Dataset on application of electrochemical and photochemical processes for sulfacetamide antibiotic elimination in water

Sulfonamide-class antibiotics are recognized as water pollutants, which have negative environmental impacts. A strategy to deal with sulfonamides is throughout the application of oxidation processes. This work presents the treatment of the sulfacetamide (SAM) antibiotic by electrochemical oxidation, UV-C/H2O2 and photo-Fenton process. It was established the main degradation routes during each process action. A DFT computational analysis for SAM structure was done and mass spectra of primary transformation products were determined. Chemical oxygen demand (COD), total organic carbon (TOC) and biochemical oxygen demand (BOD5) were also followed. Additionally, SAM treatment in simulated seawater and hospital wastewater was measured. These data can be useful for comparative purposes about degradation of sulfonamide-class antibiotics by electrochemical and advanced oxidation processes.


Data description
Information on the main degradation routes for sulfacetamide (SAM) treatment by the considered processes is initially presented. Such data are relevant to understand action of the systems on the antibiotics [1]. The considered electrochemical system is characterized by the action of active chlorine species as degrading agents (mediated route, Eqs (1)e(4)), in NaCl presence. Meanwhile, when Na 2 SO 4 is used as supporting electrolyte, oxidative species in solution bulk cannot be generated from sulfate ions, but oxidation on anode surface (direct route) can be evidenced [2e4]. Fig. 1A depicts degradation of the sulfonamide by electrochemical oxidation utilizing two supporting electrolytes (i.e., NaCl and Na 2 SO 4 ) to identify the action routes of the system. Ti/IrO 2(anode) þ 2Cl À / Cl 2 þ 2e À (1) Cl 2 , HOCl, OCl À þ organic pollutant / degradation products (4) Fig. 2 presents evolution of SAM under UV-C irradiation, hydrogen peroxide and AOP UV-C/H 2 O 2 ; this last system generates hydroxyl radical (Eq. (5)) as main degrading species (Eq. (6)) [5].
HO þ organic pollutant / degradation products (6) Specifications Table   Subject Environmental chemistry, Chemical Engineering Specific subject area Electrochemical and advanced oxidation processes Type of data Value of the Data Data show similarities and differences among the processes regarding degradation routes, primary transformation products, indicators such as COD, TOC and BOD 5 ; and matrix effects during SAM treatment. Data can benefit people working on treatment of wastewaters containing antibiotics. Data can be useful for comparative purposes about elimination of antibiotics by electrochemical and advanced oxidation processes. Data could be useful for scaling up of the process to treat organic pollutants in water. Data may be utilized in further theoretical and experimental researches on oxidation of sulfonamides by electrophilic species.
In Fig. 3 is shown SAM elimination by photo-Fenton system (which involves interaction of iron ions with hydrogen peroxide and light to produce HO, Eqs. (7) and (8) [6]). Control experiments (i.e., UV-A/ H 2 O 2 and Fenton) are also presented in Fig. 3.
Degradation of SAM under the oxidation processes can be promoted by active chlorine (e.g., electrochemistry) or hydroxyl radical (e.g., photo-Fenton and UV-C/H 2 O 2 ). These are electrophilic species able to attack electron rich moieties [1,4]. Then, computational calculations to identify regions on SAM with high electron density and susceptible to attacks by such degrading agents was carried (Fig. 4). Additionally, to determine the primary transformations, analyses of HPLC-MS were performed. Table 1 summarizes the primary products found for SAM treatment by each process; whereas, Fig. 5 contains mass spectra of the transformation products.
To establish the treatments extent, COD, TOC and BOD 5 were measured at 100% of SAM degradation by each considered process. Fig. 6A illustrates the TOC removal, whereas Fig. 6B presents the biodegradability relationship (BOD 5 /COD).
To test the ability of the processes to degrade the antibiotic in complex matrices, treatment of SAM in simulated seawater and hospital wastewater (see composition in Table 2) was performed. Fig. 7 shows the removal of SAM in these complex matrices during treatment by the three oxidation systems.

