Effects of Electrode Composition on Electrocoagulation of Rice Mill Effluent

This study investigates the effect of various electrode combinations on total organic carbon (TOC), chemical oxygen demand (COD), and turbidity reduction during the electrocoagulation (EC) treatment of rice mill effluent (RME). The EC experiments were conducted using stainless steel-aluminum (SS-Al), aluminum-aluminum (Al-Al), and iron-aluminum (Fe-Al) electrode combinations under identical operating conditions and constant current density. The sludge generated during EC of RME was characterized using SEM, EDX, and FTIR analysis. Batch EC experiments revealed that SS-Al exhibited superior treatment performance, achieving 73.3% TOC, 70.1% COD, and 88.2% turbidity removal within 90 min of process, with negligible improvement beyond 60 min. SEM images of sludge showed highly porous and agglomerated floc structures for SS-Al sludge, indicating effective sweep flocculation, while Al-Al sludge displayed smoother surfaces and Fe-Al sludge showed dense morphologies with localized cracking. EDX results confirmed dominance of electrode-derived elements, with Fe (55-70 wt.%) and O (20-30 wt.%) in Fe-based sludge and Al (35-50 wt.%) and O (40-55 wt.%) in Al-based sludge, along with trace elements (Cr, Ni, Mn, Si, P, S < 5 wt.%). FTIR spectra identified O-H stretching (3200-3500 cm^-1), H-O-H bending (1630-1650 cm^-1), Al-O-Si/Si-O-Si bands (1020-1120 cm^-1), and characteristic Fe-O (560-620 cm^-1) and Al-O (720-780 cm^-1) vibrations, confirming pollutant removal via hydroxide precipitation, adsorption, and charge neutralization. The findings highlight SS-Al as a durable and efficient electrode configuration in EC for sustainable RME treatment.