scholarly journals Photocatalytic Degradation of a Water Soluble Herbicide by Pure and Noble Metal DepositedTiO2Nanocrystalline Films

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
Katerina Pelentridou ◽  
Elias Stathatos ◽  
Helen Karasali ◽  
Dionysios D. Dionysiou ◽  
Panagiotis Lianos
Keyword(s):  
Photocatalytic Degradation ◽  
Noble Metals ◽  
Ph Value ◽  
Water Soluble ◽  
Alkaline Media ◽  
Nanocrystalline Films ◽  
First Order Kinetics ◽  
Photodegradation Rate ◽  
Valence States ◽  
Initial Ph

We present the photocatalytic degradation of a water soluble sulfonylurea herbicide: azimsulfuron in the presence of titania nanocrystalline films. Efficient photodegradation of herbicide was achieved by using low-intensity black light tubes emitting in the Near-UV. The degradation of the herbicide follows first-order kinetics according to the Langmuir-Hinshelwood model. Intermediate products were identified by the LC-MS-MS technique during photocatalytic degradation. In order to increase photodegradation rate of the herbicide, we examined the effect of titania modification by depositing noble metals at various quantities and valence states. The presence of platinum at neutral valence state and optimum concentration induced higher photodegradation rates while silver-modified titania exhibited similar photocatalytic rates with those obtained with pure nanocrystallineTiO2films. Finally, the effect of initial pH value was also examined. Acidic or alkaline media were unfavorable for azimsulfuron photodegradation.

scholarly journals Photocatalytic Degradation of a Systemic Herbicide: Picloram from Aqueous Solution Using Titanium Oxide (TiO2) under Sunlight

2020 ◽  
Vol 4 (4) ◽  
pp. 58
Author(s):  
Md. Rakibul Islam ◽  
Jahida Binte Islam ◽  
Mai Furukawa ◽  
Ikki Tateishi ◽  
Hideyuki Katsumata ◽  
...  
Keyword(s):  
Photocatalytic Degradation ◽  
Titanium Oxide ◽  
Irradiation Time ◽  
Degradation Mechanism ◽  
Chloride Ion ◽  
Reaction Rate Constant ◽  
Ammonium Ion ◽  
Light Reaction ◽  
First Order Kinetics ◽  
Initial Ph

The photocatalytic degradation of picloram (4-amino-3,5,6-trichloro-2-pyridincarboxylic acid), which is one of popular acidic herbicide, was investigated with the existence of titanium oxide (TiO2) under sunlight. The total photocatalytic degradation of 20 ppm of picloram was occurred within 30 min irradiation with TiO2, while a negligible degradation was found without TiO2 under sunlight. The influence of various parameters, like TiO2 dosage, solution initial pH, intensity of light, reaction temperature and irradiation time, was found during the photocatalytic degradation of picloram. The mineralization of picloram was proved by the deterioration of total organic carbon (TOC) of the photocatalytic process. The pseudo–first order kinetics of photocatalytic degradation was obtained according to the Langmuir–Hinshelwood model, and the reaction rate constant was 17.6 × 10−2 min−1. Chloride ion, ammonium ion, nitrate ion and CO2 were erected as the final products after completing the photocatalytic degradation of picloram. The intermediate products could not be determined by the GC–MS during the degradation of picloram. Therefore, the degradation mechanism of the picloram was proposed based on the frontier electron density and the point charge at each atom of the picloram molecule. The photocatalytic degradation method, using sunlight, may develop into as a pragmatic technique to purify picloram contaminated wastewater.

Side reactions of 4-acetamido-TEMPO as the catalyst in cellulose oxidation systems

Holzforschung ◽  
2010 ◽  
Vol 64 (5) ◽  
Author(s):  
Ilabahen Patel ◽  
Martina Opietnik ◽  
Stefan Böhmdorfer ◽  
Manuel Becker ◽  
Antje Potthast ◽  
...  
Keyword(s):  
Ph Value ◽  
Cellulose Degradation ◽  
Water Soluble ◽  
Alkaline Media ◽  
Similar Process ◽  
Side Reactions ◽  
Cellulose Oxidation ◽  
Lower Reactivity ◽  
Acidic Conditions ◽  
Neutral Conditions

