Kinetics of heterogeneous photocatalytic decomposition of 2,4-dichlorophenoxyacetic acid over titanium dioxide and zinc oxide in aqueous solution

1998 ◽  
Vol 54 (3) ◽  
pp. 269-276 ◽  
Author(s):  
Kamel Djebbar ◽  
Tahar Sehili
Keyword(s):  
Aqueous Solution ◽  
Zinc Oxide ◽  
Titanium Dioxide ◽  
Photocatalytic Decomposition ◽  
Dichlorophenoxyacetic Acid ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Kinetics Of

Photochemical decomposition of 2,4-dichlorophenoxy acetic acid (2,4-D) in aqueous solution. I. Kinetic study

1997 ◽  
Vol 35 (4) ◽  
pp. 31-39 ◽  
Author(s):  
María I. Cabrera ◽  
Carlos A. Martín ◽  
Orlando M. Alfano ◽  
Alberto E. Cassano
Keyword(s):  
Aqueous Solution ◽  
Radiation Effects ◽  
Batch Reactor ◽  
Dichlorophenoxyacetic Acid ◽  
Intrinsic Kinetics ◽  
Photochemical Decomposition ◽  
Kinetic Expression ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Dichlorophenoxy Acetic Acid ◽  
Kinetics Of

The intrinsic kinetics of the photochemical decomposition of 2,4-dichlorophenoxyacetic acid in aqueous solution has been studied using light of 253.7 nm. Experiments were carried out in a well stirred batch reactor irradiated from its bottom by means of a tubular lamp and a parabolic reflector. Results were analyzed in terms of a very simple kinetic expression. Absorbed radiation effects were duly quantified by means of a one-dimensional radiation field model. This approach incorporates a variable absorption coefficient that is a function of the 2,4-D conversion. The decomposition kinetics can be properly represented with a point valued equation of the following form: RD, λ = − ΦD,λ eλ(y).

Photodegradation of New Methylene Blue N in Aqueous Solution Using Zinc Oxide and Titanium Dioxide as Catalyst

2012 ◽  
Author(s):  
Rusmidah Ali ◽  
Boon Siew Ooi
Keyword(s):  
Aqueous Solution ◽  
Methylene Blue ◽  
Zinc Oxide ◽  
Titanium Dioxide ◽  
Optimum Condition ◽  
Metal Ion ◽  
Optimum Ratio ◽  
Photodegradation Rate ◽  
Uv Visible ◽  
Uv Lamp

Dalam kajian ini, ZnO dan TiO2 digunakan sebagai fotomangkin dalam pendegradasian pewarna New Methylene Blue N (NMBN). Kadar fotodegradasi diukur menggunakan alat spektrofotometer UV-Vis. Dalam kajian ini, New Methylene Blue N menunjukkan nilai serapan pada λ = 590 nm dan λ = 286 nm. Lampu UV (λ = 354 nm) digunakan dalam proses fotodegradasi. Dalam proses degradasi menggunakan ZnO menunjukkan 81.42% NMBN terdegradasi pada λ = 590 nm dan 77.75% pada λ = 286 nm. Sebaliknya, degradasi menggunakan TiO2 adalah 25.68% pada λ = 590 nm dan 26.37% pada λ = 286 nm. Peratus degradasi New Methylene Blue N ialah 88.89% dan 68.94% pada masing-masing λ = 590 nm dan λ = 286 nm apabila ditambahkan dengan H2O2. Campuran ZnO dan TiO2 dalam nisbah 85: 15 (0.085 g; 0.015 g) merupakan campuran fotomangkin yang paling optimum iaitu dengan peratus degradasi NMBN sebanyak 96.97% dan 93.61% pada λ = 590 nm dan λ = 286 nm. Penambahan ion logam Cu2+ memberikan peratus degradasi tertinggi berbanding ion logam lain iaitu 83.83% pada λ = 590 nm. Penambahan ion logam Pb2+ memberikan peratus degradasi tertinggi pada λ = 286 nm iaitu 81.25% pewarna terdegradasi. Keadaan optimum dicapai pada pH 5.90, dengan peratus degradasi tertinggi iaitu 92.84% dan 89.30% pada masing-masing λ = 590 nm dan λ = 286 nm. Kata kunci: New Methylene Blue N; fotodegradasi; larutan; ZnO; TiO2 In this study, ZnO and TiO2 are used as photocatalyst to degrade the dye, New Methylene Blue N (NMBN). The photodegradation rate was measured using UV-Visible spectrophotometer. In this study, New Methylene Blue N showed absorption values at λ = 590 nm and λ = 286 nm. UV lamp (λ = 354 nm) is used in the photodegradation process. Results showed that ZnO is a better photocatalyst compared to TiO2. The degradation by ZnO showed that 81% of NMBN was degraded at λ = 590 nm and 77.75% at λ = 286 nm. In contratst, the degradation using TiO2 was 25.68% at λ = 590 nm and 26.37% at λ = 286 nm. The percent degradation of New Methylene Blue N is 88.89% and 68.94% at λ = 590 nm and λ = 286 nm respectively when H2O2 was added. A mixture of ZnO and TiO2 in the ratio of 85: 15 (0.085 g: 0.015 g) is the most optimum ratio for the mixed photocatalyst where the degradation percentage of NMBN are 96.97% and 93.61% at λ = 590 nm and λ = 286 nm. The addition of Cu2+ metal ion gave the highest percentage of degradation (83.83% at λ = 590 nm) compared to other metal ions. The addition of Pb2+ gave the highest percentage of degradation at λ = 286 nm with 81.25% degradation of the dye. The optimum condition was achieved at pH 5.90, which gave the highest percentage degradation, 92.84% and 89.30% at λ = 590 nm and λ = 286 nm respectively. Key words: New Methylene Blue N; photodegradation; aqueous; ZnO; TiO2

scholarly journals Modeling of Phenoxy Acid Herbicide Mineralization and Growth of Microbial Degraders in 15 Soils Monitored by Quantitative Real-Time PCR of the FunctionaltfdAGene

2012 ◽  
Vol 78 (15) ◽  
pp. 5305-5312 ◽  
Author(s):  
Jacob Bælum ◽  
Emmanuel Prestat ◽  
Maude M. David ◽  
Bjarne W. Strobel ◽  
Carsten S. Jacobsen
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Kinetic Models ◽  
Exponential Model ◽  
Dichlorophenoxyacetic Acid ◽  
Order Kinetic ◽  
Clear Trend ◽  
Gene Copies ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Kinetics Of

ABSTRACTMineralization potentials, rates, and kinetics of the three phenoxy acid (PA) herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), and 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP), were investigated and compared in 15 soils collected from five continents. The mineralization patterns were fitted by zero/linear or exponential growth forms of the three-half-order models and by logarithmic (log), first-order, or zero-order kinetic models. Prior and subsequent to the mineralization event,tfdAgenes were quantified using real-time PCR to estimate the genetic potential for degrading PA in the soils. In 25 of the 45 mineralization scenarios, ∼60% mineralization was observed within 118 days. Elevated concentrations oftfdAin the range 1 × 105to 5 × 107gene copies g−1of soil were observed in soils where mineralization could be described by using growth-linked kinetic models. A clear trend was observed that the mineralization rates of the three PAs occurred in the order 2,4-D > MCPA > MCPP, and a correlation was observed between rapid mineralization and soils exposed to PA previously. Finally, for 2,4-D mineralization, all seven mineralization patterns which were best fitted by the exponential model yielded a highertfdAgene potential after mineralization had occurred than the three mineralization patterns best fitted by the Lin model.

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