Average Degradation Rate Research Articles

TITANIUM DIOXIDE SOL-GEL/ZINC OXIDE POWDER-COATED CLAY BEADS IN PHOTOCATALYTIC REACTOR

Catalyst Immobilization methods are important for providing better recovery of catalyst in photocatalytic treatment. The aim is to characterize and evaluate the photocatalytic performance of TiO2/ZnO-coated clay beads. The titanium dioxide/zinc oxide (TiO2/ZnO)-coated clay beads were prepared via the sol-gel process. Various ZnO powder ratios gave different TiO2/ZnO composites sol. Four layers of TiO2/ZnO sol were coated on clay beads and dried in the oven at 100°C for 30 min. The coated clay beads were calcined at 500°C for one hour for every two layers. Characterization of coated clay beads was done using a scanning electron microscope and energy dispersive spectroscopy. The increased surface area on small agglomeration and optimum loading of ZnO (5 g) resulted in the highest degradation efficiency recorded at 86.57%. An effective catalyst immobilization achieved a good recycling performance on clay beads. Degradation rate data were presented by pseudo-first-order kinetics. It was observed that the average degradation rate for TiO2/5 g ZnO is 0.00836 min–1. The actual results in this work can be applied as a guideline for the preparation of TiO2/ZnO-coated clay beads with high photocatalytic performance.

Evaluation on the corrosion resistance, antibacterial property and osteogenic activity of biodegradable Mg-Ca and Mg-Ca-Zn-Ag alloys

The rapid degradation of magnesium (Mg)-based implants in physiological environment limits its clinical applications, and alloying treatment is an effective way to regulate the degradation rate of Mg-based materials. In the present study, three Mg alloys, including Mg-0.8Ca (denoted as ZQ), Mg-0.8Ca-5Zn-1.5Ag (denoted as ZQ71) and Mg-0.8Ca-5Zn-2.5Ag (denoted as ZQ63), were fabricated by alloying with calcium (Ca), zinc (Zn) and silver (Ag). The results obtained from electrochemical corrosion tests and in vitro degradation evaluation demonstrated that the three Mg alloys exhibited distinct corrosion resistance, and ZQ71 exhibited the lowest degradation rate in vitro among them. After addition of Zn and Ag, the antibacterial potential of Mg alloys was also enhanced. The in vitro cell experiments showed that all the three Mg alloys had good biocompatibility. After implantation in a rat femoral defect, ZQ71 showed significantly higher osteogenic activity and bone substitution rate than ZQ63 and ZQ, due to its higher corrosion resistance as well as the stimulatory effects of the released metallic ions. In addition, the average daily degradation rate of each Mg alloy in vivo was significantly higher than that in vitro, as could be due to the implantation site located in the highly vascularized trabecular region. Importantly, the correlations between the in vitro and in vivo degradation parameters of the Mg alloys were systematically analyzed to find out the potential predictors of the in vivo degradation performance of the materials. The current work not only evaluated the clinical potential of the three biodegradable Mg alloys as bone grafts but also provided a feasible approach for predicting the in vivo degradation behavior of biodegradable materials.

Anaerobic mineralization of toluene by enriched soil-free consortia with solid-phase humin as a terminal electron acceptor