Reagents
Sodium sulfacetamide was provided by Corpaul (Medellín, Colombia) Sodium chloride, calcium chloride dihydrate, potassium chloride, ammonium chloride, sodium sulfate, potassium dihydrogen phosphate, urea and acetonitrile were purchased from Merck (Darmstadt, Germany). Urea was purchased from Carlo Erba (Sabadell, Spain) and formic acid was provided by Carlo-Erba (Val de Reuil, France). All chemicals were used as received. The solutions were prepared using distilled water.

Reaction systems
An electrolytic cell equipped with a Ti/IrO 2 rectangular plate of 8 cm 2 (anode, previously characterized [9]), a zirconium spiral of 10 cm 2 (cathode) and a WK electric apparatus (as current source) were used for the electrochemical experiments (Picture 1). A current density of 5 mA cm À2 and 0.05 mol L À1 of NaCl or Na 2 SO 4 as supporting electrolyte were used. The electrochemical system was   and Fe (II) respectively were used.

Analyses
The evolution of SAM during treatments was followed by sing a UHPLC Thermoscientific Dionex UltiMate 3000 instrument equipped with an Acclaim™ 120 RP C18 column (5 mm, 4.6 Â 150 mm) and a diode array detector. The injection volume was 20 mL, and a mixture of acetonitrile/aqueous formic acid  (10 mmol L À1 , pH 3.0) 40/60% V/V was used as mobile phase. The UV detection was carried out at 257, 270, 280 and 290 nm. It must be indicated that all degradation experiments were carried out at least by duplicate.
The computational analysis was performed with the Fukui function by applying the framework of functional density theory (DFT). SAM structure was optimized with the B3LYP hybrid functional density [10], with the 6-31 þ G* basis set and the continuous polarization model [11] using the dielectric constant for water. Thus, f -(i.e., electrophilic Fukui functions) values were calculated. For f -, a higher number is an indicator of a higher possibility of attack by electrophilic species.
The determination of primary transformation products was carried out at 50% of the antibiotic degradation. For such determination an ACQUITY UPLC H-Class (Waters Corporation, Milford, MA, USA) equipped with a quaternary solvent supply manager and a sampler manager coupled to an Xevo-G2-XS-Q-Tof, Mass spectrometer equipped with an electrospray interface (Waters Corporation). A Restek C18 column (50 Â 2.1 mm; 1.7 mm) was used with water (acidified by 0.1% formic acid) and acetonitrile (ACN) as eluents. The flowrate was 0.5 mL min À1 at room temperature. The gradient was from 90/10% water/ACN until 2 min, then the gradient change to 75/25% to 3 min, in 3,5 min change again to 90/10% to 6 min. ESI þ positive ionization mode and a sensitivity analysis were used for MS Determination with an analysis range of 50e700 Da, with a scan time of 0.1 s and a delay between operations of 0.01 s, for an analysis time of 6 minutes. The collision energy ramp was 10e30 V and the cone voltage was 30 V.
Chemical oxygen demand (COD) was established according to the Standard Methods for Examination of Water and Wastewater (5220 D). The closed reflux colorimetric method was used. An aliquot of 2500 mL of sample was added to a digestion vessel containing 1500 mL of digestion solution  (potassium dichromate in concentrated sulfuric acid) and 3500 mL of sulfuric acid reagent (silver sulfate in concentrated sulfuric acid). The digestion was performed at 140 C during 2 hours in a Velp Thermoreactor. Absorbance was measured at 600 nm in a Lab Scient UV-1100 spectrophotometer. Biochemical oxygen demand at 5 days (BOD 5 ) was carried out according to the Standard Methods for Examination of Water and Wastewater (5210 B) using an Oxitop respirometric system thermostatted at 20 C. The volume added to the incubation bottle contained 270 mL (10% V/V was the inoculum and 90% V/V was the sample). Prior to analysis, the pH was adjusted to near neutrality using sodium hydroxide (1.0 M), and residual hydrogen peroxide or active chlorine species were eliminated using sodium bisulfite (0.1 M).
Total organic carbon (TOC) was measured using a Teledyne Tekmar TOC analyzer. This was determined by combustion with catalytic oxidation at 680 C using high-purity oxygen gas at a flow rate of 190 mL min À1 . The apparatus had a non-dispersive infrared detector. Calibration of the analyzer was attained with standard potassium hydrogen phthalate (99.5%) solution. The injection sample volume was 50 mL.