Electrocoagulation of hypersaline tannery brines: optimisation and steel-electrode corrosion behaviour

Hypersaline brines generated from contaminated tannery curing salt represent a significant environmental and waste management challenge. Electrocoagulation (EC) using iron electrodes offers a promising treatment strategy, although electrode corrosion remains an important operational concern. Response surface methodology was applied to optimise total organic carbon (TOC) removal, while electrode corrosion behaviour was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarisation under different salinity levels and electrode surface conditions. Under optimal conditions (16 min, 371 A·m⁻²), EC achieved 88% TOC removal. Corrosion experiments showed that saturated brines (≈ 30 wt.% NaCl) exhibited substantially lower corrosive intensity than less concentrated NaCl solutions (≈ 0.3 wt.% and 3.0 wt.% NaCl). Corrosion intensity decreased nearly five-fold as NaCl concentration increased from 3 to 30 wt.%, a trend consistent with reduced dissolved oxygen availability at higher salinity. Electrode surface condition also influenced corrosion behaviour, highlighting the importance of regular electrode maintenance during operation. After dilution, the treated brine was applied in the wet-blue leather pickling process, demonstrating its potential for reintegration within leather processing operations. By enabling recovery and subsequent application of contaminated curing salt, this approach contributes to reducing landfill disposal and improving management of hypersaline industrial residues.