Effects of pH, Temperature and Various Anions on Thiourea Disappearance in Aqueous Media with Titanium Dioxide Under UV-Irradiation. Photomineralization Kinetics

2001 ◽  
Vol 66 (4) ◽  
pp. 676-684 ◽  
Author(s):  
Abdelghani Boussaoud ◽  
Gerard Duc ◽  
Jean Pierre Meille ◽  
Michelle Petit-Ramel
Keyword(s):  
Titanium Dioxide ◽  
Uv Irradiation ◽  
Initial Rate ◽  
Aqueous Media ◽  
Inorganic Anions ◽  
Disappearance Rate ◽  
Initial Concentration ◽  
Effects Of Ph ◽  
Nitrite Nitrate ◽  
Kinetics Of

Disappearance of thiourea in aqueous suspensions of TiO2 or ZnO occurs under near-UV irradiation. The effects of some parameters such as initial concentration of thiourea, temperature, pH and common inorganic anions were examined. The results indicate that the process follows the Langmuir-Hinshelwood type kinetics. In the presence of anions such as nitrates, chlorides and sulfates, the initial disappearance rate of thiourea at pH 6 drops. It is found that the initial rate of thiourea disappearance increases when temperatue of reaction mixture increases. Finally, kinetics of thiourea photomineralization to nitrite, nitrate, sulfite and sulfate are established.

KINETIC FORMULATION OF THE DENITRIFICATION PROCESS IN SOIL

1979 ◽  
Vol 59 (3) ◽  
pp. 249-257 ◽  
Author(s):  
C. M. CHO ◽  
J. G. MILLS
Keyword(s):  
Enzyme Kinetics ◽  
Maximum Concentration ◽  
Initial Rate ◽  
Zero Order ◽  
Gas Mixture ◽  
Disappearance Rate ◽  
High Accumulation ◽  
Kinetic Formulation ◽  
Initial Concentration ◽  
Denitrification Process

Kinetic formulation of denitrification process in soil was developed based on a model of competitive Michaelis-Menten type enzyme kinetics. Several values of parameters were chosen to plot the concentrations of NO−3, NO−2, N2O-N and N2-N at various times of incubation under different initial concentrations of NO−3. According to the model the disappearance rate of NO−3 was found to be independent of initial concentration of NO−3 and was nearly constant, similar to zero order rate of disappearance. The initial rate of NO−2 formation was independent of the NO−3 concentration. However, the maximum concentration of NO−2 and the time at which the maximum was found were found to be dependent upon the NO−3 concentration. When there was very little accumulation of NO−2 in the system, the initial rate of N2O formation was found to be independent of NO−3 concentration. However, if there was high accumulation of NO−2, the initial rate of N2O formation became inversely related to NO−3 concentration. The initiation of N2 formation was generally slower as the concentration of NO−3 increased. The composition of gas mixture, N2O and N2, was found to vary depending upon the initial NO−3 concentration and with the time of incubation. The formulation presented herein describes the features of denitrification experimentally observed fairly well.

scholarly journals Penggunaan Karbon Aktif Cangkang Pala - TiO2 Untuk Fotodegradasi Zat Warna Metanil Yellow

Jurnal MIPA ◽  
2014 ◽  
Vol 3 (2) ◽  
pp. 139
Author(s):  
Grace Aprianne Bellatrix Patiung ◽  
Audy D. Wuntu ◽  
Meiske S. Sangi
Keyword(s):  
Titanium Dioxide ◽  
Activated Carbon ◽  
Uv Irradiation ◽  
Irradiation Time ◽  
Weight Ratio ◽  
Initial Concentration ◽  
Metanil Yellow

