Degradation Half-life Time Research Articles

Electrospun Nanofiber Dopped with TiO2 and Carbon Quantum Dots for the Photocatalytic Degradation of Antibiotics

Novel photocatalysts were synthesized through the association of carbon quantum dots (CQDs) with commercial (P25) titanium dioxide (TiO2) by sonication. The resulting TiO2/CQDs composite was then incorporated into the polyamide 66 (PA66) biopolymer nanofibers using the electrospinning technique, considering a composite nanoparticles-to-polymer ratio of 1:2 in the electrospinning precursor solution. The produced nanofibers presented suitable morphology and were tested for the photocatalytic degradation under simulated solar radiation of 10 mg L−1 of amoxicillin (AMX) and sulfadiazine (SDZ), in phosphate buffer solution (pH 8.06) and river water, using 1.5 g L−1 of photocatalyst. The presence of the photocatalyst increased the removal of AMX in phosphate buffer solution by 30 times, reducing the AMX degradation half-life time from 62 ± 1 h (without catalyst) to 1.98 ± 0.06 h. Moreover, SDZ degradation half-life time in phosphate buffer solution was reduced from 5.4 ± 0.1 h (without catalyst) to 1.87 ± 0.05 h in the presence of the photocatalyst. Furthermore, the PA66/TiO2/CQDs were also efficient in river water samples and maintained their performance in at least three cycles of SDZ photodegradation in river water. The presented results evidence that the produced photocatalyst can be a promising and sustainable solution for antibiotics’ efficient removal from water.

Sorption, leaching, and degradation of dicamba in two Brazilian soils: A study into soil layers

Understanding the behavior in soil of soluble and mobile herbicides, such as dicamba, is essential for efficient weed management. Thus, the objective of the research was to understand the sorption, leaching and degradation processes of dicamba along the profile of two Brazilian soils (Oxisol and Ultisol). The Oxisol collected is a very deep soil, the A horizon was collected in a layer of 0.10 m deep, the B horizon 2.0 m and the C horizon ranging from 5.0 to 6.0 m. In contrast, the Ultisol presents a difference between the most superficial horizons, the A horizon was collected at a depth of 0.10 m, the B horizon at around 1.0 m depth and the C horizon at a depth of 2.0–3.0 m. A High-Performance Liquid Chromatography (HPLC) was used to determine the herbicide in the soil solution. The Freundlich sorption coefficient (Kf) values of dicamba ranged from 0.53 to 0.88 mg (1-1/n) L1/n kg−1 in Oxisol and 0.25–0.69 mg (1-1/n) L1/n kg−1 in Ultisol, indicating a low sorption capacity of the herbicide in all profiles. The dicamba mobility index was higher in the Ultisol, ranging from 4.22 to 65.8 compared to the Oxisol, which ranged from 0.46 to 8.10. The degradation half-life time (DT50) of dicamba was short (∼4 days) in the A horizon of both soils compared to the other horizons. Moreover, persistence in the B and C horizons was higher in Oxisol (182 and > 250 days) compared to Ultisol (85.6 and 52.1 days, respectively). The sorption and mobility index of dicamba showed a correlation with soil pH and DT50 values, depending on the organic matter (OM) content. The recommendation of use of dicamba should consider the physical and chemical attributes of the soil as an alternative to reduce the risk of environmental contamination.

