Primary Degradation Processes Research Articles

Determination of Kinetic and Thermodynamic Parameters of Biomass Gasification with TG-FTIR and Regression Model Fitting

In this study, the decomposition of five different raw materials (maize, wheat and piney biomass, industrial wood chips and sunflower husk) were investigated using the TG-FTIR method to obtain raw data for model-based calculations. The data obtained from the thermogravimetric analysis served as a basis for kinetic analysis with three different isoconversional, model-free methods, which were the KAS, FWO and Friedman methods. Afterwards, the activation energy and the pre-exponential factor were determined, and no significant difference could be identified among the used methods (difference was under 5%), achieving 203–270 kJ/mol of Ea on average. Thereafter, the thermodynamic parameters were studied. Based on the TG-FTIR data, a logistic regression model was fitted to the data, which gives information about the thermal degradation and the obtained components with different heating rates. The FTIR analysis resulted in differential peaks corresponding to the studied components that were detected within the temperature range of 350–380 °C. The primary degradation processes occurred within a broader temperature range of 200–600 °C. Accordingly, in this work, the use of logistic mixture models as an alternative to traditional kinetic models for the description of the TGA process was also investigated, reaching adequate performance in fitting by a validation data coefficient of determination of R2 = 0.9988.

Turbulent Particle Flow in Spent Nuclear Fuel Storage Systems

Deposition models are being developed with the commercial computational fluid dynamics software STAR-CCM+ to evaluate particulate deposition on spent nuclear fuel (SNF) canisters. The primary particulate of concern is chloride salts, which are dispersed in the atmosphere and then deposited onto the canisters. During dry storage, the primary degradation process is likely to be chloride-induced stress corrosion cracking (CISCC) at the heat-affected zones of the canister welds. It is known that stainless steel canisters are susceptible to CISCC; however, the rate of chloride deposition onto the canisters is poorly known, based on sparse field data from a small number of sites. This paper describes work looking at various approaches to modeling turbulence, such as Reynolds-averaged Navier Stokes (RANS) and large eddy simulation (LES), and its impact on particle flow and deposition within a ventilated SNF storage system. The deposition rate is determined for a vertical canister system and a horizontal canister system. LES has the potential to simulate turbulent flows more accurately versus RANS, but is much more computationally expensive. A k-omega version of the RANS turbulence model was used for this study. The computational efficient RANS steady-state model predicted a similar canister deposition result as the LES simulation for a vertical canister storage system. For a horizontal storage system, the RANS steady-state model predicted more particles depositing on the canister than the LES simulation, providing a conservative estimation for particle deposition. A wall correction factor was added to the RANS model to dampen the turbulence fluctuation normal to a surface that left undamped, leads to the RANS model overpredicting deposition along a surface for smaller particles. This work was done to further development of deposition models that could be used to plan and inform SNF canister aging management programs with predictive models for the timing and occurrence of canister CISCC. This work is part of a larger effort tasked with understanding the likelihood of canister degradation due to CISCC. These models are still under development, and testing is needed for validation. However, these models are being presented now to demonstrate to canister vendors, utilities, regulators, and stakeholders the value of this type of modeling.

The Degradation Process of Typical Neonicotinoid Insecticides in Tidal Streams in Subtropical Cities: A Case Study of the Wuchong Stream, South China.

Neonicotinoid insecticides (NEOs) are commonly used to prevent unwanted insects in urban fields. Degradation processes have been one of the important environmental behaviors of NEOs in an aquatic environment. In this research, hydrolysis, biodegradation, and photolysis processes of four typical NEOs (i.e., thiacloprid (THA), clothianidin (CLO), acetamiprid (ACE), and imidacloprid (IMI)) were examined through the adoption of response surface methodology-central composite design (RSM-CCD) for an urban tidal stream in South China. The influences of multiple environmental parameters and concentration levels on the three degradation processes of these NEOs were then evaluated. The results indicated that the three degradation processes of the typical NEOs followed a pseudo-first-order reaction kinetics model. The primary degradation process of the NEOs were hydrolysis and photolysis processes in the urban stream. The hydrolysis degradation rate of THA was the highest (1.97 × 10-5 s-1), and that of CLO was the lowest (1.28 × 10-5 s-1). The temperature of water samples was the main environmental factor influencing the degradation processes of these NEOs in the urban tidal stream. Salinity and humic acids could inhibit the degradation processes of the NEOs. Under the influence of extreme climate events, the biodegradation processes of these typical NEOs could be suppressed, and other degradation processes could be further accelerated. In addition, extreme climate events could pose severe challenges to the migration and degradation process simulation of NEOs.