The anaerobic biodegradation of toluene proceeds very slowly owing to limited electron acceptors in contaminated aquifer. The liquid reagents traditionally used to enhance this process readily migrate away from the contaminated site, and continuous addition would cause secondary pollution. In our previous study, the reduced solid-phase humic substances (humin), which are redox active, were found to act as electron donors to promote the microbial reactions. Here, we provide new evidence that humin can promote the anaerobic biodegradation of toluene as a terminal electron acceptor. When inoculating nitrate-reducing (NR) and iron-reducing (IR) consortia with toluene degradation activities, the average toluene degradation rates reached 21.20 ± 1.18 μmol/(L·d) and 15.43 ± 0.41 μmol/(L·d) in the presence of a sediment humin (HMcj), and 94.69% ± 4.26% and 93.20% ± 3.73% of the electrons released from toluene oxidation to CO2 could be recovered by the reduction of HMcj, respectively. Spectroscopy analyses revealed that quinone moieties and nitrogen-containing moieties may be the electron-accepting groups of HMcj. Based on 16S rRNA sequencing, Cellulomonas spp. were the possible functional bacteria in the culture with NR consortium as the inoculum, while Azospira spp., Cellulomonas spp. and Bacillus spp. were the possible functional bacteria in the culture with IR consortium as the inoculum. Further Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analyses indicated that toluene oxidation and extracellular electron transfer functions were more abundant in HMcj amended cultures, suggesting a possible enhancement mechanism by HMcj. Additionally, experiments using natural groundwater illustrated that toluene degradation was highly dependent on its concentration, HMcj dosage, pH, and salinity. The study of a column filled with HMcj-coated quartz sand demonstrated a desirable level of toluene degradation in a continuous-flow mode without the presence of other electron acceptors. This study provided an effective and green approach for the remediation of the toluene-contaminated groundwater.

Microbial degradation of polystyrene microplastics by a novel isolated bacterium in aquatic ecosystem

The continuous accumulation of microplastics (MPs) in water, soil, and atmosphere will pose a serious threat to the environmental ecological balance. How to reduce and eliminate MPs in the environment has become a hot issue. Here we isolated Bacillus cereus CH6 from lake sediments and investigated its ability to degrade polystyrene microplastics(PS MPs). Bacillus cereus CH6 has short generation time, high activity, and fast substrate utilization. The weight loss was 10.7% by Bacillus cereus CH6 after 50 days of incubation. Moreover, the average degradation rate reached 0.967 mg/d. We further investigated the surface morphology changes and the internal structural changes during the degradation of PS MPs. Finally, the changes of bacterial protein concentration and esterase activity during the PS MPs degradation process were observed from the perspective of biological index changes. These results are expected to provide a new candidate for PS MPs degradation.

The kinetic reaction of anaerobic microbial chloerobenzenes degradation in contaminated soil

The kinetic reactions of hexachlorobenzene (HCB) and coexisting chlorobenzene congeners in real HCB-contaminated soil and effects of environmental factors on degradation rate, such as solid-liquid ratio, pH and incubation temperatures, were investigated. The Monod model was adopted for the kinetic study and the related kinetic parameters were evaluated. The Monod model showed good fitness for HCB degradation, not for coexisting chlorobenzene congeners. For pentachlorobenzene (PeCB), 1,2,4,5-tetrachlorobenzene(1,2,4,5-TeCB) and 1,2,4-trichlorobenzene(1,2,4-TCB), the calculated value of average degradation rate may not be “positive” or “negative” invariably, depending on production and degradation of these halogenated organic compounds. For HCB, a maximum degradation rate constant of 0.0359 d−1 and half-life time of 19.3 d were achieved, respectively. The hydrogen ion played the most important role in degradation of four chlorobenzenes. However, this role could be weakened if the solubility of compound was considered. Also, the results showed that the initial weak acid to neutral pH (5 – 7) environment with the incubation temperature of 45 °C was favorable for the rapid kinetic degradation of chlorobenzenes and the removal of chlorobenzenes was evaluated to reach 46%. This study offers direct kinetic behaviors and environmental factors analysis of the biodegradation process of HCB and coexisting chlorobenzene congeners, and is beneficial to explored the potential of optimized anaerobic microbial degradation for remediation engineering of chlorobenzenes contained soil.

Reliability acceptance sampling plan for degraded products subject to Wiener process with unit heterogeneity

The acceptance sampling plan (ASP), designed with the degradation data following the Wiener process, is widely used to verify the reliability requirements of products. Previous studies mainly designed ASPs under the given sampling plan, which lacked the justification of the sampling plan; furthermore, they ignored the unit heterogeneity of products in the degradation modeling, which affects the description accuracy of risks. To solve the above problems, this paper proposes an optimal ASP design method considering the unit heterogeneity. Firstly, the determinant of the Fisher information matrix is used to characterize the parameters estimation accuracy, under the cost requirement, the optimal test time and sample size are determined by maximizing the determinant, and an optimal sampling plan is obtained. Then, with the likelihood ratio order and the monotonicity of the average failure time on the average degradation rate, the average degradation rate is taken as the acceptance index to effectively simplify the original acceptance test problem. On this basis, the decision-making criterion considering the existence of ASP is obtained by solving the risk constraint equations of both parties. Finally, the simulation and a real example are presented to demonstrate the implementation and feasibility of the proposed method.