The mRNA stability of NCAPG2, a novel contributor to breast invasive carcinoma, is enhanced by the RNA-binding protein PCBP2

Non-SMC condensin II complex subunit G2 (NCAPG2) is one of the three non-SMC subunits in condensin II, which plays a vital role in regulating chromosome condensation and segregation. Although the tumor-promoting role of NCAPG2 has been reported in several solid malignancies, its function in breast invasive carcinoma (BRCA) remains unknown. Data both from GEPIA and GSE36295 indicated that NCAPG2 mRNA expression was abnormally upregulated in cancer tissues, which was further verified in 40 paired BRCA and para-carcinoma samples. Kaplan-Meier Plotter further illustrated that BRCA patients with higher NCAPG2 expression have a poorer prognosis. Functional experiments carried out in two BRCA cell lines (MCF-7 and T-47D) showed that NCAPG2-silenced BRCA cells acquired less aggressive behavior — weakened growth and metastasis both in vitro and in vivo. Label-free proteomics quantified the protein expression patterns in MCF-7 cells, and the results revealed 684 differentially expressed proteins (|log2FC| > 1 and P < 0.05) downstream to NCAPG2. Interestingly, poly(C)-binding protein 2 (PCBP2), an RNA binding protein previously known to increase RNA stability of its target genes, was found to directly bind to and protect NCAPG2 mRNA from degradation—PCBP2 knockdown accelerated the degradation half-life time of NCAPG2 mRNA from approximately 8 h to 5 h. Taken together, our study indicates that NCAPG2 acts as a novel contributor to BRCA growth and metastasis under the regulation of PCBP2, providing insights into BRCA treatment.

Sorption-desorption and biodegradation of sulfometuron-methyl and its effects on the bacterial communities in Amazonian soils amended with aged biochar

Sulfometuron-methyl is a broad-spectrum herbicide, used throughout Brazil; however, its environmental impacts in biochar (BC) amended soils is not fully understood. Biochar is known to enhance soil quality but can also have undesired effects such as altering the bioavailability and behavior of herbicides. Microbial communities can degrade herbicides such as sulfometuron-methyl in soils; however, they are known to be affected by BC. Therefore, it is important to understand the tripartite interaction between these factors. This research aimed to evaluate the sorption-desorption and biodegradation of sulfometuron-methyl in Amazonian soils amended with BC, and to assess the effects of the interactions between BC and sulfometuron-methyl on soil bacterial communities. Soil samples were collected from field plots amended with BC at three doses (0, 40 and 80 t ha−1) applied ten years ago. The herbicide sorption and desorption were evaluated using a batch equilibrium method. Mineralization and biodegradation studies were conducted in microcosms incubated with 14C-sulfometuron-methyl for 80 days. Systematic soil sampling, followed by DNA extraction, quantification (qPCR) and 16S rRNA amplicon sequencing were performed. The presence of BC increased the sorption of the herbicide to the soil by 11% (BC40) and 16% (BC80) compared to unamended soil. The presence of BC also affected the degradation of 14C-sulfometuron-methyl, reducing the mineralization rate and increasing the degradation half-life times (DT50) from 36.67 days in unamended soil to 52.11 and 55.45 days in BC40 and BC80 soils, respectively. The herbicide application altered the bacterial communities, affecting abundance and richness, and changing the taxonomic diversity (i.e., some taxa were promoted and other inhibited). A tripartite interaction was found between BC, the herbicide and soil bacterial communities, suggesting that it is important to consider the environmental impact of soil applied herbicides in biochar amended soils.

