Significant Degradation Effect Research Articles

Pilot-scale and mechanistic study of the degradation of typical odors and organic compounds in drinking water by a combined UV/H2O2-BAC process

Odor problems are challenging issues in water treatment. Advanced oxidation has a significant degradation effect on these odors; however, some issues, such as oxidant residues and disinfection byproducts, exist in the use of advanced oxidation in actual water treatment. Because of the above issues, a combined advanced oxidation process has emerged—the UV/H2O2 -biological activated carbon (BAC) process can play a strong oxidizing role in advanced oxidation and uses the physical adsorption and biological effects of activated carbon. However, there have been few studies on the odor degradation mechanism and characteristics of activated carbon biofilms in actual water treatment. This paper systematically studied the organic and odor substances removal effects and mechanism of a pilot combined UV/H2O2-BAC process. The results showed that UV/H2O2-BAC technology had a good removal effect on odor substances under long-term stable operation. The concentrations of geosmin (GSM) and 2-methylisoborneol (2-MIB) after systemic treatment were below 5 ng/L. The removal rates of DOC, UV254 and H2O2 by the combined process were 53.60%, 73.08% and 60.20%, respectively. The results of full-scan determination of GSM and 2-MIB degradation by gas chromatography–mass spectrometry (GC–MS) were consistent with those of front-track analysis. The diversity, richness and evenness of microorganisms in the lower activated carbon layer were higher than those in the middle and upper activated carbon layers. The greater the difference in the carbon layer height was, the greater the difference in the biological community structure.

Effect of hygrothermal ageing on the mechanical performance of CFRP/AL single-lap joints

ABSTRACT Bonding technology presents several advantages over traditional mechanical connecting methods and, thus, has been widely used in the automotive industry. However, hygrothermal ageing environments may exert a significant degradation effect on the bonding structure during the service of the automobile. This study mainly investigated the effect of hygrothermal ageing on the quasi-static tensile strength of the adhesive layer of carbon fiber reinforced plastic (CFRP)-aluminium alloy (AL) single-lap joints (SLJs). A simple method, based on the finite element (FE) model, was used to determine moisture-dependent CZ properties. Numerical simulations of the quasi-static tensile properties of the CFRP/AL SLJs were also conducted, and the simulation results were consistent with the experimental findings. Results indicated that the failure strength of the adhesive and adhesively bonded CFRP/AL SLJs subjected to hygrothermal ageing declines with increasing ageing duration. Moreover, the degradation rate in the initial stages of ageing is significantly higher than that in later stages. Failure of the adhesively bonded CFRP/AL SLJs was characterised by cohesive failure and mixed failure. No carbon fiber delamination was observed in CFRP/AL SLJs following hygrothermal ageing.

Preparation of Quinone Mediator / Polyvinylidene Fluoride Functionalized Membrane

In this study, the redox mediator accelerated the degradation of dyes and improved the efficiency of dye wastewater treatment by immobilizing quinone mediators on the membrane. Specifically, polyvinylidene fluoride, quinone, and lithium chloride were used as the membrane substrate, redox mediator modifier, and porogen, respectively. By changing the type of quinone, the concentration of quinone, and the concentration of crossing-linker, the effect of quinone mediator-functionalized polyvinylidene fluoride membrane on the decolorization of dye wastewater was investigated. This study has shown that the cross-linking agent could effectively improve the compatibility of the quinone mediator casting solution system, and the increase in the addition amount of quinone mediator increased the decolorization rate of the membrane. The increase of the quinone content could also improve the decolorization effect of the dye. The decolorization rate of the original membrane without adding quinone was only 36%, whereas the decolorization rate of the blend membrane reached 75%, which shows the PVDF film with immobilized quinone mediator exhibited a significant dye degradation effect.

