Degradation Ability Research Articles

Nascently generated microplastics in freshwater stream are colonized by bacterial communities from stream and riparian sources.

The purpose of this study was to examine bacterial colonization of different types of microplastics through time in a freshwater ecosystem. Microplastics are persistent pollutants in aquatic ecosystems. Bacteria readily colonize microplastic surfaces and may contribute to their degradation, but the taxa involved, and their degradative abilities, differ based on factors such as microplastic chemistry, plastic age, and specific ecosystem types. Four different common types of newly manufactured microplastics, high-density polyethylene, low-density polyethylene, polypropylene, and polystyrene, were incubated for 7 weeks in a freshwater stream and sampled. Sample collection was timed to examine the development of early and late bacterial biofilm communities. Microplastics were analyzed for changes to buoyancy, weight, contact angles (an indicator of surface roughness), bacterial community composition, and the number of bacterial cells. Time was the only significant contributing factor in the development of bacterial biofilm communities on microplastic disks over the 7-week study. Notably, the Comamonadaceae were abundant early in the study and decreased in abundance with time, while the Methylococcaceae demonstrated the opposite trend. Different physicochemical properties among the various types of microplastics had only a minor effect on bacterial community compositions of biofilms growing on the microplastics. Additionally, the surfaces of all microplastic disks became rougher over time in the stream. Collectively, our results show that microplastic surfaces undergo surface modification and community succession as time progresses, regardless of microplastic type, in a freshwater stream ecosystem.

Electrochemical remediation of methyl orange over reusable biochar ferrite coated photocatalytic plates

Biochar (BC) obtained from biomass pyrolysis holds immense potential for environmental remediation. The efficiency of BC can further be enhanced by incorporating metal nanoparticles (NPs) in the porous carbon matrix. In the present work nanocomposites (NCs) were prepared by the addition of ferrite nanoparticles (FNPs) into an oxidized BC matrix to create BC /Fe3O4 (BCF). This process improves BC stability, electron transfer, conductivity, and photocatalytic ability for dye degradation. Microstructure and functional group analysis of BCF was performed by SEM, XRD, and FTIR showing intercalation of FNPs with surface functionalities of oxidized BC matrix. The B-H curve of FNPs and BCF reveals super paramagnetic behavior with saturation magnetization (Ms, emu/g) of 67.36 and 20.01 respectively. BET surface area analysis shows surface area (m2/gm) 45.81 and 44.19 for oxidized BC and BCF respectively, that attributed to partial blocking of porous carbon matrix by FNPs. UV-DRS supports the semiconducting behavior of BCF with a significantly reduced band gap (eV) of 2.95 over pristine BC (4.76). BCF-coated photocatalytic plates (PCPs) were developed and utilized for the remediation of methyl orange (MeO) in water samples. Degradation of MeO was investigated over time by electrochemical methods. The square wave voltammetric method showed the limit of detection and quantification of 0.09 ppm and 0.28 ppm respectively for MeO over a glassy carbon electrode in 0.1 M acetate buffer. BCF-derived PCPs rendered ∼99 % degradation efficiency against MeO (50 mgL−1) under UV radiation over 240 min. Developed PCPs demonstrate reusability up to 5 cycles without any further purification step and offer efficient degradation of MeO making them suitable for the treatment of water polluted with dyes.

Eco-friendly and sustainable synthesis of carbon quantum dots from waste sulfuric acid of alkylation

