Extent Of Degradation Research Articles

Estimation of the Mechanical Properties of Poly(3-hydroxybutyrate) from IR Data

Despite the sustainability, biodegradability, and biocompatibility of microbial polyesters, as well as their potential to replace polyolefins, the market share of these biopolymers is still marginal. The primary factors that impede the success of microbial polyesters are related to their poor thermal stability and the degradation during processing that negatively affects the mechanical performance of the final product. Due to the complexity of the mechanism of degradation and the vast number of factors that influence the mechanism, the outcome of the degradation cannot be predicted with high confidence. Our present work addresses both difficulties. First, the thermal stability of poly(3-hydroxybutyrate) was successfully improved by a stabilizer system based on pomegranate extract. Second, we have developed a computational method that can be used for the estimation of the mechanical properties of processed microbial polyesters from IR data. The computational method is based on an unprecedented hybrid model that incorporates both linear and nonlinear components. The linear component is based on multivariate data analysis and quantizes the correlation between IR data and the extent of degradation. In contrast, the second component consists of a power function in order to be able to describe the nonlinear correlation between the extent of degradation and the mechanical properties. By using the hybrid model, indicators of mechanical performance, such as tensile strength, can be estimated from IR data, which was not achieved before.

Post-high-pressure temperature and time — Overlooked parameters in high pressure treatment of bacterial spores

High pressure (HP) processing has high potential for bacterial spore inactivation with minimal thermal input. To advance HP germination and subsequent inactivation of spores, this study explored the physiological state of HP-treated spores using flow cytometry (FCM). Bacillus subtilis spores were treated at 550 MPa and 60 °C (very HP (vHP)) in buffer, incubated after the HP treatment, and stained for FCM analysis with SYTO16 indicating germination and propidium iodide (PI) indicating membrane damage. FCM subpopulations were analyzed depending on the HP dwell time (≤20 min), post-HP temperature (ice, 37 °C, 60 °C) and time (≤4 h), germination-relevant cortex-lytic enzymes (CLEs) and small-acid-soluble-proteins-(SASP)-degrading enzymes by using deletion strains. The effect of post-HP temperatures (ice, 37 °C) was additionally studied for moderate HP (150 MPa, 38 °C, 10 min).Post-HP incubation conditions strongly influenced the prevalence of five observed FCM subpopulations. Post-HP incubation on ice did not or only slowly shifted SYTO16-positive spores to higher SYTO16 levels. At 37 °C post-HP, this shift accelerated, and a shift to high PI intensities occurred depending on the HP dwell time. At 60 °C post-HP, the main shift was from SYTO16-positive to PI-positive subpopulations. The enzymes CwlJ and SleB, which are CLEs, seemed both necessary for PI or SYTO16 uptake, and to have different sensitivities to 550 MPa and 60 °C. Different extents of SASP degradation might explain the existence of two SYTO16-positive subpopulations. Shifts to higher SYTO16 intensities during post-HP incubation on ice or at 37 °C might rely on the activity and recovery of CLEs, SASP-degrading enzymes or their associated proteins from reversible HP-induced structural changes. These enzymes seemingly become active only during decompression or after vHP treatments (550 MPa, 60 °C). Based on our results, we provide a refined model of HP germination-inactivation of B. subtilis spores and an optimized FCM method for quantification of the safety-relevant subpopulation, i.e., vHP (550 MPa, 60 °C) superdormant spores.This study contributes to the development of mild spore inactivation processes by shedding light on overlooked parameters: post-HP incubation conditions. Post-HP conditions significantly influenced the physiological state of spores, likely due to varying enzymatic activity. This finding may explain inconsistencies in previous research and shows the importance of reporting post-HP conditions in future research. Furthermore, the addition of post-HP conditions as HP process parameter may open up new possibilities to optimize HP-based inactivation of spores for potential industrial applications in the food industry.

