Slide 1

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 Slide 2 Introduction: Chlorophenols are organic chemicals formed from phenol by substitution in the phenol ring with one or more atoms of chlorine. The compounds of interest in the organochlorine family are 2,4,6- Trichlorophenol(TCP) and pentachlorophenol. Exposure to TCP produces Leukamias,Liver cancer, Soft tissue sacomas, Hydgkins. Slide 3 Many literatures have reported that a lot of toxic or hazardous industrial chemicals could be destroyed by photocatlytic degradation. Photocatalysis is a new technique of decontamination of chlorophenols Photocatalytic process efficiency can be increased by the use of catalyst nanoparticles Slide 4 Objective of the project The main objective is to study the photocatalytic degradation of TCP using Ag@TiO2 nanoparticles. The specific objectives include: To study the effect of initial concentration of TCP, catalyst loading, UV lamp power and initial solution pH on the TCP degradation by carrying out batch experiments with suspended Ag@TiO 2 nanoparticles. To obtain the optimum values catalyst loading and initial solution pH for TCP degradation To evaluate the rate equation and the kinetic parameters for the TCP degradation by Ag@TiO 2 under optimum conditions. To study the effect of catalyst loading on TCP removal in a packed bed reactor with nanoparticles immobilized on activated carbon particles under continuous mode of operation. Slide 5 Preparation of Ag@TiO 2 nanoparticles The colloidal solution of TiO 2 coated silver particles was prepared as per the reported procedure by Kamat et.al[ 2004]. Ag@TiO 2 nanoparticles: 2ml of 15mM AgNO 3 solution was mixed with 18 ml of 8.3mM TTEAIP solution. 10 ml of DMF was then added into TTEAIP-Ag solution. The solution was stirred first for 15 min at room temperature and then refluxed at 80 o C with continued stirring. After 15min, the color of suspension turned to dark brown from light brown. At this point heating was stopped and suspension was stirred until it cooled to room temoerature. The cluster suspension of Ag@TiO 2 was three times centrifuged and suspended in ethanol solution. Slide 6 Schematic diagram of the laboratory-scale reactor for nanoparticle synthesis Slide 7 Preparation of Ag@TiO 2 film immobilized on Activated Carbon Immobilization of Ag@TiO 2 nanoparticles on AC was done as per the procedure reported by Bing et.al (2008) for immobilization of TiO 2 film on ceramics glaze 45g of Activated carbon of size 2.8/2 mm was washed with distilled water and dried in an oven at 100-120 o c for 2hrs. The Activated carbon was completely immersed in Ag@TiO2 nanosolution in water. The beaker with nanosolution and AC were kept in a rotary shaker at 200rpm for 10 min. These particles with immobilized nanoparticle were then dried in oven at 100- 120 o c for 2hrs and then used in continuous experiments. Slide 8 Characterization of the catalysts X-rays diffraction (XRD) Scanning Electron Microscopy Slide 9 Experimental procedure for batch operation 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 0.1Lmin1 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 0.25m 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 35 o c. 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. Slide 10 Schematic diagram and photographic image of the laboratory-scale photochemical reactor for Batch studies Slide 11 A general reaction scheme for the heterogeneous photocatalytic oxidation of chlorophenols is Photocatalysis Slide 12 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@TiO 2. 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 m 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. Experimental procedure for continuous operation Slide 13 Schematic diagram and photographic image of photochemical reactor for continuous operation Slide 14 Spectroscopy Calibration Preparation of TCP solution Reagents Preparation: Ammonium hydroxide,NH 4 OH(0.5N) Phosphate buffer solution Potassium ferricyanide solution 4-aminoantipyrine solution Slide 15 Calibration Procedure For each of the prepared 100ml std sols,2.5ml of 0.5N NH 4 OH solution was added and immediately adjusted to pH 7.9+0.1 with phosphate buffer, and then 1ml of 4-aminoantipyrine solution was added and thoroughly stirred.Finally 1ml of K 3 Fe(CN) 6 was added and mixed well.The solution was left for 15min the standard solutions were transferred to the cell and the absorbance was read against blank at 510nm using Hitachi UV-160A spectrophotometer Slide 16 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 Slide 17 Calibration table for TCP analysis SI No. Concentration (ppm) Absorbance 1 00.00 2 10.111 3 20.218 4 30.333 5 40.442 6 50.566 