scholarly journals Degradation Kinetics and Mechanism of Polychloromethanes Reduction at Co-MoS2/Graphite Felt Electrode

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 929
Author(s):  
Mohammed Dauda ◽  
Muhammad H. Al-Malack ◽  
Chanbasha Basheer ◽  
Mohammad Nahid Siddiqui ◽  
Almaz Jalilov
Keyword(s):  
Current Density ◽  
Degradation Kinetics ◽  
Bond Cleavage ◽  
Influencing Factor ◽  
Order Kinetic ◽  
Mos2 Nanosheets ◽  
Density Peak ◽  
Graphite Felt ◽  
Reduction Current ◽  
Order Kinetic Model

In this study, the electrochemical dechlorination of different polychloromethanes (CCl4, CHCl3, and CH2Cl2) on a Co-MoS2 graphite felt cathode was investigated. The Co-MoS2 electrocatalyst was prepared hydrothermally on a graphite felt support. The prepared catalyst’s characterization revealed the formation of hybridized CoSx and MoS2 nanosheets deposited on the pore structures of graphite. The influencing factor for the electro-dechlorination parameters such as applied current density, pH, and sample concentration on the dechlorination rate was optimized. A significant capacitive reduction current density peak of approximately 1 mA/cm2 was noted for CCl4 at a potential of −0.3 V (vs. AgCl). The dechlorination mechanism was attributed to the stepwise hydrogenolysis mechanism that involves the organochlorides bond cleavage by H* insertion. It was noted that the Co-MoS2 graphite felt electrode exhibited excellent catalytic activity toward the reduction of each of the chlorinated compounds with high selectivity toward the higher-order organochloride. Moreover, the dechlorination rates for each of the compounds were suited to the first-order kinetic model, and the estimated apparent rate constants showed the dechlorination in the following sequence CH2Cl2 (k3 = 9.1 × 10−5 s−1) < CHCl3 (k2 = 1.5 × 10−3 s−1) < CCl4 (k1 = 2.8 × 10−3 s−1).

scholarly journals Thermo-Analytical and Compatibility Study with Mechanistic Explanation of Degradation Kinetics of Ambroxol Hydrochloride Tablets under Non-Isothermal Conditions

Pharmaceutics ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1910
Author(s):  
Dijana Jelić ◽  
Snežana Papović ◽  
Milan Vraneš ◽  
Slobodan Gadžurić ◽  
Silvia Berto ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Active Compound ◽  
Degradation Kinetics ◽  
Practical Interest ◽  
Mechanistic Explanation ◽  
Compatibility Study ◽  
Order Kinetic ◽  
Order Kinetic Model ◽  
Synthetic Derivative ◽  
Ambroxol Hydrochloride

Ambroxol hydrochloride (AMB), used as a broncho secretolytic and an expectorant drug, is a semi-synthetic derivative of vasicine obtained from the Indian shrub Adhatoda vasica. It is a metabolic product of bromhexine. The paper provides comprehensive and detailed research on ambroxol hydrochloride, gives information on thermal stability, the mechanism of AMB degradation, and data of practical interest for optimization of formulation that contains AMB as an active compound. Investigation on pure AMB and in commercial formulation Flavamed® tablet (FT), which contains AMB as an active compound, was performed systematically using thermal and spectroscopic methods, along with a sophisticated and practical statistical approach. AMB proved to be a heat-stable and humidity-sensitive drug. For its successful formulation, special attention should be addressed to excipients since it was found that polyvinyl pyrrolidone and Mg stearate affect the thermal stability of AMB. At the same time, lactose monohydrate contributes to faster degradation of AMB and change in decomposition mechanism. It was found that the n-th order kinetic model mechanistically best describes the decomposition process of pure AMB and in Flavamed® tablets.

scholarly journals Thermal Stability and Degradation Kinetics of Patulin in Highly Acidic Conditions: Impact of Cysteine

Toxins ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 662
Author(s):  
Enjie Diao ◽  
Kun Ma ◽  
Hui Zhang ◽  
Peng Xie ◽  
Shiquan Qian ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Degradation Kinetics ◽  
Correlation Coefficients ◽  
Degradation Process ◽  
Weibull Model ◽  
Degradation Efficiency ◽  
Order Kinetic ◽  
Order Kinetic Model ◽  
Acidic Conditions ◽  
Kinetics Of