Nano Au@Cu2-xS with near-infrared photothermal and peroxidase catalytic activities redefines efficient antibiofilm-oriented root canal therapy

Killing harmful bacteria in biofilms is a major challenge for current root canal therapy. Although traditional chemical disinfectants have a good bactericidal effect on plankton, they have little efficiency for the removal and sterilization of bacterial biofilms, and even lead to the emergence of bacterial resistance and high toxic side effects. Herein, we propose for the first time biosafe nanocomposites that integrate photothermal and peroxidase-like catalytic activity for efficient removal and killing of bacterial biofilms in root canals. The integration of gold (core) and copper (Ⅰ, Ⅱ) sulfide (shell) shows excellent catalytic effect, which can catalyze the decomposition of hydrogen peroxide at biosafe concentrations to hydroxyl radicals for efficient removal of biofilms. Moreover, studies on the mechanism of antibiofilm showed that the nanocomposites (Au@Cu2-xS) have significant degradation effects on proteins and polysaccharides-the main components of biofilm. The in vitro results indicated that the synergism of free radical and heat shows higher sterilization rate against both gram-positive Enterococcus faecalis and gram-negative Fusobacterium nucleus, compared with free radical and heat treatment alone. More importantly, the bactericidal results on isolated dental slices and in root canal models and beagle dog demonstrated the Au@Cu2-xS is highly effective in inactivating the bacteria in biofilms. Hence this safe and synergistic antimicrobial system has great potential in antibiofilm-oriented root canal therapy.

A marine bacterial community capable of degrading poly(ethylene terephthalate) and polyethylene

Plastic wastes are becoming the most common form of marine debris and present a growing global pollution problem. Here, we used a screening approach on hundreds of plastic waste-associated samples and discovered a marine bacterial community capable of efficiently colonizing and degrading both poly(ethylene terephthalate) (PET) and polyethylene (PE). Using absolute quantitative 16S rRNA sequencing and cultivation methods, we obtained corresponding abundance and purified cultures of three bacterial strains that mediated plastic degradation. We further performed numerous techniques to characterize the efficient degradation of PET and PE by the reconstituted bacterial community containing these three bacteria. Additionally, we used liquid chromatography-mass spectrometry to further demonstrate the degradation of PET and PE films by the reconstituted bacterial community. We conducted transcriptomic methods to investigate the plastic degradation process and potential degradation mechanisms mediated by our reconstituted bacterial community. Lastly, we overexpressed PE degradation enzymes based on transcriptomic results and verified their significant degradation effects on the PE films. Overall, our study establishes a stable marine bacterial community that efficiently degrades PET and PE and provides insights into plastic degradation pathways and their associated biological and mechanistic processes—paving the way for developing microbial products against plastic wastes.

Robust antimicrobial photodynamic therapy with curcumin-poly (lactic-co-glycolic acid) nanoparticles against COVID-19: A preliminary in vitro study in Vero cell line as a model

BackgroundIn this study, the ability of antimicrobial photodynamic therapy (aPDT) as a treatment approach and adjuvant therapy using curcumin-poly (lactic-co-glycolic acid) nanoparticles (Cur@PLGA-NPs) to inactivate Coronavirus disease 2019 (COVID-19) in plasma was investigated. Furthermore, to verify whether the quality requirement of aPDT-treated plasma is acceptable, the differences of the levels of clotting factors, total plasma proteins, and anti-A and/or anti-B antibodies titrations in plasma of patient before and after aPDT treatment were investigated. Materials and MethodsCur@PLGA-NPs was synthesized using Electrospinning process and characterized by different analysis including Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), and Fourier Transform Infrared (FTIR) spectroscopy assays. The presence of the SARS-CoV-2 in the plasma samples of patients suspected of having COVID-19 was confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR) assay. Then, the treated plasma samples with Cur@PLGA-NPs plus blue laser were exposed to Vero cells. Eventually, cell cytotoxicity and apoptotic effects of treated Vero cells were evaluated. Levels of clotting factors including prothrombin time (PT) and activated partial thromboplastin time (APTT), total plasma proteins, and anti-A and/or anti-B antibodies measurements were performed using the coagulometer, method of Bradford, and titration procedure, respectively. ResultsThe presence of SARS-CoV-2 was positive in 84.3 % of samples. Different concentrations of Cur@PLGA-NPs (3, 5, 7, and 10 % wt.), the irradiation times of blue laser (1, 3, and 5 min), and aPDT with the maximum dosed of blue laser light (522.8 J/cm2) plus 10 % wt. Cur@PLGA-NPs had no cytotoxicity. Although there were significant cell degradation and apoptotic effects in treated Vero cells with treated plasma using 10 % wt. Cur@PLGA-NPs, and a blue laser at an energy density of 522.8 J/cm2, no visible changes in cells and apoptosis were observed following aPDT. Total plasma protein content, PT, APTT, and anti-A and/or anti-B antibodies titers showed no significant changes (P > 0.05 for all comparisons) in treated plasma as compared to untreated plasma. ConclusionaPDT exhibited in vitro anti-COVID-19 activities in the treated plasma containing SARS-COV-2 without Vero cell apoptosis and any adverse effects on plasma quality in aPDT-exposed plasma.