Integrated fate assessment of aromatic amines in aerobic sewage treatment plants

The fate and exposure of chemicals in sewage treatment plants (STPs) are major considerations in risk assessment and environmental regulation. The biodegradability and removal of seven aromatic amines were systematically evaluated using a three-tiered integrated method: a standard ready biodegradability test, an aerobic sewage treatment simulation method, and model prediction. In tier 1, the seven aromatic amines were not readily biodegraded after 28 days. In adapted aerobic active sludge, 4-isopropyl aniline, 2,4-diaminotoluene, and 4-nitroaniline among them exhibited the degradation half-life time less than 20 h, the other four aromatic amines exhibited persistent with degradation half-life of > 60 h. In tier 2 of the aerobic sewage treatment simulation testing, 2,4-diaminotoluene, 4-nitroaniline, and 4-isopropylaniline demonstrated moderately to high overall removal. Hydraulic retention time (HRT) affects the removal with the optimum HRT was determined to be 12 h to 24. 2,6-Dimethyl aniline, 2-chloro-4-nitroaniline, 2,6-diethylaniline, and 3,4-dichloroaniline were not removed during the test, indicting these four aromatic amines will enter surface water and hence pose a potential risk to aquatic ecology. Considering the lack of an STP model in China for regulation purposes, in tier 3, we developed a Chinese STP (aerobic) (abbreviated as C-STP(O)) model that reflects a universal scenario for China to predict the fate. The predicted degradation, volatilization, and absorption showed a close relationship to the physicochemical properties of the chemicals, and had same tendency with tier 2 simulation test. The prediction showed that biodegradation rather than absorption or volatilization was the main removal process of aromatic amines in aerobic STP. With the combination of modified kinetics test with C-STP (O) model, the chemical fate can be more accurately predicted than using only the readily biodegradation result.

Effect and study of reducing agent NaBH4 on Bi/BiOBr/CdS photocatalyst

Bi/BiOBr/CdS photocatalytic materials were successfully prepared in this study. X-ray diffraction studies had shown that BiOBr, CdS and Bi were successfully combined. Degradation experiment indicated that the degradation rates for norfloxacin of Bi/BiOBr/CdS-4 reached 97.4%, which was about 14.4% higher than that of BiOBr/CdS. The degradation half-life time was shortened to 10 min, and the reaction rate was 2.2 times that of BiOBr/CdS. The reason why the photocatalytic activity is enhanced is that the heterojunction formed by the higher valence band BiOBr, the lower conduction band valence CdS, and the lower Fermi level Bi metal element effectively suppresses the recombination of holes and photogenerated electrons, which leads to the enhancement of oxidation capacity.

Study of photostability of three synthetic dyes commonly used in mouthwashes

Photostability of three synthetic dyes (Carmoisine, CI 14720; Allura Red AC, CI 16035; and Patent Blue V, CI 42051) commonly used in mouthwashes was investigated for the first time. Aqueous solutions of dyes and commercial mouthwashes were submitted to simulated outdoor and indoor conditions of irradiation. All dyes demonstrated high stability in aqueous solutions but discolouration was observed in commercial products after irradiation, highlighting a strong effect of matrix composition on the dyes stability. The photochemical behaviour of dyes corresponded to a first-order reaction. Degradation half-life times of Carmoisine, Allura Red AC, and Patent Blue V under solar standard conditions of irradiation were 18.4 ± 3.3, 11.9 ± 1.6, and 6.6 ± 1.2 h respectively, for 5.0 μg mL−1 of dye spiked in a blank matrix (a mouthwash without the presence of dyes among the ingredients). Factors potentially affecting the photostability, such as temperature and the presence of oxygen, also were studied.

Reduction-Triggered Release of CPT from Acid-Degradable Polymeric Prodrug Micelles Bearing Boronate Ester Bonds with Enhanced Cellular Uptake.

The aim of this research is to develop a novel type of camptothecin (CPT) prodrug micelles bearing boronate ester bonds as a smart nanosystem with enhanced cellular uptake and controlled drug release based on diblock copolymer abbreviated as PEG-BC-PGlu-ss-CPT. Particularly, boronate ester bond was introduced to achieve acid-triggered de-PEGylation and succeeding boronic acid-mediated enhanced cellular uptake. Besides, CPT was conjugated to the prodrug monomer through a disulfide bond to realize reduction-responsive drug release. The resultant copolymer PEG-BC-PGlu-ss-CPT could self-assemble into spherical nanomicelles in water. The degradation half-life time of PEG-BC-PGlu-ss-CPT copolymer decreased sharply from 96.27 h to only 5.7 h with pH value decreasing from 7.4 to 5.0, indicating the acid-degradable potential, which corresponded to size change monitoring. The cumulative CPT release from prodrug micelles increased significantly from 8.5 ± 1.73 to 82.9 ± 2.29% with an increase of dithiothreitol (DTT) concentration from 20 μM to 10 mM at pH 7.4, illustrating the reduction-responsive drug release property of prodrug micelles. The half maximal inhibitory concentration (IC50) value of prodrug micelles against HepG2 cells decreased from 1.06 to 0.68 μg/mL with the decrement of pH value from 7.4 to 6.0, proving that the utilization of boronate ester bonds was beneficial for enhancing antiproliferative activity. Interestingly, prodrug micelles exhibited enhanced cellular uptake ability against HepG2 cells compared to that of HL7702 cells, further confirming boronic acid-mediated enhanced endocytosis. In brief, this novel type of intelligent prodrug micelles possessed great potential as a smart nanosystem for antitumor drug delivery.