The effect of solute segregated stacking faults on the corrosion behavior of Mg-Gd-Cu alloys

In order to develop new Mg alloys for fracturing tools, Mg-Gd-Cu alloys containing profuse solute segregated stacking faults (SFs) were prepared by appropriate heat treatments and the effect of SFs on corrosion behavior of the alloys was investigated. It was found that the presence of SFs greatly changed corrosion behavior of the Mg-Gd-Cu alloys. Specifically, the alloys containing SFs presented higher initial corrosion rate due to the increased volume fraction of the cathodic phase associated with the SFs; while the rapid formation ability as well as uniform and complete distribution of corrosion films resulted in a lower average degradation rate.

Study of clay degradation in an earthslide combining OBIA and roughness analysis of UAV‐based optical images

AbstractFlow‐like landslides in clay slopes pose major threats to people and infrastructure, which has led to numerous studies in recent decades. However, the mechanisms leading to the solid–fluid transition in clay are still poorly understood, despite numerous studies on its rheological evolution. The aim of this study is to contribute to quantify the degradation of clay at the surface of the Harmalière landslide (French Alps) from the analysis of a series of three unmanned aerial vehicle (UAV) acquisitions. Two approaches were combined to process the acquired optical images. First, image classification was performed applying object‐based image analysis (OBIA) to the red, green and blue (RGB) and surface roughness layers. Second, deeper analysis of the surface roughness allows to describe the morphology evolution and to interpret the degradation scheme from undegraded clay to degraded clay.The study shows that the applied methodology is appropriate to perform a thorough analysis of the material degradation pattern on the surface of a landslide. The temporal analysis shows an average degradation rate leading to the complete degradation of a block in about 2 years. Meanwhile, a spatial analysis shows that non‐degraded clays degrade faster in the lower part of the study area, reactivated 30 years ago, than in the upper part, reactivated only a few years ago. In addition, roughness analyses enabled to highlight the evolution of the morphology during the degradation process of the clay blocks, from angular blocks to mounds.

Immobilized Stenotrophomonas maltophilia KB2 in Naproxen Degradation.

Immobilization is a commonly used method in response to the need to increase the resistance of microorganisms to the toxic effects of xenobiotics. In this study, a plant sponge from Luffa cylindrica was used as a carrier for the immobilization of the Stenotrophomonas maltophilia KB2 strain since such a carrier meets the criteria for high-quality carriers, i.e., low price and biodegradability. The optimal immobilization conditions were established as a temperature of 30 °C, pH 7.2, incubation time of 72 h, and an optical density of the culture of 1.4. The strain immobilized in such conditions was used for the biodegradation of naproxen, and an average rate of degradation of 3.8 µg/hour was obtained under cometabolic conditions with glucose. The obtained results indicate that a microbiological preparation based on immobilized cells on a luffa sponge can be used in bioremediation processes where it is necessary to remove the introduced carrier.

Investigation of kinetics in bioaugmentation of crude oil via high-throughput sequencing: Enzymatic activities, bacterial community composition and functions

The enzymes and the characteristics of the community of the petroleum-degrading bacteria play a crucial role in the crude oil biodegradation. The prediction of kinetics of the key groups of hydrocarbons in crude oil was important to evaluate the bioremediation speed and constant. Most of the n -alkanes (C9–C29) were degraded in 25 days, and the average degradation rates of C 18 ∼C 27 higher than 100 μg g -1 d -1 . The hopanes, such as H 30 , had a biodegradation rate more than 10 μg g -1 d -1 . The related enzymes activities changed along with the crude oil biodegradation, especially dehydrogenase. The 16S rRNA gene amplicon sequencing revealed that Proteobacteria, Firmcutes, Bacteroidetes, Actinobacteria, Acidobacteria were the main petroleum hydrocarbon degraders during the crude oil biodegradation, and the top two highest relative abundance of the genera were Alcaligenes and Acinetobacter . Acinetobacter presented positive correlation to biodegradation of n -alkanes and PAHs. Based on COG analysis, the largest group involved in the general function was amino acid transport and metabolism. The functional categories of bacterial communities were mainly focused on the carbohydrate and amino acid metabolism, xenobiotics biodegradation and metabolism, membrane transport, and so on. Overall, these findings highlight the potential guideline for more adequate monitoring of microbial degradation of crude oil.