The influence of chain scission on the molecular weight of conjugated polymers in a continuous flow reactor

The conjugated polymer PTB7 was found to undergo flow-induced chain scission under conditions typically employed in the flow synthesis of conjugated polymers, supporting that polymer degradation is a key side reaction that can influence the molecular weight of conjugated polymers synthesized in flow. Flow synthesis is becoming an increasing important method for the rapid and reproducible synthesis of conjugated polymers with optimal molecular weight. Increasing the length of time the polymerization solution remains in the flow system (the residence time), initially leads to an increase in molecular weight, but declines are observed at longer residence times. Our results support that conjugated polymers undergo mechanochemical chain scission in flow and that reactor temperature, polymer molecular weight, and polymer concentration are important factors that influence the extent of degradation. These results should aid in the future optimization of conjugated polymer syntheses in flow.

In-depth structural and compositional assessment of aged terpenoid varnish layers by nonlinear optical microscopy

Varnishes are employed in painted artworks for protection from atmospheric pollution and oxidation and for improving the esthetic appearance by providing an even and brilliant surface finish. Also, in some cases, colored varnishes are applied intentionally to modify the chromatic appearance of paintings. Varnishes undergo complex and differentiated structural and chemical changes over time depending on their composition and conservation conditions. The present work investigates the extent of degradation of the outermost layers of varnish coatings due to aging as a function of depth by using nonlinear optical microscopy (NLOM) in the modality of multiphoton excitation fluorescence (MPEF). This non-invasive technique has been employed for the determination of the thickness, with a microscopic axial and lateral resolution, of the affected regions of pictorial terpenoid varnish layers, such as dammar, mastic, shellac and sandarac, subjected to various types and degrees of aging, artificial, natural and a combination of both. A homemade nonlinear optical microscope, based on a tightly focused pulsed femtosecond laser emitting at 800 nm, was used for the investigation. Single-photon laser-induced fluorescence (LIF) measurements served to determine the degree of surface aging and the optimum NLOM-MPEF operating conditions and helped to interpret the results obtained by applying the latter. These results signpost the correlations between the extent of degradation, non-invasively determined by NLOM-MPEF, the type and length of aging, the nature of the varnish and the initial thickness of the varnish layer.

Uptake and Transformation of Hexachlorocyclohexane Isomers (HCHs) in Tree Growth Rings at a Contaminated Field Site.

The potential transformation of hexachlorocyclohexane isomers (HCHs) within tree trunks could have a significant impact on the use of phytoscreening. However, the transformation mechanisms of HCH in trunks particularly in growth rings are not yet well understood. Therefore, a field study on an HCH-contaminated field site was conducted to investigate the fate of HCH, particularly α-HCH in tree trunks using multielement compound-specific isotope analysis (ME-CSIA) and enantiomer fractionation. The results indicate that α-HCH was transformed, as evidenced by higher δ13C and δ37Cl values detected across different growth ring sections and in the bark compared to those in muck and soil. Remarkably, in the middle growth ring section, δ13C values of HCH were only marginally higher or comparable to those in muck, whereas δ37Cl values were higher than those of the muck, indicating a different transformation mechanism. Moreover, the δ37Cl values of β-HCH also increased in the tree trunks compared to those in soil and muck, implying a transformation of β-HCH. Additionally, dual-element isotope analysis revealed that there are different transformation mechanisms between the middle growth rings and other sections. Our findings suggest that the transformation of HCHs in trunks could bias quantitative phytoscreening approaches; however, ME-CISA offers an option to estimate the degradation extent.

Effects of microstructure on radiolytic degradation of nuclear grade cationic resins: Gel versus macro-porous

A study was undertaken to evaluate the effect of gamma radiation on the physico-chemical and functional properties of strong cationic ion exchange resins with varying microstructures i.e., gel and macro-porous type, used in purification systems of water-cooled nuclear reactors. The effect of metal ion loading on degradation behavior was probed to simulate the in-situ irradiation scenario in used resin. The resins are expected to undergo physico-chemical and functional degradation due to different oxidizing and reducing species from water radiolysis. Nevertheless, evaluating the extent of degradation based on the morphological and structural differences was of interest. The extent of resin degradation was estimated by analyzing the change in pH, conductivity, total organic carbon (TOC), chemical oxygen demand (COD) and the extent of reactive site loss from the leached ions. Leaching of SO42− ions and the formation of lower organic acids resulted in decreased pH and increased conductivity, TOC and COD values. The change in exchange capacity and physical and structural changes in the irradiated resin's surface was probed with X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and Field emission scanning electron microscopy (FE-SEM). Gel resin showed more significant functional group loss, while hydrogen generation was more from macroporous resin due to its more rigid and dense structure.