Waste sulfuric acid of alkylation (WSAA) poses a challenge in industrial alkylation oil production due to its substantial yield and high treatment costs. This study introduces a novel hydrothermal method that ingeniously couples the treatment of WSAA with the synthesis of high-quality carbon quantum dots (CQDs), offering a cost-effective and controllable approach. Through this method, the particle size and surface functional groups of the resulting CQDs can be precisely regulated. The average particle size tunes from 17.97 nm to 2.42 nm via increasing the hydrothermal temperature, and nitrogen-containing groups can be introduced through adding nitrogen sources during hydrothermal process. The prepared CQDs exhibit notable performance in photocatalysis and heavy metal detection, such as CQDs modified graphite carbon nitride has improved photocatalytic degradation ability and Hg (II) detection ability. Additionally, the environmental impact of the proposed method is substantially minimized, demonstrating a smaller footprint on ecosystems compared to conventional industrial disposal processes. Moreover, the economic cost associated with the method is significantly reduced by approximately 48.4 %, further highlighting its efficiency. Utilizing WSAA as a raw material for CQDs not only facilitates the recycling and sustainable utilization of waste but also enables low-cost production of high-performance carbon materials, presenting a mutually beneficial approach.

Termite gut microbiome being a rich source of potential lignocellulolytic bacterial strains

A study was carried out to identify prospective cellulose degrading bacteria isolated from termite gut collected from various agriculture sites. Eight of the bacterial isolates displayed a very distinct zone of clearing on CMC (Carboxylmethyl cellulose) agar media after staining with 1% Congo red, indicating that they may have cellulose degrading ability. On a CMC agar plate, CRDB6 had the largest colony diameter (3.08 cm) as well as clear zone diameter (0.96 cm), however CRDB 1 has maximum cellulolytic activity (1.45 cm) followed by CRDB5 and CRDB6 (1.33 cm and 1.28 cm) respectively. CRDB3, CRDB4 and CRDB9 showed Gram negative reaction among crop residue degrading bacterial isolates, while the remainder showed Gram positive reaction. The morphological characteristics of the bacteria isolates, such as colony shape, elevation, margin, colour and opacity, differed. Isolates CRDB6 produced highest β-glucosidase activity (12.66 m L-1) followed by CRDB1 (12.20 mg m L-1) and CRDB5 (10.21 m L-1) in Luria broth culture. Indole acetic acid production (with tryptophan) was greater in CRDB1 (389.33 mg/ml), CRDB6 (356.9 m L-1) and CRDB3 (315.96 m L-1) while as P-solubilization potential was peaked in CRDB6 (2.41 m L-1) followed by CRDB4 (1.76 m L-1) and CRDB3. Overall, isolate CRDB6 exhibited the highest cellulolytic activity as compared to rest of the bacterial isolates. These results will help in preparing bacterial consortia for the management of crop residues.

High Degree of Polymerization of Chitin Oligosaccharides Produced from Shrimp Shell Waste by Enrichment Microbiota Using Two-Stage Temperature-Controlled Technique of Inducing Enzyme Production and Metagenomic Analysis of Microbiota Succession.

The direct enzymatic conversion of untreated waste shrimp and crab shells has been a key problem that plagues the large-scale utilization of chitin biological resources. The microorganisms in soil samples were enriched in two stages with powdered chitin (CP) and shrimp shell powder (SSP) as substrates. The enrichment microbiota XHQ10 with SSP degradation ability was obtained. The activities of chitinase and lytic polysaccharide monooxygenase of XHQ10 were 1.46 and 54.62 U/mL. Metagenomic analysis showed that Chitinolyticbacter meiyuanensis, Chitiniphilus shinanonensis, and Chitinimonas koreensis, with excellent chitin degradation performance, were highly enriched in XHQ10. Chitin oligosaccharides (CHOSs) are produced by XHQ10 through enzyme induction and two-stage temperature control technology, which contains CHOSs with a degree of polymerization (DP) more significant than ten and has excellent antioxidant activity. This work is the first study on the direct enzymatic preparation of CHOSs from SSP using enrichment microbiota, which provides a new path for the large-scale utilization of chitin bioresources.

