Effect of solution pH on the performance of three electrolytic advanced oxidation processes for the treatment of textile wastewater and sludge characteristics

Comparative removal of COD and color from real textile wastewater using three different electrolytic advanced oxidation processes, namely, electro-Fenton (EF), peroxicoagulation (PC) and pH-regulated peroxicoagulation (PC-pH) processes were analyzed in the present study. Graphite plates were used as both electrodes in the EF process, while an iron plate replaced the graphite anode in the PC and PC-pH processes; moreover, the effect of voltage and solution pH on the performance of these processes was compared. Sludge production was observed in peroxicoagulation processes, indicating that the removal of pollutants took place by both degradation and electrocoagulation processes. The sludge production increased with an increase in solution pH, indicating that the electrocoagulation process dominates the degradation process at higher pH. A reduction of 97% in color was observed in the EF and PC-pH processes, while in the PC process was 82% after 60 min of electrolysis. At the same time, 64%, 70% and 75% of COD was removed by the EF, PC-pH and PC processes, respectively. Moreover, 47.7% of organic pollutant was mineralized via the EF process, and the sludge produced was characterized using the SEM, XRD and FTIR techniques. Furthermore, the sludge produced from the peroxicoagulation process was used as a heterogeneous EF catalyst for the degradation of textile wastewater, and removal of 97% of color, 47% of COD and 33.2% of TOC was observed.