PHOTOCATALYTIC DEGRADATION OF 2,4,6-TRICHLOROPHENOL USING Ag@TiO2 NANOPARTICLES. Under the guidance of Dr.Vidya Shetty.K. Presented by Y. Sri Lakshmi 07PD06F. Introduction:.
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USING Ag@TiO2 NANOPARTICLES
Under the guidance of Dr.Vidya Shetty.K
Y. Sri Lakshmi
Many literatures have reported that a lot of toxic or hazardous industrial chemicals could be destroyed by photocatlytic degradation.
A 150mL solution of 2,4,6 Trichlorophenol of required concentration was prepared by dissolving required quantity of TCP in distilled water. The required amount of catalyst was added into the reactor. Air at a flow-rate of 0.1Lmin−1 was bubbled through the suspension. The suspension was magnetically stirred continuously. At the start of the experiment UV source which are two numbers UV lamps are placed at a fixed distance of 7cm on either side of the reactor were put on. Samples of 2mL were withdrawn from the reactor at different time intervals. The withdrawn samples were filtered with two numbers of 0.25μm Millipore filters for removal of the nanoparticles. These samples were analysed for TCP using Hitachi UV-160 A spectrophotometer. The results are based on average temperature of 35oc. The concentration of 2,4,6 -Trichlophenol as a function of irradiation time were obtained. Analysis of each sample was repeated three times and the concurrent was used.
Schematic diagram and photographic image of the laboratory-scale photochemical reactor for Batch studies
A general reaction scheme for the heterogeneous photocatalytic oxidation of chlorophenols is
Synthetic waste water of the required concentration of 2,4,6 -Trichlorophenol concentration was prepared by dissolving calculated amount of TCP in water. The reactor was operated at room temperature and packed with 45 g of 2.8/2 mm granular activated carbon immobilized with Ag@TiO2. Air at a flow-rate of 1Lmin−1 was bubbled through column. Water was pumped to the bottom of the column at required flow rate. At the start of the experiment UV source, placed at a fixed distance of 7cm from the reactor was put on. Samples of 2mL were collected at outlet at different time intervals. The withdrawn samples were filtered with two numbers of 0.25 μm Millipore filters to remove the AC fines. The clear solution was separated and analysed for TCP concentration using Hitachi UV-160 A spectrophotometer. Analysis of each sample was repeated three times and the concurrent was used.
reactor for continuous operation
From the values of absorbance and concentration of tcp presented will get calibration curve. To get the concentrations of unknown sample , sample taken in a 100ml std flask. the above said reagents were added and mixed well. Flask was made up to 100ml by adding distilled water. The solution was left for 15min.The sample and blank were transferred to the cell and absorbance's were read. The absorbance was interpretated with the calibration curve and concentration of unknown samples were obtained
Calibration plot for TCP analysis
XRD pattern of Ag@TiO2 nanoparticles
Particle size corresponding to selected peak
SEM micrographs of core/shell structured Ag@TiO2composite particles with EDAX
SEM Micrograph of the Activated Carbon increase of 2000 times
SEM with EDAX micrographs of Activated Carbon immobilized with 0.05gAg@TiO2/gACcore-shell structured Ag@TiO2 composite particles before and after reaction
Batch experiments on photocatalytic degradation of 2,4,6-TCP with Ag@TiO2 nanoparticles in suspension in 150mL reactor volume was conducted to study the effect of catalyst loading, initial 2,4,6-TCP concentration, initial solution pH and UV lamp power.
Effect of photocatalyst loading on 2,4,6-TCP degradation: initial concentration 50 ppm, air flow rate 0.1L min−1, natural pH, time 24 hrs, temperature 35 ◦C, UV lamp 40W.
