granules were primarily formed through cell growth and biofilm formation. As granule size increased, EPS secretion and chemical precipitation became more influential in the granulation process. In the large-size granules, chemical precipitation and interspecies interaction, including synergistic effects with nitrifying, denitrifying, and filamentous bacteria, as well as metabolic cross-feeding, played significant roles in aggregation. This interplay ultimately contributed to higher anammox activity in the large-size granules. By fully understanding the mechanisms involved in granulation, this study provides valuable insights for the acclimation of anammox granules with optimal sizes under different operational conditions.

The potential application of an efficient MOF-derived visible light-responsive photocatalyst based on Au/C/ZnO for tetracycline antibiotic photodegradation.

A series of porous photocatalysts, Au-carbon-doped ZnO (Au/C/ZnO), were synthesized successfully via calcination using MOF-5 as template, with the matrix impregnated with Au nanorods through the seed-mediated method. The catalytic performance was investigated by the photodegradation of tetracycline hydrochloride (TC-HCl). Ninety percent of TC was degraded by Au/C/ZnO sample within 360 min under visible light, showing an efficient photocatalytic activity. The enhanced activity was mainly ascribed to the effect of oxygen vacancies produced by C doping during calcination process of MOF-5 and Au nanorods. The density functional theory (DFT) calculation shows that due to the intermediate energy level, the electron-hole pairs generated by photoelectricity transition were transitioned from valence band (VB) to the intermediate energy level, and further to the conduction band (CB) under irradiation. Thus, the separation efficiency of photogenerated carrier was improved in this process. Meanwhile, the surface plasmon resonance (SPR) and electromagnetic field effect of Au nanorods which were loaded on the C/ZnO promoted the separation efficiency of change carriers, and this process also provided more hot electrons for free radicals generation. This work provides an efficient method for the design and synthesis of noble metal- and non-metal-doped oxide photocatalysts and provides an effective photocatalytic technique for the antibiotic degradation under visible light, which possesses the huge application potential in the environmental purification.

The Predominant Sources of Heavy Metals in Different Types of Fugitive Dust Determined by Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) Modeling in Southeast Hubei: A Typical Mining and Metallurgy Area in Central China.

To develop accurate air pollution control policies, it is necessary to determine the sources of different types of fugitive dust in mining and metallurgy areas. A method integrating principal component analysis and a positive matrix factorization model was used to identify the potential sources of heavy metals (HMs) in five different types of fugitive dust. The results showed accumulation of Mn, Fe, and Cu can be caused by natural geological processes, which contributed 38.55% of HMs. The Ni and Co can be released from multiple transport pathways and accumulated through local deposition, which contributed 29.27%. Mining-related activities contributed 20.11% of the HMs and showed a relatively high accumulation of As, Sn, Zn, and Cr, while traffic-related emissions contributed the rest of the HMs and were responsible for the enrichment in Pb and Cd. The co-applied source-identification models improved the precision of the identification of sources, which revealed that the local geological background and mining-related activities were mainly responsible for the accumulation of HMs in the area. The findings can help the government develop targeted control strategies for HM dispersion efficiency.

The potential contributions to organic carbon utilization in a stable acetate-fed Anammox process under low nitrogen-loading rates.

The unique ability of Anammox bacteria to metabolize short-chain fatty acids have been demonstrated. However, the potential contributions of active Anammox species to carbon utilization in a mixotrophic Anammox-denitrification process are less well understood. In this study, we combined genome-resolved metagenomics and DNA stable isotope probing (DNA-SIP) to characterize an Anammox process fed with acetate under COD/TN ratios of around 0.30-0.40 and low nitrogen-loading rates. A draft genome of "Candidatus Jettenia caeni" and a novel species that was phylogenetically close to "Candidatus Brocadia sinica" were recovered. Essential genes encoding the key enzymes for acetate metabolism and dissimilatory nitrate reduction to ammonium were identified in the two Anammox draft genomes. The DNA-SIP revealed that Ignavibacterium, "Candidatus Jettenia caeni," Thauera, Denitratisoma, and Calorithrix predominantly contributed to organic carbon utilization in the acetate-fed Anammox process. In particular, the "Candidatus Jettenia caeni" accounted for a higher proportion of 13C-DNA communities than "Candidatus Brocadia sinica." This result well confirmed the theory of maintenance energy between the interspecies competition of the two Anammox species under low nitrogen-loading rates. Our study revealed its potential important role of the Anammox genus "Candidatus Jettenia" in the treatment of wastewater containing low organic matter and ammonia.

Combined genome-centric metagenomics and stable isotope probing unveils the microbial pathways of aerobic methane oxidation coupled to denitrification process under hypoxic conditions.

Obligate aerobic methanotrophs have been proven to oxidize methane and participate in denitrification under hypoxic conditions. However, this phenomenon and its metabolic mechanism have not been investigated in detail in aerobic methane oxidation coupled to denitrification (AME-D) process. In this study, a type of hypoxic AME-D consortium was enriched and operated for a long time in a CH4-cycling bioreactor with strict anaerobic control and the nitrite removal rate reached approximately 50 mg N/L/d. Metagenomics combined with DNA stable-isotope probing demonstrated that the genus Methylomonas, which constitutes type I aerobic methanotrophs, was the dominant member and contributed to methane oxidation and partial denitrification. Metagenomic binning recovered a near-complete (98%) draft genome affiliated with the family Methylococcaceae containing essential genes that encode nitrite reductase (nirK), nitric oxide reductase (norBC) and hydroxylamine dehydrogenase (hao). Metabolic reconstruction of the selected Methylococcaceae genomes also revealed a potential link between methanotrophy and partial denitrification.

Treatment of wastewater containing Reactive Brilliant Blue KN-R using TiO2/BC composite as heterogeneous photocatalyst and adsorbent.

Heterogeneous photocatalysis namely titanium dioxide (TiO2) supported on coconut shell biochar (BC) was synthesized by sol-gel method (calcined at 450 °C) in the paper, which was innovatively applied to the decolorization of Reactive Brilliant Blue KN-R. The transmission electron microscopy (TEM) and X-ray diffraction patterns (XRD) results demonstrated that anatase TiO2 film was firmly immobilized on the surface and pores of BC. The photocatalysis tests under UV high pressure xenon lamp (300 W) showed highest decolorization efficiency occurred at strong acid and alkali conditions (pH = 1 and 11) reached as 99.71% and 96.99% respectively within 60 min. Therefore, the TiO2/BC composites demonstrated both photocatalytic and adsorption capacity on KN-R decolorized, and presented quite durable and reusable in regeneration cycles, indicating a widely application possibility in anthraquinones dyeing wastewater treatment.