Degradation Ratio Research Articles

Characterization of a novel aromatic ring-hydroxylating oxygenase, NarA2B2, from thermophilic Hydrogenibacillus sp. strain N12.

Polycyclic aromatic hydrocarbons (PAHs) are harmful to human health due to their carcinogenic, teratogenic, and mutagenic effects. A thermophilic Hydrogenibacillus sp. strain N12 capable of degrading a variety of PAHs and derivatives was previously isolated. In this study, an aromatic ring-hydroxylating oxygenase, NarA2B2, was identified from strain N12, with substrate specificity including naphthalene, phenanthrene, dibenzothiophene, fluorene, acenaphthene, carbazole, biphenyl, and pyrene. NarA2B2 was proposed to add one or two atoms of molecular oxygen to the substrate and catalyze biphenyl at C-2, 2 or C-3, 4 positions with different characteristics than before. The key catalytic amino acids, H222, H227, and D379, were identified as playing a pivotal role in the formation of the 2-his-1-carboxylate facial triad. Furthermore, we conducted molecular docking and molecular dynamics simulations, notably, D219 enhanced the stability of the iron center by forming two stable hydrogen bonds with H222, while the mutation of F216, T223, and H302 modulated the catalytic activity by altering the pocket's size and shape. Compared to the wild-type (WT) enzyme, the degradation ratios of acenaphthene by F216A, T223A, and H302A had an improvement of 23.08%, 26.87%, and 29.52%, the degradation ratios of naphthalene by T223A and H302A had an improvement of 51.30% and 65.17%, while the degradation ratio of biphenyl by V236A had an improvement of 77.94%. The purified NarA2B2 was oxygen-sensitive when it was incubated with L-ascorbic acid in an anaerobic environment, and its catalytic activity was restored in vitro. These results contribute to a better understanding of the molecular mechanism responsible for PAHs' degradation in thermophilic microorganisms.IMPORTANCE(i) A novel aromatic ring-hydroxylating oxygenase named NarA2B2, capable of degrading multiple polycyclic aromatic hydrocarbons and derivatives, was identified from the thermophilic microorganism Hydrogenibacillus sp. N12. (ii) The degradation characteristics of NarA2B2 were characterized by adding one or two atoms of molecular oxygen to the substrate. Unlike the previous study, NarA2B2 catalyzed biphenyl at C-2, 2 or C-3, 4 positions. (iii) Catalytic sites of NarA2B2 were conserved, and key amino acids F216, D219, H222, T223, H227, V236, F243, Y300, H302, W316, F369, and D379 played pivotal roles in catalysis, as confirmed by protein structure prediction, molecular docking, molecular dynamics simulations, and point mutation.

Biodegradation mechanism of chlorpyrifos by Bacillus sp. H27: Degradation enzymes, products, pathways and whole genome sequencing analysis

Chlorpyrifos (CP) is a pesticide widely used in agricultural production. However, excessive use of CP is risky for human health and the ecological environment. Microbial remediation has become a research hotspot of environmental pollution control. In this study, the effective CP-degrading strain H27 (Bacillus cereus) was screened from farmland soil, and the degradation ratio was more than 80%. Then, the degradation mechanism was discussed in terms of enzymes, pathways, products and genes, and the mechanism was improved in terms of cell motility, secretory transport system and biofilm formation. The key CP-degrading enzymes were mainly intracellular enzymes (IE), and the degradation ratio reached 49.6% within 30 min. The optimal pH for IE was 7.0, and the optimal temperature was 25 °C. Using DFT and HPLC‒MS analysis, it was found that degradation mainly involved oxidation, hydrolysis and other reactions, and 3 degradation pathways and 14 products were identified, among which TCP (3,5,6-trichloro-2-pyridinol) was the main primary degradation product in addition to small molecules such as CO2 and H2O. Finally, the whole genome of strain H27 was sequenced, and the related degrading genes and enzymes were investigated to improve the metabolic pathways. Strain H27 had perfect genes related to flagellar assembly and chemotaxis and tended to tolerate CP. Moreover, it can secrete esterase, phosphatase and other substances, which can form biofilms and degrade CP in the environment. In addition, CP enters the cell under the action of permeases or transporters, and it is metabolized by IE. The degradation mechanism of CP by strain H27 is speculated in this study, which provided a theoretical basis for enriching CP-degrading bacteria resources, improving degradation metabolic pathways and mechanisms, and applying strain H27 to environmental pollution remediation.

