Effects of ultraviolet intensity and wavelength on the photolysis of triclosan

2007 ◽  
Vol 55 (1-2) ◽  
pp. 209-216 ◽  
Author(s):  
H.-S. Son ◽  
S.-B. Choi ◽  
K.-D. Zoh ◽  
E. Khan
Keyword(s):  
Kinetic Model ◽  
Hydroxyl Radicals ◽  
Direct Photon ◽  
Order Kinetic ◽  
First Order ◽  
Photodegradation Rate ◽  
Order Kinetic Model ◽  
Pseudo First Order ◽  
First Time ◽  
Subordinate Role

The effects of ultraviolet (UV) intensity and wavelength on triclosan (TCS) photodegradation kinetic, efficiency, mechanisms and pathway were studied. The TCS photodegradation followed the pseudo-first order kinetic model at all UV intensities examined at the wavelengths of 254 and 365 nm and the photodegradation rate increased with increasing UV intensity. TCS photodegradation efficiencies of 90 to 98% and 79 to 90% were obtained at the wavelengths of 254 and 365 nm, respectively. TCS was degraded mainly by photon induced hydroxyl radicals while the direct photon reaction with TCS played a subordinate role. Chlorophenol, dichlorophenol and phenol were the intermediates detected in all experiments conducted. Dibenzodichloro-p-dioxin and dibenzo-p-dioxin were observed as the intermediates only at lower UV intensities investigated at the wavelength of 365 nm. Based on these intermediates, a complete TCS photolysis pathway was proposed for the first time.

Characteristics and kinetics of hexavalent chromium reduction by gallic acid in aqueous solutions

2015 ◽  
Vol 71 (11) ◽  
pp. 1694-1700 ◽  
Author(s):  
ZiFang Chen ◽  
YongSheng Zhao ◽  
Qin Li
Keyword(s):  
Kinetic Model ◽  
Gallic Acid ◽  
Hexavalent Chromium ◽  
Ph Value ◽  
Order Kinetic ◽  
First Order ◽  
Molar Ratios ◽  
Wide Range ◽  
Order Kinetic Model ◽  
Pseudo First Order

Gallic acid (GA) is a naturally occurring plant polyphenol compound. Experiments were conducted to study the kinetics and effects of pH, temperature, irradiation, and initial hexavalent chromium (Cr(VI)) concentration on Cr(VI) reduction by GA. Results indicated that Cr(VI) could be reduced to chromium oxide (Cr(III)) with GA in a wide range of pH values from 2.0 to 8.5. The reaction followed a pseudo-first-order kinetic model with respect to Cr(VI) and GA in acid conditions (pH 2.0–5.0). However, the reaction did not follow the pseudo-first-order kinetic model at pH 6.5 and 8.5. Removal efficiencies and reaction rate constants of Cr(VI) significantly increased with decreasing pH value and increasing temperature. The effect of irradiation on Cr(VI) reduction increased with increasing pH, and irradiation improved the removal efficiency of Cr(VI) by 11.29% at pH 6.5. At pH 2.0, nearly all molar ratios of GA required for the reduction of Cr(VI) were 1:2 (±0.1) under different initial Cr(VI) concentrations; however, the molar ratios of GA required for the reduction of Cr(VI) were 1:1.29, 1:1.43, and 1:1.69, respectively, when the initial Cr(VI) concentrations were 10, 25, and 50 mg/L at pH 5.5.

Sorption of Pb2+ on Mg-Al-Fe Hydrotalcite-Like Compounds

2012 ◽  
Vol 573-574 ◽  
pp. 86-91
Author(s):  
Xue Feng Liang ◽  
Wan Guo Hou ◽  
Ying Ming Xu ◽  
Lin Wang ◽  
Yue Bing Sun
Keyword(s):  
Kinetic Model ◽  
Rate Increase ◽  
Freundlich Isotherm ◽  
Order Kinetic ◽  
Sorption Mechanism ◽  
Chemical Binding ◽  
First Order ◽  
Maximum Sorption ◽  
Order Kinetic Model ◽  
Pseudo First Order

Hydrotalcite-like compounds containing Mg2+, Al3+ and Fe3+ with a constant M2+/M3+ ratio but varying Al3+/Fe3+ ratios have been prepared. The effects of iron contents on the structural and sorption of Pb2+ by Mg-Al-Fe HTlc samples were investigated. The maximum sorption amounts were about 88-201 mg/g for Mg-Al-Fe HTlc samples. The sorption isotherm and kinetic processes can be described with Freundlich isotherm and pseudo first order kinetic model, respectively. The sorption amounts and rate increase with the increase of iron contents in HTlc samples. The sorption mechanism of Pb2+ on Mg-Al-Fe HTlcs may be the surface-induced precipitation and chemical binding adsorption.