Binary metal–organic framework composites as environmentally friendly photocatalysts: Green synthesis and visible light-assisted pollutant degradation

Green synthesis of MOF-on-MOF is an effective method to prepare the environmentally friendly photocatalyst using metal–organic frameworks (MOFs). Herein, ZIF-8 was synthesized on MIL-100 (Fe) (ZM composites) with different weight percent ratios of ZIF-8 and denoted as ZM21, ZM11 and ZM12. They were investigated as environmentally friendly photocatalysts for the degradation of Methylene Blue (MB) using visible light. XRD, FT-IR, SEM, EDX, and DRS were used to characterize the synthesized materials (ZIF-8, MIL-100, ZM21, ZM11, and ZM12). The ZM11 composite had the highest dye degradation ability. The MB photocatalytic degradation for the ZIF-8, MIL-100, ZM21, ZM11, and ZM12 were 12.59%, 31.27%, 29.45%, 86.3, and 31.51%, respectively. MB degradation by ZM11 composite followed the first-order kinetic model. The effective radical for the MB photocatalytic degradation was the superoxide radical (•O2–). The ZM11 composite had the ability of 76% dye removal from water after 3 cycles of MB degradation.

The Impact of Gelatin and Fish Collagen on Alginate Hydrogel Properties: A Comparative Study.

Hydrogel materials based on sodium alginate find versatile applications in regenerative medicine and tissue engineering due to their unique properties, such as biocompatibility and biodegradability, and the possibility of the customization of their mechanical properties, such as in terms of the individual requirements of separate clinical applications. These materials, however, have numerous limitations in the area of biological activity. In order to eliminate their limitations, sodium alginate is popularly applied in combination with added gelatin, which represents a product of collagen hydrolysis. Despite numerous beneficial biological properties, matrix materials based on gelatin have poor mechanical properties and are characterized by their ability for rapid degradation in an aqueous environment, particularly at the physiological temperature of the body, which significantly limits the independent application opportunities of this type of composition in the range of scaffolding production dedicated for tissue engineering. Collagen hydrogels, unlike gelatin, are characterized by higher bioactivity, dictated by a greater number of ligands that allow for cell adhesion, as well as better stability under physiological conditions. Fish-derived collagen provides a material that may be efficiently extracted without the risk of mammalian prion infection and can be used in all patients without religious restrictions. Considering the numerous advantages of collagen indicating its superiority over gelatin, within the framework of this study, the compositions of hydrogel materials based on sodium alginate and fish collagen in different concentrations were developed. Prepared hydrogel materials were compared with the properties of a typical composition of alginate with the addition of gelatin. The rheological, mechanical, and physicochemical properties of the developed polymer compositions were evaluated. The first trials of 3D printing by extrusion technique using the analyzed polymer solutions were also conducted. The results obtained indicate that replacing gelatin with fish collagen at an analogous concentration leads to obtaining materials with a lower swelling degree, better mechanical properties, higher stability, limited release kinetics of calcium ions cross-linking the alginate matrix, a slowed process of protein release under physiological conditions, and the possibility of extrusion 3D printing. The conducted analysis highlights that the optimization of the applied concentrations of fish collagen additives to composition based on sodium alginate creates the possibility of designing materials with appropriate mechanical and rheological properties and degradation kinetics adjusted to the requirements of specific applications, leading to the prospective opportunity to produce materials capable of mimicking the properties of relevant soft tissues. Thanks to its excellent bioactivity and lower-than-gelatin viscosity of the polymer solution, fish collagen also provides a prospective solution for applications in the field of 3D bioprinting.