Integrated system-level prognosis for hybrid systems subjected to multiple intermittent faults

Considering the condition that multiple intermittent faults occur sequentially or simultaneously in hybrid systems, this paper proposes an integrated system-level prognosis scheme. The scheme is built by integrating model-based fault estimation and data-driven system-level remaining useful life (RUL) prediction. As for fault estimation, the level-based learning swarm optimization is utilized to identify state/value changes of intermittently faulty components based on the constructed hybrid system model. With estimation results, the system-level prognosis framework can be designed as follows: 1) The abnormal duration index (ADI) is established to quantify the system degradation extent under multiple intermittent faults. In view of the stochasticity of intermittent fault appearance and disappearance, the ADI is assessed approximately by as pessimistic as possible and as optimistic as possible indicators. 2) A synthetical degradation evaluator is developed to determine the moment to activate predictor, which ensures the obtained fault features can sufficiently reflect the evolutionary trend of the intermittently faulty component when activating RUL predictor. 3) Considering sequential or simultaneous intermittent faults and variations of modes for hybrid systems, the system-level prognosis module is designed, where the optimized support vector regression is adopted for system RUL prediction. Finally, the experimental study is investigated to verify the proposed scheme.

Land Degradation Causes, Consequences and Sustainability of the Restoration Efforts: The Case of Soro Wereda, Hadiya Zone, Southern Ethiopia

Land degradation is a global issue and it is more severe in developing countries like Ethiopia. To address the problems of land degradation in Ethiopia, many efforts have been made since 1970s. From then onwards many attempts have been made and integrated watershed management in one among these. The study was undertaken in Soro Wereda, Hadiya Zone, and SNNPR with the objective of examining land degradation causes, consequences and sustainability of the restoration efforts. In order to achieve the stated objectives, both primary and secondary data were generated by employing qualitative and quantitative methods. Systematic sampling technique was used to select 97 representative households from three kebeles. The quantitative data was analyzed by using frequency, percentage, mean and standard deviation. The qualitative data was analyzed through narration. The findings of the study showed that gully formation, stoniness of land, absence of grasses and vegetation cover, decline in crop productivity and change in soil color are the main symptoms of land degradation. The major extent of land degradation as perceived by the local people was severe. Only very few of the households opted that highly severe regarding the extent of land degradation. The major causes of land degradation in the study were soil erosion, deforestation and over cultivation. In addition, topography, overgrazing, lack of conservation methods and cultivation of marginal land were the other important causes with the certain degree of variation. The core impacts of land degradation were the declining of yield year after year, food insecurity| poverty and drought and famine. The remaining increases of inputs, malnutrition, desertification and displacement of people ranked two up to five followed by the above mentioned impacts. It is very difficult to restore the degraded land without the full participation of relevant stakeholders. The main stakeholders that participate in the restoration process include government, NGOs, farmers and DAs and each of these stakeholders have its own roles. Adopting of the participatory approach, promoting the awareness of rural communities as well as other stakeholders, management of restored land, and combining of the restoration efforts with local knowledge are core issues to the sustainability of the restoration process. In order to run the restoration efforts in sustainable way strengthening of community participation, capacity building of stakeholders, providing of incentives for those achieve the restoration process and scale up of the best practices are needed.