Effect of photocatalyst loading on 2,4,6-TCP degradation: initial concentration 50 ppm, air flow rate 0.1L min−1, natural pH, time 24 hrs, UV lamp 40W
Effect of photocatalyst loading on initial rate of degradation of 2,4,6-TCP : initial concentration 50 ppm, air flow rate 0.1L min−1, natural pH, time 24 hrs, UV lamp 40W
Effect of initial pH on 2,4,6-TCP degradation: temperature 35 ◦C, photocatalyst loading 0.03% (w/w), excess air flow rate 0.1 L min−1, initial TCP concentration 50 ppm, time 24 hrs, UV lamp 40W.
Effect of initial pH on 2,4,6-TCP degradation:, photocatalyst loading 0.03% (w/w), air flow rate 0.1 L min−1, initial TCP concentration 50 ppm, time 24 hrs, UV lamp 40W.
Effect of UV lamp power on 2,4,6-TCP degradation: photocatalyst loading 0.03% (w/w), air flow rate 0.1 L min−1, initial TCP concentration 50 ppm, pH=3.
Initial rate of degradation of 2,4,6-TCP at different UV lamp power during the batch operation, initial concentration 50 ppm, 0.03%(w/w) catalyst loading, air flow rate 0.1 L min−1, initial solution pH 3.
Effect of initial concentration on 2,4,6-TCP degradation: Catalyst loading 0.03% (w/w), natural pH, time 24 hrs, UV lamp 40 W, air flow rate 0.1 L min−1.
Effect of initial concentration on 2,4,6-TCP initial rate of degradation during the batch operation, 0.03%(w/w)catalyst loading, air flow rate 0.1 L min−1, natural pH, UV lamp 40W.
Effect of initial concentration of 2,4,6-TCP degradation on reaction rate constant: catalyst loading 0.03% (w/w), initial solution pH 3, time 24 hrs, UV lamp 40W, air flow rate 0.1L min−1.
The experimental data can be rationalized in terms of the modified form of Langmuir–Hinshelwood kinetic treatment, which has already been successfully used to describe solid–liquid reactions. The rate of unimolecular surface reaction is proportional to the surface coverage assuming that the reactant is strongly adsorbed on the catalyst surface than the products. The effect of solute concentration on the rate of photocatalytic degradation is given in the form of the following equation:
where k1, k2 and C0 are adsorption constant, specific rate constant and initial concentration of TCP in µM respectively. The applicability of equation was confirmed by the linear plot obtained by reciprocal of initial rate 1/r against reciprocal of initial concentration of the TCP 1/Co.
Effect of initial concentration of 2,4,6-TCP degradation on reaction rate constant: catalyst loading 0.03% (w/w), natural pH, time 24 hrs, UV lamp 40W, air flow rate 0.1L min−1.
Effect of photocatalyst loading on 2,4,6-TCP degradation during continuous operation: initial concentration 50 ppm, excess air flow rate 0.1mL min−1, natural pH, temperature 35 ◦C, UV lamp 40W.
Based on the results of present investigation and from the available scientific information derived from the review of the relevant literature, following conclusions are drawn
From the batch studies on photocatalytic degradation of 2,4,6-TCP with Ag@TiO2nanoparticle with different UV lamp power, it can be concluded that with increase in UV lamp power the initial rate of degradation increases, But the ultimate degradation at the end of 24hrs remained the same.
Continuous experiments on photocatalytic degradation of 2,4,6-TCP with Activated carbon immobilized with Ag@TiO2nanoparticles at different catalyst loadings was conducted. It can be concluded that the steady state percentage degradation increased with increased catalyst loading. And maximum 60% degradation of 50ppm TCP could be achieved in continuous reactor.AC particles are not suitable to be used as nanoparticle support materials in photocatalytic reaction.
Based on the results of present investigation the following suggestions are made for future research as a logical continuation of present work
1.To study the performance packed bed reactor with different support materials for Ag@TiO2nanoparticle immobilization.
2. To study the photocatalytic degradation by fluidized bed reactor
3. To obtain optimum ratio of Ag@TiO2nanoparticle to TCP loading for photocatalytic degradation.
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