Dataset on photodegradation of tetracycline antibiotic with zinc stannate nanoflower in aqueous solution – Application of response surface methodology

Removal of pharmaceutical ingredients such as tetracycline from aqueous solution has a great importance. The aim of the current study was to investigate the degradation of tetracycline antibiotic in the presence of a triode semiconductor oxide as well as modeling of the photocatalytic degradation process in order to determine optimal condition Zinc stannate nanoflower (Zn2SnO4) was synthesized by hydrothermal process and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) techniques. Response surface methodology (RSM) was used to model and optimize four key independent variables, including photocatalyst dosage, initial concentration of tetracycline antibiotic (TC) as model pollutant, pH and reaction time of photocatalytic degradation. The proposed quadratic model was in accordance with the experimental results with a correlation coefficient of 98%. The obtained optimal experimental conditions for the photodegradation process were the following: zinc stannate (ZTO) dosage=300 mg L-1, initial concentration of TC= 10 mg L-1, reaction time= 100 min and pH=4.5. Under the optimal conditions, the predicted degradation efficiency was 95.45% determined by the proposed model. In order to evaluate the accuracy of the optimization procedure, the confirmatory experiment was carried out under the optimal conditions and the degradation efficiency of 93.54% was observed, which closely agreed with the predicted value.

pH¼4. 5. Under the optimal conditions, the predicted degradation efficiency was 95.45% determined by the proposed model. In order to evaluate the accuracy of the optimization procedure, the confirmatory experiment was carried out under the optimal conditions and the degradation efficiency of 93.54% was observed, which closely agreed with the predicted value.
Where Y is the TC degradation degree, and A, B, C, and D are the real values of pH, photocatalyst dosage, initial concentration of TC, and reaction time. The predicted values of the tetracycline degradation are presented in Table 1 with a model. Drawing the predicted values with a model, according to the real values ( Fig. 1), a line was achieved with the correlation coefficient of 0.98, which shows that the model is satisfactory.
The results obtained from the ANOVA, which are driven from the Mini Tab software, are presented in Table 2.
P values related to the terms of the proposed model for the TC degradation process during the UV/ ZTO process are presented in Table 3.
The optimized values of the chosen variables and the maximum predicted value for the tetracycline degradation are presented in Table 4. To evaluate the validity of the predicted value, the experimental would be done via CCD in the same proposed condition and with a value of 95.45% for the TC degradation in the optimized conditions.

Evaluation of synthesized nano-particles properties
FT-IR studies on the synthesized ZTO via the 500-4000 cm À 1 hydrothermal method are evaluated and the result is shown in Fig. 2.
Position and relative intensity of peaks in the XRD pattern of the synthesized ZTO indicates the presence of crystal phases (with the cart No. of 2184-074-01) in the structure of the synthesized photocatalyst (Fig. 3).
The SEM images of the synthesized ZTO via the hydrothermal method are presented in Fig. 4. It was observed that the ZTO is in the form of nano flowers.

Effect of initial concentration of pollutant and photocatalyst dosage on the tetracycline degradation
The tetracycline degradation degree for the reaction time of 70 min and pH of 7.5, as a function of photocatalyst dosage, is shown in Fig. 6-b. The obtained results from the diagram indicate that in the low concentration of pollutant, the degradation degree increases as a result of the existence of numerous absorption sites.

Effects of pH and initial concentration of pollutant on tetracycline degradation
In Fig. 5-b in the conditions that the time is equal to 70 min and pollutant concentration is 20 mg L À 1 in the acidic medium the highest amount of degradation occurs as a result of the electrostatic attraction between the pollutant and the photocatalyst surface.

Properties of tetracycline antibiotic
The properties of the tetracycline antibiotic as pollutant sample are shown in Table 5.

Synthesis of Zn 2 SnO 4
The following steps were taken to synthesize Zn 2 SnO 4 :1.5 mg of SnCl 4 .5H 2 O and 3 mg of Zn (NO 3 ) 2 .6H 2 O were separately dissolved in 20 ml of double distilled water. Then, 20 ml of sodium

Evaluation of the photocatalytic destruction of the synthesized nanoparticle
A Photocatalytic activity of the synthesized ZTO for destruction of the TC was evaluated under irradiation of UV light (30 W) (UV-C). In order to carry out the experiment, 100 ml of the solution of the pollutant was poured in 200 ml Bécher as a reactor with magnetic stirrer (Fig. 6).
In order to determine the concentration of pollutant at any time, the sampling accrued in intervals of 0-100 min and the absorption of antibiotic solution was recorded with the spectrophotometer in the wavelength of 359 nm. The removal degree was calculated using the following equation [3][4][5][6][7][8][9].
Where C 0 is initial concentration of TC and C t is the concentration of TC at time t.

Optimizing the photocatalytic degradation process
To optimize the process of the photocatalytic degradation, central composite design (CCD) was used-RSM's common form [10][11][12][13][14]. Considering the initial experiments, the four factors of pH, initial density, photocatalyst dosage and reaction time, were investigated as the main effective factors and the antibiotic degradation degree was considered as the response. Table 6 shows Levels of independent variables for photocatalytic degradation of TC. The intended design, presented in Table 7 is based on CCD and considers the four variable including 31 experiments with various conditions. These experiments include 16 factorial experiment at factor levels of -1 and þ1, seven experiments at central levels (0), and eight experiments at axial points (α¼2). To create connection between Table 7 Designing of experiment via the CCD method based on the real values of the variables.
Where, y is the response predicted by the model, x i is the encoded amount of levels of variables and b o , b i , b ii , and b ij are the coefficients of the model.