SEDIMENT CHARTERSTICS, ORGANIC CARBON AND CALCIUM CARBONATE IN CORE SEDIMENTS OF KRISHNA RIVER DELTA, EAST COAST OF INDIA

The present study is an attempt to understand sediment charterstics and distribution of organic carbon and calcium carbonate in four cores viz. Turumella, Inturu, Ponnapalli and Nizampatnam of the Krishna River delta. Grain size data indicates that the sediments in the study area are dominantly composed of sandy clay and silty clay. The average organic carbon in Turumella (1.69%), Ponnapalli (1.55%), Nizmpatnam (1.18%) and Inturu (1.14%). Organic matter controlled by vegetative roots and quick sedimentation and CaCO3 persentage related to institu authegenic shell fragments. Semi arid environmental conditions and pedogenic processes for long time exposure of mud flats and flood plains before deposition of other sediments on it. Organic carbon in plants and soil undergo the primary degradation process driven by bacterial and fungal action, which alters their molecular composition before their input into riverine environment. The organic carbon (OC) is often a good index for deciphering depositional environment. It plays a major role in controlling the redox potential of the sediments constituting the source material for petroleum. The first time in the Krishna River delta, where in shallow drilling was carried out upto the 160m depth undisturbed samples have been used for the purpose.

Detection of degraded forests in Guinea, West Africa, based on Sentinel-2 time series by inclusion of moisture-related spectral indices and neighbourhood effect

Unlike deforestation, forest degradation implies a change in forest structure, with no modification in land use; thus, it is subtle and less visible than deforestation. Moreover, forest degradation is a major concern, as the potential for carbon sequestration is reduced. Degradation is related to location, anthropogenic drivers, climate, and forest types, and there is no unique detection methodology to map this phenomenon on a global scale. This study proposes a procedure for detecting degraded forests using Sentinel-2 (S2) multispectral imagery in Guinea, West Africa, and demonstrates that consideration of context improves degraded forest detection. In Guinea, the primary degradation process is selective logging in the massif forest, in addition to forest fragmentation caused by land use change. Monitoring forest degradation using remote sensing methods usually requires significant overhead in terms of photo-interpretation expertise. We proposed an approach to monitoring degradation through a semi-automated classification procedure with minimum photo-interpretation costs. First, the radiometric values of the Sentinel-2 data were explored using a photo-interpreted reference map and ground observations carried out with a local forester. Many of the ground observations found that forests considered as intact in the photo-interpreted reference map were degraded. This suggests photo-interpretation can be affected when investing in a single-date image. Our results showed that radiometric moisture-related indices (canopy water content [CWC], moisture stress index [MSI]), associated with leaf area index (LAI) retrieved from S2 data, were strongly related to the degree of degradation. Second, we improved the mapping of degraded forests through photo-interpretation of S2 data. Third, classification methodologies involving LAI, MSI, and CWC were established, and the results were compared with the improved photo-interpreted map. Two types of classification were compared: standard pixel-based classification and a hybrid method of classification that took contextual information into account by including neighbour pixel values in the algorithm to consider the pixel context, similar to the photo-interpretation methods. The inclusion of neighbour pixels in the semi-automated classification process led to a substantial improvement in the results. When contextual information was included, photo-interpretation of 1.6% of the latest year's data was sufficient to reach an overall accuracy above 85% requiring no use of past reference maps. Our method strongly supports the photo-interpretation procedure for less time-consuming and expensive map production, offering a significant foundation for degraded forest delineation in regions under similar conditions of canopy opening.