The thermal stability and degradation kinetics of patulin (PAT, 10 μmol/L) in pH 3.5 of phosphoric-citric acid buffer solutions in the absence and presence of cysteine (CYS, 30 μmol/L) were investigated at temperatures ranging from 90 to 150 °C. The zero-, first-, and second-order models and the Weibull model were used to fit the degradation process of patulin. Both the first-order kinetic model and Weibull model better described the degradation of patulin in the presence of cysteine while it was complexed to simulate them in the absence of cysteine with various models at different temperatures based on the correlation coefficients (R2 > 0.90). At the same reaction time, cysteine and temperature significantly affected the degradation efficiency of patulin in highly acidic conditions (p < 0.01). The rate constants (kT) for patulin degradation with cysteine (0.0036–0.3200 μg/L·min) were far more than those of treatments without cysteine (0.0012–0.1614 μg/L·min), and the activation energy (Ea = 43.89 kJ/mol) was far less than that of treatment without cysteine (61.74 kJ/mol). Increasing temperature could obviously improve the degradation efficiency of patulin, regardless of the presence of cysteine. Thus, both cysteine and high temperature decreased the stability of patulin in highly acidic conditions and improved its degradation efficiency, which could be applied to guide the detoxification of patulin by cysteine in the juice processing industry.

Anaerobic degradation kinetics of a cholesteryl ester

2003 ◽  
Vol 48 (6) ◽  
pp. 141-147
Author(s):  
S. Gutiérrez ◽  
M. Viñas
Keyword(s):  
Palmitic Acid ◽  
Anaerobic Degradation ◽  
Drop Size ◽  
Degradation Kinetics ◽  
Relative Rate ◽  
Hydrolysis Rate ◽  
Order Kinetic ◽  
Order Kinetic Model ◽  
The Difference ◽  
Kinetics Of

The most important components of wool scouring effluent grease are esters of sterols. Cholesteryl palmitate (CP) is the main ester in this grease. In this paper, the influence of the ester concentration in the anaerobic digestion and the relative rate of the different degradation steps, are studied. The experiment was carried out to measure methane production in the anaerobic degradation of acetate, palmitic acid (PA) and CP. A first-order kinetic model was assumed for hydrolysis and Monod models were assumed for both the methanogenic and acetogenic steps. Maximum hydrolysis rate was found to be around 20 times faster than the maximum methanogenic reaction rate during the experience. The lanolin emulsion drop size effect was also evaluated employing fine and coarse stock lanolin emulsions and no adapted sludge. Concentrations of 13.7 to 4.6 gCOD.l-1 were employed. In a previous study, the effect of palmitic acid emulsion size was found important when similar sludge was tested. When esters are degraded, a significant effect of drop size on the degradation rate was not found. The difference between CP and PA emulsions behavior could be due to the fact that cholesterol produced during the ester degradation has a protective effect on the sludge.

scholarly journals Photocatalytic Degradation of a Basic Dye Using Zinc Oxide Nanocatalyst

2019 ◽  
Vol 81 ◽  
pp. 18-26 ◽  
Author(s):  
Maureen O. Chijioke-Okere ◽  
Nnaemeka John Okorocha ◽  
Basil N. Anukam ◽  
Emeka E. Oguzie
Keyword(s):  
Zinc Oxide ◽  
Malachite Green ◽  
Uv Light ◽  
Degradation Kinetics ◽  
Catalyst Loading ◽  
Order Kinetic ◽  
X Ray Diffraction ◽  
First Order ◽  
Malachite Green Dye ◽  
Order Kinetic Model

The potential of Calcinated and uncalcinated zinc oxide as effective Photocatatlyst for the degradation of malachite green dye, MG from aqueous medium using UV light has been identified. The photocatalysts were characterized using scanning electron microscope, SEM and x-ray diffraction, XRD. The SEM investigations of the calcinated ZnO revealed highly dispersed nanomaterials and the particles were of nanometer size in agreement with the XRD result. The uncalcinated zinc oxide, ZnO revealed some pronounced nanoparticles. The degradation of MG by the photocatalyst was found to be influenced by adsorbent loading and irradiating time. The optimum degradation was obtained at 0.5g catalyst loading of both calcinated and uncalcinated zinc oxide which is 98.48% and 96.31 % respectively at 150 minutes. The degradation kinetics conformed to the pseudo-first-order kinetic model. The present study showed that calcinated and uncalcinated zinc oxide ZnO can be effectively used as efficient photocatalyst for the degradation of Malachite green dyes from aqueous solutions and effluents.

scholarly journals Removal of ciprofloxacin from aqueous solution by electro-activated persulfate oxidation using aluminum electrodes