Preliminary assessment of a degraded river in the Niger Delta, Nigeria using physico-chemical characteristics and water quality index

Surface water degradation is increasingly becoming a national issue in Nigeria as it affects the suitability of water for its various uses. The preliminary study of the physicochemical parameters and water quality index of the Orogodo River was conducted to ascertain the extent of degradation from multiple sources of contamination. Water samples were collected from four sites that were impacted by various anthropogenic activities along the Orogodo River in Delta State during the months of February (number of samples = 16) and September (number of samples = 16) 2020. The water samples were analyzed using standard methods. The results of the physicochemical analysis using ANOVA showed significant differences (P<0.05) only in biochemical oxygen demand and turbidity across the four sites. The biochemical oxygen demand (3.05±2.47) and turbidity (8.35±5.162) at site 3 espectively that is a major abattoir discharge point were above the Nigeria Standard for Drinking Water Quality acceptable limits for drinking water and could portend harm to water users and ecosystem integrity. The water quality index analysis revealed that sites 1 and 4 showed good water quality and those of sites 2 and 3 showed poor water quality. The study demonstrated that water quality index analysis and physicochemical characteristics were critical factors in evaluating the deteriorating conditions of the Orogodo River. Periodic monitoring of the river quality and integrity is vital as the river water will require extensive treatment for safe usage.

Probing river health status: a study based on index of biotic integrity (IBI) in Tapti River of Deccan plateau, India.

Anthropogenic activities impacted the ecological health of rivers by altering the physical habitat and water flow as well as by pollution. Monitoring of biotic groups for gauging the river health is a prerequisite for assessing the extent of degradation and formulating management guidelines for river restoration. An assessment using fish-based index of biotic integrity (IBI) was carried out in the Central Indian river, Tapti, for probing its health status. For the multimetric index, twelvemetrics were adopted under five categories: taxonomic richness, habitat composition, tolerance indicators, species resilience, and trophic composition. Among the studied sites, Betul in the upper stretch was selected as the reference site for River Tapti, which almost meets the upper expectation of the metrics explored. Continuous scoring method was applied to evaluate the biotic integrity in the selected sites of the river. The IBI score based on the pooled fish abundance data in River Tapti ranged from 33 to 60. Assessment of the ecological health revealed that three-fourth of the river stretch was moderately impaired (25-50% of impairment) and the most deteriorated site was Kamrej with 45% of impairment which might be due to its location in the urban area with high influx of domestic sewage and industrial effluents. The IBI scores were plotted and compared with an independent estimate of water quality. The CCA with environmental and IBI variables revealed higher correlation with each other and the functional groups such as carnivores, herbivores, and fishes with high population doubling time (PDT) were found in close association with nitrate-N, total alkalinity, and specific conductivity. The study urges the need for the adoption of proper management and mitigation measures to restore the health and wealth of aquatic ecosystem.

Forever no more: Complete mineralization of per- and polyfluoroalkyl substances (PFAS) using an optimized UV/sulfite/iodide system

As the global issue of PFAS contamination in water continues to grow there exists a need for technologies capable of fully mineralizing PFAS in water, with destruction being measured as both a loss of the initial PFAS and a quantitative recovery of the resultant fluoride ions. This study investigates the use of sulfite and iodide in a bicarbonate-buffered alkaline system activated with ultraviolet (UV) light to destroy PFAS. The UV/sulfite/iodide system creates a reductive environment through the generation of aqueous electrons, which can degrade PFAS. The extent of degradation and defluorination was explored for perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), 6:2 fluorotelomer sulfonic acid (6:2 FTS), and perfluorobutane sulfonic acid (PFBS). An initial UV/sulfite/iodide system achieved 100 % degradation and > 90 % defluorination for PFOS, PFOA, and 6:2 FTS, but was not capable of completely degrading PFBS. Transformation product elucidation experiments were performed for PFOS under different UV systems, and 6:2 FtSaB using the initial UV/sulfite/iodide system. Several transformation products were identified including -nF/+nH PFOS (n = 1–13), -F/+H shorter-chain PFSAs, 6:2 fluorotelomer sulfonamidoamine (6:2 FtSaAm), 6:2 fluorotelomer sulfonamide, and 6:2 fluorotelomer unsaturated sulfonamide. Novel identification of -F/+H perfluoropropane sulfonic acid (PFPS) and -F/+H perfluoroethane sulfonic acid (PFES) following degradation of PFOS confirms CC bond cleavage, and different isomers of -F/+H PFOS confirms the potential for CF bond cleavage to occur throughout the perfluoroalkyl chain. Additional optimization experiments were performed aiming to fully degrade PFBS. The optimal protocol found in this study involved an elevated initial sulfite concentration and adding additional sulfite at regular intervals during UV-activation, achieving >99.9 % destruction and complete quantitative defluorination of PFBS.