A sequentially coupled chemical-mechanical damage constitutive model for carbonate rocks

Modelling the constitutive relations of chemically corroded carbonate rocks is important for the design and stability evaluation of engineering constructions in karst areas (e.g., mines, tunnels and dams, etc.) [1-4]. This paper presents a sequentially coupled chemical-mechanical (C-M) damage constitutive model for engineering rocks in karst areas. First, the chemical damage caused by carbonate dissolution and the mechanical damage caused by external loads are investigated based on experimental results. After that, the chemical damage is expressed by the degradation ratio of Young's modulus under the effect of the chemically induced secondary pores compaction. The chemically induced secondary pore is quantified by reactive transport behavior considering the geochemical procedure of free-face dissolution and precipitation under different H+ concentrations, temperature and corrosion periods [5]. The mechanical damage is formulated based on a statistical theory [6,7], which underlines the strength of the mesoscopic element and considers the damage initiation threshold. To capture the nonlinear strength responses of the mesoscopic element at various chemical damage and confining pressures, a modified Mohr-Coulomb (M-C) criterion is introduced, in which the instantaneous friction angle and cohesion are expressed as functions of the confining pressure and chemical damage. The proposed model is validated and shows good agreement with experimental data.
 Result of this research shows that: (1) the porosity increases with increasing corrosion period and the increase rate (i.e., the slope of the porosity curve) is steep initially and then decreases gradually (see Fig. 1 (a)). (2) As shown in Fig. 1 (b), Young's modulus decrease with porosity growth. (3) The C-M coupled damage evolution curve is S-shaped and consists of four stages (see Fig. 1(c)), i.e., a linear elastic stage, a stable damage stage, a damage acceleration stage and a post-peak stage. In damage stage 1, stress is lower than the mechanical damage initiation threshold and the stress-strain curve is in a linear elastic state. At this stage, mechanical damage doesn’t initiate (i.e., ). Therefore, the total damage (Dcm) evolution curve is horizontal and only contains chemical damage (Dc=0.165) caused by carbonate dissolution. Once the axial strain exceeds the mechanical damage initiation threshold, the damage enters stage 2. In this stage, total damage (Dcm) begins to slightly rise and steadily increases with the increasing load. In damage stage 3, the damage-strain curve rises concave upward. After the peak strength point, damage development comes to stage 4, i.e., the post-peak stage.

Experimental and numerical fatigue damage characterization in multidirectional thermoplastic glass/polypropylene laminates based on in-situ damage observations

Quantifying microscopic damage mechanisms in opaque composite laminates with multiple off-axis plies throughout fatigue experiments is challenging. However, if successful, important relations can be revealed between actual evolving damages and their contribution to the mechanical laminate response. This study characterizes the evolution of matrix cracking in ±45 and 90 embedded off-axis plies together with effects of delamination and relates them to the global mechanical property reductions in Glass/Polypropylene laminates. [0/45/0/-45]s and [0/45/90/-45]s laminates are tested under tension-tension fatigue over 500 000 cycles at three different stress levels. In-situ edge damage detection by optical measurements are performed as well as the validation of damages by detailed post-mortem microscopy. Moreover, through-the-width sectioning is applied to reveal the damages inside the laminate after testing. Additionally, the effects of different fabrication histories on damage progression are assessed. Influences of 45-ply thickness and different ply neighbouring orientations on the damage behaviour are discussed with their contribution to the normalized stiffness degradation and Poisson's ratio evolution. Moreover, experimental results are compared with a modelling approach by which the effects of damages in multiple plies can be considered, showing very good accordance.