Enhanced electrochemical disinfection for decentralized sewage treatment through nickel foam cathode modified with CoFe2O4-spinel ferrite and multi-way carbon nanotubes

Electrochemical disinfection is characterized by its simple operation and maintenance, along with effective sterilization capabilities, making it ideal for decentralized wastewater treatment in rural areas. As a bimetallic oxide, spinel ferrite exhibits excellent catalytic activity for the oxygen reduction reaction (ORR). Herein, a novel cathode was fabricated from nickel foam modified with spinel ferrite and multi-way carbon nanotubes (CoFe2O4-MWCNTs@NF). The modification successfully strengthens the electrochemical cathode reaction to generate strong oxidants such as hydrogen peroxide and Hydroxyl radical, enabling the disinfection of water bodies with low chloride concentrations. Compared to other influencing factors (including current density, aeration rate, and electrode spacing), the impact of conductivity on hydrogen peroxide generation is relatively minor. Modified electrodes still exhibited effective disinfection capabilities in water with low conductivity. At a current density of 2 mA/cm², the CoFe2O4-MWCNTs@NF electrode achieved 4.00 log removal of E.coli in real treated sewage within 15 minutes, with an energy consumption of 1.038 kWh/m³. Electrochemical disinfection also had a certain degradation ability for sulfonamides and quinolones antibiotics in water. The disinfection and antibiotic removal effects of the modified electrode demonstrated its potential for practical applications.

Iskanje in določanje bakterij, ki so sposobne razgraditi celulozo s pomočjo IAA kot potencialnih pospeševalcev rasti rastlin

Strains with both straw degradation and plant growth promotion ability were selected from the cultivated soil in Bac Kan, Vietnam to solve the problems of poor soil microbial diversity status, weak corrosion promotion effect, and poor crop growth caused by fungal rot diseases. Among seventeen bacteria isolated, strain NR1 presented the highest value for cellulase enzyme activity (Hydrolysis index = 24.8 mm), and IAA production (20.15 mg l-1), and was identified as Bacillus amyloliquefaciens Priest et al., 1987. Inoculation with NR1 significantly increased the rot promotion rate of straw under liquid fermentation by 54.71 % compared with the control and increased the root length and average diameter, and SPAD value of maize under soil culture by 18.3 %, 22.0 %, and 5.24 % respectively (p < 0.05). In addition, fertilizing 8 or 9 tons of NR1-degraded compost fertilizer per hectare had the best effect on the growth, development, and productivity of the L14 peanut variety. These results suggest strain NR1 could be used to produce multi-functional humus, accelerate the decomposition of straw in the cultivated soil, and promote crop growth.

Boronate-modified electro-spun Fe doped carbon nanofibrous membrane for selective dye adsorption, catalytic degradation, and bacterial inhibition in treatment of water

Recently, dye and microorganism have become the main sources of water pollution due to the rapid development of modern industries and wantonly draining of living sewage. Therefore, the efficient removal of dye and microorganism from the wastewater have attracted considerable attentions of the scientists and engineers around the world. In this regard, a novel phenyl boronic acid (PBA) modified electro-spun Fe doped carbon nanofibrous membrane, C/Fe@PBA, was fabricated in this study for simultaneously selective removal of dye and efficient inhibition of bacteria in water. Firstly, the C/Fe@PBA displayed selective adsorption towards Congo Red (CR) among other dyes by the adsorption order of CR>Methyl Orange (MO) > Neutral Red (NR) > Methylene Blue (MB) > Malachite Green (MG) > Rhodamine B (RhB) with adsorption ability at 25.75, 8.41, 7.11, 7.02, 5.41, and 3.13 mg·g−1. The pseudo first order kinetics and Langmuir isotherm model is calculated to better match the adsorption process of the as prepared membrane towards CR. After 7 rounds of adsorption desorption or 5 degradation cycles, the carbon membrane showed a removal efficiency of 62.2 % or 57.4 %, respectively. Furthermore, the C/Fe@PBA can be employed as effective catalyst to degrade CR in presence of H2O2 under 808 nm near-infrared (NIR) irradiation by the photothermal effect, and the possible catalytic mechanisms and degradation pathway were proposed. Moreover, the as prepared membrane exhibited high bactericidal rate of 99.94 % and 97.44 % against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. In conclusion, the as prepared carbon membrane with ability of selective adsorption, catalytic degradation, and bacterial inhiation is a promising candidate of filtration membrane in practical sewage management.

