Effects of synthesis Ni doped Ti[O.sub.2] on photocatalytic degradation process.
In several years, various kinds of organic pollutants to be decomposed by using Ti[O.sub.2] nanoparticles extensively because Ti[O.sub.2] particles had a lot of efficiency of high oxidative power, non-toxicity, photostability and water insoluble properties under most conditions . Moreover, Ti[O.sub.2] photocatalysts were low prices, chemical stability and no toxicity and which can be completely declorization and immobilization of many toxic organic pollutants . Ti[O.sub.2] modification has been justified to various kinds of approaches by metal-ion doped Ti[O.sub.2] and non-metal doped-Ti[O.sub.2]. By using transition metal for metal-ion doped-Ti[O.sub.2] are Cu, Co, Ni, Cr, Mn, Mo, Nb, V, Fe, Ru, Au, Ag and Pt and non-metal doped-Ti[O.sub.2] are N, S, C, B, P, I and F . A transition metalion of doped-Ti[O.sub.2] has been experiment by improving photocatalytic activity of semiconductor oxides .
Nickel is one of transition elements used to modify the titania surface. The effects of [Ni.sup.2+] on the photocatalytic properties of Ti[O.sub.2] have been investigated by several authors . More importantly, the existence of [Ni.sup.2+] greatly suppressed recombination of electron-hole pairs on the surface of the photocatalyst . On the other hand, low valence [Ni.sup.2+] ion dopant improves the photocatalytic activity of certain semiconductor photocatalyst [5,9]. However, the photocatalytic activity of the prepared metal-doped Ti[O.sub.2] photocatalysts depends strongly on the species and concentration of the dopant ion . Ti[O.sub.2] mediated heterogeneous photocatalysis conducted potentially advantages by improving ambient conditions and many organic pollutants of harmless products of C[O.sub.2], [H.sub.2]O and mineral acids by perfect mineralization . In this study is to decolorized azo dyes by different volume amount of doped-Ti[O.sub.2] and compare the effects of this photocatalysts under sunlight irradiation.
MATERIALS AND METHODS
Titanium isopropoxide (Ti[(O[C.sub.3][H.sub.7]).sub.4]), ethanol([C.sub.2][H.sub.5]OH), acetic acid(C[H.sub.3]COOH), nickel chloride hexahydrate (Ni[Cl.sub.2].6[H.sub.2]O) and Acid orange 7 ([C.sub.16][H.sub.11][N.sub.2]Na[O.sub.4]S) were purchased.
The doped Ti[O.sub.2] photocatalysts were prepared by calcination of synthesis Ti[O.sub.2] product with nickel chloride hexahydrate (Ni[Cl.sub.2].6[H.sub.2]O) as precursor for Ni-doped Ti[O.sub.2]. 10ml Ti[(O[C.sub.3][H.sub.7]).sub.4] and 17ml C2H5OH are mixed and stirring well. After one hour, 1ml of distilled water was added drop by drop into this solution. 20ml volume ratio of 0.5 mole precursor was added at three hour of synthesis solution and continues stirring one hour by vigorously. And then, 1.7ml of C[H.sub.3]COOH is added and 1min stirred with this solution. Moreover, the solution is changed and reflux three hours for becomes sol-gel type. After reflux time, the sol-gel are filtered and dried in oven at 70C for 24 hour. Finally, the doped Ti[O.sub.2] catalyst particles were obtained through calcination in a muffle furnace at 500C for 2 hr.
The photocatalytic degradation experiments of 30mg/l AO7 solutions were investigated in under sunlight irradiation in 0.3g of synthesis and doped Ti[O.sub.2] suspensions. The 500ml of AO7 solutions were prepared from stock solution by dilution with ultra-pure water. The experiments are done for 6 hour and 20ml of water samples were collected at 0, 0.5, 1, 1.5, 2, 3, 4, 5 and 6 hr. To obtain the clear water samples by using 0.45 m membrane filter paper was used for collecting all samples to remove the synthesis Ti[O.sub.2] and synthesis doped Ti[O.sub.2] particles.
RESULTS AND DISCUSSION
SEM analysis obtained results:
Figure 1 (a) and (b) shown scanning electron microscopy observation of synthesis Ti[O.sub.2] and Ni-doped Ti[O.sub.2] powders. The aggregate formed by the emulsifantgelation technology has an average size in the range of 1 [micro]m. And then the aggregate has a spherical shape with an average diameter of around 200 to 300 nm can be observed for both synthesis powders.
Photocatalytic activity of AO7 on Ni- doped-Ti[O.sub.2] suspensions:
Figure 2 illustrated that the effect of photocatalytic degradation activity of 30mg/l Acid Orange 7 by synthesis Ti[O.sub.2] and Ni-doped Ti[O.sub.2] suspensions. In this results, more adsorption efficiency in nickel doped Ti[O.sub.2] compared with synthesis Ti[O.sub.2]. The photodegradation percent of synthesis Ti[O.sub.2] and Ni-doped Ti[O.sub.2] are 58% and 66%, respectively. Moreover, [Ni.sup.2+] activated an important role in trapping the electrons and helps in charge separation, therefore photocatalytic activity is comparatively good.
Kinetics analysis for the photocatalytic degradation of single and binary azo dye solutions:
Table 1 was shown the [k.sub.app] values for the photocatalytic degradation of synthesis Ti[O.sub.2] and Ni-doped Ti[O.sub.2] powders. The Langmuir-Hinshelwood model mentioned equivalent to concern with the pseudo first-order kinetics of photocatalytic degradation of basic azo dyes . The [k.sub.app] value for synthesis Ti[O.sub.2] and Ni-doped Ti[O.sub.2] were 0.0024 and 0.0025 respectively. Therefore, the value of synthesis Ni-doped Ti[O.sub.2] is larger than that of synthesis Ti[O.sub.2] under approximate conditions. The [R.sup.2] of synthesis Ti[O.sub.2] is 0.8275 and Ni-doped Ti[O.sub.2] is 0.9975.
Both synthesis powders have spherical shape and average size are around 200-300nm. But the color removal percentage of Ni-doped Ti[O.sub.2] is more than synthesis Ti[O.sub.2] in photocatalytic degradation process. And then, the kinetics value of Ni-doped Ti[O.sub.2] is also larger than synthesis Ti[O.sub.2].
Received 25 March 2014
Received in revised form 20 April 2014
Accepted 15 May 2014
Available online 5 June 2014
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Corresponding Author: Ohm Mar Min, School of Environmental Engineering, University Malaysia Perlis, 02600 Arau, Perlis
(1) Ohm Mar Min, (1) Soon-An Ong, (1) Yee-Shian Wong, (2) Li-Ngee Ho
(1) School of Environmental Engineering, University Malaysia Perlis, 02600 Arau, Perlis
(2) School of Material Engineering, University Malaysia Perlis, 02600 Arau, Perlis
Table 1: Values of [k.sub.app] for the photodegradation degradation of 30mg-l AO7 by synthesis Ti[O.sub.2] and Ni-doped Ti[O.sub.2] suspensions. Synthesis Ti[O.sub.2] Synthesis Ni-doped Ti[O.sub.2] [k.sub.app] [R.sup.2] [k.sub.app] [R.sup.2] 0.0024 0.8297 0.0025 0.9975
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|Author:||Min, Ohm Mar; Ong, Soon-An; Wong, Yee-Shian; Ho, Li-Ngee|
|Publication:||Advances in Environmental Biology|
|Date:||Jun 20, 2014|
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