Fabrication and Photocatalytic Decolorization Performance of ZnO

2011 ◽  
Vol 396-398 ◽  
pp. 823-826
Author(s):  
Jie Cheng ◽  
Jian Zhang Li ◽  
Jun Bo Zhong ◽  
Wei Hu
Keyword(s):  
Methyl Orange ◽  
Kinetic Model ◽  
Uv Irradiation ◽  
Precipitation Method ◽  
Order Kinetic ◽  
First Order ◽  
Photocatalytic Decolorization ◽  
Langmuir Hinshelwood Mechanism ◽  
Order Kinetic Model ◽  
Pseudo First Order

Paralled flaw precipitation method has been employed to synthesize nanostructured ZnO. The prepared photocatalyst was characterized by BET, XRD. The paper reveals that Methyl Orange (MO) can be decolorized effectively in ZnO suspension system under UV irradiation. The optimal loading of photocatalyst in our experimental condition for the decolorization of MO is 1g/L. The present study, on the base of Langmuir-Hinshelwood mechanism, illustrates that the decolorization reaction is a pseudo first order kinetic model with the limiting rate constant of 8.48×10-2 mgL-1min-1 and equilibrium adsorption constant 0.335 L/mg, respectively.

scholarly journals Kinetics and reaction mechanism of photochemical degradation of diclofenac by UV-activated peroxymonosulfate

RSC Advances ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 6804-6817
Author(s):  
Yunlan Peng ◽  
Hongle Shi ◽  
Zhenran Wang ◽  
Yongsheng Fu ◽  
Yiqing Liu
Keyword(s):  
Reaction Mechanism ◽  
Kinetic Model ◽  
Order Kinetic ◽  
Photochemical Degradation ◽  
First Order ◽  
Order Kinetic Model ◽  
Pseudo First Order

Compared to UV alone and PMS alone systems, diclofenac was removed more efficiently in UV/PMS system at pH 7.0 due to the contribution of SO4˙− and HO˙ and its degradation followed the pseudo-first order kinetic model.

scholarly journals Photochemical Reactivity of Humic Substances in an Aquatic System Revealed by Excitation-Emission Matrix Fluorescence

2021 ◽  
Vol 9 ◽  
Author(s):  
Xin-yuan Wang ◽  
Qi-peng Yang ◽  
Shi-jie Tian ◽  
Fan-hao Song ◽  
Fei Guo ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Humic Substances ◽  
Regional Integration ◽  
Critical Role ◽  
Order Kinetic ◽  
Photochemical Reactivity ◽  
First Order ◽  
Excitation Emission Matrix ◽  
Photodegradation Rate ◽  
Order Kinetic Model

The photochemical reactivity of humic substances plays a critical role in the global carbon cycle, and influences the toxicity, mobility, and bioavailability of contaminants by altering their molecular structure and the mineralization of organic carbon to CO2. Here, we examined the simulated irradiation process of Chinese standard fulvic acid (FA) and humic acid (HA) by using excitation-emission matrix fluorescence combined with fluorescence regional integration (FRI), parallel factor (PARAFAC) analysis, and kinetic models. Humic-like and fulvic-like materials were the main materials (constituting more than 90%) of both FA and HA, according to the FRI analysis. Four components were identified by the PARAFAC analysis: fulvic-like components composed of both carboxylic-like and phenolic-like chromophores (C1), terrestrial humic-like components primarily composed of carboxylic-like chromophores (C2), microbial humic-like overwhelming composed of phenolic-like fluorophores (C3), and protein-like components (C4). After irradiation for 72 h, the maximum fluorescence intensity (Fmax) of C1 and C2 of FA was reduced to 36.01–58.34%, while the Fmax of C3 of both FA and HA also decreased to 0–9.63%. By contrast, for HA, the Fmax of its C1 and C2 increased to 236.18–294.77% when irradiated for 72 h due to greater aromaticity and photorefractive tendencies. The first-order kinetic model (R2 = 0.908–0.990) fitted better than zero-order kinetic model (R2 = 0–0.754) for the C1, C2, and C3, of both FA and HA, during their photochemical reactivity. The photodegradation rate constant (k1) of C1 had values (0.105 for FA; 0.154 for HA) that surpassed those of C2 (0.059 for FA, 0.079 for HA) and C3 (0.079 for both FA and HA) based on the first-order kinetic model. The half-life times of C1, C2, and C3 ranged from 6.61–11.77 h to 4.50–8.81 h for FA and HA, respectively. Combining an excitation-emission matrix with FRI and PARAFAC analyses is a powerful approach for elucidating changes to humic substances during their irradiation, which is helpful for predicting the environmental toxicity of contaminants in natural ecosystems.