Degradation of poly(butylene adipate-co-terephthalate) by Stenotrophomonas sp. YCJ1 isolated from farmland soil

In recent years, poly (butylene adipate-co-terephthalate) (PBAT) has been widely used. However, PBAT-degrading bacteria have rarely been reported. PBAT-degrading bacteria were isolated from farmland soil and identified. The effects of growth factors on the degradation of PBAT and the lipase activity of PBAT-degrading bacteria were assessed. The degradation mechanism was analyzed using scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, X-ray diffraction, and liquid chromatography-mass spectrometry. The results showed that Stenotrophomonas sp. YCJ1 had a significant degrading effect on PBAT. Under certain conditions, the strain could secrete 10.53 U/mL of lipase activity and degrade 10.14 wt.% of PBAT films. The strain secreted lipase to catalyze the degradation of the ester bonds in PBAT, resulting in the production of degradation products such as terephthalic acid, 1,4-butanediol, and adipic acid. Furthermore, the degradation products could participate in the metabolism of YCJ1 as carbon sources to facilitate complete degradation of PBAT, indicating that the strain has potential value for the bioremediation of PBAT in the environment.

Study on the Degradation Effect of Plant-Derived Active Ingredients on Organophosphorus Pesticides

In order to explore new ways and methods for the degradation of organophosphorus pesticides, the degradation effects of plant-derived active ingredients on three organophosphorus pesticides were studied. Rhubarb, Pittosporum bark, Hibiscus bark, and Chinese gall in 9:4:3:2 parts were mixed by mass, ground and soaked in water, and the concentration changes of organic phosphorus pesticide before and after the test were compared through GC-MS quantitative detection method and rapid pesticide residue measurement method to clarify its degradation effect on organophosphorus pesticides. The results showed that the degradation rates of chlorpyrifos and parathion were 93.2% and 92.9% respectively in the extract within 2 minutes; the degradation rate of dichlorvos was 66.67% in the extract within 17 hours, and the degradation rate of chlorpyrifos was 48.69% within 11 hours. This study shows that the extracts of rhubarb, sea tongs bark, hibiscus bark, and gallnut have significant degradation effects on chlorpyrifos, parathion, dichlorvos and other organophosphorus pesticides.

Role of UV irradiation of Nafion membranes on ionic groups responsible for proton conduction and mechanical strength: A FTIR spectroscopic analysis

This work presents an evidence of why proton conductivity of Nafion increases with increase in UV-radiation dosage and drops beyond ultraviolet radiation dosage of 198 mJ cm−2. FTIR spectroscopic analysis is used to analyse the shifting of the peaks of groups responsible for proton conduction (i.e. sulfonic acid (–SO3H) and hydronium (H3O+) ions) of Nafion irradiated by various dosages of UV-radiation. The analysis showed that crosslinking of –SO3H increases up-to UV-radiation dosage of 198 mJ cm−2. Beyond this optimum UV-radiation dosage the chain-scission of these groups takes place. On the other hand, UV-radiation has significant degradation effect on H3O+. FTIR spectra of H3O+ show that even with slightest dosage of UV-radiation, chain-scission takes place. Further, the effect of UV-radiation of Nafion on the groups responsible for providing mechanical strength, i.e. -CF2 is also analysed using FTIR spectroscopy. The analysis showed that the intensity of transmission spectrum of -CF2 increases up-to UV-radiation dosage of 198 mJ cm−2 and drops beyond this dosage indicating that there is a possibility of enhancing the mechanical stability up to this dosage. These analysis show that optimum dose of UV-radiation is an effective tool for enhancing the proton-hopping mechanism and thereby, proton conductivity, and also the mechanical stability of Nafion.

