scholarly journals Effect of partial oxidation by ozonation on the photocatalytic degradation of humic acids

2003 ◽  
Vol 5 (2) ◽  
pp. 75-80 ◽  
Author(s):  
Aslihan Kerc ◽  
Miray Bekbolet ◽  
Ahmet Mete Saatci
Keyword(s):  
Humic Acid ◽  
Photocatalytic Degradation ◽  
Humic Acids ◽  
Partial Oxidation ◽  
Photocatalytic Oxidation ◽  
Natural Waters ◽  
Adsorption Model ◽  
Pseudo First Order Reaction ◽  
Adsorption Characteristics ◽  
Degradation Rates

In this study humic acids, which are known to be a heterogeneous group of organic macromolecules found in natural waters, were oxidized using ozonation and photocatalysis in a sequential system. Ozonation was employed for achieving partial oxidation of humic acids prior to photocatalytic oxidation. Degradation of humic acid was explained by using pseudo first order reaction rate model based on UV-vis measurements. An improvement was achieved in the photocatalytic degradation rates with respect to the degree of pre-oxidation by ozonation. Due to the surface oriented nature of photocatalysis, adsorption characteristics of partially oxidized humic acid samples onTiO2photocatalyst were evaluated by the application of the Freundlich adsorption model. The photocatalytic degradation rates did not correlate well with the dark adsorption characteristics of the pre-ozonated as well as untreated humic acid samples.

Photocatalytic oxidation and subsequent adsorption characteristics of humic acids

1996 ◽  
Vol 34 (9) ◽  
pp. 65-72 ◽  
Author(s):  
Miray Bekbölet ◽  
Ferhan Çeçen ◽  
Gülhan Özkösemen
Keyword(s):  
Activated Carbon ◽  
Humic Acid ◽  
Humic Acids ◽  
Photocatalytic Oxidation ◽  
Irradiation Time ◽  
Batch Reactor ◽  
Freundlich Isotherm ◽  
Oxidation Products ◽  
Adsorption Characteristics ◽  
Significant Change

Effect of TiO2 photocatalyzed oxidation on the degradation and decolorization of humic acids was studied. The photocatalytic oxidation products were further investigated in terms of adsorptivity on activated carbon. With photocatalytic oxidation in a lab-scale batch reactor significant decolorization and a decrease in UV280 and UV254 took place. Simultaneously there was a decrease in TOC and COD. Parallel to this an evolution of BOD5 was observed. Thus the BOD5/COD ratio increased with irradiation time and more biodegradable substances have been formed. A significant change in the structure of compounds in humic acid took place only after 3-4 hours of irradiation as determined by the decrease in COD/TOC ratio. Generally there was a slight decrease of adsorptivity after irradiation as concluded from the comparison of Freundlich isotherm constants for raw and irradiated humic acid. This decrease increased as the irradiation time increased. But for irradiation times to be used in practice in photocatalytic oxidation no significant change in adsorption is expected.

Effects of oxidative treatment techniques on molecular size distribution of humic acids

2004 ◽  
Vol 49 (4) ◽  
pp. 7-12 ◽  
Author(s):  
A. Kerc ◽  
M. Bekbolet ◽  
A.M. Saatci
Keyword(s):  
Humic Acid ◽  
Size Distribution ◽  
Humic Acids ◽  
Photocatalytic Oxidation ◽  
Irradiation Time ◽  
Molecular Size ◽  
Treatment Techniques ◽  
Degradation Rates ◽  
Distribution Ranges ◽  
Molecular Size Distribution

In this study ultrafiltration has been used for the fractionation of humic acid samples. Humic acids were treated in a sequential oxidation system in which ozonation was followed by photocatalytic oxidation using TiO2. Evaluation of the spectroscopic characteristics of the oxidized and fractionated humic acid samples have shown that molecular size distribution ranges shift to lower molecular sizes depending on the oxidation stages. Applied ozone dosage and irradiation time during the photocatalysis stage are the factors affecting the molecular size distribution in the treated humic acid samples. Formation of lower molecular weight compounds during the ozonation stage resulted in increased degradation rates during the photocatalysis stage.