Degradation and reliability analysis of photovoltaic modules after operating for 12 years: A case study with comparisons

The long-term performance monitoring and characterization of field-exposed solar photovoltaic (PV) modules are essential for efficient power generation. This paper is an attempt at performance evaluation of the amorphous silicon (a-si), Heterojunction Intrinsic Thin layer (HIT), and Multi-Crystalline (mc-si) technologies after twelve years of outdoor exposure in the composite climate of India. Characterization techniques such as Visual Inspection, Infra-Red (IR) Thermography, Electroluminescence (EL) Imagining, and Electrical characterization have been carried out. I–V measurements, power losses, current degradation, and voltage degradation calculations are carried out. The percentage of electrical decline is 8.61%, 2.73%, and 29.08%, for Isc, Voc, and PMP respectively in a-si solar modules. For HIT modules 1.97%, 0.68%, and 0.48% for Isc, Voc, and VMP respectively. Finally, for the mc-si PV modules, these are 3.76%, 0.5%, and 1.44% for Isc, Voc, and PMP respectively over 12 years. The average degradation rates are found to be 1.24%/year, 0.14%/year, and 1.50%/year for a-si, HIT, and mc-si modules respectively. The EL imagining of the a-si modules shows the localized shunt over the surface of the modules as well as disconnected cell interconnects whereas no such defects are over the m-ci and HIT modules.

Investigation of the reversible performance degradation mechanism of the PEMFC stack during long-term durability test

This paper reports on 3-cell PEMFC stack durability test of 2500 h in dynamic conditions and different recovery procedures. After electrochemical impedance spectroscopy (EIS) analysis, it was determined that the primary cause of the stack performance degradation is the oxidation of platinum (Pt), which is reversible. The air starvation operation reduced the cathode voltage to less than 0.2 V, part of PtO was reduced, and the stack performance loss was partially recovered. However, the recovery of the three cells varies due to defects in the three-cell stack and uneven gas distribution. The fast load-up operation brought the short-term severe air starvation of the three cells to a similar level, the remaining platinum oxide (PtO) was fully reduced, the stack performance improved again, and the voltage consistency of the three cells was restored significantly. With the optimization of operating parameters and combined recovery procedures, the average degradation rate of the stack voltage is 3.08 μV/h within 2500 h. The results indicated that our combined strategy is of huge importance to mitigate the reversible performance degradation and significantly extend the service life of PEMFC stack and be a very appropriate procedure used in laboratories and systems.

Super enhancement of methanethiol biodegradation by new isolated Pseudomonas sp. coupling silicone particles

A new strain, Pseudomonas sp. SJ-1, which was able to remove model odorous organics methanethiol (MT) has been isolated from the wastewater treatment plant and identified via 16S rRNA analysis. Initial MT concentration, temperature and pH played an important role in MT removal, and up to 100% of 260 mg L−1 of MT could be removed within 11 h under the optimum conditions (30 °C, pH 7.0) with an average degradation rate of 23.6 mg L−1 h−1, which was the highest one in literature so far. The silicone particles were added as the non-aqueous phases (NAP) to enhance the performance of MT degradation. The results indicated that the maximum degradation rate and specific cell growth of strain SJ-1 were 2.36 times and 1.31 times by Haldane kinetic model analysis in the NAP added test. The SO42− was identified as the major intermediate and CO2 as a final product in MT biodegradation. Overall, this is the first report that a newly isolated Pseudomonas sp. could use high concentration MT as sole energy source and carbon source and its activity could be enhanced by adding NAP. The results provide a suggestion for the development of more effective and reliable biological treatment processes.