Experimental study on property modification of jointed rocks subjected to chemical corrosion

The chemical corrosion has a significant degradation effect on the mechanical properties of non-persistently jointed rocks. In order to improve their physical and mechanical properties, the modification test was carried out by using silicone immersion and resin filling in the pre-existing joint with different geometries after chemical corrosion. This modification influence on the mechanical properties is verified by triaxial compression tests. Experimental results indicate that peak strength, elastic modulus and deformation modulus of jointed rock improved significantly after modification. Finally, the mechanism of strength improvement induced by the modification was revealed by SEM and EDS analysis.

Influence of Antibiotics on the Denitrification Process of Antibiotic Resistant Denitrifying Bacteria and the Analysis of Microbial Community Structure

The removal rate of some antibiotics in urban sewage by conventional treatment is low, which leads to an increase in antibiotic resistant bacteria in natural water environments. To reduce the ecological harm of antibiotics to the water in towns, a risk control technique for degradation of microantibiotics by the co-metabolism of antibiotic resistant denitrifying bacteria was proposed. Using sodium acetate as an electron donor and maintaining the concentration of ofloxacin (OFLX) at 1 μg·g-1, gradually increasing the dominant growth of antibiotic degradation bacteria, denitrifying bacteria (DnB1), trace antibiotics and sodium acetate, and denitrifying bacteria (DnB2) with the presence of sodium acetate and nitrogen elements were cultured. The degradation effect of antibiotics through denitrification and the effects of antibiotics on denitrification of resistant denitrifying bacteria and the changes to the microbial community were investigated. The results showed that DnB2 had a significant degradation effect on OFLX compared to DnB1. The degradation to OFLX by DnB1 and DnB2 was 0.31 μg·g-1 and 16.14 μg·g-1, respectively. Increased OFLX concentration inhibited DnB1 denitrification activity in the short term. The denitrification process of DnB2 was less affected by OFLX. At the same time, high-throughput sequencing using the Illumina MiSeq platform was used. Based on the operational taxonomic unit information formed by the clustering of sequencing results, the diversity of each sample was compared and analyzed. The research results show that the relative abundance and diversity of the microbial community of DnB1 are higher than those of DnB2.

Influence mechanism of alkali metals on CO2 gasification properties of metallurgical coke

In order to clarify the function mechanism of alkali metal on degradation of metallurgical coke in blast furnace, the influence of alkali metal potassium and sodium on carbon structure change was investigated by gaseous adsorption method, and also the catalytic gasification reaction behaviors of alkali metal adsorbed coke samples was further studied. The results showed that the alkali metal vapor absorbed on coke has significant degradation effect on high temperature metallurgical properties of coke, which has catalytic effect and significantly increases gasification reactivity, and the catalytic limit of potassium vapor and sodium vapor was about 5% and 3%, respectively. Besides, potassium adsorption could also cause more fine coke particles to be produced, further aggravating degradation of coke in blast furnace. The analysis of physicochemical structures of different samples shows that the destruction of aromatic ring structure with dense and stable carbon structure in coke by alkali metal vapor adsorption process was the essential cause of coke reactivity increase and fracture. Kinetics analysis study shows that the random pore model (RPM) has the best performance representing the catalytic gasification process, and for different samples the activation energy first increases and then decreases with the increase of alkali metal adsorption content. It was also confirmed that there existed the kinetic compensation effect in the gasification process.

Detoxification of Deoxynivalenol by 60Co γ-ray Irradiation and Toxicity Analyses of Radiolysis Products

