Compare Removal of Reactive Red 195 and Blue 19 by Nano TiO 2-ZnO

In this study, TiO2-ZnO particles were synthesized by the sol-gel method. XRD, SEM, EDX and UV-vis techniques were used to characterize optimize doped TiO2-ZnO sample Aim of this research is investigation of possibility of mixture TiO2-ZnO in degradation reactive dye. In addition, Influence of effective parameters on photodegradation reaction such as TiO2-ZnO concentration and initial concentration of dyes on the removal were investigated. Results showed that removal efficiency of dyes by increasing of TiO2-ZnO concentration was increased. In addition, the best dye removal for both dyes were obtained 11mg.L-1.

using advanced oxidation (AOPs) such as photocatalysts is TiO 2 [3].Titanium dioxide is a compound that has high photocatalytic activity.And a lot of research for the study and application of this important characteristic of titanium dioxide has been done [4][5][6][7] .Also titanium dioxide Due Chemical stability, Non-toxicity And Low Cost A lot of considered.However, the application of photocatalytic titanium dioxide has been limited for two reasons 8 .1.
The band gap of titanium dioxide is in the ultraviolet region.While Only 3% of The spectrum sunlight is Area Ultraviolet[9.

2.
Pairing fast electron -hole in photocatalytic activity of titanium dioxide causing the loss it.
Therefore,In recent years, various methods for improving energy band gap and increase the optical activity of titanium dioxide that has been done, including reduce the particle size, increased specific surface area, a pair of titanium dioxide with other semiconductor refine of titanium dioxide with metals and non-metals include titanium dioxide and increased activity [10][11][12][13][14][15][16] .
In this research, the effect of doped Tio 2 with ZnO for degradation two important dye(for dying cotton, rayon and wool) in the textile industry was studied.

Materials
The Reactive Blue 19 was purchased from the Dystar (Germany) and The Reactive Red 195 was purchased from the SUN COLOUR (Korean) and used without further purification.Solutions were prepared with the dye using distilled deionized water (Table1).Titanume (IV) isoporopoxid (TTIP) Zinc nitrate hexahydrate (Zn(NO 3 ) 2 •6H 2 O), Fe(NO 3 ) 3 •9H 2 O, glacial acetic acid, etanol, "Degussa-P25" with size 30 nm werefrom Merk chemical Company and Zno with particle size 20nm werefrom nanomore company., werefrom Merk chemical Company.The pH of the solution was adjusted with HCl or NaOH .

Preparation of nanocoposites
The TiO 2 /ZnO were prepared through the sol-gel process [17][18][19][20] .Precursor A: 12.83 ml (C 4 H 9 O) 4 Ti and 14.60 ml C 2 H 5 OH were mixed together and stirred for 1.0 h at room temperatures.Precursor B: 1.35 ml H 2 O, 7.30 ml C 2 H 5 OH, 2.20 ml CH 3 COOH and a proper amount of zinc nitrate (with TiO 2 :ZnO=10:3) were mixed together with Fast stirring.Meanwhile, a certain quantity of hydrochloric acid (HCl) solution was also added for controlling the solution pH value between 2.0 and 3.0.Here, acid was used as an inhibitor to reduce quick hydrolysis of TTIP.Afterwards, the precursor B was dropped into the precursor A with vigorous stirring.The resultant mixture was further stirred for 1 h and the yellow transparent sol was gained.The obtained gel was dried at 60ºC for 10 h in a vacuum oven and ground to obtain powder.The heat-treatment of 400ºC for 2.5 h in the air was applied to the sample.

