ENHANCED PHOTOCATALYTIC ACTIVITY OF Ag-DOPED TiO2 NANO PARTICLES TOWARDS DEGRADATION OF RHODAMINE -B DYE
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Mushtaq Ahmad Rather1, M.S.Charoo2, Rahul Goel3,6 Saurabh Singh4, Hemanshi Sarangal5, Rahaul Panwar , Department of Chemical Engineering NIT Hazratbal Srinagar, India -190006 Email:
[email protected] 2 Department of Mechanical Engineering NIT Hazratbal Srinagar-190006 3-6 Department of Chemical Engineering NIT Hazratbal Srinagar, India-190006
Key words: Photocatalysis, Ultraviolet light, Degradation, Dye Abstract: Presence of azo dyes in textile waste water poses serious threat to environment. The water requires removal of dyes before being discharged into open streams. This study focused on enhancement of photocatalytic degradation capability of commercial Degussa P25 by doping of ‘Ag’ with it. Ultraviolet light emitting diodes (UV-LED) are employed as an alternate source of radiation (traditional UV sources available are Hg lamps) in photocatalytic degradation of model dye rhodamine-B .Complete mineralization of 4×10−6 M dye solution was confirmed by above process. Activity of Ag loaded TiO2 was enhanced in comparison to commercial Degussa P25 TiO2 under same conditions. 1. Introduction Titanium dioxide has been widely used in heterogeneous photocatalysis due to its good photocatalytic activity and stable physiochemical properties1.TiO2 has strong reduction and oxidation capability, is low cost and harmless to environment. About 1-20 % of total production of world dyes is lost in dying process and is released in textile effluent. Among several techniques used to treat such dyes, advanced oxidation processes (AOPs) is being used increasingly because final oxidation products are CO2 and H2O2. While using TiO2 as photocatalyst its high band energy gap of about 3.2 eV requires ultra violet light for photo excitation. Traditional UV sources comprise of high pressure mercury lamps emitting over broad spectral wave length range. During operation these types of lamps cause over heating in system, have low photonic efficiency, have longer exposure time and have small life period (1000 Hrs.).The mercury used in these types of lamps is a specified hazardous air pollutant (HAP) by U.S Environmental protection agency. Light emitting diodes (UV-LEDs) are new safer and energy efficient alternative for gas discharge sources .UV-LED is a directional light source with maximum emitting power in the direction perpendicular to emitting surface. These have also better life time (about 100000 Hrs.)1. The objective of present work is to study photodegradation of rhodamine-B as model dye in a small locally fabricated photocatalytic reactor setup utilizing UV radiation from UVLED’s. The efficacy of Degussa P25 towards degradation of dye with and without doping ‘Ag’ to it has been evaluated 2. Experimental Modified Ag doped TiO2 nanoparticles are synthesized by using AgNO3 as silver source, and deposited upon TiO2 nanoparticles(NPs). Synthesized particles are characterized by X-ray crystallography (XRD) and high resolution transmission electron microscopy (HRTEM).Photocatalytic reactor consisted of a 500 ml borosil glass beaker in which 100 ml of MB solution (4x10-6M) as initial concentration (C0) was taken for degradation. Forty numbers of UVLEDs were mounted in the holes drilled on a 5mm thick Perspex sheet which is mounted above reactor for providing UV illumination. During degradation samples were withdrawn at constant time intervals of 15 minutes and concentration of dye ‘C’ was found by using UV visible spectrophotometer (Modal T80 of PG Instruments UK). 3. Results and Discussion Figure 1 shows the XRD pictograph of Ag doped TiO2 NPs.
Fig. 1) XRD of Ag/TiO2 Peak at 2θ of 56.620 confirms the presence of rutile TiO2 (Corresponding JCPDS angle is 56.70) while as peak at 38.080 (Corresponding JCPDS is 38.110) confirms presence of Ag. The Scherer formula given in Eq. 1 is used to find the size of NPs. Particle size D=0.9λ/ (β cos θ)
(1)
Where λ is the wavelength of the X-rays, θ is the diffraction angle, and β is the corrected full width, at half-maximum of the peak. Scherer particle size is 18nm. Comparison of degradation of dye by various concentrations of commercial Degussa P25 TiO2 is shown in Fig. 2 .Comparison at concentration of 0.0625 gm catalyst per 100 ml solution with Ag doped TiO2 is also shown. As is clear degradation is enhanced by utilization of Ag doped TiO2 at corresponding catalyst concentration.
Fig. 2) Degradation of dye at different catalyst concentrations as function of time 4. Conclusion Study focused on the application of ultraviolet light emitting diodes (UV-LED) as an alternate source for the photocatalytic degradation of synthesized rhodamine-B (model dye) solution. A simple reactor arrangement was made to carry out the photocatalytic degradation. The effect of catalyst loading on degradation has been investigated with commercial Desussa P25 and Ag loaded TiO2. The complete mineralization of MB dye (4× 10−6 M) was confirmed. Results demonstrated that the UVLED/TiO2 process can effectively degrade rhodamine-B dye. Activity of Ag loaded TiO2 was enhanced in comparison to commercial Degussa P25 TiO2 under same conditions. 5. References 1. Rather M.A, Bhaskarwar A.N et al. ‘TiO2 Photocatalytic Degradation of Methylene Blue Dye by Utilizing Ultra Violet Light Emitting Diodes as Radiation Source’ Int. Conf. NANOCON14 (2014) Pune India. 2. Tayade R.J, Natarajan T.S, Bajaj H.C 'Photocatalytic Degradation of Methylene Blue Dye Using Ultraviolet Light Emitting Diodes'Ind. Eng. Chem. Res. 2009, 48, 10262–10267