Tetracycline degradation in the system of peracetic acid activation by liquid discharge plasma

The oxidative degradation ability of peracetic acid (PAA) for organic pollutants can be enhanced by different activation methods. This study investigated the degradation efficiency and mechanisms of tetracycline (TC) using PAA activated by liquid-phase discharge plasma. An 86.08 % degradation efficiency for TC after 60 min treatment was achieved in the Plasma/PAA system, much higher than that of the sole Plasma (46.64 %) and PAA (15.19 %). Acidic conditions and neutral conditions were more favorable for TC removal than alkaline conditions. Inorganic ions generally inhibited TC degradation, though notably, low concentrations of Cl− and NO3− promoted it. Free radical quenching experiments and electron paramagnetic resonance (EPR) analysis confirmed the crucial roles of OH, RO, and 1O2 in TC degradation. Three-dimensional fluorescence spectroscopy (3DFS) and ultraviolet–visible absorption spectroscopy (UV–VIS) elucidated the TC degradation mechanism, revealing key aspects of antibiotic structural decomposition. Further analysis of the degradation products by liquid chromatography-mass spectrometry (LC-MS) indicated three potential degradation pathways. Biotoxicity evaluations indicated that the synergistic system significantly reduced the biotoxicity of the degradation products. This study demonstrated an efficient method for plasma-activated PAA in degrading persistent pharmaceutical pollutants. It also confirmed the system’s applicability across a broad spectrum of organic pollutants and water bodies, highlighting its potential for a wide range of environmental protection applications.

Novel Starch-Modified NiCrMn-LDH-Based Composite for Photocatalytic Degradation of Reactive Orange 13

Water pollution has become a great challenge today. To address this problem regarding wastewater treatment by removing toxic synthetic dyes from wastewater, this research focused on the synthesis of a novel starch-modified NiCrMn-layered double hydroxide composite through the coprecipitation method and applied it as a photocatalyst for the degradation of reactive orange 13 dye. The synthesized photocatalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), point of zero charges (PZC), dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Zeta potential techniques. These techniques revealed different characteristics of photocatalysts, like surface and structural properties. According to BET analysis, the final composite had 2.5 × 102 m2/g BET-specific surface area with a 45.56 nm pore radius value, and the overall composite found as mesoporous. Similarly, in DLS analysis, bare NiCrMn-LDH had 404 nm hydrodynamic size, which increased for the final starch composite up to 667 nm. Zeta potential value changed from −14.56 mV to 0.95 mV after the incorporation of starch with NiCrMn-LDH. They confirmed the incorporation of starch with trimetallic NiCrMn-layered double hydroxide (2:1:2). Starch association improved the properties of the photocatalyst like surface area. Different parameters like pH value, initial dye concentration, photocatalyst dose, hydrogen peroxide concentration, effect of sacrificial reagent, and effect of inorganic anions were studied for degradation of RO13. Overall, the photocatalysis process for RO13 followed pseudo-first-order kinetics. Photocatalytic degradation reactions for reactive orange 13 were conducted with an initial dye concentration of 10 mg/L, photocatalyst dosage of 20 mg/50 mL, and pH value at 3 in the presence of sunlight, resulting in an impressive degradation removal rate of 86.68%. This remarkable degradation ability of the photocatalyst for reactive orange 13 proves this composite was highly efficient.