Reductive defluorination of Perfluorooctanesulfonic acid (PFOS) by hydrated electrons generated upon UV irradiation of 3-Indole-acetic-acid in 12-Aminolauric-Modified montmorillonite

Per-and poly-fluoroalkyl substances (PFASs) are a class of persistent compounds that are resistant to degradation. Here we developed an effective method of degrading perfluorooctanesulfonate (PFOS) by hydrated electrons (eaq−) that are generated from 3-indole-acetic-acid (IAA) upon UV irradiation. The method takes advantage of spatial proximity of IAA and PFOS by their co-sorption to an organic polymer, 12-aminolauric acid (ALA), which was pre-intercalated into the interlayer space of an expandable clay mineral, montmorillonite. The interlayer spacing of this clay nanocomposite is greatly expanded relative to unmodified montmorillonite. The maximum adsorption capacity of IAA and PFOS is 168 and 1550 mmol/kg, respectively. This process achieved 40–70% defluorination of a 10 ppm PFOS solution at neutral pH in a 325 mL vessel. The presence of bicarbonate and chloride ions, or natural groundwater showed a minimal impact on PFOS degradation. Based on identification of prominent degradation products, a degradation pathway is proposed, where the primary degradation process is breakage of the C-F bonds (with fluorine replaced by hydrogen), with some cleavage of the CC bond. This approach provides an alternative for treating concentrated PFAS solutions under ambient conditions.

The composition difference of macrophyte litter-derived dissolved organic matter by photodegradation and biodegradation: Role of reactive oxygen species on refractory component.

The overgrowth of macrophytes has become serious due to increasing eutrophication in shallow lakes. The primary degradation processes of macrophytes litter, including photodegradation and biodegradation, induce considerable patchiness in the concentration and bioavailability of dissolved organic matter (DOM). In this study we investigated the composition evolution of DOM derived from emergent aquatic plant litter, Phragmites australis, in microbial degradation, photodegradation, and the combination of bio- and photo-degradation. Results revealed that the effects of photo- and biodegradation on the composition difference of macrophyte litter-derived DOM during short- and long-term degradation phase were different. Although large changes in DOM were observed after five days of incubation, the abundance and chemical composition were similar in the three treatments. However, more concentration of DOM was produced by combined photo- and biodegradation at the long-term degradation phase, and the composition of DOM showed less lignin-like formulae, as well as less condensed aromatic and aromatic compounds when compared to sole treatments. More reactive oxygen species (ROS) were found under the combined treatments, thus the contents of refractory components (condensed aromatic- and aromatic compound groups) were reduced. This study provide deeper insight into the fate of DOM and relevant biogeochemical processes in eutrophic lakes.

Chemical, Structural, and Electronic Aspects of Formation and Degradation Behavior on Different Length Scales of Ni-Rich NCM and Li-Rich HE-NCM Cathode Materials in Li-Ion Batteries.

In order to satisfy the energy demands of the electromobility market, both Ni-rich and Li-rich layered oxides of NCM type are receiving much attention as high-energy-density cathode materials for application in Li-ion batteries. However, due to different stability issues, their longevity is limited. During formation and continuous cycling, especially the electronic and crystal structure suffers from various changes, eventually leading to fatigue and mechanical degradation. In recent years, comprehensive battery research has been conducted at Karlsruhe Institute of Technology, mainly aiming at better understanding the primary degradation processes occurring in these layered transition metal oxides. The characteristic process of formation and mechanisms of fatigue are fundamentally characterized and the effect of chemical composition on cell chemistry, electrochemistry, and cycling stability is addressed on different length scales by use of state-of-the-art analytical techniques, ranging from "standard" characterization tools to combinations of advanced in situ and operando methods. Here, the results are presented and discussed within a broader scientific context.