Photocatalytic degradation of azo dye in TiO2 suspended solution

2001 ◽  
Vol 43 (2) ◽  
pp. 313-320 ◽  
Author(s):  
C.-H. Hung ◽  
P.-C. Chiang ◽  
C. Yuan ◽  
C.-Y. Chou
Keyword(s):  
Reaction Time ◽  
Light Intensity ◽  
Photocatalytic Degradation ◽  
Azo Dye ◽  
Batch Reactor ◽  
Reaction Rates ◽  
Pseudo First Order Reaction ◽  
Degradation Rates ◽  
Orange G ◽  
Degradation Of Azo Dye

The photocatalysis of azo dye, Orange G, by P-25 anatase TiO2 was investigated in this research. The experiments were conducted in a batch reactor with TiO2 powder suspension. Four near-UV lamps were used as the light source. The experimental variables included solution pH level, amount of TiO2, illumination light intensity, and reaction time. A pseudo-first order reaction kinetic was proposed to simulate the photocatalytic degradation of Orange G in the batch reactor. More than 80% of 10 mg/L Orange G decomposition in 60-minute reaction time was observed in this study and fast decomposition of Orange G only occurred in the presence of both TiO2 and suitable light energy. Faster degradation of Orange G was achieved under acid conditions. The degradation rates of Orange G at pH = 3.0 were about two times faster than those at pH = 7.0. Faster degradation of azo dye was observed for greater irradiated light intensity and more TiO present during the reaction. The reaction rates were proportional to TiO2concentration and light intensity with the power order of 0.726 and 0.734, respectively.

Photocatalytic degradation of parathion in aqueous TiO2 dispersion: the effect of hydrogen peroxide and light intensity

1998 ◽  
Vol 37 (8) ◽  
pp. 187-194 ◽  
Author(s):  
Tsu-feng Chen ◽  
Ruey-an Doong ◽  
Wen-gang Lei
Keyword(s):  
Hydrogen Peroxide ◽  
Light Intensity ◽  
Photocatalytic Degradation ◽  
Photocatalytic Oxidation ◽  
Pseudo First Order Reaction ◽  
Direct Photolysis ◽  
First Order ◽  
The Relationship ◽  
Effect Of Light ◽  
H2o2 System

The photodegradation of parathion in the direct photolysis, UV/TiO2, UV/H2O2 and UV/TiO2/H2O2 systems was investigated at 25°C. The effect of light intensity was also examined to clarify the relationship between the photo flux and decomposition rate of parathion. Results of the study demonstrated that no obvious degradation of parathion in dark reaction occurred within 24 hours. However, the addition of TiO2 and/or H2O2 promotes the degradation efficiency of parathion. Adding H2O2 was more effective in the photocatalytic oxidation of parathion than TiO2. Also, hydrogen peroxide was found as an intermediate with the maximum concentration of 55 μM in UV/TiO2 system during the photodegradation of parathion. A higher intensity of lamp could increase the degradation rate of parathion. However, the quantum efficiency for degradation of parathion decreased from 0.053 to 0.006 when light intensity increased from 100 W to 450W. Photodecomposition followed a pseudo-first-order reaction. The rate constants of parathion ranged from 0.003 min−1 for direct photolysis to 0.023 min−1 for UV/TiO2/H2O2 system. This study indicated that photocatalytic degradation is a highly promising technology for detoxifying parathion.

scholarly journals Photocatalytic degradation of natural organic matter: Kinetic considerations and light intensity dependence

2004 ◽  
Vol 6 (2) ◽  
pp. 73-80 ◽  
Author(s):  
Ceyda Senem Uyguner ◽  
Miray Bekbolet
Keyword(s):  
Humic Acid ◽  
Light Intensity ◽  
Photocatalytic Degradation ◽  
Rate Constants ◽  
Reaction Rates ◽  
Order Reaction ◽  
First Order Reaction ◽  
Pseudo First Order Reaction ◽  
First Order ◽  
Pseudo First Order

The current study was conducted to investigate the photocatalytic degradation kinetics of humic acid at different light intensities using commercialTiO2powders. The pseudo first order kinetic model and Langmuir-Hinshelwood (L-H) rate equation in modified forms were used to compare the photocatalytic activities ofTiO2materials as a function of light intensity. Under constant irradiation conditions, the pseudo first order reaction rates as well as L-H rates were found to be decreasing in the following trend; Degussa P-25, Millennium PC-500 and Millennium PC-100. The pseudo first order rate constants showed the same decreasing trend as the pseudo first order reaction rates while L-H rate constants exhibited a light intensity related change in the ordering of the photocatalysts. At the lowest light intensity, L-H rate constants decreased as follows: Millennium PC-500>Millennium PC-100>Degussa P-25. However, increasing the light intensity changed the order to; Millennium PC-100>Millennium PC-500>Degussa P-25 revealing the significance of the L-H adsorption constant. Under constant irradiation conditions, ionic strength dependent changes in the structure of humic acid did not alter degradation efficiency trend of the photocatalyst specimens and they were ordered such as; Degussa P-25>Millennium PC-500>Hombikat UV-100>Millennium PC-100 > Merck. The results presented in this research also confirmed the effectiveness of Degussa P-25 as a photocatalyst for the degradation of humic acid.