2019 ◽  
Vol 80 (3) ◽  
pp. 587-596
Author(s):  
Mohammad Malakootian ◽  
Mohammad Ahmadian
Keyword(s):  
Current Density ◽  
Oxidation Process ◽  
Radical Scavenger ◽  
Initial Contact ◽  
Order Kinetic ◽  
Optimal Conditions ◽  
Optimum Conditions ◽  
Persulfate Oxidation ◽  
Order Kinetic Model ◽  
Ft Ir

Abstract The aim of this study was to determine the removal of ciprofloxacin (CIP) by the electro-persulfate (EC-PS) process using aluminum (Al) electrodes. The effects of variables including pH, contact time, PS concentration, initial CIP concentration and current density on the removal efficiency of CIP were studied. In order to determine the mechanisms of the EC-PS process, the radical scavenger tests, as well as energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR) were performed on the sludge. The results showed that the PS process alone had no effect on the CIP removal, and the EC process alone could remove 25% of CIP after 160 min. However, the EC-PS process under the optimum conditions: pH of 7, time of 40 min, current density of 2.75 mA/cm2, CIP concentration of 20 mg/L, and PS concentration of 0.84 mM removed 90% of CIP. The effect of the EC-PS process on the actual hospital wastewater was 81% in optimal conditions. The kinetic study also showed that the second-order kinetic model was the most consistent. The oxidation process during the initial contact was dominant in the EC-PS process and, over time, the EC process was dominant for CIP removal.

scholarly journals THERMAL DEGRADATION KINETICS OF KAEMPFEROL AND QUERCETIN IN THE PRE-FORMULATED OF THE STANDARDIZED EXTRACTS OF POINCIANELLA PYRAMIDALIS (TUL.) L. P. QUEIROZ OBTAINED BY SPRAY DRYER

2017 ◽  
Vol 9 (6) ◽  
pp. 123 ◽  
Author(s):  
Agna HÉlia De Oliveira ◽  
Renata Da Silva Leite ◽  
FabrÍcio Havy Dantas ◽  
Valmir Gomes De Souza ◽  
JosÉ VenÂncio Chaves JÚnior ◽  
...  
Keyword(s):  
Degradation Kinetics ◽  
Processing Parameters ◽  
Thermal Degradation Kinetics ◽  
Response Analysis ◽  
Order Kinetic ◽  
Spray Dryer ◽  
Independent Variables ◽  
Significant Difference ◽  
Order Kinetic Model ◽  
The Stability

Objective: The aim of this work was to evaluate the stability and determine the kinetic parameters of degradation of biomarkers kaempferol and quercetin, present in the pre-formulated of the extract of Poincianella pyramidalis obtained by a spray dryer.Methods: A 23experimental design coupled with RSM was applied to evaluate and optimize the effects of processing parameters on the content of chemical markers in dry extracts by a spray dryer. Stability testing was performed to verify the influence of temperature on the degradation of kaempferol and quercetin present in the pre-formulated. The markers contents were determined by HPLC.Results: Surface response analysis showed the influence of the independent variables on the responses of the concentration kaempferol and quercentin biomarkers on the process. The variables of the inlet air temperature, flow feed rate and the adjuvant ratio presented negative responses with significant difference (p<0.05). According to the data obtained in the stability of the pre-formulated studied zero and second orders kinetics models the for degradation of the kaempferol and only second order kinetic model for the quercetin. It was also evaluated reducing the concentration of both biomarkers studied throughout the study.Conclusion: In the present study, it was observed that all independent variables of the drying process by spray dryer showed the greatest influence on the concentration of the studied markers. Two markers had a different thermal behavior compared to the different excipients studied and there was degradation of both the quercentin biomarker and kaempferol during the study period.

scholarly journals The effect of microwave pre-treatment of rapeseed on the degradation kinetics of lipophilic bioactive compounds of the oil during storage

2018 ◽  
Vol 69 (1) ◽  
pp. 233 ◽  
Author(s):  
A. Rękas ◽  
A. Siger ◽  
M. Wroniak
Keyword(s):  
Antioxidant Capacity ◽  
Degradation Kinetics ◽  
Storage Period ◽  
Zero Order ◽  
Order Kinetic ◽  
Carotenoid Concentration ◽  
Capacity Degradation ◽  
Order Kinetic Model ◽  
Pre Treatment ◽  
Kinetics Of