Photocatalytic degradation of metoprolol by TiO2 nanotube arrays and UV-LED: Effects of catalyst properties, operational parameters, commonly present water constituents, and photo-induced reactive species

The aim of this study was to evaluate the use of self-organized TiO2 nanotube arrays (TNAs) as immobilized catalyst and UV-LED as light source (UV-LED/TNAs) for photocatalytic degradation of the β-blocker metoprolol (MTP) from aqueous solution. Firstly we employed electrochemical anodization to synthesize self-organized TNAs, and the effect of anodization potential and annealing temperature was examined. Characterization by SEM demonstrated a linear relation between the diameter of TiO2 nanotubes produced and the anodization potential, while Raman measurement revealed the vital role of annealing on crystallographic composition of the anodic produced TiO2 nanotubes. Regarding their performance in photocatalytic MTP degradation, surface morphology and crystallographic composition of the TNAs were found to impose crucial influence: only TNAs with diameter not smaller than 53nm enabled rapid MTP degradation, and highest MTP degradation was obtained when a mixture of anatase and rutile were present in the TNAs. Secondly, the effect of operational parameters, i.e initial MTP concentration, pH, was investigated. Initial MTP concentration at low level had no detrimental effect on the process performance. Rapid MTP degradation and high total removal were achieved in a wide pH range (3–11). To evaluate the applicability of TNAs for water treatment, experiments were first carried out in the presence of three different commonly present water constituents, i.e bicarbonate ions, phosphate ions, and natural organic matters (NOMs). The results show that bicarbonate and phosphate ions have no inhibitory effect at concentration levels up to 200mg/L, and NOMs exhibit detrimental effect when their concentration exceeds 5mg/L. The total removal MTP degradation reduced from 87.09±0.09% to 62.05±0.08% when tap water samples were applied, demonstrating reasonable efficacy for practical applications. Regarding the degradation mechanism, formic acid and tert-butanol were added as scavenger for photo-generated holes (h+) and hydroxyl radicals (·OH), respectively. The obtained results demonstrate that primary degradation process occurred in liquid phase with participation of hydroxyl radicals in the liquid phase (·OH liquid), while smaller portion of MTP were degraded on the catalysis surface via reaction with h+ and hydroxyl radicals adsorbed on the catalyst surface (·OH surface). Other reactive species, e.g photo generated electrons and superoxide radical anions, did also play a minor role in MTP degradation. The mechanistic aspect was further confirmed by identification of degradation products by LC–MS/MS. The TNAs exhibited good stability after repeated use under varied operation conditions.

Remediating TCE‐contaminated groundwater in low‐permeability media using hydraulic fracturing to emplace zero‐valent iron/organic carbon amendment

AbstractA field pilot test in which hydraulic fracturing was used to emplace granular remediation amendment (a mixture of zero‐valent iron [ZVI] and organic carbon) into fine‐grained sandstone to remediate dissolved trichloroethene (TCE)‐contaminated groundwater was performed at a former intercontinental ballistic missile site in Colorado. Hydraulic fracturing was used to enhance the permeability of the aquifer with concurrent emplacement of amendment that facilitates TCE degradation. Geophysical monitoring and inverse modeling show that the network of amendment‐filled fractures extends throughout the aquifer volume targeted in the pilot test zone. Two years of subsequent groundwater monitoring demonstrate that amendment addition resulted in development of geochemical conditions favorable to both abiotic and biological TCE degradation, that TCE concentrations were substantially reduced (i.e., greater than 90 percent reduction in TCE mass), and that the primary degradation processes are likely abiotic. The pilot‐test data aided in re‐evaluating the conceptual site model and in designing the full‐scale remedy to address a larger portion of the TCE‐contaminated groundwater plume. © 2012 Wiley Periodicals, Inc.

Effect of sample preparation on the thermal degradation of metal-added biomass

The present study investigates the effect of different sample preparation methods on the pyrolysis behaviour of metal-added biomass; Willow samples were compared in the presence of two salts of zinc and lead containing sulphate and nitrate anions which were added to the wood samples with three different techniques as dry-mixing, impregnation and ion-exchange. The effect of acid and water wash as common demineralisation pre-treatments were also analysed to evaluate their roles in the thermal degradation of the biomass. Results from thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and pyrolysis-mass spectrometry (Py-MS) measurements indicated that these pre-treatments change the matrix and the physical–chemical properties of wood. Results suggested that these structural changes increase the thermal stability of cellulose during pyrolysis. Sample preparation was also found to be a crucial factor during pyrolysis; different anions of metal salts changed the weight loss rate curves of wood material, which indicates changes in the primary degradation process of the biomass. Results also showed that dry-mixing, impregnation or ion-exchange influence the thermal behaviour of wood in different ways when a chosen metal salt was and added to the wood material.