TiO2-assisted photocatalytic degradation of humic acids: effect of copper ions

2010 ◽  
Vol 61 (10) ◽  
pp. 2581-2590 ◽  
Author(s):  
C. S. Uyguner ◽  
M. Bekbolet
Keyword(s):  
Humic Acid ◽  
Photocatalytic Degradation ◽  
Humic Acids ◽  
Rate Constants ◽  
Copper Ions ◽  
Degradation Kinetics ◽  
Spectral Characteristics ◽  
Molecular Size ◽  
Spectroscopic Techniques ◽  
Concentration Effects

The present study investigated the removal efficiency of aqueous humic acid solutions by TiO2 photocatalytic degradation in the presence of Cu(II) species. The pseudo-first-order kinetics revealed rate constants as 9.87 × 10−3, 7.19 × 10−3, 3.81 × 10−3 min−1 for Color436, UV254 and TOC, respectively. Comparatively, lower rate constants were attained with respect to photocatalytic degradation of humic acid. Considering the source-dependent diverse chemical and spectral characteristics of NOM, a particular interaction would be expected for humic acid with Cu(II) species (0.1 mg L−1). The presence of copper ions significantly altered the photocatalytic degradation kinetics of humic acids in relation to the concentration effects of humic acid as expressed by spectroscopic parameters and TOC. Batch equilibrium adsorption experiments revealed a distinct Langmuirian-type adsorptive behavior of humic acid onto TiO2 both in terms of UV254 and Color436 and a C-type adsorption isotherm was attained for TOC. KF values displayed an inconsistent effect of Cu(II) species, while adsorption intensity factor 1/n<1 denoted a prevailing favorable type of adsorption for Color436 and UV254. Because of the role of intra- and intermolecular interactions between copper ions and humic molecular size fractions, spectroscopic techniques were also employed for the assessment of the adsorption as well as photocatalytic degradation efficiencies.

scholarly journals Photolytic Degradation of Tetracycline in the Presence of Ca(II) and/or Humic Acid

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2078
Author(s):  
Si Li ◽  
Yiyan He ◽  
Fanguang Kong ◽  
Weiling Sun ◽  
Jiangyong Hu
Keyword(s):  
Humic Acid ◽  
Rate Constants ◽  
Natural Waters ◽  
Light Emitting Diode ◽  
Metal Species ◽  
Pseudo First Order Reaction ◽  
Fluorescence Measurements ◽  
Promotional Effect ◽  
Photolytic Degradation ◽  
Oxygen Groups

Photolytic degradation of tetracycline (TC) was investigated in mono- and binary solute systems of Ca(II) and humic acid (HA) under UVA light emitting diode (UVA-LED) light irradiation. TC photolysis proceeded via pseudo-first-order reaction kinetics. The presence of Ca(II) significantly accelerated the degradation rate constants of TC, with the highest value at 0.0314 ± 0.0019 min−1 when the Ca(II) concentration was 5.0 mM. The promoted degradation was attributed to complexation of TC with Ca(II), which increased the light absorption. Absorbance and fluorescence measurements revealed that the strong complexation between TC and Ca(II) likely occurred via the C11 and C12 oxygen groups in the phenolic-diketone moiety of TC in nearly neutral solutions. The formation of HA-Ca(II) complex was found in the binary solute system of HA and Ca(II). Thus, the promotional effect of Ca(II) on photolysis was diminished by HA addition. The largest reduction of 32.5% in rate constants was observed with the highest Ca(II) concentration. Scavenger studies revealed that TC could undergo direct photolysis and self-sensitization by 1O2. These results suggest that the coexistence of HA and Ca(II) greatly influences the fate of TC in natural waters, which has important implications for understanding the behavior of antibiotics coexisting with other metal species and ligands.

