Experimental data on antibiotic cephalexin removal using hydrogen peroxide and simulated sunlight radiation at lab scale: Effects of pH and H2O2

Cephalexin (CPX) is a β-lactam antibiotic widely used to treat bacterial infections in the respiratory tract, skin, bones, and ear; a situation that has contributed to its discharge into wastewater (mainly through excretion after ingestion) and its accumulation in water bodies. CPX presence on environmental compartments could interfere in the physiological functions of animals and humans due to the induction of mutagenic and carcinogenic effects. Different technologies have been evaluated to remove CPX from aqueous matrices. In this way, this work presents the main data regarding the use of the combination of hydrogen peroxide and simulated sunlight radiation in CPX removal. Effects of H2O2 initial concentration and solution pH were evaluated using a face-centered, central composite design and the response surface methodology. Optimized conditions, under the evaluated experimental range, were established. In addition, data about the total organic carbon and anions content in treated samples were collected. These data can be useful for the evaluation of the use of H2O2 and light radiation on organic pollutants removal, the comparison of the effectiveness of different technologies on CPX elimination, and as a starting point to carry out this type of process at pilot or real scale.


a b s t r a c t
Cephalexin (CPX) is a β-lactam antibiotic widely used to treat bacterial infections in the respiratory tract, skin, bones, and ear; a situation that has contributed to its discharge into wastewater (mainly through excretion after ingestion) and its accumulation in water bodies. CPX presence on environmental compartments could interfere in the physiological functions of animals and humans due to the induction of mutagenic and carcinogenic effects. Different technologies have been evaluated to remove CPX from aqueous matrices. In this way, this work presents the main data regarding the use of the combination of hydrogen peroxide and simulated sunlight radiation in CPX removal. Effects of H 2 O 2 initial concentration and solution pH were evaluated using a face-centered, central composite design and the response surface methodology. Optimized conditions, under the evaluated experimental range, were established. In addition, data about the total organic carbon and anions content in treated samples were collected.
These data can be useful for the evaluation of the use of H 2 O 2 and light radiation on organic pollutants removal, the comparison of the effectiveness of different technologies on CPX elimination, and as a starting point to carry out this type of process at pilot or real scale.
© 2020 The Author(s

Value of the data
• Data show that UV/hydrogen peroxide is an appropriate technique to remove antibiotic cephalexin from water. • Data could benefit researches and institutions working on wastewater treatment, organic pollutants elimination, and advanced oxidation technologies application. • Data can be employed for the evaluation of the potential use of H 2 O 2 and light radiation on organic pollutants removal, and as a starting point to carry out this type of process at pilot or real scale. • Data present optimized conditions that allow to increase CPX removal using H 2 O 2 and sunlight. • Data include information regarding the variation of the total organic carbon, nitrates and sulphates of treated samples. • Data may be useful in future research on antibiotics removal from aquatic environments.

Data description
Data presented in this work describes the cephalexin removal by the combination of H 2   organic pollutants [3] .
The reaction kinetics of the UV/H 2 O 2 process is a function of the solution pH, the peroxide initial concentration and the physicochemical properties of the target pollutant [4] . In addition, as part of the solar radiation has a wavelength corresponding to the UV range, there is a possibility of implementing photo-treatment systems using solar light and H 2 O 2 for water treatment [5] . The potential application of H 2 O 2 and simulated sunlight was evaluated considering a facecentered central composite experimental design and the response surface methodology (response: pollutant removal after 30 min of reaction). Table 1 shows the factors and levels evaluated on antibiotic removal using simulated sunlight and H 2 O 2 ; and Table 2 corresponds to the experimental results obtained after carried out the proposed experimental design. Total number of experiments: 11. Fig. 1 shows the obtained response surface for CPX removal under simulated sunlight radiation and H 2 O 2, which allows to predict the pollutant removal under different combinations of pH and H 2 O 2 initial conditions. Fig. 2 corresponds to the associated main effects plot for CPX removal. This figure is useful to determine the effect of each factor on CPX removal without considering the effect of the other variables that intervene in the process. Fig. 3 is the associated Pareto chart and indicates the magnitude and significance of the effect of each factor and interaction on pollutant elimination.
Statgraphics Centurion XVI software allowed to determine the model ( Eq. (2) ) that relates the response factor with the evaluated experimental parameters. According to model, conditions that conduct to a higher CPX removal were pH 3.0 and 6.9 mg L −1 H 2 O 2 initial concentration. Coefficient of determination, R 2 , between experimental data and model was 0.986. In addition, Table 2 presents the calculated values regarding CPX removal using the proposed model, which shows that equation predicts CPX elimination, under the studied conditions,   Table 3 and Fig. 4 show CPX removal under different experimental conditions including H 2 O 2 /sunlight radiation at optimized conditions, photolysis, hydrolysis (at pH 3.0), oxidation with H 2 O 2 and the effect of the presence of a scavenger agent (isopropyl alcohol).
Finally, Fig. 5 presents information regarding the total organic matter (TOC), nitrates and sulfates content in treated samples.

Sample
Time (

Materials
All the aqueous solutions were prepared using ultra-pure water (Milli-Q water, 18.2 M cm). Cephalexin (98.0%, AK Scientific), H 2 O 2 (35.0% w/w, Merck) and isopropyl alcohol (99.9%, Merck) were used to carry out the experiments. Control of pH was done using concentrated solutions of NaOH (0.1 N) and HCl (1.0 N) obtained from Alfa-Aesar. Sodium thiosulfate pentahydrate (Na 2 S 2 O 3 • 5H 2 O, Sigma Aldrich) was employed for quenching remaining H 2 O 2 after sampling process; and acetonitrile for chromatographic analysis was of LC/MS grade.

Photocatalytic system
Pyrex flasks containing 50.0 mL of solution (CPX initial concentration 2.0 mg L −1 ) were used for photo-treatment. Solutions pH was adjusted after the additon of CPX and H 2 O 2 . Experiments were carried out using a Suntest CPS + (Atlas) photosimulator equipped with a xenon lamp that delivered ligth with a spectrum similar to that of the sun. Irradiance during experiments was 500 W m −2 . Distance from the lamp to the liquid surface was ∼20.0 cm, and the liquid depth inside the flasks was ∼5.0 cm.

Experimental design
The effects of solution pH and H 2 O 2 initial concentration were evaluated using a facecentered central composite design, and considering the levels presented by Table 1 . The total number of experiments was 11 (three central points). Data were analyzed using the Statgraphics Centurion XVI software with a confidence level of 95.0%.
Optimized conditions were selected having into account the polynomical model stablished, after a non-linear regresion of data, by the statistical software ( Eq. (2) ) Tests regarding polluntat removal under optimized conditions, hydrolysis, photolysis, oxidation with H 2 O 2 and effect of an scavenger agent presence were done in triplicate.

Analytical methods
Samples of 0.75 mL were withdrawn at different time intervals during the experiments, then 0.25 mL of Na 2 S 2 O 3 • 5H 2 O (100 mg L −1 ) were added to inhibit the potential oxidative effect of remaining H 2 O 2 .
Total Organic Carbon (TOC), nitrates and sulfates were determined using an APOLLO 90 0 0 Combustion TOC Analyzer (Teledyne Tekmar) and a Dionex Integrion HPIC system (Thermo Scientific) respectively. Standard Methods for the Examination of Water and Wastewater (2017) [6] methods 526D (High temperature combustion method) and 4110B (Determination of anions by ion chromatography) were also employed.