Abstract TEMPO/hypochlorite oxidation of cellulosics are frequently used to obtain water-soluble polyglucuronates or nano-disperse materials. The reaction under neutral conditions offers a big advantage over hitherto applied alkaline systems as base-induce β-elimination reactions causing severe cellulose degradation are suppressed. Although 4-acetamido-TEMPO seems to offer high initial activities in cellulose oxidation, the TEMPO derivative is irreversibly converted into species with much lower reactivity. The degradation pathways and the chemical structure of the 4-acetamido-TEMPO-derived (by)products have been clarified. Degradation is strongly dependent on the pH value of the reaction mixture. In acidic conditions (pH<5), 4-oxo-TEMPO is formed by an oxidative deamination process, the 4-oxo-derivative still being capable of performing cellulose oxidation. In alkaline media, a similar process proceeds, but is immediately followed by a Favorskij rearrangement to a pyrrolidine-3-carboxylic acid (PROXYL) derivative. In both cases, the released acetamido moiety is slowly converted into methylamine by a decarboxylative rearrangement (Hofmann degradation). The results suggest that the instability and the chemical fate of 4-acetamido-TEMPO needs to be considered when cellulose oxidations and their kinetics are addressed: the recyclability of the 4-acetamido-TEMPO catalyst is rather limited.

The Flocculation of Dilute Latex by Zinc Sulfate

1954 ◽  
Vol 27 (2) ◽  
pp. 481-493
Author(s):  
Pierre Thirion
Keyword(s):  
Ph Value ◽  
Systematic Investigation ◽  
Point Of View ◽  
Water Soluble ◽  
Zinc Salt ◽  
Two Samples ◽  
Initial Ph ◽  
The Stability ◽  
Necessary And Sufficient ◽  
Salt Index

Abstract Within a particular range of temperatures and a particular concentration of rubber, the flocculation of diluted latex by a water-soluble zinc salt is characterized by a critical amount of zinc, termed the salt index, which is necessary and sufficient to destroy abruptly the colloidal equilibrium of the dispersion. In the course of an investigation of a preliminary nature, measurements were made of the changes of the salt index as a function of the concentration and of the initial pH value of different field latexes and of two samples of latex preserved with ammonia. The influence of centrifugation and of buffering agents was likewise investigated. On a theoretical basis, the phenomenon appears to be governed to a major degree by chemical reactions of the zinc with certain substances which are either in solution in the serum or are adsorbed on the rubber particles. From the practical point of view, a systematic investigation is underway to determine whether the salt index as thus defined can be accepted as a new test of the stability of Fresh latex and preserved latex.

scholarly journals Simultaneous synthesis-immobilization of nano ZnO on perlite for photocatalytic degradation of an azo dye in semi batch packed bed photoreactor

2012 ◽  
Vol 14 (4) ◽  
pp. 69-76 ◽  
Author(s):  
Ali Khani ◽  
Mahmoud Reza Sohrabi
Keyword(s):  
Photocatalytic Degradation ◽  
Packed Bed ◽  
Acid Orange 7 ◽  
Operational Parameters ◽  
Kinetic Rate Constant ◽  
Nano Zno ◽  
First Order Kinetics ◽  
Initial Ph ◽  
On Line ◽  
Simultaneous Synthesis

Abstract A novel, simple and simultaneous synthesis-immobilization of nano ZnO on perlite (nZnO-P) as a photocatalyst for photocatalytic degradation of Acid orange 7 (AO7) in aqueous solution was investigated. The effect of operational parameters such as initial dye concentration, initial pH, flow rate, photocatalyst granule size, temperature and the kinetic of the removal of AO7 in terms of the Langmuir-Hinshelwood model in a designed semi batch packed bed photoreactor connected to an on-line sampling UV-Vis spectrophotometer was studied. The results showed that AO7 removal efficiency increased with nZnO-P using the designed setup and the proposed photocatalyst was more efficient than TiO2 as a standard catalyst. Our results confirmed the pseudo-first-order kinetics model. The values of the adsorption equilibrium constant, KAO7, the kinetic rate constant of surface reaction, kc, and the activation energy (Ea) were found to be 0.57 (mg.l−1)−1, 0.41 mg.l−1.min−1 and 11.44 kJ/mol, respectively.

scholarly journals Enhanced Photocatalytic Degradation and Mineralization of Furfural Using UVC/TiO2/GAC Composite in Aqueous Solution

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Bahram Ghasemi ◽  
Bagher Anvaripour ◽  
Sahand Jorfi ◽  
Neematollah Jaafarzadeh
Keyword(s):  
Photocatalytic Degradation ◽  
Removal Efficiency ◽  
Irradiation Time ◽  
Titanium Dioxide Nanoparticles ◽  
Sol Gel ◽  
Total Pore Volume ◽  
Operational Parameters ◽  
Experimental Conditions ◽  
First Order Kinetics ◽  
Initial Ph