Environmental fate of emamectin benzoate after tree micro injection of horse chestnut trees.

Emamectin benzoate, an insecticide derived from the avermectin family of natural products, has a unique translocation behavior in trees when applied by tree micro injection (TMI), which can result in protection from insect pests (foliar and borers) for several years. Active ingredient imported into leaves was measured at the end of season in the fallen leaves of treated horse chestnut (Aesculus hippocastanum) trees. The dissipation of emamectin benzoate in these leaves seems to be biphasic and depends on the decomposition of the leaf. In compost piles, where decomposition of leaves was fastest, a cumulative emamectin benzoate degradation half-life time of 20 d was measured. In leaves immersed in water, where decomposition was much slower, the degradation half-life time was 94 d, and in leaves left on the ground in contact with soil, where decomposition was slowest, the degradation half-life time was 212 d. The biphasic decline and the correlation with leaf decomposition might be attributed to an extensive sorption of emamectin benzoate residues to leaf macromolecules. This may also explain why earthworms ingesting leaves from injected trees take up very little emamectin benzoate and excrete it with the feces. Furthermore, no emamectin benzoate was found in water containing decomposing leaves from injected trees. It is concluded, that emamectin benzoate present in abscised leaves from horse chestnut trees injected with the insecticide is not available to nontarget organisms present in soil or water bodies. Environ Toxicol Chem 2014;9999:1–6. © 2014 The Authors. Published 2014 SETAC

Degradation dynamics of emamectin benzoate in tobacco

By using the high performance liquid chromatography(HPLC),this paper detected the degradation dynamics and final residue of 0.5% emamectin benzoate microemulsion and found the degradation of 0.5% emamectin benzoate microemulsion tobacco conformed to the first class kinetics equation of the chemical reaction,its degradation curve equation was C= 0.255 8e-0.325 3t,and the degradation half-life times were 2.13 days,linear correlation coefficient(R2) was 0.884 3.The final residue test showed that residues of emamectin benzoate was very low in tobacco samples 20 days later after its being sprayed,lower than 0.006 mg/kg.there was no emamectin benzoate detected in tobacco 30 days after its being sprayed.

Chlorpropham and phenisopham: phototransformation and ecotoxicity of carbamates in the aquatic environment

In this study, a comparison of two carbamic pesticides, chlorpropham and phenisopham, was carried out in terms of both photodegradability and ecotoxicity. The photochemical behaviour of the two pesticides was investigated under environmental-like conditions (aqueous media, UVB or solar irradiation). The photochemical kinetic parameters were calculated by irradiating 5 × 10(-5) M solutions (H₂O-CH₃CN, 9 : 1 v/v) using UVB lamps. For chlorpropham and phenisopham similar half-life times (39.0 and 55.0 min) were determined. Irradiation by sunlight leads to longer degradation half-life times (about 3 months), while it is possible to observe the formation of the same photoproducts. The well-known dechlorination reaction to a hydroxyphenylcarbamate was observed for chlorpropham. Phenisopham undergoes photo-Fries reaction to give rearranged products (hydroxybenzamides) and fragmentation products (hydroxyphenylcarbamate and N-ethylaniline). Acute and chronic toxicity tests of pesticides and their photoproducts were performed on organisms from two levels of the freshwater aquatic chain, the anostraca crustacean Thamnocephalus platyurus, the rotifer Brachionus calyciflorus and the alga Pseudokirchneriella subcapitata. The acute results showed that chlorpropham had median lethal concentrations for the crustacean T. platyurus and the rotifer B. calyciflorus of 10.16 and 35.19 mg L(-1), respectively, and phenisopham did not show any acute toxicity as the derivatives up to 10 mg L(-1). The only exception was N-ethylaniline which exhibited an acute LC₅₀ value of 0.46 mg L(-1). Phenisopham was the most toxic in the long term exposure while its five derivatives showed lower chronic potential for rotifers and algae. The same trend was observed for chlorpropham except for rotifers.