Accelerated weathering of furanoate polyesters: Effect of molecular weight, crystallinity, and time

AbstractFilms of poly(ethylene furanoate) (PEF) and poly(neopentyl furanoate) (PNF) of different molecular weights were artificially weathered in a Q‐SUN test chamber for up to 500 h. The chemical and physical changes of the films have been evaluated with a wide range of techniques. All films, independent of molecular weight or crystallinity, show evidence of partial cross‐linking and the formation of new carbonyl species. Furthermore, all irradiated films show changes in thermal properties and crystallization behavior. The extent of degradation was higher for the amorphous films as compared to their semi‐crystalline counterparts, suggesting that UV degradation predominantly occurs in the amorphous phase. The apparent higher UV‐sensitivity of PNF, as compared to PEF, suggests that the nature of the diol, and the resulting polymer properties, affects the UV‐stability of the polymer. Nevertheless, comparison with poly(ethylene terephthalate) (PET) shows that the different electronic structure and properties of the furan ring are the most likely cause of the observed UV‐instability.

Construction of high-proportion dual bismuth-based Z-scheme Bi3O4Cl/Bi2MoO6 photocatalytic system via in-situ growth of Bi2MoO6 on Bi3O4Cl for enhanced photocatalytic degradation of organic pollutants

In this study, a high-proportion dual bismuth-based Z-scheme Bi3O4Cl/Bi2MoO6 photocatalytic system was constructed via the in-situ growth of Bi2MoO6 on Bi3O4Cl for enhanced visible-light driven photocatalytic degradation of organic pollutants in wastewater. The effects of the particle ratio of Bi3O4Cl and Bi2MoO6, organic pollutant initial concentration, catalyst dosage, visible-light irradiation time, degradation kinetics and reused times on the photocatalytic activity of the Z-scheme Bi3O4Cl/Bi2MoO6 photocatalyst were investigated. Moreover, the study compares the photocatalytic degradation extents of norfloxacin, tetracycline, crystal violet, acridine orange and methylene blue using the Z-scheme Bi3O4Cl/Bi2MoO6 photocatalyst, and proposes a possible mechanism on the Z-scheme Bi3O4Cl/Bi2MoO6 photocatalytic system. The results indicate that the high-proportion dual bismuth-based Z-scheme Bi3O4Cl/Bi2MoO6 photocatalyst performs superior photocatalytic activity at a 1.0:1.0 particle ratio. The fuzzy contact interfaces can be formed between Bi2MoO6 and Bi3O4Cl nanoparticles due to the direct in-situ growth of Bi2MoO6 on Bi3O4Cl, which can provide channels for the photo-generated electron transfer to construct the Z-scheme Bi3O4Cl/Bi2MoO6 photocatalytic system. After five cycles, the Z-scheme Bi3O4Cl/Bi2MoO6 photocatalyst maintains high photocatalytic performance. During the photocatalytic degradation, the photo-generated holes play dominant roles, while the contributions of superoxide radical and hydroxyl radical remain approximate. Thus, this photocatalytic technology displays promising application prospects for handling organic contaminants, including antibiotics and dyes, in wastewater.

The effect of Cl, Br, and F on high-temperature corrosion of heat-transfer alloys

The impact of small alkali halide additions on the melting behavior and corrosivity of a synthetic sulfate deposit at 500, 550, and 600 °C was investigated. Three differently alloyed commercial heat-transfer materials; low-alloyed 10CrMo9-10, stainless AISI 347, and high-alloyed Sanicro 28, were studied. The samples were exposed for 168 h in a tube furnace to a K2SO4 + Na2SO4 mixture containing 0.85 mol% KCl, KBr, or KF. The extent of material degradation was determined by weight loss measurements, while the morphology, thickness, and composition of the formed oxide scale were characterized with SEM-EDS. Additionally, the melting behavior of the mixtures was studied with TG-DTA. It could be concluded that already small amounts of reactive alkali halides in an otherwise inert K2SO4 + Na2SO4 mixture change significantly the corrosion and melting behavior of the mixture.