Titanium dioxide nanoparticles were immobilized on granular activated carbon (GAC) as a porous and low-density support for photocatalytic degradation of furfural. The TiO2/GAC composite was synthetized using the simple sol-gel method and fully characterized. The effects of the operational parameters of furfural concentration (200–700 mg/L), initial pH (2–12), TiO2/GAC composite dosage (1–3.5 g/L), and irradiation time (20–120 min) were studied. The synthetized TiO2/GAC composite exhibited a total pore volume of 0.13 cm3/g and specific surface area of 35.91 m2/g. Removal efficiency of up to 95% was observed at initial pH of 10, TiO2/GAC dosage of 2.5 g/L, irradiation time of 80 min, and initial furfural concentration of 500 mg/L. The photocatalyst could be reused at least four consecutive times with a mere 2% decrease in furfural removal efficiency. Mineralization efficiency of 94% was obtained within 80 min. Pseudo-first-order kinetics best fit the photocatalytic degradation of furfural under experimental conditions.

scholarly journals Evaluation of emulsifier stability of biosurfactant produced by Saccharomyces lipolytica CCT-0913

2009 ◽  
Vol 52 (2) ◽  
pp. 285-290 ◽  
Author(s):  
Álvaro Silva Lima ◽  
Ranulfo Monte Alegre
Keyword(s):  
Ph Value ◽  
Water Solution ◽  
Diesel Oil ◽  
Biological Origin ◽  
Water Emulsion ◽  
First Order Kinetics ◽  
Oil In Water ◽  
Initial Ph ◽  
Oil In Water Emulsion ◽  
Surface Active Compounds

Surface-active compounds of biological origin are widely used for many industries (cosmetic, food, petrochemical). The Saccharomyces lipolytica CCT-0913 was able to grow and produce a biosurfactant on 5% (v/v) diesel-oil at pH 5.0 and 32ºC. The cell-free broth emulsified and stabilized the oil-in-water emulsion through a first order kinetics. The results showed that the initial pH value and temperature influenced the emulsifier stability (ES), which was the time when oil was separated. The biosurfactant presented different stabilization properties for vegetable and mineral oil in water solution, despite the highest values of the ES occurring with vegetable oil. The biosurfactant presented smallest ES when compared to commercial surfactants; however, this biosurfactant was not purified.

scholarly journals Effect of oxidants in the photocatalytic degradation of DEET under simulated solar irradiation in aqueous TiO2 suspensions

2014 ◽  
Vol 16 (3) ◽  
pp. 507-515 ◽  
Keyword(s):  
Photocatalytic Degradation ◽  
Alkaline Media ◽  
Solar Irradiation ◽  
Quantum Yields ◽  
Oh Radicals ◽  
Solution Ph ◽  
Photodegradation Rate ◽  
Degradation Rates ◽  
Decreasing Ph ◽  
Simulated Solar Irradiation

<div> <p>Recently, considerable efforts have been devoted to overcome a major limitation in semiconductor photocatalysis, the recombination of photogenerated e<sup>-</sup>-h<sup>+</sup> pairs which leads to reduced quantum yields. Considering the impacts of various parameters on the photocatalytic degradation efficiency, our attention has been mainly focused on the improvement of the TiO<sub>2</sub> mediated photocatalysis for the degradation of a representative emerging micro-pollutant, DEET (N,N-dimethyl-<em>m</em>-toluamide), a widespread insect repellent. The efficiency of TiO<sub>2</sub> photocatalysis to degrade DEET was investigated in the presence of hydrogen peroxide and persulfate ions as oxidants-sacrificial electron acceptors under simulated solar irradiation (SSL). The degradation rates were found to be strongly influenced by the addition of oxidants. Higher degradation rates were observed in the presence of oxidants with the following order: S<sub>2</sub>O<sub>8</sub> <sup>2-</sup> &gt; H<sub>2</sub>O<sub>2. </sub>Τhe effect of solution pH in the range of 3&ndash;10 was investigated and the photodegradation rate was found to increase along with decreasing pH. Scavenging experiments indicated that that sulfate radicals were predominant species at acidic pH while <sup>&bull;</sup>OH radicals were principally responsible for DEET degradation in alkaline media using SSL/TiO<sub>2</sub>/S<sub>2</sub>O<sub>8</sub><sup>2-</sup>, the most efficient process.</p> </div> <p>&nbsp;</p>

Molecularly Imprinted Sensor for Ascorbic Acid Based on Gold Nanoparticles and Multiwalled Carbon Nanotubes

2020 ◽  
Vol 16 (7) ◽  
pp. 905-913
Author(s):  
Youyuan Peng ◽  
Qingshan Miao
Keyword(s):  
Carbon Nanotubes ◽  
Gold Nanoparticles ◽  
Ascorbic Acid ◽  
Multiwalled Carbon Nanotubes ◽  
Ph Value ◽  
Biological Fluids ◽  
Water Soluble ◽  
Multiwalled Carbon ◽  
Experimental Conditions ◽  
Molecularly Imprinted