Telah dilakukan penelitian untuk mengetahui pengaruh perbandingan berat karbon aktif cangkang pala (KA) : titanium dioksida (TiO2), konsentrasi awal metanil yellow, dan lama penyinaran UV pada jumlah metanil yellow yang terdegradasi menggunakan KA-TiO2. KA dibuat melalui aktivasi arang cangkang pala menggunakan NaCl pada 700 oC. Pembuatan fotokatalis KA-TiO2 dengan perbandingan berat 0,1:9,9 (KA 1%) dan 0,5:9,5 (KA 5%) dilakukan dengan cara sonifikasi. Interaksi KA-TiO2 dengan metanil yellow dilakukan pada konsentrasi awal 2, 4, 6, 8, 10, 20, 30, 40, dan 50 ppm selama 3 jam. Eksperimen pengaruh lama penyinaran dilakukan pada variasi 1, 2, 3, 4, 5, 18, dan 20 jam. Hasil penelitian menunjukkan bahwa makin tinggi konsentrasi awal dan makin lama penyinaran, makin banyak metanil yellow terdegradasi. Fotokatalis dengan perbandingan berat KA:TiO2 0,1:9,9 mendegradasi metanil yellow lebih banyak dengan persen degradasi maksimum 66% pada konsentrasi awal 6 ppm.A research had been done to determine the effect of weight ratio of nutmeg shell activated carbon (KA) : titanium dioxide TiO2, initial concentration of metanil yellow, and UV irradiation time on the quantity of metanil yellow degraded using KA-TiO2. KA was prepared by activating nutmeg shell charcoal using NaCl at 700 oC. KA-TiO2 having weight ratio of 0.1:9,.9 (KA 1%) and 0.5:9.5 (KA 5%) were prepared by sonification. Interaction of KA-TiO2 with metanil yellow was performed at initial concentration of 2, 4, 6, 8, 10, 20, 30, 40, and 50 ppm for 3 hours. The experiment of UV irradiation time was performed at 1, 2, 3, 4, 5, 18, and 20 hours. The results showed that the higher the initial concentration of metanil yellow and that the longer the irradion time, the higher the amount of metanil yellow degraded. KA:TiO2 having weight ratio of 0.1:9.9 degraded more metanil yellow than that of 0.5:9.5 with maximum degradation of 66% at initial concentration of 6-10 ppm.

Photocatalytic degradation of MC-LR in water by the UV/TiO2/H2O2 process

2015 ◽  
Vol 16 (1) ◽  
pp. 34-43 ◽  
Author(s):  
Wei-ying Li ◽  
Yao Liu ◽  
Xiu-li Sun ◽  
Feng Wang ◽  
Lin Qian ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Titanium Dioxide ◽  
Free Radicals ◽  
Synergistic Effect ◽  
Photocatalytic Degradation ◽  
Uv Irradiation ◽  
Removal Rate ◽  
Optimum Conditions ◽  
Initial Concentration ◽  
High Production

The ultraviolet (UV)/titanium dioxide (TiO2)/hydrogen peroxide (H2O2) process (UTHP) has been proven to be effective in removing organics because of its high production of free radicals. In this study, UTHP was further investigated for the photocatalytic degradation of microcystin-LR (MC-LR). Results showed that three mechanisms could realize MC-LR photocatalytic degradation using TiO2. H2O2 could effectively inhibit recombination and considerably improve the production of radicals and superoxides. From a correlation of the removal rate with the isomerization and decomposition of MC-LR under UV irradiation it was inferred that isomerization was crucial for MC-LR degradation during photocatalysis given the vulnerability of the exposed conjugated double bonds. The photocatalysis of MC-LR was apparently dependent on pH and MC-LR initial concentration. Under the optimum conditions of pH 3.5, 0.05 g/L TiO2, and 0.05 mmol/L H2O2, 100% MC-LR (308 μg/L) could be removed within 60 min. This process was accompanied by a synergistic effect during the initial 10 min.

Effect of pH and inhibitors on beta-amyloid fibril assembly

1996 ◽  
Vol 54 ◽  
pp. 752-753
Author(s):  
Beverly E. Maleeff ◽  
Timothy K. Hart ◽  
Stephen J. Wood ◽  
Ronald Wetzel
Keyword(s):  
Amyloid Fibril ◽  
Peptide Fragment ◽  
Hydrophobic Peptides ◽  
Amyloid Fibril Formation ◽  
Effects Of Ph ◽  
Severity Of The Disease ◽  
Kinetics Of ◽  
The Brain