Synergistic degradation levofloxacin through dielectric barrier discharge and sodium persulfate

The release of antibiotics that are difficult to degrade by themselves into the environment have received increasing attention because they have posed great threat to natural ecosystem and human health. Sodium persulfate (PS) is used to treat organic wastewater because of its strong oxidation, but it needs to be activated. Dielectric barrier discharge (DBD) can product stable gas discharge plasma that is suitable for activating PS. The synergistic degradation process of levofloxacin (LFX) by air DBD plasma with PS were investigated. The effects on the degradation ratio and energy efficiency of LFX were studied, including input power, air flow rate, original concentration, discharge spacing, and PS dosage. The degradation kinetics and synergistic factors were calculated under different PS additions. After plasma alone treatment 45 min, the maximum degradation ratio of LFX was 58.74 % and 88.63 % via plasma alone and plasma synergistic with PS under 15 W input power and 50 mg·L−1 LFX original concentration. The energy efficiency, the first-order reaction rate constant and the synergistic factor SI was 0.1532 g·(kW·h)−1, 4.116 × 10−2 min−1 and 1.64, respectively. The change of ozone concentration in the reaction system after adding PS was measured. The effects on the synergistic degradation of LFX of two radical scavengers, methanol (MeOH), and tert-butanol (TBA), were investigated. After calculation, the contribution ratios of ·OH and SO4-· were 48.08 % and 26.97 %, respectively. The intermediate products were analyzed by LC-MS in the decomposition process of LFX, and the probable decomposition pathway of LFX was presented.

Synthesis and sonocatalytic performance of Dy2Sn2O7/Sepiolite nanocomposite

Sepiolite is a natural clay that has been used in many fields and has attracted increasing attention. The Dy2Sn2O7 nanoparticles were successfully supported by sepiolite and used as the ultrasonic catalyst for the degradation of Acid Orange 7 in this paper. The Dy2Sn2O7/Sepiolite composite was synthesized by a simple hydrothermal method and performed well in ultrasonic degradation. Within 90 min ultrasound vibration, a better degradation ratio of 84.03% was achieved in the Dy2Sn2O7/Sepiolite system compared with the sepiolite and Dy2Sn2O7. The prepared sonocatalysts were characterized by XRD, SEM, TEM, BET, and XPS. The scavenge tests and ESR results revealed that h+ and ·OH were the primary active species for Acid Orange 7 degradation, and ·O2− also played an important role. The results indicated that Dy2Sn2O7/Sepiolite has the potential as a sonocatalyst in the process of remedying the environment and provides a new idea for exploiting and utilizing natural minerals.

A novel magnetic photocatalyst SnO2/SrFe12O19 applied in degradation for Rhodamine B

A novel photocatalyst SnO2/SrFe12O19 (SS) was fabricated by a two-step hydrothermal method, and was characterized by XRD, SEM, EDS, XPS, BET, UV-Vis DRS. The photocatalytic activity was assessed through degrading solution of Rhodamine B (RhB) under simulated solar irradiation. The results showed that composite of wt 5% SrFe12O19 (SS-5) had superior photocatalytic activity, and the degrading ratio could reach 83.8% within 120 min, which was more than the pure phase SnO2. Moreover, specific surface area, cumulative pore volume, and average adsorption pore size of SS-5 slightly enhanced, the light absorption range expanded to the visible light direction, and the band gap energy decreased. Meanwhile, the VSM test showed that the magnetization saturation of SS-5 was 1.42 emu/g, and magnetic separation could be achieved. In the photocatalytic degradation process, RhB was successfully degraded under the effect of superoxide radical (·O2−), and photogenerated hole (h+). Based on these findings, possible photocatalytic mechanism was investigated and explained. The fabricated SnO2/SrFe12O19 could be used as a valuable photocatalyst for the treatment of sewage.

Study on the poly(methyl methacrylate-acrylic acid)/calcium phosphate cement composite bound by chelation with enhanced water absorption and biomechanical properties