Background: L-Ascorbic acid (AA) is a kind of water soluble vitamin, which is mainly present in fruits, vegetables and biological fluids. As a low cost antioxidant and effective scavenger of free radicals, AA may help to prevent diseases such as cancer and Parkinson’s disease. Owing to its role in the biological metabolism, AA has also been utilized for the therapy of mental illness, common cold and for improving the immunity. Therefore, it is very necessary and urgent to develop a simple, rapid and selective strategy for the detection of AA in various samples. Methods: The molecularly imprinted poly(o-phenylenediamine) (PoPD) film was prepared for the analysis of L-ascorbic acid (AA) on gold nanoparticles (AuNPs) - multiwalled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE) by electropolymerization of o-phenylenediamine (oPD) and AA. Experimental parameters including pH value of running buffer and scan rates were optimized. Scanning electron microscope (SEM), fourier-transform infrared (FTIR) spectra, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized for the characterization of the imprinted polymer film. Results: Under the selected experimental conditions, the DPV peak currents of AA exhibit two distinct linear responses ranging from 0.01 to 2 μmol L-1 and 2 to 100 μmol L-1 towards the concentrations of AA, and the detection limit was 2 nmol L-1 (S/N=3). Conclusion: The proposed electrochemical sensor possesses excellent selectivity for AA, along with good reproducibility and stability. The results obtained from the analysis of AA in real samples demonstrated the applicability of the proposed sensor to practical analysis.

Well-defined polyindole–Au NPs nanobrush as a platform for electrochemical oxidation of ethanol

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Magdalena Warczak ◽  
Marianna Gniadek ◽  
Kamil Hermanowski ◽  
Magdalena Osial
Keyword(s):  
Conducting Polymers ◽  
Hybrid Material ◽  
Noble Metals ◽  
Electrochemical Impedance ◽  
Electrochemical Sensing ◽  
Alkaline Media ◽  
X Ray Diffraction ◽  
Long Term Stability ◽  
Sensing Applications ◽  
Energy Conversion Devices

Abstract Over the recent decades, conducting polymers have received great interest in many fields including microelectronics, energy conversion devices, and biosensing due to their unique properties like electrical conductivity, stability, and simple synthesis. Modification of conducting polymers with noble metals e.g. gold enhances their properties and opens new opportunities to also apply them in other fields like electrocatalysis. Here, we focus on the synthesis of hybrid material based on polyindole (PIN) nanobrush modified with gold nanoparticles and its application towards electrooxidation of ethanol. The paper presents systematic studies from synthesis to electrochemical sensing applications. For the characterization of PIN–Au composites, scanning electron microscopy and X-ray diffraction analyses were used. The electrocatalytic performance of the proposed hybrid material towards alcohol oxidation was studied in alkaline media by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy techniques. The results show that PIN–Au hybrid can be employed as an effective and sensitive platform for the detection of alcohols, which makes it a promising material in electrocatalysis or sensors. Moreover, the proposed composite exhibits electrocatalytic activity towards ethanol oxidation, which combined with its good long-term stability opens the opportunity for its application in fuel cells.

scholarly journals Effects of Sugar Cane Molasses Addition on the Fermentation Quality, Microbial Community, and Tastes of Alfalfa Silage

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 355
Author(s):  
Runbo Luo ◽  
Yangdong Zhang ◽  
Fengen Wang ◽  
Kaizhen Liu ◽  
Guoxin Huang ◽  
...  
Keyword(s):  
Sugar Cane ◽  
Ph Value ◽  
Electronic Tongue ◽  
Water Soluble ◽  
Soluble Carbohydrates ◽  
Cane Molasses ◽  
Fermentation Quality ◽  
Alfalfa Silage ◽  
Additive Control

The objective was to study the effects of sugar cane molasses addition on the fermentation quality and tastes of alfalfa silage. Fresh alfalfa was ensiled with no additive (Control), 1% molasses (M1), 2% molasses (M2), and 3% molasses (M3) for 206 days. The chemical composition and fermentation characteristics of the alfalfa silages were determined, the microbial communities were described by 16S rRNA sequencing, and the tastes were evaluated using an electronic tongue sensing system. With the amount of added molasses (M), most nutrition (dry matter and crude protein) was preserved and water-soluble carbohydrates (WSC) were sufficiently used to promote the fermentation, resulting in a pH reduction from 5.16 to 4.48. The lactic acid (LA) content and LA/acetic acid (AA) significantly increased, indicating that the fermentation had turned to homofermentation. After ensiling, Enterococcus and Lactobacillus were the dominant genus in all treatments and the undesirable microbes were inhibited, resulting in lower propionic acid (PA), butyric acid (BA), and NH3-N production. In addition, bitterness, astringency, and sourness reflected tastes of alfalfa silage, while umami and sourness changed with the amount of added molasses. Therefore, molasses additive had improved the fermentation quality and tastes of alfalfa silage, and the M3 group obtained the ideal pH value (below 4.5) and the best condition for long-term preservation.

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