Abstract Background: Deoxynivalenol (DON) is a type B trichothecene that occurs predominantly in grains such as wheat, maize, and barley and has been implicated in incidents of mycotoxicoses in both humans and farm animals. Objective: In the present study, we chose 60Co γ-ray irradiation to degrade DON. Methods: First, the degradation effect of irradiation on DON was analyzed. Second, the toxicity analyses of radiolysis products were studied by oral gavage. Results: The results indicated that 60Co γ-ray irradiation had significant degradation effect on pure DON: when 20 kGy γ-ray irradiation was used for 2 μg/mL DON in acetonitrile–water, the degradation efficiency of DON was 83%, and 2 μg/mL DON in ultra-pure water was completely degraded after 5 kGy γ-ray irradiation. The concentration of 200 μg/mL DON in ultra-pure water had significant toxicity to mice: decreased body weight gain and feed consumption as well as pathological changes in liver and kidney were observed compared with the control group. Conclusions: No significant toxicity was observed in mice that were given these degraded solutions treated by γ-ray irradiation, which indicated that the toxicity of radiolysis products in ultra-pure water had significantly decreased after treatment by γ-ray irradiation. Highlights: This research offered some reference to detoxify DON in cereal grains.

Preparation and Analyses of the Multifunctional Properties of 2D and 3D MOFs Constructed from Copper(I) Halides and Hexamethylenetetramine.

In this article, two two-dimensional and three-dimensional metal–organic frameworks are synthesized by the self-assembly of copper(I) halide and the hexamethylenetetramine (hmt) ligand. Compound 1 is a two-dimensional metal–organic framework composed of a pyramidal Cu4I5 cluster and hexamethylenetetramine, in which hmt-bridged Cu clusters form a two-dimensional (4,4)-connected net with a point symbol of (44·62) (44·62). Compound 2 is a homochiral three-dimensional metal–organic framework material generated through an unusual spontaneous crystallization from achiral precursors. The two compounds were characterized by a series of analyses such as infrared spectroscopy, elemental analysis, circular dichroism spectroscopy, and powder X-ray diffraction. Both of them exhibit unexpected stability under a wide range of conditions of acid and base. In addition, the fluorescence intensity changes regularly under acid–base conditions. Stokes shift shows a good linear relationship with −log [H+], which makes them become promising acid–base sensors. Compounds 1 and 2 also display selective adsorption and a significant degradation effect on the organic dye methylene blue. In addition, the fluorescence study indicated that compound 2 could be used as a sensor to detect Cr3+.

Research on the potential-induced degradation (PID) of PV modules running in two typical climate regions

Abstract In order to accurately select photovoltaic modules under different climatic conditions, three kinds of polycrystalline silicon photovoltaic modules were prepared for this study using different properties of packaging materials and two typical climatic zones of China were selected for installation and operation of these photovoltaic (PV) modules. The photoelectric parameters (maximum power, open-circuit voltage, short-circuit current, etc.) and electroluminescence images of these modules were analysed before and after their operation for 6 months. The study found that the performance of PV modules in different climatic regions shows different decay tendency and degradation mechanism. There was a significant difference in the degradation of the three different types of PV modules in the sub-humid-hot region (Suzhou, Jiangsu); two kinds of photovoltaic modules using relatively poorly performing package materials showed significant potential-induced degradation effects. However, the degradation trend of the three different types of PV modules in the warm-temperate region (Kenli, Shandong) was consistent and no significant potential-induced degradation effect was observed.

Durability of structural adhesive joints for facade applications exposed to the extended cataplasm test

ABSTRACTThe effects of exposure to humid conditions in the extended cataplasm ageing test, based on ISO 9142, Procedure E2 on the mechanical properties of adhesively bonded joints, were investigated as a part of a comprehensive study on the ageing of an acrylate adhesive and a Silane-terminated polymer (STP) adhesive. The adhesives were applied in aluminium and Zn-electroplated steel substrates with various surface treatments (a smooth surface, a roughened surface, and anodized and blank aluminium) to observe the effect of ageing on joints with various substrates. The predominant effect of high relative humidity in the cataplasm test was compared with the results of immersion in water according to ETAG 002. It is shown that both ageing methods had a significant degrading effect on bond strength, on stiffness, and on the failure mode. However, water immersion had a more serious effect on the acrylate adhesive, especially in anodized aluminium joints, and the cataplasm test caused slightly greater worsening of the adhesive properties of STP.