Novel 2D layered g-C3N4 nanocomposite materials for sustainable wastewater treatment by catalytic degradation of toxic dye

The photocatalytic degradation technique is one of the suitable ways of dealing with environmental pollutant decontamination. This study demonstrates the ability of graphitic carbon nitride (g-C3N4) nanocomposites containing tellurium (Te) and molybdenum disulfide (MoS2) to photocatalytically destroy organic cationic methylene blue (MB) dye, which is primarily used in the textile industry. Using the alkali treatment approach, layered graphitic carbon nitride (g-C3N4) was created. Using MoS2 and Te, several g-C3N4 nanocomposites were created using ultrasonic calcination techniques. After the MoS2 and Te were immobilized individually, the composites underwent a methodical characterization process utilizing a variety of instruments, including XRD and SEM. Using a 2D layered nano-g-C3N4 substrate, the photo-catalytic degradation reaction of MB was observed, and a UV spectrophotometer was used to determine the absorbance of the MB dye. Using 0.2 % MoS2/g-C3N4 and 5 % Te/g-C3N4, the photocatalytic degradation efficiency of the MB dye (10, 15, and 20 mg/L) solution was examined. In comparison to other produced nanocomposites, the 5 % Te/g-C3N4 composite was shown to have the highest photocatalytic activity in terms of dye degradation ability, and about 100 % of the MB dyes were degraded in less than 60 minutes. As the concentration of MB increased, the dye degradation efficiency of g-C3N4 nanocomposites steadily dropped, and the degradation rate of MB was around 1.5 mg/L.

Soil-derived cellulose-degrading bacteria: screening, identification, the optimization of fermentation conditions, and their whole genome sequencing.

Straw cellulose is an abundant renewable resource in nature. In recent years, the conversion of cellulose from waste straw into biofuel by specific microorganisms' fragmentation has attracted extensive attention. Although many bacteria with the ability to degrade cellulose have been identified, comprehensive bioinformatics analyses of these bacteria remain limited, and research exploring optimal fragmentation conditions is scarce. Our study involved the isolation and screening of bacteria from various locations in Yangzhou using carboxymethyl cellulose (CMC) media. Then, the cellulose-degrading bacteria were identified using 16S rRNA and seven candidate bacterial strains with cellulose degrading ability were identified in Yangzhou city for the first time. The cellulase activity was determined by the 3,5-dinitrosalicylic acid (DNS) method in different fragmentation conditions, and finally two bacteria strains with the strongest cellulose degradation ability were selected for whole genome sequencing analysis. Sequencing results revealed that the genome sizes of Rhodococcus wratislaviensis YZ02 and Pseudomonas Xanthosomatis YZ03 were 8.51 Mb and 6.66 Mb, containing 8,466 and 5,745 genes, respectively. A large number of cellulose degradation-related genes were identified and annotated using KEGG, GO and COG analyses. In addition, genomic CAZyme analysis indicated that both R. wratislaviensis YZ02 and P. Xanthosomatis YZ03 harbor a series of glycoside hydrolase family (GH) genes and other genes related to cellulose degradation. Our finding provides new options for the development of cellulose-degrading bacteria and a theoretical basis for improving the cellulose utilization of straw.

Photocatalytic coatings with self-cleaning properties for indoor air treatment

In this work we have studied the photocatalytic and self-cleaning properties of TiO2 layers immobilized on polymeric panels, as passive elements for air treatment. In order to achieve easy scale-up technologies for the preparation of coatings, roller-coating technique was selected, comparing the results with those prepared by dip-coating. Composites were characterized by SAXRD, UV–Vis DRS spectroscopy, profilometry, N2 adsorption–desorption, SEM and AFM microscopy. The adherence of the coating was evaluated according the ASTM D3359 standard adhesive tape test. The photocatalytic properties of the materials were evaluated by the photodegradation of trichloroethylene or formaldehyde, as model volatile organic compounds, in the gas phase. The hydrophilic-hydrophobic properties were measured by studying the in-situ variation of the water contact angle with time and UV-A irradiation. Moreover, the self-cleaning properties were analyzed according to ISO 27448:2009 for oleic acid removal. Although coatings of approximately ca. 250 nm layer thickness can be prepared by both techniques, roller-coating allows the material deposition with a coral-like structure in a single and simple step. Surface roughness was promoted by roller process. The developed materials present high photocatalytic performance for the elimination of both model pollutants in the gas phase. Aging tests under outdoor conditions and Scotch tape test show the stability and resistance of the coatings. In-situ irradiation measurements show the superhydrophilic character of the coatings. Water contact angle lower than 10 ° after 300 min of UV-A irradiation was achieved for oleic acid removal. The combination of TiO2 nanoparticles with different crystal structures and sizes improves the photocatalytic performance. A correlation between the ability for pollutants degradation in gas phase and the self-cleaning properties (in-situ or oleic acid measurements) was determined.