Review on the Degradation of Poly(lactic acid) during Melt Processing.

This review paper presents an overview of the state of the art on process-induced degradation of poly(lactic acid) (PLA) and the relative importance of different processing variables. The sensitivity of PLA to degradation, especially during melt processing, is considered a significant challenge as it may result in deterioration of its properties. The focus of this review is on degradation during melt processing techniques such as injection molding and extrusion, and therefore it does not deal with biodegradation. Firstly, the general processing and fundamental variables that determine the degradation are discussed. Secondly, the material properties (for example rheological, thermal, and mechanical) are presented that can be used to monitor and quantify the degradation. Thirdly, the effects of different processing variables on the extent of degradation are reviewed. Fourthly, additives are discussed for melt stabilization of PLA. Although current literature reports the degradation reactions and clearly indicates the effect of degradation on PLA's properties, there are still knowledge gaps in how to select and predict the processing conditions that minimize process-induced degradation to save raw materials and time during production.

Radiation damage in GaN/AlGaN and SiC electronic and photonic devices

The wide bandgap semiconductors SiC and GaN are commercialized for power electronics and for visible to UV light-emitting diodes in the case of the GaN/InGaN/AlGaN materials system. For power electronics applications, SiC MOSFETs (metal–oxide–semiconductor field effect transistors) and rectifiers and GaN/AlGaN HEMTs and vertical rectifiers provide more efficient switching at high-power levels than do Si devices and are now being used in electric vehicles and their charging infrastructure. These devices also have applications in more electric aircraft and space missions where high temperatures and extreme environments are involved. In this review, their inherent radiation hardness, defined as the tolerance to total doses, is compared to Si devices. This is higher for the wide bandgap semiconductors, due in part to their larger threshold energies for creating defects (atomic bond strength) and more importantly due to their high rates of defect recombination. However, it is now increasingly recognized that heavy-ion-induced catastrophic single-event burnout in SiC and GaN power devices commonly occurs at voltages ∼50% of the rated values. The onset of ion-induced leakage occurs above critical power dissipation within the epitaxial regions at high linear energy transfer rates and high applied biases. The amount of power dissipated along the ion track determines the extent of the leakage current degradation. The net result is the carriers produced along the ion track undergo impact ionization and thermal runaway. Light-emitting devices do not suffer from this mechanism since they are forward-biased. Strain has also recently been identified as a parameter that affects radiation susceptibility of the wide bandgap devices.

Composite crosslinked chitosan beads with zeolitic imidazolate framework-67 as peroxymonosulfate activator for increased dye degradation

In this study, a biodegradable cobalt-based peroxymonosulfate (PMS) activator for a dye degradation process was fabricated from crosslinked chitosan (CS) and zeolitic imidazolate framework-67 (ZIF-67) beads. Green synthesis of ZIF-67 produced a good yield, and its particles had an average size of 242 nm and a specific surface area of 1129 m2/g. These particles were then incorporated with the crosslinked CS beads at different loadings (2.5–10 %). The catalytic performance of these composite beads was evaluated for rhodamine B (RhB) degradation. Maximum degradation of 98 % was achieved with CS/7.5 %ZIF-67 and a PMS concentration of 0.15 g/L. The degradation equilibrium was obtained within 5 min, with a degradation rate of 0.957 min−1. The pH of the solution had no significant effect on the degradation extent. The predominant radical species in RhB degradation were sulfate radical anions, and a high concentration of coexisting anions decreased the degradation efficiency. The composite beads effectively degraded RhB over five cycles without any chemical recovery treatments. Furthermore, the PMS activating-composite beads effectively facilitated the degradation of various other dyes. This approach is a simple, practical, and cost-effective method for preparing a PMS activator that can efficiently increase dye degradation with ease of separation and recovery.

