Efficient removal of ammoniacal nitrogen from textile printing wastewater by electro-oxidation considering the effects of NaCl and NaOCl addition

Abstract

In this study, an electro-oxidation (EO) process using graphite electrodes as electrode pairs was used for the removal of chemical oxygen demand (COD), ammoniacal nitrogen (NH4+-N), and color from real textile printing wastewater. The effects of solution pH, sodium chloride (NaCl) dosage, sodium hypochlorite (NaOCl), which is the oldest and still most important chlorine-based bleach, dosage, and oxidation time were investigated on the removal efficiencies. Operating conditions for the EO reactor were applied to current density 1 mA/cm2, distance between the electrodes: 2 cm, 150 min operation time, and stirring speed of 500 rpm. At optimum conditions: pH 9.5, applied current density 1 mA/cm2, NaCl dosage of 8 g/L, NaOCl dosage of 44.4 mg/L and 150 min electro-oxidation time, the obtained removal efficiencies were 86.5% and 91.1% for chemical oxygen demand (COD) and ammoniacal nitrogen, respectively. Efficiency was increased to 91.1% for ammoniacal nitrogen from 21.7% after applying EO combined with NaOCl addition compared to individual NaOCl addition. HIGHLIGHTS Ammonia concentrations can be high in textile dye wastewater due to the usage of nitrogen-based substances.; Various oxidation processes are not effective for ammonium removal.; The aim of this study was to determine the efficiency of individual EO and EO with an addition of NaCl and NaOCl.; EO assisted NaOCl and NaCl is a promising technology for the oxidation of both carbon and nitrogen-based contaminants.;

Keywords

• ammonium removal
• cod removal
• dye removal
• electro-oxidation
• textile printing wastewater