Slide 18 CALIBRATION GRAPH Calibration plot for TCP analysis Slide 19 Characterization of the catalysts X-rays diffraction (XRD) Scanning Electron Microscopy Results and Discussion Slide 20 X-rays diffraction (XRD): selected peak 2121 2222 =(2 2 -2 1 )/2L=k / cos 38.48 o 38.438.60.184.2 39.1 o 39.00939.305 o 0.107578.5 Particle size corresponding to selected peak XRD pattern of Ag@TiO 2 nanoparticles Slide 21 Scanning Electron Microscopy (SEM) : SEM micrographs of core/shell structured Ag@TiO 2 composite particles with EDAX Slide 22 Slide 23 SEM Micrograph of the Activated Carbon increase of 500 times. SEM Micrograph of the Activated Carbon increase of 2000 times Slide 24 SEM micrographs of Activated carbon with EDAX Slide 25 Slide 26 SEM with EDAX micrographs of Activated Carbon immobilized with 0.05gAg@TiO 2 /gAC core-shell structured Ag@TiO 2 composite particles before and after reaction Slide 27 Batch studies Batch experiments on photocatalytic degradation of 2,4,6-TCP with Ag@TiO 2 nanoparticles in suspension in 150mL reactor volume was conducted to study the effect of catalyst loading, initial 2,4,6-TCP concentration, initial solution p H and UV lamp power. Slide 28 Effect of catalyst loading: Effect of photocatalyst loading on 2,4,6-TCP degradation: initial concentration 50 ppm, air flow rate 0.1L min1, natural p H, time 24 hrs, temperature 35 C, UV lamp 40W. Slide 29 Effect of photocatalyst loading on 2,4,6-TCP degradation: initial concentration 50 ppm, air flow rate 0.1L min1, natural p H, time 24 hrs, UV lamp 40W Slide 30 Effect of photocatalyst loading on initial rate of degradation of 2,4,6-TCP : initial concentration 50 ppm, air flow rate 0.1L min1, natural p H, time 24 hrs, UV lamp 40W Slide 31 Effect of initial solution pH on Batch degradation 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 min1, initial TCP concentration 50 ppm, time 24 hrs, UV lamp 40W. Slide 32 Effect of initial p H on 2,4,6-TCP degradation:, photocatalyst loading 0.03% (w/w), air flow rate 0.1 L min1, initial TCP concentration 50 ppm, time 24 hrs, UV lamp 40W. Slide 33 Effect of UV lamp power on Batch degradation of TCP Effect of UV lamp power on 2,4,6-TCP degradation: photocatalyst loading 0.03% (w/w), air flow rate 0.1 L min1, initial TCP concentration 50 ppm, pH=3. Slide 34 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 p H 3. UV lamp power(watts)Initial rate(Mmin- 1 ) 402.96 803.12 Slide 35 Effect of initial concentration of 2,4,6-TCP: 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 min1. Slide 36 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 min1, natural pH, UV lamp 40W. Slide 37 Kinetic analysis: Slide 38 Concentrationrate constant (min 1 ) 2530.002 177.20.003 101.20.003 Effect of initial concentration of 2,4,6-TCP degradation on reaction rate constant: catalyst loading 0.03% (w/w), initial solution p H 3, time 24 hrs, UV lamp 40W, air flow rate 0.1L min 1. Slide 39 The experimental data can be rationalized in terms of the modified form of LangmuirHinshelwood kinetic treatment, which has already been successfully used to describe solidliquid 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 k 1, k 2 and C 0 are adsorption constant, specific rate constant and initial concentration of TCP in M 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/C o. Slide 40 Effect of initial concentration of 2,4,6-TCP degradation on reaction rate constant: catalyst loading 0.03% (w/w), natural p H, time 24 hrs, UV lamp 40W, air flow rate 0.1L min1. Slide 41 Effect of catalyst loading during Continuous operation: Effect of photocatalyst loading on 2,4,6-TCP degradation during continuous operation: initial concentration 50 ppm, excess air flow rate 0.1mL min1, natural pH, temperature 35 C, UV lamp 40W. Slide 42 CONCLUSIONS 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 Photocatalytic degradation of TCP can be efficiently carried out using nanoparticles. The initial rate of degradation increases with catalyst loading up to a value and then decreases in batch degradation studies.Catalyst loading 0.03% was found to be optimum for 50ppm initial TCP concentration It was found from the Batch studies that with increase in p H of TCP solution from 2.0 to 3.0 degradation of TCP has increased. Further increase in p H from 3.0 to 9.0 has lead to decrease in TCP degradation. p H 3 was found to be the optimum for photocatalytic degradation of TCP by Ag@TiO 2 nanoparticles. Slide 43 From the batch studies on photocatalytic degradation of 2,4,6-TCP with Ag@TiO 2 nanoparticle 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. The initial rate of degradation increased with increase in initial TCP concentration. Kinetic model was formulated for the photocatalytic degradation of 2,4,6-TCP solution with Ag@TiO 2 nanoparticle. The photocatalytic degradation of TCP obeyed pseudo first order kinetics and the rate constant is 0.0027min -1. Slide 44 Continuous experiments on photocatalytic degradation of 2,4,6-TCP with Activated carbon immobilized with Ag@TiO 2 nanoparticles 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. Slide 45 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@TiO 2 nanoparticle immobilization. 