Preparation, Preliminary Characterization and Complexation of a Crystalline Redox‐based Chemical Delivery System for Dopamine

The synthesis of a redox-based chemical delivery system for dopamine (DA-CDS) was modified to yield a crystalline final product that had an improved stability profile during storage. Oxidation was the primary degradation process observed in crystalline DA-CDS samples, while hydration was a major degradation process in amorphous samples. Amorphous samples showed significant appearance of the 5,6-water addition product during storage. The crystalline DA-CDS was soluble in aqueous hydroxypropyl-β-cyclodextrin (HP-β-CyD). Lyophilized samples of the drug-HP-β-CyD complex had decreased stability compared to pure crystalline DA-CDS samples, which was attributed to the known hygroscopic properties of HP-β-CyD. In-vivo distribution was examined after intraperitoneal administration of a prototype aqueous formulation containing HP-β-CyD. Results indicate that the drug can reach target sites in the central nervous system after intraperitoneal dosing.

Analytical monitoring of the photo-induced degradation of 3,6-dichloro-2-methoxybenzoic acid in homogeneous and heterogeneous systems

The photo-induced degradation of 3,6-dichloro-2-methoxybenzoic acid present at the trace level in aqueous solutions has been studied by comparing the UV photolytic treatment with the processes operating in the presence of either irradiated TiO2 aqueous suspensions and irradiated hydrogen peroxide. The efficiency of the treatments was evaluated by monitoring the kinetics of the primary degradation process, the chloride release and the DOC evolution. The identification of aromatic intermediates by means of GC-MS and LC-MS analysis evidenced a common degradation path for TiO2- and H2O2-mediated degradation, whereas the photolytic mechanism resulted quite different. The mixed TiO2-t-H2O2−UV treatment was found to exhibit the best performances.

An automated workstation for forced degradation of active pharmaceutical ingredients

This article describes a system capable of performing and analysing multiple degradation experiments on drug substances as part of the process of developing stability indicating separations methods. Qualitative data are generated on the significant primary degradation processes of the drug of interest. Ten samples are refluxed with stirring in a single heating block. The robot arm is equipped with a sampling device capable of removing aliquots, during the reflux experiment, and transferring them to an HPLC injector. On-line analysis using fast HPLC with diode array and electrospray mass spectrometric detection allows identification of degradants. The methods described offer a significant time savings compared to the previously applied manual approach, and also provide data from multiple time points for each reaction. This increased knowledge about the progress of the reaction aids us in focussing efficiently on the primary degradation processes. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91: 884–892, 2002

Modeling lifetime and degradability of organic compounds in air, soil, and water systems (IUPAC Technical Report)

Abstract Degradability of organic compounds in air, soil, and water is the most important factor for evaluating their environment fate as well as possible adverse effects to humans and the environment. The primary degradation process in the troposphere is the reaction with the hydroxyl radical. For water and soil compartments, the primary degradation process is biodegradation. The objectives of this report are: (i) to review published models and their evaluation studies, (ii) to perform an in-house evaluation of general models for estimating tropospheric degradation and biodegradation of organic compounds, and (iii) to recommend reliable procedures for estimating degradability of organic compounds in the environment. The extensive evaluation procedure has shown that the most accurate method for estimating tropospheric degradation is Atkinson's group contribution method. Although this method has some limitations, it seems to be a method of choice. A viable alternative to Atkinson's method is a direct calculation, performed today almost routinely, of the reaction rate constants with hydroxyl radicals. Recently, a methodology based on reliable semiempirical potential energy surfaces was developed that enables the calculation of reaction rate constants within a factor of 2 of their measured values. A partial least squares (PLS) model and a set of seven biodegradation rules have been found to be the most reliable in estimating complete biodegradation of organic compounds. However, it is recommended to use all four evaluated methods to estimate biodegradation in the environment. If their results agree, such estimates are very reliable.