Degradation potential of bisphenol A by Lactobacillus reuteri

In order to explore the safety of bisphenol A (BPA) degradation in food packaging, the degradation effect of six common probiotics to BPA was first explored in this paper. The result showed that the degradation rate of BPA by Lactobacillus reuteri was the highest among the six common probiotics, which was 69.83%. In addition, no toxic substances were found in the degradation products of Lactobacillus reuteri by GC-MS analysis. Based on this, the enzyme microsphere sustain-released preparation (EMSP) of Lactobacillus reuteri was prepared and characterized. Then the effects of different treatment conditions on the degradation rate of BPA were investigated. Finally, it was applied to orange juice, black tea and mung bean cold tea. The contents of BPA in canned beverage (black tea beverage, orange juice beverage and mung bean cold tea) added with EMSP decreased by 92.74%, 92.33% and 92.33%, respectively, after storage of 1 d. After 27 d, the contents of BPA in these three kinds of canned beverages reached 0. It can be seen that Lactobacillus reuteri has a significant degradation effect on BPA and has great potential and commercial value.

Analysis for Effect of Chemical Pollutants on Wetland Ecology

Wetlands play an important role in maintaining ecological balance and promoting the development of surrounding economy. Chemical pollutants in industrial wastewater cause serious damage to the wetland ecosystem. For this, taking the polycyclic aromatic hydrocarbons (PAHs), one typical chemical organic pollutant in industrial wastewater as examples, this paper studies the effects of PAH on plants and microorganisms in wetlands. Then, the experimental simulation was conducted to study the degradation and absorption effects of wetland soil sediments and wetland plant (Spartina alterniflora) on PAHs, and also analyse the effects of PAHs on total biomass and microbial active enzymes in wetlands. The results show that the wetland ecosystem has significant absorption and degradation effects on chemical pollutants. The average removal rate of PHE is 26%, and the average removal rate of PYR is 20%; the content of PHE and PYR in leaves of Spartina alterniflora (S. alterniflora) is much smaller than that of root system, indicating that the root system of S. alterniflora is the main part of absorbing PAHs. PAHs pollution will cause serious damage to the distribution and content of microorganisms in the wetland. PHE causes the microbial content in the leaves of S. alterniflora to decrease by more than 35%, while PYR causes it to decrease by more than 26%. The plant-microbial combined treatment system in the wetland system can resist the harmful effects of chemical pollutants to a certain extent, and the bacteria in the plant roots are more sensitive to the response of chemical pollutants. This can provide a new research idea for the microbe-plant joint degradation of chemical pollutants in wetland ecosystems.

Experimental measurement of structural steel corrosion

Corrosion is recognized as the most significant degradation effect of the structural steel. This degradation process is affecting the cross-sectional and structural element resistance and deformation parameters of structure. To estimate the speed of corrosion loss in the case of steel plates, rapid test in corrosion chamber were done. Such measurements have their significance, however for their evaluation and confrontation with the results measured in situ much more data from corrosion processes observed in actual environment are still needed. Therefore, the paper also presents the results of first round of experimental measurement of corrosion losses carried out on specimens of structural steel placed on several bridge structures built in different places. Effects of local microclimate factors on corrosion process resulting from the type of bridge structures or their individual elements is pointed. To underline justification of experimental program, the influence of corrosion on flexural load-carrying capacity of three chosen structural elements from bridges in service is presented, as well.

Impedance change and capacity fade of lithium nickel manganese cobalt oxide-based batteries during calendar aging

Abstract The calendar aging of commercial 18650 lithium-ion batteries with lithium nickel manganese cobalt oxide cathode and graphite anode is studied by regular electrochemical characterization of batteries stored at defined conditions. The cell capacity is found to decrease linearly with time and shows a faster decrease at higher storage temperatures. From current pulse tests, it is determined that both higher temperature and higher state of charge (SOC) cause accelerated resistance increase with storage time. Changes in different battery parameters during storage are also quantified by analyzing electrochemical impedance spectroscopy (EIS) spectra. The cell degradation causes a gradual increase of the ohmic and the total polarization resistance with storage duration, where the latter one is found to be the main contributor to the increased cell impedance. An increase in the mean relaxation time constant and changes in the porous structure for the electrode processes are observed from EIS analysis. Resistance for this cell chemistry is found to be current independent by comparing the cell resistance calculated from the current pulse method after 1s and from the EIS analysis at 1 Hz. Furthermore, it is seen that the additional charge throughput due to the periodic electrochemical characterization induces significant cell degradation effects.