2. To study the photocatalytic degradation by fluidized bed reactor 3. To obtain optimum ratio of Ag@TiO 2 nanoparticle to TCP loading for photocatalytic degradation. SCOPE FOR FUTURE WORK Slide 46 1 ) mez-De Jesu.A. G., Romano-Baez.F.J., L. Leyva-Amezcua. L., Jua rez-Ram rez.C.,Ruiz-OrdazN., Gal ndez-Mayer.J. (2009) Biodegradation of 2,4,6-trichlorophenol in a packed-bed biofilm reactor equipped with an internal net draft tube riser for aeration and liquid circulation J. Hazard. Mater. 161, 11401149 2) Kathiravan.A., Kumar.P.S., Renganathan.R., Anandan.S.(2008) Photoinduced electron transfer reactions between meso-tetrakis (4-sulfonatophenyl) porphyrin and colloidal metal-semiconductor nanoparticles Colloids Surf A Physicochem. Eng. Aspects. 3) Rao.A.N., Sivasankar.B., Sadasivam.V. (2009) Kinetic study on the photocatalytic degradation of salicylic acid using ZnO catalyst J. Hazard. Mater. 4) Estevinho.B.N., Martins.I., Ratola.N., Alves.A., Santos.L.(2007) Removal of 2,4-dichlorophenol and pentachlorophenol from waters by sorption using coal fly ash from a Portuguese thermal power plant J. Hazard. Mater. 143,535540 5) Hameed.B.H.(2007) Equilibrium and kinetics studies of 2,4,6-trichlorophenol adsorption onto activated clay Colloids Surf A Physicochem. Eng. Aspects 307,4552. 6) Rotta.H.C.E.L. Chloroperoxidase mediated oxidation of chlorinated phenols using electrogenerated hydrogen peroxideElectronic Journal of Biotechnology ISSN: 0717-3458 REFERENCES Slide 47 8) Kusvuran.E., Samil.A., Atanur.O.M.,Erbatur.O. (2005) Photocatalytic degradation kinetics of di- and tri- substituted phenolic compounds in aqueous solution by TiO2/UV Appl. Catal. B: Environ.58,211216. 9) Barcelona.M.R.( 2003) Fenton and UV-vis based advanced oxidation processes in wastewater treatment: Degradation, mineralization and biodegradability enhancement Universitat De Barcelona Facultat De Quimica Departament DEnginyeria Quimica I MetalLurgia, Miguel Rodrguez Barcelona. 10) Lente. G.and Espenson.J.H. Oxidation of 2,4,6-trichlorophenol by hydrogen peroxide. Comparison of different iron-based catalysts DOI: 0.1039/b411269e http//www.rsc.org 11) MA. H.M., Wohlers.J., Meierhenrich.U., Bernecker.A., Suling.V., Thiemann.W, (2001) Oxidative Degradation of 2,4,6-Trichlorophenol in the Presence of Air Ions Chinese Chemical Letters 12( 3), 211214 12) Tan.I.A.W., Ahmad.A.L. Hameed.B.H. (2009) Adsorption isotherms, kinetics, thermodynamics and desorption studies of 2,4,6-trichlorophenol on oil palm empty fruit bunch-based activated carbon J. Hazard. Mater. 164,473482. 13) Ochuma.I.J., Fishwick.R. P., Wood. J., Winterbottom.J.M.. (2007) Photocatalytic oxidation of 2,4,6- trichlorophenol in water using a cocurrent downflow contactor reactor (CDCR).J. Hazard. Mater. 144,627 633. Slide 48 14)I. Poulios,D. Makri,X. Prohaska(1999). Photocatalytic treatment of olive milling waste water:Oxidation of protocatechuic acid Global Nest: the Int. J. 1( 1),55-62,. 15) Sun. J., Wang. X., Sun. J., Sun. R., Sun.S., Qiao. L. (2006) Photocatalytic degradation and kinetics of Orange G using nano-sized Sn(IV)/TiO 2 /AC photocatalyst J. Mol. Catal. A 260 241246. 16) Sun.J., Wang.Y., Sun. R., Dong.S., (2009) Photodegradation of azo dye Congo Red from aqueous solution by the WO3TiO2/activated carbon (AC) photocatalyst under the UV irradiation Materials Chemistry and Physics 115, 303308. 17) Halhouli. K.A. (2008) Effect of pH and temperature on degradation of dilute dihydroxybenzene, in aqueous titanium dioxide suspension irradiated by UV light J. Photochem. Photobiol. A: Chem. 200, 421 425. 18) BehnajadyY.M.A.,.Modirshahla.,N., Shokri.B.,Rad.M.( 2008) Enhancement of Photocatalytic activity of TiO 2 nanoparticles by Silver doping:Photodeposition versus liquid impregnation methods Global NEST Journal 10( 1), 1-7,. 19) Seery. M. K., George. R., Floris.P., Pillai. S.C. (2007) Silver doped titanium dioxide nanomaterials for enhanced visible light photocatalysis J. Photochem. Photobiol. C 189, 258263. 20) Kiefer.M.C., Hengraprom.S., Knuteson.S.( 1998) organochlorines:Analysis of the Chlorophenol Group EE&S 845 Environmental Engineering Chemistry II:Environmental Organic Chemistry Spring,http//www.leeorg1.htm Slide 49 THANKING YOU