Photocrosslinkable biodegradable elastomers based on cinnamate-functionalized polyesters

Synthetic biodegradable elastomers are an emerging class of materials that play a critical role in supporting innovations in bioabsorbable medical implants. This paper describes the synthesis and characterization of poly(glycerol-co-sebacate)-cinnamate (PGS-CinA), a biodegradable elastomer based on hyperbranched polyesters derivatized with pendant cinnamate groups. PGS-CinA can be prepared via photodimerization in the absence of photoinitiators using monomers that are found in common foods. The resulting network exhibits a Young’s modulus of 50.5–152.1kPa and a projected in vitro degradation half-life time between 90 and 140days. PGS-CinA elastomers are intrinsically cell-adherent and support rapid proliferation of fibroblasts. Spreading and proliferation of fibroblasts are loosely governed by the substrate stiffness within the range of Young’s moduli in PGS-CinA networks that were prepared. The thermo-mechanical properties, biodegradability and intrinsic support of cell attachment and proliferation suggest that PGS-CinA networks are broadly applicable for use in next generation bioabsorable materials including temporary medical devices and scaffolds for soft tissue engineering.

A highly-ordered porous carbon material based cathode for energy-efficient electro-Fenton process

Electro-Fenton process for water purification utilizes electrical energy for chemical transformation. However, its key step, oxygen reduction reaction (ORR) to generate H2O2, suffers from added energy consumption due to a side reaction of H2 evolution. This study attempted to make this process energy effective by using an innovative gas diffusion electrode (GDE) fabricated from a carbon material with highly-ordered pores and large surface area (CMK-3). It was found that the employment of this cathode enabled a low cathodic potential of −0.5V (vs. SCE), at which H2 evolution could be greatly eliminated. Meanwhile, the H2O2 built-up at CMK-3 GDE was 3.1 and 4.4 times higher than those at the other two carbon electrodes (graphite GDE and carbon paper). Moreover, dimethyl phthalate (DMP) degradation in the electro-Fenton process using CMK-3 GDE occurred much more rapidly with a reaction apparent rate constant about 8.8 and 11.5 times higher than those using the other two types of electrodes, respectively, whereas the corresponding energy consumption on CMK-3 GDE at the degradation half-life time was only 50% and 27%, respectively.

Determination and Microbial Degradation of Lambda-Cyhalothrin

This work presents laboratory studies on the degradation of lambda-cyhalothrin. At first, a rapid quantitative determination method of lambda-cyhalothrin in food was developed by high performance liquid chromatography. Lambda-cyhalothrin-degrading bacterium F37 was isolated from the sewage of a pesticide factory outlet and was identified as Citrobacter braakii. The effects of environmental factors including carbon and nitrogen sources, initial pH, medium volume, incubating temperature and substrate concentration on the degradation rate were investigated. The addition of sucrose and yeast extract at the concentrations of 4.0 and 3.0 g/L, respectively, was the best for the degradation of lambda-cyhalothrin. F37 showed higher degradation activity at the range of moderate pH value (pH 6.5-8.0). After 72-h stirring culture, the degradation rates of lambda-cyhalothrin reached 81.1% at pH 7.0. The degradation dynamics analysis showed that the degradation half-life times of lambda-cyhalothrin in the culture liquid of F37 were only 5.7, 1.9 and 4.9 days at pH 9.0, 7.0 and 5.0, respectively. In addition, cypermethrin and triazophos could also be degraded by F37, showing that F37 was a broad-spectrum pesticide- degrading bacterium. Application of F37 on eliminating pesticide in vegetable showed that 68% of lambda-cyhalothrin was removed after treatment for 48 h. The results indicated that Citrobacter braakii F37 is effective in the elimination of pesticide and may provide a potent application in detergent industry and environmental restoration.