Polymethylmethacrylate (PMMA) bone cement has been widely used as a critical material for fixing prostheses and filling bone defects. The shrinkage of PMMA bone cement was addressed by the additives, however, the uneven integral water absorption and expansion performance as well as the deteriorated mechanical properties of the modified bone cement after immersion in phosphate buffered saline (PBS) and simulation body fluid (SBF) affected the long-term stability after implantation. Calcium phosphate cement (CPC) is a biomaterial with promising applications in orthopedics, whose hydration reaction provides an important driving force for the transfer of water. Besides, the mechanical properties of CPC can be enhanced with the curing process. In this study, CPC was utilized to modify the poly(methyl methacrylate-acrylic acid) [P(MMA-AA)] bone cement. The results demonstrated the successful construction of interconnected CPC water delivery networks in the P(MMA-AA)/CPC composite, the water absorption ratio and expansion ratio of the composite were up to 131.18 ± 9.14% and 168.19 ± 5.44%, respectively. Meanwhile, the transformation of CPC water delivery networks into rigid mechanical support networks as well as the chelation interaction between organic-inorganic enhanced the mechanical properties of the composite after immersion, the compressive strength after immersion reached 62.97 ± 0.97 MPa, which was 27.65% higher than that before immersion. The degradation ratio of the composite was up to 13.76 ± 0.23% after 9 days of immersion, which was 16.4% higher than that of CPC. Furthermore, composites exhibited superior biocompatibility as the release of Ca2+. Therefore, P(MMA-AA)/CPC composite serves as a promising medical filling material for clinical use.

Microbial Consortium HJ-SH with Very High Degradation Efficiency of Phenanthrene.

Phenanthrene (PHE) is one of the model compounds of polycyclic aromatic hydrocarbons (PAHs). In this study, a natural PHE-degrading microbial consortium, named HJ-SH, with very high degradation efficiency was isolated from soil exposed to long-term PHE contamination. The results of GC analysis showed that the consortium HJ-SH degraded 98% of 100 mg/L PHE in 3 days and 93% of 1000 mg/L PHE in 5 days, an efficiency higher than that of any other natural consortia, and even most of the engineered strains and consortia reported so far. Seven dominating strains were isolated from the microbial consortium HJ-SH, named SH-1 to SH-7, which were identified according to morphological observation and 16S rDNA sequencing as Pseudomonas sp., Stenotrophomonas sp., Delftia sp., Pseudomonas sp., Brevundimonas sp., Curtobacterium sp., and Microbacterium sp., respectively. Among all the seven single strains, SH-4 showed the strongest PHE degradation ability, and had the biggest degradation contribution. However, it is very interesting that the microbial consortium can hold its high degradation ability only with the co-existence of all these seven single strains. Moreover, HJ-SH exhibited a very high tolerance for PHE, up to 4.5 g/L, and it can degrade some other typical organic pollutants such as biphenyl, anthracene, and n-hexadecane with the degradation ratios of 93%, 92% and 70%, respectively, under 100 mg/L initial concentration in 5 days. Then, we constructed an artificial consortium HJ-7 consisting of the seven single strains, SH-1 to SH-7. After comparing the degradation ratios, cell growth, and relative degradation rates, it was concluded that the artificial consortium HJ-7 with easier reproducibility, better application stability, and larger room for modification can largely replace the natural consortium HJ-SH. In conclusion, this research provided novel tools and new insights for the bioremediation of PHE and other typical organic pollutants using microbial consortia.

Green Synthesis Strategy of Template-Free S-Doped g-C3N4 with Cystine for Efficient Photocatalytic Degradation of RhB.

Constructing a nanostructure with a high surface area and regulating the band gap by nonmetallic doping are two effective methods for improving the photocatalytic activity of catalysts. A green template-free synthesis strategy of S-doped g-C3N4 nanosheets is proposed via doping cystine as both the structural additive and S source. The features of S-doped samples (GCN-x%) were systematically studied, including morphology and textural and photoelectric properties, which demonstrated that the introduction of cystine and simple manipulation of the preparation process could realize self-exfoliation of g-C3N4 into nanosheets. The GCN-3% sample showed a surface area (131.88 m2·g-1) 10.7 times enlarged compared with bulk g-C3N4 (bulk-phase carbon nitride). Obvious redshift on the absorption edge induced by S doping can be observed, revealing a narrowed band gap and enhanced efficiency of photogenerated charge carrier separation. The DFT calculation results also verified that the introduced C-S site could lead to polarization of the local electric field and thus decrease the bandgap of g-C3N4 nanosheets. GCN-3% showed a 99.3% photocatalytic degradation ratio of rhodamine B in 60 min at a rate of 0.17 min-1. By scavengers experiment revealed that superoxide anion (·O2-) radicals and holes (h+) were vital active components during the photocatalytic degradation.