Long‐Term Operation of Nb‐Coated Stainless Steel Bipolar Plates for Proton Exchange Membrane Water Electrolyzers

Proton exchange membrane water electrolysis (PEMWE) is the most promising technology for green hydrogen production using renewable electricity, but it is expensive due to the Ti bipolar plates (BPPs). Herein, a PEMWE stack with coated stainless steel (ss) BPPs (Nb/Ti/ss‐BPP and Nb/ss‐BPP) is reported, which operates for about 14 000 h at 1.63 ± 0.12 A cm−2 and 65 °C. The average degradation rate is as low as 1.2% or 5.5 μV h−1. Scanning electrode microcopy reveals no signs of corrosion of the ss beneath the coatings. The interfacial contact resistance increases due to the formation of poorly conductive amorphous Nb oxides, as shown by atomic force microscopy and X‐Ray photoelectron spectroscopy, although it does not affect the cell performance. The results prove that Ti is not needed anymore as base material for manufacturing the BPPs, thus the cost of PEMWE can be significantly reduced.

Evaluating test method of air cleaning devices for ozone removal (ASHRAE RP-1579)

As awareness of the adverse health effects of ozone and its byproducts increases, a dedicated filtration system that removes ozone from ambient air has become a required or preferred component of building ventilation systems. A test method that can provide accurate information on the performance and service life of ozone removal devices is key to their wide application. This study investigates the temporal change of ozone removal efficiency of air cleaning devices that use activated carbon and proposes a prolonged test protocol called “Ozone Stress Test”; it compares this new test protocol to the protocol described in ANSI/ASHRAE Standard 145.2-2016. Results show that activated carbon-based devices had a high degradation rate at the beginning of exposure to ozone or exposure to significantly increased ozone, so a short test (i.e., 1-h initial efficiency test and 4-h capacity test in Standard 145.2) overestimated filter performance. Filter capacity at 95% breakthrough could not be measured using the Standard 145.2 method or the prolonged test method because the filters had exceedingly low degradation rates after few hours’ exposure to ozone. However, the average degradation rate during the capacity test can serve as an indicator of filter capacity.

Voltage degradation of high-temperature PEM fuel cells operating at 200 °C under constant load and start-stop conditions

High temperature proton exchange membrane fuel cells (HT-PEM) offer significant advantages over conventional low temperature fuel cells (LT-PEM), including improved fuel impurity tolerance and increased electrode kinetics. These advantages enable use of reformate fuels with potentially lower costs and simplified handling versus ultra-pure hydrogen fuel required for LT-PEM. Although HT-PEM fuel cell operation has been demonstrated at temperatures above 120 °C, relatively few studies have focused on operation at 200 °C or higher where fuel impurity tolerance is maximized, but at the cost of accelerated performance degradation. To help address this research gap, the present study investigated the voltage degradation of HT-PEM fuel cells operating at 200 °C and 0.4 A/cm2 under continuous load conditions, and at 200 °C and 0.6 A/cm2 during start-stop cycling. Results based on triplicate measurements show an average constant load degradation rate of 102 μV/h, as compared to literature values of 10 μV/h or less at lower temperature and current density. The start-stop experiments showed relatively high degradation rates per cycle up to 50 cycles, with decreasing average degradation rates over 80 and 100 cycles.

Degradation Behaviour of Arrowroot Fibre (Maranta Arundinacea) Reinforced Arrowroot Starch Biocomposite Films

This research is being driven by environmental legislation that requires the consumption and usage of environmentally friendly products. The focus of this research is to develop and characterize thermoplastic arrowroot starch (TPAS) based biocomposite films incorporating arrowroot fibre (AF) at various compositions (0–10 wt.%) using the solution casting method. The biodegradation behaviour of newly developed composite films was examined. The average degradation rates of TPAS and TPAS/AF–10 films were 8 and 9.84%/day, respectively. The soil burial results revealed that the weight loss of TPAS/AF biocomposite films was higher compared to TPAS film. The biocomposite films revealed arrowroot fibre, a novel waste resource that is both eco-friendly and simple to produce. Overall, incorporating arrowroot fibre with TPAS film improves biodegradability, making them more suitable for environmentally friendly food packaging.

