Removal of colour and COD from synthetic textile wastewaters using O 3, PAC, H 2O 2 and HCO 3−

Abstract

This study aimed to investigate removal of colour and chemical oxygen demand (COD) from synthetic textile wastewaters using O 3, powder activated carbon (PAC), H 2O 2 and HCO 3 − in a semi-batch reactor. 1:2 metal complex dyestuffs containing two molecules of dyestuffs versus a chromium atom was used. Experiments were conducted under the various pHs (3–12), temperatures (18–70 °C), ozone doses (164–493 mg min −1). The combined effect of substances used on the removal of colour and COD was investigated. The mechanisms of colour and COD removal on the PAC were explained on the basis of the results of Fourier transform infrared spectroscopy (FTIR). In addition, the zeta potential values of PAC, ozonated PAC and ozonated PAC contaminated with intermediates were determined. The zeta potential values and FTIR plots of PAC particulates showed that PAC acted as an adsorbent in the combined processes. It was thought that all of the substances used in the semi-batch reactor had the combined effect on the removal of colour and COD because of the short treatment time of 5 min and high efficiencies of the removal of colour and COD. The efficiencies of removal of colour and COD in combination were compared with adsorption and ozonation only. In this study, the efficiencies of colour and COD removal during a reaction time of 30 min were obtained as 99 and 95%, respectively. At the result of this study, it was concluded that O 3, PAC and H 2O 2 were an important substances for the removal of colour and COD from synthetic textile wastewater when they were used in combination.