Dataset on photocatalytic degradation of Levofloxacin using hydroxyapatite photocatalyst: Optimization by response surface methodology

The upsurge of antibiotic usage in the 20th century has resulted in increasing levels of pharmaceutical compounds in bodies of water. A particular antibiotic, levofloxacin, is a third-generation quinolone known to target Gram-positive organisms like atypical pathogens. Chronic toxic effects of levofloxacin to some microorganisms lead to the disruption of marine ecosystems. Unfortunately, a relatively low concentration of levofloxacin in water bodies discourages researchers from exploring potential risk assessment and removal in wastewater treatment plants. In this article, aqueous levofloxacin was degraded using hydroxyapatite catalyst under UV-irradiation. Response Surface Methodology (Box Behnken Model) was used to model and optimize the degradation efficiency parameter. The response was fitted into a 2-factor interaction equation revealing a satisfactory ANOVA evaluation (R2=97.08%, adjusted R2= 94.89, predicted R2=91.1%). An optimal photodegradation efficiency was determined to attain the following conditions: 1.5 g/L catalyst dose, 4 ppm levofloxacin, and a pH level of 10. The model predicted a value of 71.6% degradation efficiency, which is very close to 70.6% generated experimentally.


a b s t r a c t
The upsurge of antibiotic usage in the 20th century has resulted in increasing levels of pharmaceutical compounds in bodies of water. A particular antibiotic, levofloxacin, is a third-generation quinolone known to target Gram-positive organisms like atypical pathogens. Chronic toxic effects of levofloxacin to some microorganisms lead to the disruption of marine ecosystems. Unfortunately, a relatively low concentration of levofloxacin in water bodies discourages researchers from exploring potential risk assessment and removal in wastewater treatment plants. In this article, aqueous levofloxacin was degraded using hydroxyapatite catalyst under UV-irradiation. Response Surface Methodology (Box Behnken Model) was used to model and optimize the degradation efficiency parameter. The response was fitted into a 2-factor interaction equation revealing a satisfactory ANOVA evaluation (R 2 = 97.08%, adjusted R 2 = 94.89, predicted R 2 = 91.1%). An optimal photodegradation efficiency was determined to attain the following conditions: 1.5 g/L catalyst dose, 4 ppm levofloxacin, and a pH level of 10. The model predicted a value of 71.6% degradation efficiency, which is very close to 70.6% generated experimentally. UV-Vis: The spectra for the degradation were obtained using Shimadzu UV-Visible spectrophotometer UV-2600. Settings were set to 2 nm slit width, medium scan speed, and wavelength range of 20 0-40 0nm. Baseline correction using deionized water was employed before sample runs.

Data format
Raw and Analyzed Description of data collection Hydroxyapatite catalyst was prepared from mussel shell pre-cursor. Photocatalytic activity of hydroxyapatite was evaluated by the absorbance of levofloxacin obtained after UV irradiation. Box Behnken Modelling was used to optimize three parameters: catalyst dose (0.5-1.6 g/L), LEVO concentration (4-10 ppm), and pH (4-10). Photodegradation efficiency was obtained after 5-hour irradiation subsequently after subjecting to dark conditions (30 mins). Verification of the model was simulated using optimum conditions from the model (

Value of the Data
• This work presents empirical and statistical data on the photodegradation of levofloxacin via photocatalytic process. The data given here as well as the experimental parameters exhibit the effectivity of hydroxyapatite as an alternative green photocatalyst. Researchers may opt to modify this photocatalyst to further enhance the degradation properties. • The results of the Box-Behnken modelling and analysis can be used by other investigators to test and compare the influence of experimental parameters (catalyst dosage, LEVO concentration, and pH) on the efficiency of the system in the photodegradation of other related organic compounds. • The data presented herein can be used in the optimization of similar photocatalytic systems (i.e. hydroxyapatite /UV) for both small and large scale studies. These data can be referenced by academic investigators looking at photocatalytic system designs, testing, and optimization. Scientific professionals working in industries such as wastewater treatment and organic waste disposal facilities may use these data in improving the current methods.