Novel membrane bioreactor with iron-tannin-framework based membrane for effluent quality improvement and fouling control

A 10 L membrane bioreactor (MBR) was constructed with novel iron-tannin-framework ultrafiltration membrane (ITUM) for membrane fouling mitigation and effluent quality improvement. Compared to commercial ultrafiltration membrane (CUM) in the same MBR, ITUM exhibited hydrophilicity with a contact angle of 64.18° (71.36° for CUM), resulting the permeance of ITUM (50.2 L m-2h−2 bar−1) 1.8 times higher than CUM. During 70-day operation, ITUM was consistently run at lower transmembrane pressure. After operation, the polyethersulfone (PES) peak intensity of ITUM reduced less than 1 % (85 % for CUM), which indicated a thinner sludge layer on ITUM. Meanwhile, the average effluent chemical oxygen demand concentration for ITUM and CUM achieved 16.69 and 17.60 mg L-1 in stable phase, respectively. For NH4+-N, it could reach 0 and 0.04 mg L-1. 16 s RNA results showed that Saccharibacteria accounted for 1.48 % and 1.20 % on ITUM and CUM, respectively. According to first-principles density functional theory simulations, simulated adsorption energies was −1.330 eV for gram-positive bacteria (such as Saccharibacteria). It was −0.867 eV for Fe(Ⅲ) to gram-negative bacteria. It suggests that ITUM could easily attract microorganisms with the ability of polysaccharide degradation, while reducing this type of pollutants deposition on membrane. Therefore, the ITUM received a more superior effluent quality and membrane fouling resistance.

Bimetallic Ag/Fe-MOG derived flake-like Ag2O/Fe2O3 p-n heterojunction for efficient photodegradation organic pollutants within a wide pH range

In this paper, we reported a facile and clean strategy to prepare the flake-like Ag2O/Fe2O3 bimetallic p-n heterojunction composites for photodegradation organic pollutants. The surface morphology, crystal structure, chemical composition and optical properties of Ag2O/Fe2O3 were characterized by SEM, high-resolution TEM images with EDX spectra, XRD, XPS, FT-IR and UV–vis DRS spectra respectively. The formation of Ag2O/Fe2O3 p-n heterojunction facilitated the interfacial transfer of electrons as well as the separation of charge carries. Hence, the as-synthesized Ag2O/Fe2O3-3 composites exhibited ultra-high photocatalytic activity. Under the experimental conditions of catalyst dosage of 0.4 mg mL−1 and irradiation time of 60 min, the degradation conversion rate of rhodamine B reached 96.1 %, which was 5.0 and 2.8 times of pure phase Ag2O and Fe2O3, respectively. Meanwhile, the degradation performance of Ag2O/Fe2O3-3 was not limited by pH, and it can achieve high degradation efficiency under 3–11. In addition, Ag2O/Fe2O3-3 also showed superb degradation ability for other common anionic dyes, cationic dyes and antibiotics. XPS and FT-IR spectra showed that Ag2O/Fe2O3-3 retained a carbon skeleton that facilitated electron transport and light absorption conversion. And the analyses of quenching experiment and EPR demonstrated •O2−, •OH and h+ were crucial reactive oxidant species contributing to the rapid organic pollutant degradation. This work provides new insights into obtaining p-n photocatalysts heterojunction with excellent catalytic activity for removing organic pollutants from wastewater.