scholarly journals Utilization of copper plating effluents in the degradation of the dye Sanodure Green in the presence of H2O2

Chemija ◽  
2021 ◽  
Vol 32 (1) ◽  
Author(s):  
Edita Sodaitienė ◽  
Danutė Kaušpėdienė ◽  
Audronė Gefenienė ◽  
Vladas Gefenas ◽  
Romas Ragauskas ◽  
...  
Keyword(s):  
Reaction Time ◽  
Kinetic Model ◽  
Oxidative Degradation ◽  
Order Kinetic ◽  
Nanostructured Catalyst ◽  
Copper Plating ◽  
First Order ◽  
Order Kinetic Model ◽  
Degradation Reaction ◽  
Pseudo First Order

Oxidative degradation of metal complex dye Sanodure Green (SG) in the presence of H2O2 and nanostructured catalyst CuO prepared from copper plating effluents has been investigated. The activity of the CuO catalyst in the oxidative degradation reaction depended on the SG concentration, reaction time and temperature. The reaction followed a pseudo-first order kinetic model, and the rate constant was highly dependent on the increase in temperature, but only slightly on the SG concentration. Thermodynamic studies have shown that the degradation reaction of SG is endothermic. The use of copper plating effluents for the preparation of nanostructured catalyst CuO makes it possible to avoid the accumulation of difficult-to-recycle copper oxide sludge formed during effluent neutralization, and to manage copper plating and aluminum dyeing effluents more economically.

scholarly journals Efficient Removal 17-Estradiol by Graphene-Like Magnetic Sawdust Biochar: Preparation Condition and Adsorption Mechanism

2020 ◽  
Vol 17 (22) ◽  
pp. 8377
Author(s):  
Yahui Zhou ◽  
Shaobo Liu ◽  
Yunguo Liu ◽  
Xiaofei Tan ◽  
Ni Liu ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Adsorption Capacity ◽  
Adsorption Mechanism ◽  
Langmuir Model ◽  
Maximum Adsorption Capacity ◽  
Order Kinetic ◽  
First Order ◽  
Micropore Filling ◽  
Order Kinetic Model ◽  
Pseudo First Order

The occurrence of environmental endocrine disrupting chemicals (EDCs) in aquatic environments has caused extensive concern. Graphene-like magnetic sawdust biochar was synthesized using potassium ferrate (K2FeO4) to make activated sawdust biochar and applied for the removal of 17-estradiol (E2). The characterization showed that the surface morphology of five graphene-like magnetic sawdust biochars prepared with different preparation conditions were quite different. The specific surface area and pore structure increased with the increment of K2FeO4 addition. The results have shown that graphene-like magnetic sawdust biochar (1:1/900 °C) had the best removal on E2. The experimental results indicated that pseudo-first-order kinetic model and the Langmuir model could describe the adsorption process well, in which the equilibrium adsorption capacity (qe,1) of 1:1/900 °C were 59.18 mg·g−1 obtained from pseudo-first-order kinetic model and the maximum adsorption capacity (qmax) of 1:1/900 °C were 133.45 mg·g−1 obtained from Langmuir model at 298K. At the same time, lower temperatures, the presence of humic acid (HA), and the presence of NaCl could be regulated to change the adsorption reaction in order to remove E2. Adsorption capacity was decreased with the increase of solution pH because pH value not only changed the surface charge of graphene-like magnetic sawdust biochar, but also affected the E2 in the water. The possible adsorption mechanism for E2 adsorption on graphene-like magnetic sawdust biochar was multifaceted, involving chemical adsorption and physical absorption, such as H-bonding, π-π interactions, micropore filling effects, and electrostatic interaction. To sum up, graphene-like magnetic sawdust biochar was found to be a promising absorbent for E2 removal from water.