Studies on hexolic anhydride based polyesters, III. Mechanistic and comparative aspects of the product distributions in the thermal degradation

AbstractTwo systems of unsaturated polyesters based on maleic anhydride, phthalic anhydride, hexolic anhydride (5,6,7,8,9,9‐hexachloro‐1,2,3,4,4a,5,8,8a‐octahydro‐5,8‐methanonaphthalene‐2,3‐dicarboxylic anhydride) and 2‐butene‐1,4‐diol or 2,3‐dichloro‐2‐butene‐1,4‐diol were synthesized. The polyesters were pyrolysed under programmed heating from 40° to 400°C at a rate of 10 K/min. The volatile pyrolysates were separated and identified by combined gas chromatography/mass spectrometry. The formation of anhydrides, diols, hydrocarbons, chloro compounds and polychlorinated cyclopentadiene compounds etc., is explained in the light of single and double β‐scission, acyl‐oxygen and alkyl‐oxygen bond fission and carbon‐carbon bond homolysis mechanisms. It is observed that β‐scission plays a vital role in the primary degradation process of polyesters. The decreasing number of β‐hydrogens in the diol part of the polyester is reflected in the quantity of anhydrides ejected from the polymer backbone. Further it is observed that hexachlorocyclopentadiene and related compounds are ejected from the hexolic anhydride set free during pyrolysis and not from the hexolic moiety incorporated in the polymer backbone. An approximate calculation shows that about 75% of the total amount of maleic anhydride, formed in the pyrolysis of saturated diol based polyesters having fullest number of β‐hydrogens in the diol part, is derived from β‐scission and the rest via alkyl‐oxygen bond fission mechanism. A similar observation is also noted‐indirectly for the formation of hexolic anhydride.

The role of β-hydrogen in the degradation of polyesters

Linear polyesters based on phthalic anhydride and any one of the following C 4 diols, 1,4-butanediol, 2-butene-1,4-diol or 2-butyne-1,4-diol were synthesised by the melt condensation technique and characterised by infrared spectroscopy. The thermal degradation of the polyesters was carried out under high vacuum and the products separated and identified using gas chromatography—mass spectrometry. The results revealed that a decrease in the β-hydrogen content of the diol component leads to a decrease in the amount of phthalic anhydride formed during degradation. It was also observed that the amount of diol released during the degradation of the polyesters increases with the decrease in the β-hydrogen content of the diol component. The results emphasise the fact that β-scission is one of the primary degradation processes in polyesters when β-hydrogen atoms are available in the diol component.

Radiation-induced Carbonium Ion Reactions and the Chain Nature of Acid Catalyzed Isomerization

Piper-chromatographic and radioactive-tracer methods showed that gamma irradiation of oxygenated D-mannose solutions gives D-mannuronic acid, D-mannonic acid, Darabinose. D-erythrose, two-carbon aldehydic fragments. formic acid. and carbon dioxide. Changes in acidity, absorption spectra, and the rate of formation of hydrogen peroxide were measured. Primary and secondary products are distinguished by reference to the yield-dose curves than were obtained from isotope dilution analysis and paper chromatography; there is good agreement between the two methods. Experiments using D/sup -1-14C!mannose indicate directly that the primary degradation processes are (a) oxidation at C(6) and C(1) give mannuronic acid and mannonic acid. respectively: (b) direct scission between C(1) and C(2) io form D-arabinose and formaldehyde; and (c) scission between C(2) and C(3) to give D-erythrose and a two-carbon aldehydic fragment with. simultaneously, direct conversion of the hexose molecule into three two- carbon aldehydic figments. These account for 80% of the initial amount of D- mannose degraded (G 3.5). The results also indicate secondary formation of D- arabinose, D-lyxose, oxalic acid, formic acid. and carbon dioxide. (auth)