Enhanced biodegradation of benzo[a]pyrene with Trametes versicolor stimulated by citric acid.

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants with carcinogenic, mutagenic and teratogenic effects. The white-rot fungi in the fungal group have significant degradation ability for high molecular weight organic pollutants. However, exogenous fungi are easily antagonized by indigenous microorganisms. Low molecular weight organic acids, a small molecular organic matter secreted by plants, can provide carbon sources for soil microorganisms. Combining organic acids with white rot fungi may improve the nutritional environment of fungi. In this study, immobilized Trametes versicolor was used to degrade benzo[a]pyrene in soil, and its effect on removing benzo[a]pyrene in soil mediated by different low molecular weight organic acids was investigated. The results showed that when the degradation was 35days, the removal effect of the experimental group with citric acid was the best, reaching 43.7%. The degradation effect of Trametes versicolor on benzo[a]pyrene was further investigated in the liquid medium when citric acid was added, and the effects of citric acid on the biomass, extracellular protein concentration and laccase activity of Trametes versicolor were investigated by controlling different concentrations of citric acid. In general, citric acid can act as a carbon source for Trametes versicolor and promote its extracellular protein secretion and laccase activity, thereby accelerating the mineralization of benzo[a]pyrene by Trametes versicolor. Therefore, citric acid can be used as a biostimulant in the remediation of PAHs contaminated soil with Trametes versicolor.

Study on methane degradation by microbial agents based on chelating wetting agent carriers

Due to the low permeability characteristics of the deep gas-containing coal seam, the conventional prevention and control measures that cannot solve the problems of gas outbursts are unsatisfactory for the prevention and control of the coal and gas outbursts disaster. Therefore, in this study, a strain of methane-oxidizing bacteria M07 with high-pressure resistance, strong resistance, and high methane degradation rate was selected from coal mines. The growth and degradation abilities of M07 in chelating wetting agent solutions to assess its adaptability and find the optimal agent-to-M07 ratio. It provides a new method for integrating the reduction of impact tendency and gas pressure in deep coal mines. The experimental results show that M07 is a Gram-positive bacterium of the genus Bacillus, which has strong resistance and adaptability to high-pressure water injection. By degrading 70 mol of methane, M07 produces 1 mol of carbon dioxide, which can reduce gas pressure and reduce the risk of gas outbursts in coal mines. As the experiment proves, the best effect was achieved when the M07 concentration of the chelating wetting agent was 0.05%. The methane-oxidizing bacteria based on the chelating wetting agent as carriers prove a new prevention and control method for the integrated prevention and control of coal and gas outbursts in coal mines and also provide a new idea for microbial application in coal mine disaster control.

Synthesis and mechanism of hierarchical porous Ag/CuxO (x = 1, 2) nanowire hybrids for high photocatalytic degradation

To improve organic pollutant degradation ability, this work aims at designing a novel porous Cu-Ag bimetal hybrid with unique architecture, fertile porosity as well as Schottky junction. Herein, a free-standing hybrid with Ag nanoparticles modified CuxO (x = 1, 2) nanowires in-situ grown on the nanoporous Cu-Ag bimetal network (Ag/CuxO@NP-CuAg) was successfully synthesized by dealloying and then anodizing process. Compared with monometallic CuxO nanowires integrated with nanoporous Cu substrate (CuxO@NPC), the Ag/CuxO@NP-CuAg hybrids with the Ag/CuxO Schottky junction and SPR effect of Ag nanoparticles, are favorable to accelerate the transportation of photo-generated carriers and avoid the recombination of electrons (e-) and holes (h+), thus exhibiting the enhanced photocatalytic performance for RhB. Such remarkable performance is also contributed to the multimodal hierarchical porous structure and the integration design strategy. Moreover, by density functional theory (DFT) calculation, a typical Z-scheme mechanism is proposed to better understand the photocatalytic degradation process. The formation mechanism of the Ag/CuxO nanowires is also investigated.