Alzheimer's disease is characterized post-mortem in part by abnormal extracellular neuritic plaques found in brain tissue. There appears to be a correlation between the severity of Alzheimer's dementia in vivo and the number of plaques found in particular areas of the brain. These plaques are known to be the deposition sites of fibrils of the protein β-amyloid. It is thought that if the assembly of these plaques could be inhibited, the severity of the disease would be decreased. The peptide fragment Aβ, a precursor of the p-amyloid protein, has a 40 amino acid sequence, and has been shown to be toxic to neuronal cells in culture after an aging process of several days. This toxicity corresponds to the kinetics of in vitro amyloid fibril formation. In this study, we report the biochemical and ultrastructural effects of pH and the inhibitory agent hexadecyl-N-methylpiperidinium (HMP) bromide, one of a class of ionic micellar detergents known to be capable of solubilizing hydrophobic peptides, on the in vitro assembly of the peptide fragment Aβ.

Carbon tetrachloride biodegradation in a fixed-biofilm reactor and its kinetic study

1998 ◽  
Vol 38 (8-9) ◽  
pp. 155-162 ◽  
Author(s):  
G. Jin ◽  
A. J. Englande
Keyword(s):  
Carbon Tetrachloride ◽  
Continuous Flow ◽  
Model Comparison ◽  
Biofilm Reactor ◽  
Pseudomonas Cepacia ◽  
Initial Concentration ◽  
Biphasic Model ◽  
Providencia Stuartii ◽  
Kinetics Of ◽  
Fixed Biofilm

Kinetics of Carbon Tetrachloride biodegradation are evaluated in a continuous-flow fixed-biofilm reactor with controlled initial redox potential. The column was seeded with a mixed culture of indigenous microorganisms Pseudomonas cepacia and Providencia stuartii. The fixed biofilm reactor exhibited 98%–99.9% biodegradation of CT introduced into the reactor at an initial concentration of about 200 μg/l for retention times of 1 to 4 days respectively. Four models were employed to evaluate the kinetics of CT biodegradation. These included: Eckenfelder (1989), Arvin (1991), Bouwer and McCarty (1985) and a biphasic model. Comparison of calculated results with observed results between these models agreed very closely to each other (0.968 < R2 < 0.999). Predicted performance was best described by the model of Bouwer and McCarty (1985). However, the biphasic and Eckenfelder models provided excellent correlations and were much simpler to apply. The biphasic model yielded very good correlations of the data for all detention times evaluated; whereas, the Eckenfelder model effected comparable results only at the longer retention times studied.

The mechanism of the anionic coordination polymerization of isoprene

1980 ◽  
Vol 45 (9) ◽  
pp. 2391-2399 ◽  
Author(s):  
Miroslav Kašpar ◽  
Jiří Trekoval
Keyword(s):  
Chromatographic Method ◽  
Initial Period ◽  
Reaction Scheme ◽  
Polymerization Kinetics ◽  
Coordination Polymerization ◽  
Initial Concentration ◽  
The Cross ◽  
Gas Chromatographic Method ◽  
Kinetics Of

The polymerization kinetics of isoprene (2-methyl-1,3-butadiene) in benzene with butyllithium as the initiator was investigated by the gas chromatographic method. After completion of the initial period of the reaction, its order with respect to the initial concentration of initiator is negative at the concentrations of the latter between 0.01 and 0.25 mol/l, and positive at higher concentrations. A reaction scheme has been suggested with respect to the "cross" association of butyllithium and of the "living" oligoisoprene.

The effect of electrondonors on the polymerization kinetics of isoprene

1980 ◽  
Vol 45 (12) ◽  
pp. 3338-3346
Author(s):  
Miroslav Kašpar ◽  
Jiří Trekoval
Keyword(s):  
Induction Period ◽  
Ethyl Ether ◽  
Reaction Order ◽  
Propagation Rate ◽  
Reaction Scheme ◽  
Polymerization Kinetics ◽  
Polymerization Rate ◽  
Constant Concentration ◽  
Initial Concentration ◽  
Kinetics Of