The impact of Sm substitution on structural and optical properties of LaFeO3: their application as a photocatalyst for the degradation of methylene blue under visible light irradiation

The objective of the present study is to enhance the photocatalytic activity of LaFeO3 by inserting Sm ions on the La site for the degradation of methylene blue. We employed citric sol–gel techniques to produce ultrafine powders of the La1-xSmxFeO3 (0.0 ≤ x ≤ 0.5) nanoperovskite samples. All samples confirmed the presence of a pure Pbnm orthorhombic phase structure. The decrease of lattice constants, crystallite sizes and cell volumes, and increase in microstrains suggest a deformation of the structure due to the addition of Sm ion on the La site of the La1-xSmxFeO3. The images of HR-TEM and FE-SEM for all samples revealed a homogeneous distribution of almost spherical nanoparticles, with decreasing average particle sizes ranging from 49.95 ± 3.12 to 34.28 ± 4.38 nm, as Sm ratios increases from 0.0 to 0.5%. The spectra of FTIR confirmed the formation of a Lax-1SmxFeO3 perovskite phase by the appearance of lower frequency bands Fe–O-Fe and La-O-La at ∼ 400 cm−1 and a higher absorption band Fe -O and La -O at ∼ 564 cm−1. The Raman spectra were employed to investigate the formation of phonon modes of La1-xSmxFeO3. Diffused reflectance spectroscopy (DRS) demonstrated the decrease of energy gap (Eg) values from 2.38 to 1.86 eV and the increase in Sm content from 0.0 to 0.5%. Since these Eg values fall within the visible light region, the photocatalytic activity of La1-xSmxFeO3 samples demonstrated a gradual increase in the degradation ratio of MB from 31.7 to 73.2% with increasing Sm content from 0.0 to 0.5%, respectively, under visible light illumination.

Photodegradation of tetracycline using surface oxygen vacancy-enriched PEO coating under visible light

In this study, it was indicated that hydrothermal post-alkali-treated plasma electrolytic oxidation (PEO) coating using NaOH as the reducing agent is an effective catalyst for tetracycline (TC) visible light photodegradation. The post-alkali treatment can not only change the coating surface morphology but also introduce oxygen vacancies (OVs) into them, resulting in extending the light response to visible light and inhibiting the recombination of photogenerated electron-hole (e−-h+) pairs. The visible-light-driven photocatalytic degradation ratio of TC over NaOH hydrothermal post-alkali-treated PEO coating is up to 93.5%, and its degradation rate constant is 10.15 times higher than that of plain PEO coating. Several factors contribute to the excellent photocatalytic activity (PA) of the PEO coating that has undergone NaOH hydrothermal post-alkali treatment. These factors include a high concentration of surface OVs (Ti3+ defect energy level), the development of an anatase-rutile-Na2Ti3O7 ternary heterojunction, increased hydrophilicity, and a nanosheet-like morphology that provides more surface active sites. Finally, appropriate scavengers were utilized to investigate the role of various photogenerated reactive species and to detail the photocatalytic mechanism.

Development and validation of a mathematical model for evaluating shear-induced damage of von Willebrand factor

