Di sodium hydrogen phosphate anhydrous

The chemicals used during the experiments were of analytical grade and were not further purified before usage. Graphite rods (6 mm diameter, 99.995% purity); potassium chloride (KCl, 99.98%); sodium dihydrogen phosphate (NaH₂PO₄, 100%) and di-sodium hydrogen phosphate anhydrous (Na₂HPO₄, 99.7%) were supplied by VWR Chemicals (Leuven, Belgium). Sodium acetate anhydrous (CH₃COONa, ≥99.0%); ammonium sulphate ((NH₄)₂SO₄, ≥99.0%), sodium chloride (NaCl, 99.5%); sodium carbonate anhydrous (Na₂CO₃, 99.3%), magnesium chloride hexahydrate (MgCl₂∙6H₂O, 99–102%); magnesium sulphate (MgSO₄, 99%); magnesium nitrate hexahydrate (Mg(NO₃)₂∙6H₂O, 99%) were provided by REACTIVUL Bucuresti (Bucharest, Romania). Potassium ferrocyanide K₄[Fe(CN)₆] and L(+)-Ascorbic acid (C₆H₈O₆, AA, ≥99%) were acquired from Merck (Darmstadt, Germany). Sodium acetate anhydrous (CH₃COONa, ≥99.0%) was purchased from ChimReactiv SRL (Bucharest, Romania). N,N-dimethylformamide (DMF) was acquired from Fluka Chemie GmbH (Buchs, Switzerland), while boric acid (H₃BO₃, 99%) was provided by Andra Chim SRL (Bucharest, Romania). The MQuant^® Nitrite Test (Merck KGaA, Darmstadt, Germany) was employed for UV-Vis investigation of nitrite solutions. Deionized water with a resistivity of at least 18.2 MΩ × cm was used to prepare all solutions.

Hydrogen peroxide (H₂O₂, 30% w/v), ferrous sulfate heptahydrate (FeSO₄.7H₂O, 99.0% purity), sodium sulfite (Na₂SO₃, 98.0% purity), sodium hydroxide (NaOH, 99.0% purity), sulfuric acid (H₂SO₄, 97–98% purity) and nitric acid (HNO₃, 65% purity) were purchased from Panreac. Pure liquid toluene (99% purity) (chemical formula C₇H₈, molar mass = 92.14 g mol⁻¹) and di-sodium hydrogen phosphate anhydrous (99% purity) were purchased from VWR Chemicals.
A commercial activated carbon, Norit GAC 1240 AF, was used as the initial material to prepare all modified activated carbons and AC-Fe catalysts. Melamine (C₃H₆N₆, ≥ 99% purity) and iron (III) nitrate nonahydrate (FeH₁₈N₃O₁₈, 99% purity) were obtained from Fluka.

Every chemical utilized was of the analytical grade and was not further purified before usage. Graphite rods (6 mm diameter, 99.995% purity), potassium chloride (KCl, 99.98%), Sunset Yellow FCF (SY, dye content 90%) and Tartrazine (TRZ, dye content ≥ 85%) were purchased from Sigma-Aldrich (Kandel, Germany). Sodium dihydrogen phosphate (NaH₂PO₄, 100%) and di-sodium hydrogen phosphate anhydrous (Na₂HPO₄, 99.7%) were supplied from VWR Chemicals (Leuven, Belgium). Sodium acetate anhydrous (CH₃COONa, ≥99.0%) and ammonium sulfate (NH₄)₂SO₄, ≥99.0%) were provided from REACTIVUL Bucuresti (Romania). Potassium ferrocyanide K₄[Fe(CN)₆, L(+)-Ascorbic acid (C₆H₈O₆, AA, ≥99%), and citric acid (C₆H₈O₇, CA, ≥99.5%) were acquired from Merck (Darmstadt, Germany). N,N-dimethylformamide (DMF) and ammonium thiocyanate (NH₄SCN, ≥99%) were acquired from Fluka Chemie GmbH (Buchs, Switzerland). Deionized water with a resistivity of at least 18.2 MΩ × cm was used to prepare all solutions.