Microwave-Assisted Photocatalytic Degradation of Dimethyl Phthalate Over a Novel ZrOx Catalyst

A novel microwave-assisted photocatalytic active ZrOx catalyst, which has mix-valences and wide bandgap, has been prepared by cetyltrimethylammonium bromide–assisted hydrothermal method. Structural and optical properties were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, N2 adsorption–desorption, and UV–vis techniques. Total organic carbon (TOC) removal of dimethyl phthalate (DMP) (100 mL, 50 mg L−1) with 1 g L−1 ZrOx approached 84% after a 30-min reaction, which was about 15% and 11% higher than ZrO2 and P25 TiO2, respectively. TOC removal of DMP by microwave-assisted photocatalytic process followed pseudo–first-order kinetics in all cases, and ZrOx evidently accelerated the degradation of DMP. Degradation half-life time of DMP using ZrOx was shortened 43% and 34%, compared with ZrO2 and P25 TiO2, respectively. A possible catalytic mechanism of ZrOx was proposed based on microwave response and interfacial charge transfer analyses. Further research on ZrOx may develop a promising new generation of highly efficient catalysts for the microwave-assisted photocatalytic process for environmental remediation.

Efficient microwave-assisted photocatalytic degradation of endocrine disruptor dimethyl phthalate over composite catalyst ZrO x/ZnO

A highly active ZrO x /ZnO catalyst for microwave-assisted photocatalytic (MW/PC) degradation of endocrine disruptor dimethyl phthalate (DMP) has been prepared via cetyltrimethylammonium assisted hydrothermal method. The ZrO x /ZnO was characterized by XPS, XRD, UV-Vis, BET and SEM techniques. The XPS result showed that Zr oxides with different valences (+2, +3, +4) co-existed in ZrO x /ZnO. By using the ZrO x /ZnO (0.1 g), the TOC removal efficiency of DMP (100 mL of 50 mg/L) was 88% after 30 min reaction, which was about 15% higher than P25 TiO 2. It was found that the removal process of DMP by MW/PC followed pseudo first-order kinetics in all cases, and ZrO x /ZnO significantly accelerated the degradation of DMP. The degradation half-life time of DMP was shortened 45% compared with P25 TiO 2. A possible catalytic mechanism was proposed based on microwave response and interfacial charge transfer. ZrO x /ZnO could be reused for six times without obvious decrease in catalytic activity. The study offers new insights into designing highly efficient catalysts for MW/PC process and is applicable for MW/PC environmental remediation.

Degradation half-life times of PCDDs, PCDFs and PCBs for environmental fate modeling

Literature search of the knowledge on the degradation of persistent organic pollutants (POPs) in environmental compartments air, water, soil and sediment was done in purpose to find properties of POPs of interest for modeling. One degradation process, hydrolysis (chemical degradation), was omitted as negligibly slow for POPs studied. The other two, photolysis and biodegradation processes, were considered separately in purpose to develop estimation procedures. The estimates can be given as pseudo first-order rate constants kP for photolysis and kB for biodegradation. For each compartment, an overall degradation rate isktot=kP+kBandlifetimet1/2=ln2/ktot.The latter values, lifetimes in each compartment, will be used as input parameters to the Baltic Sea model.