A preliminary investigation on the photocatalytic degradation of a model humic acid

1996 ◽  
Vol 33 (6) ◽  
pp. 189-194 ◽  
Author(s):  
Miray Bekbölet ◽  
Gölhan Özkösemen
Keyword(s):  
Humic Acid ◽  
Photocatalytic Degradation ◽  
Acidic Medium ◽  
Photocatalytic Oxidation ◽  
Degradation Rate ◽  
Oxidation Process ◽  
Preliminary Investigation ◽  
Retardation Factor ◽  
Acid Solutions ◽  
Fluorescent Lamp

The research reported addresses the destructive removal of humic acid in aqueous medium by a photocatalytic oxidation process. Bench scale experiments were carried out using titanium dioxide as the photocatalyst and Black Light Fluorescent Lamp as the irradiation source. Following 1 h irradiation 40 % TOC and 75% Color400 removals were attained for 50 mg/L humic acid solution in the presence of 1.0 mg/mL TiO2. The optimum TiO2 loading was found to be 1.0 mg/mL. Acidic medium accelerated the photocatalytic degradation rate whereas a retardation factor of 0.4 was recorded in alkaline medium. The evaluation of the THMFPs of the photocatalytically treated humic acid solutions revealed that the destructive removal of humic acid was effective enough to keep the THM levels below the maximum contaminant level of 0.10 mg/L (USEPA).

Photocatalytic oxidation technology for humic acid removal using a nano-structured TiO2/Fe2O3 catalyst

2003 ◽  
Vol 47 (1) ◽  
pp. 211-217 ◽  
Author(s):  
S. Qiao ◽  
D.D. Sun ◽  
J.H. Tay ◽  
C. Easton
Keyword(s):  
Humic Acid ◽  
Acid Concentration ◽  
Humic Acids ◽  
Photocatalytic Oxidation ◽  
Ph Value ◽  
Bet Surface Area ◽  
Catalyst Loading ◽  
Temperature Sensitive ◽  
Illumination Time ◽  
Nano Size

A novel TiO2 coated haematite photocatalyst was prepared and used for removal of colored humic acids from wastewater in an UV bubble photocatalytic reactor. XRD analysis confirmed that nano-size anatase crystals of TiO2 were formed after calcination at 480°C. SEM results revealed that nano-size particles of TiO2 were uniformly coated on the surface of Fe2O3 to form a bulk of nano-structured photocatalyst Fe2O3/TiO2. The porous catalyst had a BET surface area of 168 m2/g. Both the color and total organic carbon (TOC) conversion versus the residence time were measured at various conditions. The effects of pH value, catalyst loaded, initial humic acid concentration and reaction temperature on conversion were monitored. The experimental results proved that the photocatalytic oxidation process was not temperature sensitive and the optimum catalyst loading was found to be 0.4 g/l. Degradation and decolorization of humic acids have higher efficiency in acidic medium and at low initial humic acid concentration. The new catalyst was effective in removing TOC at 61.58% and color400 at 93.25% at 180 minutes illumination time and for 20 mg/l neutral humic acid aqueous solution. The kinetic analysis showed that the rate of photocatalytic degradation of humic acids obeyed the first order reaction kinetics.

Photocatalytic Degradation of Polycyclic Aromatic Hydrocarbons on Soil Surfaces Using Fe2O3 under UV Light

2011 ◽  
Vol 189-193 ◽  
pp. 420-423 ◽  
Author(s):  
Li Hong Zhang ◽  
Nan Jia ◽  
Cheng Bin Xu ◽  
Xue Mei Li
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Humic Acid ◽  
Photocatalytic Degradation ◽  
Aromatic Hydrocarbons ◽  
Uv Light ◽  
First Order Kinetics ◽  
Degradation Rates ◽  
Polycyclic Aromatic ◽  
Alkaline Conditions ◽  
Neutral Conditions

The photocatalytic degradation of phenanthrene (PHE), pyrene (PYRE) and benzo[a]pyrene (BaP) on soil surfaces in the presence of Fe2O3 using ultraviolet (UV) light source was investigated. The effects of various factors, namely Fe2O3, soil pH, and humic acid, on the degradation performance of polycyclic aromatic hydrocarbons (PAHs) were studied. The results show that photocatalytic degradation of PAHs follows the pseudo-first-order kinetics. Catalyst Fe2O3 accelerated the photodegradation of PHE, PYRE and BaP significantly. In acidic or alkaline conditions, the photocatalytic degradation rates of the PAHs were greater than those in neutral conditions. Humic acid significantly enhanced the PAH photocatalytic degradation by sensitizing radicals capable of oxidizing PAHs.

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