PurposeTo develop a mathematical model for predicting shear-induced von Willebrand factor (vWF) function modification which can be used to guide ventricular assist devices (VADs) design, and evaluate the damage of high molecular weight multimers (HMWM)-vWF in VAD patients for reducing clinical complications. MethodsMathematical models were constructed based on three morphological variations (globular vWF, unfolded vWF and degraded vWF) of vWF under shear stress conditions, in which parameters were obtained from previous studies or fitted by experimental data. Different clinical support modes (pediatric vs. adult mode), different VAD operating states (pulsation vs. constant mode) and different clinical VADs (HeartMate II, HeartWare and CentriMag) were utilized to analyze shear-induced damage of HMWM-vWF based on our vWF model. The accuracy and feasibility of the models were evaluated using various experimental and clinical cases, and the biomechanical mechanisms of HMWM-vWF degradation induced by VADs were further explained. ResultsThe mathematical model developed in this study predicted VAD-induced HMWM-vWF degradation with high accuracy (correlation with experimental data r2 > 0.99). The numerical results showed that VAD in the pediatric mode resulted in more HMWM-vWF degradation per unit time and per unit flow rate than in the adult mode. However, the total degradation of HMWM-vWF is less in the pediatric mode than in the adult mode because the pediatric mode has fewer times of blood circulation than the adult mode in the same amount of time. The ratio of HMWM-vWF degradation was lower in the pulsation mode than in the constant mode. This is due to the increased flushing of VADs in the pulsation mode, which avoids prolonged stagnation of blood in high shear regions. This study also found that the design feature, rotor size and volume of the VADs, and the superimposed regions of high shear stress and long residence time inside VADs affect the degradation of HMWM-vWF. The axial flow VADs (HeartMate II) showed higher degradation of HMWM-vWF compared to centrifugal VADs (HeartWare and CentriMag). Compared to fully magnetically suspended VADs (CentriMag), hydrodynamic suspended VADs (HeartWare) produced extremely high degradation of HWMW-vWF in its narrow hydrodynamic clearance. Finally, the study used a mathematical model of HMWM-vWF degradation to interpret the clinical statistics from a biomechanical perspective and found that minimizing the rotating speed of VADs within reasonable limits helps to reduce HWMW-vWF degradation. All predicted conclusions are supported by the experimental and clinical data. ConclusionThis study provides a validated mathematical model to assess the shear-induced degradation of HMWM-vWF, which can help to evaluate the damage of HMWM-vWF in patients implanted with VADs for reducing clinical complications, and to guide the optimization of VADs for improving hemocompatibility.

Enhanced photocatalytic activity of tourmaline modified BiFeO3 nanoparticles by efficient charge transfer

The development of green and efficient photocatalytic materials for the industrial wastewater has become a current research focus. In this work, bare BiFeO3 (BFO) and tourmaline modified BFO composites were synthesized by the sol-gel method to investigate the photocatalytic degradation efficiency of the different content tourmaline modified BFO for methyl orange dyes. The SEM and elemental mapping images display that BFO nanoparticles are uniformly distributed on the surface of tourmaline. The increased photocurrent density and band gaps indicate that higher effective separation for photogenerated electron-hole pairs were obtained by introducing the tourmaline. The photocatalytic activities shows that T-BFO composite exhibits an obvious enhancement of methyl orange degradation ratio under visible light irradiation, which is higher than that of the bare BFO. Moreover, the electron transport mechanism of T-BFO composites were particularly investigated through active species trapping experiments. These results provide a new approach to develop the high performance of photocatalyst.

Revealing the critical roles of silver species on TNT film for photocatalytic decomposition of volatile organic pollutants under UV or visible light irradiation: From mechanism study to scaled-up test

Ag nanoparticles are commonly employed as co-catalysts to promote photocatalytic reactions. In addition to their apparent roles as electron traps and catalytic active sites, nanoparticulate Ag can also generate hot electrons under visible light irradiation, which endows visible light photocatalytic activity to its supporting material. On the other hand, Ag0 can be easily converted to Ag2O, however, few studies focus on its formation and roles during the photocatalytic process. In this work, we have successfully fabricated and optimized the preparation procedures of titania nanotube (TNT) and Ag species deposited TNT to get the optimum photochemical activities of Ag modified TNT. Specifically, the roles of Ag species on TNT film have been investigated by photoelectrochemical (PEC) measurements and photocatalytic decomposition of volatile organic pollutants under UV or visible light irradiation. Toluene (30 ppm) can be effectively decomposed (∼83.3%) and mineralized (∼70.7%) by Ag species modified TNT in 3 h under UV–visible light irradiation, while the degradation and mineralization ratios are only about 60.0% and 33.3% under visible light irradiation. The results demonstrate that appropriate Ag/Ag2O ratio on TNT film are crucial for improving PEC and photocatalytic performance, and the interconversion between Ag and Ag2O influences the photochemical stability of Ag/TNT film. The scaled-up tests (∼1.0 m3 reactor) on the degradation of low concentration of toluene and formaldehyde prove that the optimized Ag/TNT film can be considered as a promising photocatalyst for indoor air purification.