This study examined the storage stability of tocochromanols and carotenoids in the oils prepared from microwave pre-treated (MV) rapeseeds (2-10 min, 800W) during storage at 20 °C for 12 months. In line with lipophilic antioxidant degradation throughout the storage period, changes in the antioxidant capacity of the oil were monitored. Microwaving significantly affected the concentration of lipophilic antioxidants in the oil. After 10 min of MV pre-treatment the highest content of total tocochromanols (76.64 mg/100g) was achieved, whereas a maximum carotenoid concentration (861.28 μg/100g) was obtained following 6 min seed MV pre-treatment. The degradation kinetics for the tocochromanols and carotenoids followed a zero-order kinetic model. From the kinetic analysis, it was shown that the degradation rate constant (k) of both tocochromanols and carotenoids decreased with longer seed exposure to MV radiation. The kinetics of antioxidant capacity degradation during the storage of oils followed a zero-order reaction. The rate of antioxidant capacity degradation in the control oil was higher (k=9.1 x 10-2 mmol TEAC/l/month) compared with oils prepared from MV pre-treated seeds (k=6.8-8.0 x 10-2 mmol TEAC/l/month).

scholarly journals Application of Silver-Loaded Composite Track-Etched Membranes for Photocatalytic Decomposition of Methylene Blue under Visible Light

Membranes ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 60 ◽  
Author(s):  
Anastassiya A. Mashentseva ◽  
Murat Barsbay ◽  
Nurgulim A. Aimanova ◽  
Maxim V. Zdorovets
Keyword(s):  
Methylene Blue ◽  
Visible Light ◽  
Degradation Kinetics ◽  
Composite Membranes ◽  
Degradation Process ◽  
Decomposition Reaction ◽  
Photocatalytic Decomposition ◽  
Order Kinetic ◽  
Langmuir Hinshelwood Mechanism ◽  
Order Kinetic Model

In this study, the use of composite track-etched membranes (TeMs) based on polyethylene terephthalate (PET) and electrolessly deposited silver microtubes (MTs) for the decomposition of toxic phenothiazine cationic dye, methylene blue (MB), under visible light was investigated. The structure and composition of the composite membranes were elucidated by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction technique. Under visible light irradiation, composite membrane with embedded silver MTs (Ag/PET) displayed high photocatalytic efficiency. The effects of various parameters such as initial dye concentration, temperature, and sample exposure time on the photocatalytic degradation process were studied. The decomposition reaction of MB was found to follow the Langmuir–Hinshelwood mechanism and a pseudo-first-order kinetic model. The degradation kinetics of MB accelerated with increasing temperature and activation energy, Ea, was calculated to be 20.6 kJ/mol. The reusability of the catalyst was also investigated for 11 consecutive runs without any activation and regeneration procedures. The Ag/PET composite performed at high degradation efficiency of over 68% after 11 consecutive uses.

Chitosan-based Magnetic Composites - Efficient Adsorbents for Removal of Pb(II) and Cu(II) from Aqueous Mono and Bicomponent Solutions

2018 ◽  
Vol 69 (9) ◽  
pp. 2323-2330 ◽  
Author(s):  
Daniela C. Culita ◽  
Claudia Maria Simonescu ◽  
Rodica Elena Patescu ◽  
Nicolae Stanica
Keyword(s):  
Aqueous Solutions ◽  
Metal Ions ◽  
Chemical Properties ◽  
Order Kinetic ◽  
Mass Ratio ◽  
Magnetic Adsorbent ◽  
Magnetic Composites ◽  
Initial Ph ◽  
Order Kinetic Model ◽  
Physical And Chemical

A series of three chitosan-based magnetic composites was prepared through a simple coprecipitation method. It was investigated the influence of mass ratio between chitosan and magnetite on the physical and chemical properties of the composites in order to establish the optimum conditions for obtaining a composite with good adsorption capacity for Pb(II) and Cu(II) from mono and bicomponent aqueous solutions. It was found that the microspheres prepared using mass ratio chitosan / magnetite 1.25/1, having a saturation magnetization of 15 emu g--1, are the best to be used as adsorbent for the metal ions. The influence of different parameters such as initial pH values, contact time, initial concentration of metal ions, on the adsorption of Pb(II) and Cu(II) onto the chitosan-based magnetic adsorbent was investigated in details. The adsorption process fits the pseudo-second-order kinetic model in both mono and bicomponent systems, and the maximum adsorption capacities calculated on the basis of the Langmuir model were 79.4 mg g--1 for Pb(II) and 48.5 mg g--1 for Cu(II) in monocomponent systems, while in bicomponent systems were 88.3 and 49.5 mg g--1, respectively. The results revealed that the as prepared chitosan-based magnetic adsorbent can be an effective and promising adsorbent for Pb(II) and Cu(II) from mono and bicomponent aqueous solutions.

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