Coral reef degradation at an atoll of the Western Colombian Caribbean.

Coral reef decline is an issue of concern around the globe. Remote and uninhabited coral areas are not exempt from facing changes in species composition and functionality due to global drivers. Quitasueño is a remote atoll within the Seaflower Biosphere Reserve, in the Southwestern Caribbean Sea. To evaluate the current status of the coral reefs in Quitasueño we sampled 120 stations through Rapid Ecological Assessment and evaluated four stations through Planar Point Intercept to compare the current percent cover of benthic groups with previous studies in the area. We found pronounced changes in coral and macroalgae covers in time, and great conspicuousness of multiple conditions of deterioration along Quitasueño, including diseases, coral predation, and aggression and invasion of coral colonies by macroalgae and sponges. The reef ecosystem seems to be facing a phase shift, in which the benthic cover previously dominated by hard corals is currently dominated by fleshy macroalgae. It is essential to evaluate the possible drivers of the extent of degradation of Quitasueño to understand the process of deterioration and mitigate the impacts.

Design of hydrodynamic cavitation-based advanced oxidation process for degradation of recalcitrant micropollutants originating from tertiary effluent streams: a case study with norfloxacin

Abstract Treatment of micropollutants even after tertiary treatment and developing cost-effective, sustainable and energy-efficient technology for the same still remains an active area of research. The present study reports the feasibility and efficacy of hydrodynamic cavitation (HC)-based advanced oxidation process (AOP) for the degradation of norfloxacin. Experiments using HC were carried out in a sequential manner starting with the optimization of the cavitating device (orifice plate) using computational fluid dynamics (CFD) followed by optimizing the operational parameters such as pH, inlet pressure and initial concentration. An experimental study revealed that under optimized conditions of pH – 2, inlet pressure – 6 bar and initial conc – 250 μg/L, NRF degradation of 22.26% was obtained using HC in an experimental run of 60 min. For further improvement of the HC process, experiments were carried out by integrating with H2O2, O3 and Fenton's reagent. Under the optimized conditions, integrating with H2O2, O3 and Fenton's reagent enhanced the extent of NRF degradation. The energetics of the process was further evaluated to understand the techno-economic viability. The study revealed that HC + H2O2 consumed less energy of 8.01 kWh/m3 at the economics of Rs. 82.53/m3. Thus, HC combined with oxidizing agents can be a novel technique in the genre of AOP for the degradation of micropollutants.

Applying Material Science Principles to Chemical Stability: Modelling Solid State Autoxidation in Mifepristone Containing Different Degrees of Crystal Disorder

Ball-milling and harsh manufacturing processes often generate crystal disorder which have practical implications on the physical and chemical stabilities of solid drugs during subsequent storage, transport, and handling. The impact of the physical state of solid drugs, containing different degrees/levels of crystal disorder, on their autoxidative stability under storage has not been widely investigated. This study investigates the impact of differing degrees of crystal disorder on the autoxidation of Mifepristone (MFP) to develop a predictive (semi-empirical) stability model. Crystalline MFP was subjected to different durations of ambient ball milling, and the resulting disorder/ amorphous content was quantified using a partial least square (PLS) regression model based on Raman spectroscopy data. Samples of MFP milled to generate varying levels of disorder were subjected to a range of (accelerated) stability conditions, and periodically sampled to examine their recrystallization and degradation extents. Crystallinity was monitored by Raman spectroscopy, and the degradation was evaluated by liquid chromatography. The analyses of milled samples demonstrated a competition between recrystallization and degradation via autoxidation of MFP, to different extents depending on stability conditions/exposure time. The degradation kinetics were analyzed by accounting for the preceding amorphous content, and fitted with a diffusion model. An extended Arrhenius equation was used to predict the degradation of stored samples under long-term (25°C/60% RH) and accelerated (40°C/75% RH, 50°C/75% RH) stability conditions. This study highlights the utility of such a predictive stability model for identifying the autoxidative instability in non-crystalline/partially crystalline MFP, owing to the degradation of the amorphous phases. This study is particularly useful for identifying drug-product instability by leveraging the concept of material sciences.