Toc l csh csn

The mineralization of AO7 dye by a heterogeneous EF process was carried out in a cylindrical glass cell with an effective volume of 200 mL. The cathode (pC@CF800/5h) and anode (Ti/Ni) were placed in parallel with a distance of 3 cm between them. The electrolysis solution was prepared by adding Na₂SO₄ (50 mM) into the AO7 solution (0.1 mM) and stirring vigorously until complete dilution of the supporting electrolyte. Compressed air (atmospheric air) was bubbled for 15 min at flow rate of 1 dm³ m⁻¹ prior to the experiment in order to oxygenate the solution.
The mineralization of AO7 dye was started by applying the desired electrical current at −40 mA using DC power supply (Lambda Electronique, Melville, Long Island, NY, USA). The current remained constant during the electrolysis and aliquots for testing were withdrawn over the specific period of time. The AO7 mineralization was identified using a TOC-L CSH/CSN Shimadzu (Kyoto, Japan) analyzer to measure the total organic carbon (TOC) removal. Calibration curves for total carbon (TC) and inorganic carbon (IC) analysis were built up by automatic dilution of standard solutions of potassium hydrogenophtalate (TOC) and sodium hydrogen carbonate (IC). The mineralization was performed for 8 h, after which the electrolyte and dye solution was replaced with a freshly prepared solution.

The starting contaminant solution and the aliquots withdrawn at given time intervals during the treatments were analyzed by TOC-L CSH/CSN (Shimadzu, Tokyo, Japan), equipped with a chemiluminescence gas analyzer for N_TOT detection. The analyses were conducted according to the following instrumental conditions: furnace temperature = 720 °C; carrier gas flow = 150.0 mL/min; supply gas pressure = 285.0 kPa.
Accordingly, the EO performances were estimated in terms of N_TOT removal (%) using the following equation: $$N_{TOT} removal (\%)=\frac{N_{TOT}\left(t=0\right)-N_{TOT}\left(t\right)}{N_{TOT}\left(t=0\right)}.$$
In addition, NO₃⁻ measurement was performed using a Lambda 40, spectrometer, with an optical path = 1.00 cm (Perkin Elmer, Waltham, MA, USA).

For chemical analysis, 20 ml of the water samples were filtered through a 0.2 μm Whatman® nucleopore track-etch membrane, and the concentration of phosphorous was determined by the colorimetric method with ascorbic acid (AOAC, 1980 ), using a spectrophotometer (Espectro Max Plus, model 384, Molecular Devices Corporation, Sunnyvale, United States). The remaining unfiltered water samples were sent to the Laboratorio Universitario de Nanotecnología Ambiental (Mexico City) where total nitrogen (N) and carbon (TC) were determined using high temperature platinum catalyzed combustion (TOC-L CSH/CSN Shimadzu, Japan). Total inorganic carbon (IC) was analyzed using the same method, after acidification of the samples with 1 M HCl, and total organic carbon (OC) was calculated as TC-IC.