Surface atomic oxygen species mediated the in-situ formation of hydroxyl radicals on Fe3C decorated biochar for enhancing catalytic ozonation

Developing highly efficient and anti-interference catalysts was still a challenge for the practical application of heterogeneous catalytic ozonation (HCO) in water decontamination. Herein, a magnetic Fe3C decorated biochar (Fe3C/BC) was prepared for HCO to achieve efficient degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The Fe3C/BC catalytic ozonation system promoted the degradation ratio of 2,4-D from 58.7% (ozonation alone) to 90.0% within 10 mins when the ozone dosage was 1.0 mg/L. And the observed degradation rate constant (kobs) of 2,4-D under catalytic ozonation system was 2.58 times that of ozonation alone. Fe3C/BC exhibited negligible adsorption on 2,4-D but with a significant enrichment to ozone, which realized the cooperating process of “adsorption-catalysis” at the solid–liquid interface, thus avoiding the ineffective decomposition of ozone. The dissociative adsorption of ozone molecules on the surface Fe3C generated surface atomic oxygen species (O* and O2*), which mediated the in-situ formation of hydroxyl radicals (·OH). ATR-FTIR, in-situ Raman, isotope tracing tests, and theoretical calculations were used to disclose the interface reaction processes and reveal the ·OH formation mechanism. Free radical reactions at the interface efficiently avoid the interference of coexisting ions dissolved in water. The presence of 3 mM (183 mg/L) bicarbonate had essentially little effect on the degradation of 2,4-D. The consecutive use of Fe3C/BC did not influence its catalytic performance and stable structure. This study provided new insight into the ·OH-dominated interfacial reaction in the HCO process.

Characterization and biological evaluation of new PLGA/fibrin/lignin biocomposite electrospun scaffolds

In this study, we produced electrospun scaffolds from 10% pure PLGA solution, and 10% polyblend solutions of PLGA/Fibrin, PLGA/Lignin, and PLGA/Fibrin/Lignin with proportions of 9:1, 8:2, 7:3, 7:2:1, 6:2:2, and 5:2:3 and characterized them physiochemically and biologically. FTIR and EDX results verified the chemical composition of the fibers. All scaffolds exhibited homogenous nanostructures with fiber diameters ranging from 0.1 to 2.5 μm and the highest average fiber diameter belonged to PLGA/Lignin fibers. Increasing the lignin proportion led to a decrease in fibers diameter and a change in color to brown. Fibrin improved the hydrophobicity of the scaffolds, and the incorporation of fibrin, lignin, or fibrin/lignin improved the absorption capacity of the scaffolds (up to 91.7%). From day 45 onwards, fibrin-containing scaffolds started to degrade much faster. By day 90, PLGA/20%Fibrin/30%Lignin showed the highest degradation ratio of 82%, while PLGA/10%Lignin showed the lowest at 51.4%. All scaffolds exhibited high porosity percentage (over 78%), with porosity enhanced by increasing fibrin and decreasing lignin. The pure PLGA scaffold and PLGA/10%Lignin showed the highest stiffness and tensile strength, respectively. The addition of natural components gradually decreased the scaffolds’ tensile strength and fracture strain. MTT results showed higher absorbance reading at 490 nm for PLGA, PLGA/10%Fibrin, and all three PLGA/Lignin scaffolds from day 3 to day 7. On day 7, PLGA/10%Fibrin exhibited the highest cell viability, followed by PLGA/10%Lignin and PLGA/20%Fibrin/10%Lignin. SEM micrographs revealed the presence of h-ADSCs with spindle-like morphologies, attached and proliferated well on all scaffolds. PLGA/10%Fibrin, PLGA/10%Lignin, and PLGA/20%Fibrin/10%Lignin were selected as the preferred options from each set of scaffolds. Among them, PLGA/20%Fibrin/10%Lignin exhibited superior physical features and actively enhanced the biological responses of the cells due to its physio-mechanical signals and the advanced features of lignin, making it suitable for tissue engineering, wound dressing, drug delivery, and other biomedical applications.