Kinetics of Reductive Dechlorination of DDT in Soil with Zero-Valent Iron

2011 ◽  
Vol 295-297 ◽  
pp. 1236-1239
Author(s):  
Yin Hai Lang ◽  
Min Jie Wang ◽  
Nan Nan Wang
Keyword(s):  
Kinetic Model ◽  
Reductive Dechlorination ◽  
Reaction Rate ◽  
Zero Valent Iron ◽  
Order Kinetic ◽  
First Order ◽  
Reaction Rate Constants ◽  
Order Kinetic Model ◽  
Pseudo First Order ◽  
Kinetics Of

In this study, reductive dechlorination of DDT compounds by zero-valent iron in Jiangxi red soil was investigated. DDT compounds were effectively dechlorinated by zero-valent iron. The pseudo-first-order kinetic model for 2,4¢-DDT and 4,4¢-DDT reduction with zero-valent iron was proposed. The reaction rate constants for 2,4¢-DDT and 4,4¢-DDT were 1.19´10-2(min-1) and 1.44´10-2(min-1), respectively. The dechlorination of 2,4¢-DDT and 4,4¢-DDT were mainly affected by the specific surface area of iron. The data from the variable-pH experiments (between 3.6 and 8.8) suggested that pH does not play a role in the rate-determination step.

Treatability study of organic and colour removal in desizing/dyeing wastewater by UV/US system combined with hydrogen peroxide

1999 ◽  
Vol 40 (1) ◽  
pp. 153-160 ◽  
Author(s):  
P. C. Fung ◽  
Q. Huang ◽  
S. M. Tsui ◽  
C. S. Poon
Keyword(s):  
Hydrogen Peroxide ◽  
Kinetic Model ◽  
Oxidation Process ◽  
Order Kinetic ◽  
Dyeing Wastewater ◽  
Colour Removal ◽  
First Order ◽  
Effects Of Ph ◽  
Order Kinetic Model ◽  
Pseudo First Order

Treatability of a model dye, cuprophenyl yellow RL, in wastewater by the UV/H2O2/Ultrasonication (US) process was studied on a bench-scale UV/US combined reactor. The effects of pH, hydrogen peroxide dosage and US on the oxidation process were investigated, and the performance of the process on colour removal were evaluated. It was found that degradation of the dye followed a pseudo-first-order kinetic model at different pH and hydrogen peroxide dosages. The relationships between the rate constants and pH as well as hydrogen peroxide dosages were established.

Adsorption of Cr (VI) by Cross-Linked Magnetic Hydroxamated Chitosan

2013 ◽  
Vol 842 ◽  
pp. 175-179
Author(s):  
Liang Jia ◽  
Jing Song Wang ◽  
Qing Wei Guo ◽  
Xiao Liang Zou ◽  
Lei Xie
Keyword(s):  
Reaction Time ◽  
Kinetic Model ◽  
High Efficiency ◽  
Order Kinetic ◽  
First Order ◽  
Batch Systems ◽  
Adsorption Removal ◽  
Order Kinetic Model ◽  
Pseudo Second Order ◽  
Pseudo First Order

This paper aims to investigate the adsorption of Cr (VI) by cross-linked magnetic hydroxamated chitosan (MHCTS). The adsorption experiments were carried out in batch systems. To determine the optimum condition of the adsorption, factors such as pH, reaction time, initial Cr (VI) concentration and adsorbent dosage were considered. The experimental results showed that MHCTS can adsorb Cr (VI) with high efficiency. Optimum adsorption was observed at pH 4.0, and the highest adsorption removal reached 99.2%. The equilibrium was established within 90 min. The process could be described by pseudo-first-order and pseudo-second-order kinetic model.

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