The effect of small additions of 1-octene, butyl ethyl ether and triethylamine on the polymerization kinetics of isoprene (2-methyl-1,3-butadiene) in benzene initiated with butyllithium was investigated by employing the GLC analysis. The addition of 1-octane was reflected only in a shorter induction period of the reaction; the effect on the propagation rate was insignificant. With the increasing amount of butyl ethyl ether, the polymerization rate increases linearly, while the reaction order with respect to the concentration of triethylamine is variable and increases from 0.33 to 0.66 with the increasing concentration of the initiator. For a constant concentration of triethylamine, the reaction order with respect to the initial concentration of the initiator was found to vary considerably, reaching even negative values. A reaction scheme was suggested, taking into account the competition between two different solvates of alkyllithium.

scholarly journals Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Khémesse Kital ◽  
Moumouny Traoré ◽  
Diégane Sarr ◽  
Moussa Mbaye ◽  
Mame Diabou Gaye Seye ◽  
...  
Keyword(s):  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Initial Rate ◽  
Reaction Medium ◽  
Standard Entropy ◽  
Step Size ◽  
Formation Reaction ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Complex Formation Process

Abstract The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

scholarly journals Kinetics of Microcystin-LR Removal in a Real Lake Water by UV/H2O2 Treatment and Analysis of Specific Energy Consumption

Toxins ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 810
Author(s):  
Sabrina Sorlini ◽  
Carlo Collivignarelli ◽  
Marco Carnevale Miino ◽  
Francesca Maria Caccamo ◽  
Maria Cristina Collivignarelli
Keyword(s):  
Energy Consumption ◽  
Specific Energy ◽  
Lake Water ◽  
Harmful Effect ◽  
Specific Energy Consumption ◽  
World Health ◽  
Oh Radicals ◽  
H2o2 Treatment ◽  
Initial Concentration ◽  
Kinetics Of

The hepatotoxin microcystin-LR (MC-LR) represents one of the most toxic cyanotoxins for human health. Considering its harmful effect, the World Health Organization recommended a limit in drinking water (DW) of 1 µg L−1. Due to the ineffectiveness of conventional treatments present in DW treatment plants against MC-LR, advanced oxidation processes (AOPs) are gaining interest due to the high redox potential of the OH• radicals. In this work UV/H2O2 was applied to a real lake water to remove MC-LR. The kinetics of the UV/H2O2 were compared with those of UV and H2O2 showing the following result: UV/H2O2 > UV > H2O2. Within the range of H2O2 tested (0–0.9 mM), the results showed that H2O2 concentration and the removal kinetics followed an increasing quadratic relation. By increasing the initial concentration of H2O2, the consumption of oxidant also increased but, in terms of MC-LR degraded for H2O2 dosed, the removal efficiency decreased. As the initial MC-LR initial concentration increased, the removal kinetics increased up to a limit concentration (80 µg L−1) in which the presence of high amounts of the toxin slowed down the process. Operating with UV fluence lower than 950 mJ cm−2, UV alone minimized the specific energy consumption required. UV/H2O2 (0.3 mM) and UV/H2O2 (0.9 mM) were the most advantageous combination when operating with UV fluence of 950–1400 mJ cm−2 and higher than 1400 mJ cm−2, respectively.

Preparation and Application of Titanate Nanotubes on Methylene Blue Degradation from Aqueous Media

2011 ◽  
Vol 117-119 ◽  
pp. 786-789 ◽  
Author(s):  
Wen Churng Lin ◽  
Wein Duo Yang ◽  
Zen Ja Chung ◽  
Hui Ju Chueng
Keyword(s):  
Methylene Blue ◽  
Surface Area ◽  
Uv Irradiation ◽  
Aqueous Media ◽  
Hydrothermal Process ◽  
Reaction Times ◽  
Titanate Nanotubes ◽  
Methylene Blue Degradation ◽  
Bet Analysis

Titanate nanotubes were synthesized at various hydrothermal temperatures and reaction times by the hydrothermal process and used as photocatalyst. BET analysis was conducted in order to find out the surface area of these as-prepared samples and it was found that the surface area increases with rise in temperature till 130 oC. Synthesized as-prepared titanate nanotubes were applied on methylene blue degradation from aqueous media by UV irradiation. It was observed that dye removes ~99% from the aqueous media at a titanate nanotubes dose of 2 g/L.

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