Sodium alginate coating on biodegradable high-purity magnesium with a hydroxide/silane transition layer for corrosion retardation

Fast degradation of magnesium (Mg) and its alloys in the physiological environment has impeded their clinical use as temporary implants. To control degradation of Mg in the physiological environment, a sodium alginate coating is fabricated on alkalinized high-purity Mg with a silane transition layer by spin coating. The surface morphology and composition are investigated by scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, and Fourier transform infrared spectroscopy. Electrochemical and immersion tests are performed in the simulated body fluid (SBF) at 37 °C. The composite coating with a thickness of 10.3 µm is uniform and adheres well to the Mg substrate. Compared to the bare substrate, the corrosion current density of the sample with the composite coating decreases from 130.9 ± 6.2–1.3 ± 0.3 μA cm−2 and the charge transfer resistance increases by 190 times. The average degradation rate in SBF drops to 0.80 ± 0.26 mm year−1 from 3.47 ± 0.25 mm year−1 of the pristine Mg substrate and the composite coating is demonstrated to impede corrosion of the Mg substrate after immersion in SBF for 14 days. The excellent protection rendered by the composite coating is ascribed to the effective barrier effects of the dense and adhering sodium alginate coating and blocking effect of chelate compounds of sodium alginate and Mg ions formed during the corrosion process.

Construction and Degradation Performance Study of Polycyclic Aromatic Hydrocarbons (PAHs) Degrading Bacterium Consortium

PAHs are widely distributed in the environment and pose a serious threat to ecological security and human health. The P&A (Pseudomonas aeruginosa and Alcaligenes faecalis) bacterium consortium obtained in this study comes from oily sludge and is reused for the degradation of PAHs mixture in oily sludge. Few articles pay attention to the PAHs mixture in oily sludge and reuse the bacterium consortium for its degradation. The PAHs solution degradation efficient of P&A bacterial consortium under different environmental conditions, bioaugmentations, and exogenous stimulations were studied by ultraviolet visible spectrophotometer and gas chromatography–mass spectrometry. The result shows that, after 8 days of degradation under 35 °C, pH 7, with 5% (volume percent) of the inoculation amount, the degradation rate of NAP, PHE, and PYR solution could higher than 90%, 80%, and 70%, respectively. The additional crude oil could further improve the NAP, PHE, and PYR degradation efficiency. The minimum inhibitory concentration of Cu2+, Zn2+, and Pb2+ to bacterium were 2.002, 17.388, and 9.435 mM, respectively. The addition of surfactants had negative or limited positive effect on the PAHs degradation rate. Furthermore, the average degradation rates of NAP, PHE, and PYR, in oily sludge of local petroleum polluted area by P&A bacterial consortium, could all reach above 80%. Based on gas chromatography–mass spectrometry test results before and after incubation, P&A bacterial consortium also provides more opportunities for other organic compounds’ degradation.

Mechanical stability and biological activity of Mg–Sr co-doped bioactive glass/chitosan composite scaffolds

The freeze-drying method was used to synthesize biological scaffold. The properties of the as-prepared scaffolds were investigated by various techniques. Results showed that the magnesium (Mg) and strontium (Sr) co-doped bioactive glass/chitosan (MSBG/CS) composite scaffolds exhibited a three-dimensional honeycombed porous structure. With the increase in the added content of MSBG powders, the porosity, average pore size, swelling, and degradation rate of composite scaffolds decreased gradually. When the mass ratio of MSBG to CS was 2:4, compressive modulus of composite scaffold reached the maximum value of 1.12±0.019 MPa. It could be attributed to the hydrogen bond between the negatively charged silicon hydroxyl (Si–OH) in MSBG and positively charged amino group (–NH2) in CS molecular chain. In vitro experiment indicates that MSBG could significantly improve the generation capacity of hydroxyapatite in composite scaffold. Thus, the as-formed composite scaffold with remarkable performance acts as a promising candidate for bone tissues engineering.