Data Description
The range and levels of the defined variables considered in the Box Behnken design model is shown in Table 1 . These are the catalyst dose (A), levofloxacin concentration (B), and pH value (C). The model equation computing the efficiency is given in Equation (1) . In the model, A, B, C, AB, and AC represent the catalyst dosage, levofloxacin concentration, pH value, the interaction of catalyst dosage-levofloxacin, and the interaction of catalyst dosage-pH heavily influencing the behavior of the degradation efficiency, respectively. In Table 2 , the efficiency response with different values of the three variables are enumerated. It shows photodegradation efficiency towards levofloxacin. Evaluation of the best fitted equation is given in Table 3 demonstrating that the 2-Factor Interaction describes the curve due to having the highest regression values. The analysis of variance is used to determine the significant factors that affect the photodegradation efficiency. It is also used to evaluate the quality of fit and adequacy of the model ( Table 4 ). The Fisher (F) and probability (P) values are used to determine the significant variables. Values of "Prob > F" less than 0.0500 indicate model terms are significant whereas the opposite indicate non-significance [1] . The generated regression equation representing the photodegradation efficiency of levofloxacin is given in Equation 1 . The coefficients of determination (R 2 ) and adjusted R 2 are satisfactory to support the significance of the model [2] . Normal probability plot of standardized residuals and predicted vs actual plot is shown in Fig. 1 and 2 , respectively. Surface interaction plots of the variables are shown in Fig. 4 . Results show favorability for high catalyst Table 1 Range and Levels of Box Behnken Design.    dosage and pH with low levofloxacin concentration. The software response optimization was set to have the maximum response which obtained the optimum conditions of 1.5 g/L catalyst dose, 4 ppm levofloxacin concentration and pH 10. This generated a predicted efficiency of 71.6% (5 hours). The optimum conditions were simulated experimentally ( Fig. 4 a) and the observed photodegradation efficiency was 70.6%. Thus, verifying the efficacy of the model. The kinetics of degradation follows pseudo first order equation ( Fig. 4 b).

Hydroxyapatite preparation
Biowaste mussel shells were soaked and cleaned with boiling water and were left to dry. The dried shells were crushed using mortar and pestle and calcined at 10 0 0 °C using a furnace. Powdered calcium oxide was produced after this step and was finely grounded using mortar and pestle. Grounded CaO weighing 1.00g was acquired and dissolved in a 20 mL of 2.50 M HNO 3 forming Ca(NO 3 ) 2 solution. The pH of this solution was then adjusted to 10 using ammonium hydroxide. To this solution, 25 mL of 0.427 M (NH 4 ) 2 HPO 4 was added dropwise under sonication (40 Hz) for 1 hour. The resulting mixture was centrifuged, washed with deionized water, and dried overnight at 100 °C to obtain the hydroxyapatite powder [3] .

Determination of levofloxacin photodegradation efficiency
The photodegradation of Levofloxacin was carried out in a reactor that was designed and built in our laboratory. The type of UV lamp used was Sankyo Denki 20 W, λ = 254 monochromatic light. A constant flow of water (20 °C) in between the jacketed beaker was set to control the temperature. A mass of Hydroxyapatite was transferred to a 100 mL levofloxacin solution with constant stirring. The pH of the reaction mixture was adjusted by careful addition of a solution of NaOH or HCl. The solution was allowed to stand while stirring in the dark for 30 mins and then was UV-illuminated at constant stirring (400 RPM). The acquired sample solution was centrifuged to remove the suspension. The extent of degradation was determined spectrophotometrically using Shimadzu UV-Visible spectrophotometer UV-2600 at 287 nm. Percent degradation efficiency was calculated as follows [ 4 , 5 ], Where Co = initial concentration and C = variable concentration

Box-Behnken experiments
The software used for the modeling is Minitab 17. The model is based on Box-Behnken design with 15 experimental runs. The parameters analyzed were (A) catalyst dose, (B) LEVO concentration, and (C) pH. Photodegradation efficiency (after 5 -hour UV-irradiation) was set as the response. Predicted optimum parameters for the photodegradation were obtained after setting the response to maximum.

Verification of Box-Behnken model
Predicted parameters (1.5 g/L catalyst dose, 4ppm LEVO, and pH 10) from the model were simulated in an actual experiment. An aliquot (5mL) of the levofloxacin solution was obtained every 60-minute interval to determine the concentration and evaluate the photodegradation behavior.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data Availability
Dataset on photocatalytic degradation of Levofloxacin using hydroxyapatite photocatalyst: Optimization by response surface methodology (Original data) (Mendeley Data).