Step by step procedures: Degradation of polycyclic aromatic hydrocarbons in potable water using photo-Fenton oxidation process

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Subject area Engineering
More specific subject area Environmental Engineering Method name Step by step procedures: degradation of polycyclic aromatic hydrocarbons from potable water using via photo-Fenton oxidation process Name and reference of original method The preparation method for the aqueous solution containing PAHs was based on the method used by Sakulthaew et al. [1] and Sabaté et al. [2]. The molarity of hydrogen peroxide (H 2 O 2 ) and ferrous sulfate (FeSO 4 ) was based from Baker et al. [3]. The reaction time, pH and molarity ratio of H 2 O 2 :FeSO 4 were analyzed for the photo-Fenton oxidation process [4][5][6][7][8][9][10][11] 1. Baker JR, Milke MW, Mihelcic JR (1999) Relationship between chemical oxygen demand and theoretical oxygen demand for specific classes of organic chemicals. Water Res 33 (2)

Method details
To date, the application of the photo-Fenton oxidation process for PAHs treatment were from contaminated soil (review paper) [12], landfill leachate [13], municipal solid waste leachate [14], sanitary landfill leachate (Tânia et al., 2013), aniline wastewater [15], ammunition wastewater [16] and saline aqueous solutions [17]. As for potable water, the application of Fenton reagent aided with photo treatment [5,6] or electrolysis [4] were not focusing on PAHs removal. Therefore, this MethodsX is presented to researchers as a step by step procedures of batch experiments for the degradation of PAHs in potable water using photo-fenton oxidation process. The designed reactor for batch experiments is shown in Fig. 1. Design of the reactor in this study was referred to the previous researchers' designs [18][19][20][21].  [17] and Bertilsson and Widenfalk [23] for their PAHs treatments. The molarity of H 2 O 2 and FeSO 4 for the photo-Fenton oxidation process were theoretically calculated and referred to Baker et al. [3]. Table 1 showed the list of parameters and equipments used for the research.
The analyzed variables were reaction time, pH and molarity ratio (MR) of H 2 O 2 :FeSO 4 . Researchers may conduct the batch experiment starting with observation of reaction time at neutral pH followed by acidic pH and alkaline pH while recording the degradation of parameters under study. The mixing by a magnetic stirrer for complete homogeneity during the reaction is needed. Aliquots must be pipet at the targeted time: (a) 2 mL of aliquot for chemical oxygen demand (COD) and; (b) 20 mL of aliquot for total organic carbon (TOC). If researchers are measuring COD, the pH of the solution need to be adjusted to more than pH 10 to decompose the H 2 O 2 to oxygen and water to reduce interference in the COD determination. Additional of sodium hydroxide (NaOH) at few drops will be sufficient for the pH adjustment purpose. As photo-Fenton oxidation process involves additional of FeSO 4 , researchers The degradation of PAHs using photo-Fenton treatment method in potable water samples was studied based on degradations of TOC (along with integrated kinetic rates) and quantification of 17-USEPA PAHs concentrations after the treatment via gas chromatography mass spectrometry (GCMS) analysis.
The determination of TOC was conducted using TOC analyzer (Shimadzu, Japan). The 20 mL volume of collected sample is required for TOC measurement. This measurement is crucial to monitor the degradation of organic compound during the treatment. The use of TOC as proxies for PAHs concentration is justified by Vela et al. [22]. These parameters also were previously reported and used as indications for other water pollutants like 1,2-dichloroethane [24], 2,4-dichlorophenol [19], aniline [15] and ammunition [16] wastewater.
As for the gas chromatography mass spectrometry analysis, the type of PAHs extraction used was solid phase extraction [25], consisted of column HyperSep Retain PEP 60 mg bed weight 3 mL column by Thermo Fisher Scientific Inc (Product Code: 10505905) was used. The cartridge used was C18 Cartridge: 12102052 Bond Elut C18, 500 mg 6 mL, 30 pk from Agilent J & W. Before loading samples, the cartridge was first conditioned with 10 mL DCM/n-hexane (1:3, v/v), then with 10 mL methanol to remove air and leach impurity and then with 10 mL ultrapure water to equilibrate the phase. Next, a 500 mL water sample was loaded at the flow rate of 5.0 mL/min. After loading, the cartridge was kept vacuum for 30 min to remove residual water. The objects retained on the cartridge were eluted by 15 mL/min by 15 mL of DCM/n-hexane (1:3, v/v) at the flow rate of 1 mL/min. The sample reconcentration was done using a type of nitrogen evaporator by Thermo Fisher Scientific namely Reacti-VapTM Evaporators with 9 ports (Product Code: TS-18825). The samples were collected into a test tube and condensed to dryness under gentle flow of nitrogen at room temperature and redissolved with 1 mL of DCM:n-hexane (1:3, v/v). Then, the samples were transferred into the 1.5 mL sept vials, ready for GCMS analysis. Samples need to be analyzed within 40 days after the reconcentration ( [25]; Agilent Technologies, 2011).
A good calibration for 17 USEPA-PAHS reference standards are required for the quantification of PAHs in the samples before and after treatments. Researchers may test the real water samples of interest before and after treatment too. After calibration, calibration curves must be constructed from scratch by referring on the chromatograms obtained from the calibration (response against ranges of concentrations (eg. 1 mg/L, 2 mg/L and 3 mg/L) for every PAHs tested). For a good validation, the correlation coefficient for calibrations curves (R 2 ) must be more than 0.95. Researchers may refer on calibration curves of 17 USEPA-PAHs reference standards as per documented in Abd Manan et al. [26].
To sum up, the prescribed method aforementioned above was a recommended steps on the photo-Fenton oxidation process for the degradation of PAHs in potable water conducted by Abd Manan et al. [26]. The optimization products and outcomes were presented by [26]. Authors are hoping that the procedures will be a helpful guide for researchers to conduct water research experiment especially for advanced oxidation processes with some adjustment accordingly wherever necessary.