Photocatalytic activity measurement
The photodegradation studies were carried out in a batch reactor system.The setup consists of a UV chamber made of MDF having dimensions (68 × 50 × 43 cm) and two lamps TUV PL-L 18 W (Philips), fitted on the top of the chamber.An exhaust fan is fitted on the side wall of the chamber to maintain a constant temperature.The reactor used is a cylindrical quartz flask, which has a diameter of 2.5cm and is 15 cm in height.To characterize the photocatalytic activity of the nano composite under UV-C irradiation, measurements on photodegradation of reactive dyes in the model wastewater were carried out at room temperature.
For each experiment, 11mg nanocomposite was put in a cylindrical flask containing 25 ml, water solution of Reactive dyes whit concentration 20 mgL -1 .The solution was magnetically stirred for 30min in dark to establish an adsorption/desorption equilibrium of Reactive dyes on the surfaces of the catalyst, then the light was turned on to initiate the photocatalytic reaction.After irradiation for 45 minute, the suspension was extracted at regular time (15 min) and centrifuged at the rate of 4000 rpm for 5 min to remove the catalyst.The concentrations of Reactive red 195 and blue19 before and after photocatalytic degradation were calibrated by the intensity of its characteristic absorption peak located at 542 and 592 nm measured with UV-vis spectrometer Respectively (Jenway 6405).
The degree of photodegradation (X) as a function of time is given by: where C 0 is the concentration of Reactive dyes before illumination and C is the concentration after irradiation time.
we use the Energy dispersive X-ray (EDX) spectrum.The element of Titanium, zinc and oxygen were determined as well in (Fig. 2).The effects of nano photocatalyst in the degradation of dye Studies show that by increasing the amount of nanophotocatalysts to 11 mg.L -1 maximum destruction have for both dyes.Further increasing the amount of nanophotocatalysts appears that the nanoparticles (the suspended particles) create error in the assessment of their destruction.
Figure 5 shows a typical time-dependent UV spectrum of Reactive dyes solution during photoirradiation.Reduce the degradation of RR195 indicates the presence of azo bond (-N=N-) at the RR195 caused the structure more susceptible than RB19 is attacked by hydroxyl radicals.

Effect of Concentration of Reactive Dye
Effect of initial dyes concentration on degradation was examined in the range of 10-50 mg.L -1 at 11mg.L -1 catalyst loading under UV irradiation shown in Figure 6.
It was found that the rate of degradation of the dyes decreased at higher concentrations.With increasing the amounts of RR195 and RB19, more of the dyes molecules will be adsorbed on the surface of the photocatalyst and the active sites of the photocatalysts will be reduced.so, with increasing occupied space of photocatalyst surface, the generation of hydroxyl radicals will be decreased.Also, increasing concentration of dyes can be lead to decreasing the number of photons that is arrived to the surface of catalysts.As more light is absorbed by molecules of dyes, the excitation of photocatalyst particles by photons will be reduced.Therefore, degradation efficiency would be diminished.
The kinetics of disappearance of RB19 and RR195 for an initial concentration of 20 mg.L -1 under optimized conditions show in (fig.7).The results showed that the photocatalytic degradation of the dyes in aqueous solution TiO 2 -ZnO can be described by the first order kinetic model as ln (C 0 / C) = kt, where C 0 is the initial concentration and C is the concentration at any time 21 .The semi logarithmic plots of the concentration data gave rise to a straight line.The correlation constant for the fitted line and rate constant were calculated RB19 and RR195 as R 2 =0.998, 0.997 and 0.068 ,0.094 min -1 respectively.According to results Rate constant of RR195 was more RB19.

Fig. 1 :Fig. 2 :
Fig. 1: XRD patterns of TiO 2 -ZnO nanocomposite Average particle size was determined using Debye-Scherrer formula with Full-width at Half Maximum (FWHM).The sizes were found to be 23.45 nm.Morphology of TiO 2 -ZnO nano particles was evaluated by Scanning Electron Microscopy (SEM )The SEM images of nano TiO 2 -ZnO prepared is shown in Figure.3 At first Nano-photocatalysts TiO 2 /ZnO synthesized by sol-gel method, result shown that degradation of reactive dye by nano (TiO 2 -ZnO) more than TiO 2 and ZnO alone.(Fig4).