Efficient persulfate activation by photo-excited organic dyes: Mechanism and application for actual dyeing wastewater self-purification

Sulfate Radical-Advanced Oxidation Processes are considered an efficient way for purifying dyeing wastewater, which commonly resists conventional treatment processes owing to the complex components, low biodegradability and high toxicity. However, this emerging technique is associated with issues of secondary pollution and great energy consumption during peroxymonosulfate (PMS) or persulfate (PS) activation processes. Herein, a dye pollutant/PS/visible light self-catalytic system was constructed, based on the photosensitive property of organic dyes for PS activation without catalyst and energy input. In this system, the degradation ratio of 100 mL 10 mg L−1 basic fuchsin, rhodamine B and eosin Y significantly increased by 60%, 76% and 50%, compared with the process without light irradiation. Such improvements were attributable to an efficient photo-induced electron transfer from photo-excited dyes to PS, which has the precondition that the lowest unoccupied molecular orbital (LUMO) energy level of the dye is higher than that of PS, thereby generating oxidizing species like ·SO4−, ·OH and 1O2 for pollutants degradation. Due to the high performance of pollutants simultaneous removal, wide pH adaptability and anti-interference, the complex self-catalytic system consisted of nine dyes and bis-phenol A exhibited the possibility for practical application. Expectedly, the actual dyeing wastewater self-purification system featured a decolorization efficiency of 54% accompanied by the removal of co-existing aromatic proteins and tryptophan-like substances; moreover, the acute bio-toxicity of the raw wastewater greatly decreased by 61.6%. Owing to its high efficiency, eco-friendliness and low consumption, the constructed “using waste to treat waste” system provides a promising way for wastewater treatment.

Hydrazine-thermal syntheses, structures, and photocatalytic properties of tellurostannate hybrids with iron (II) complex unit

Iron containing tellurostannates [Fe(dien)2]2Sn2Te6 (dien = diethylenetriamine) (1), [Fe(tepa)(N2H4)]2Sn2Te6 (tepa = tetraethylenepentamine) (2), and [{Fe(trien)}2(μ-1κ:2κ-SnTe4)] (trien = triethylenetetramine) (3) were solvothermally prepared in different ethylene polyamines with the assistance of hydrazine in lower temperature range. In 1 and 2, two SnTe4 tetrahedral units are joined via edge-sharing forming a free dimeric [Sn2Te6]4− anion with Fe(II) complex cation acting the counter ion. In compound 3, the SnTe4 tetrahedron connected two [Fe(trien)]2+ complex units as a bidentate μ-1κ:2κ bridging ligand, to generate the neutral binuclear complex [{Fe(trien)}2(SnTe4)]. The compounds 1–3 had narrow semiconducting band gaps of 1.76, 1.73 and 1.71 eV, respectively. They showed sensitive photocurrent response under Xe light irradiation with steadied current densities in the range of 0.45–0.76 μA·cm−2. They were catalytically active in the photodegradation of crystal violet (CV) with the degradation ratio varying between 59.5% and 93.5%. Compound 3 exhibited the highest photocatalytic activity, which was attributed to its highest strength of photocurrent response.

The design and preparation of Mg and Zn co-doped carbon nitride with enhancing photocatalytic degradation efficiency for methylene blue

Carbon nitride (g-C3N4) is a potential material that can be used for the treatment of the wastewater contains organic dyes. However, the photocatalytic efficiency of g-C3N4 is limited by the wide band gap and fast recombination of photon-generated carriers. In this work, the co-doped with Mg and Zn of MgZn0.07-g-C3N4 was designed and prepared to enhance the photocatalytic efficiency. The co-doped Mg and Zn shorted the band gap of g-C3N4 from 2.74 eV to 2.50 eV. Interestingly, according to the DFT calculation, a Zn-bridge is formed between the interlayers of g-C3N4. The Zn-bridge reduces the electron localization and prolongs the existence time of photon-generated carriers. The as-prepared MgZn0.07-g-C3N4 was applied for the photodegradation of methylene blue. The degradation ratios and photodynamic parameter of MgZn0.07-g-C3N4 are higher than that of g-C3N4 and Mg-g-C3N4 (29.51 × 10−3 min vs 8.00 × 10−3 min).