Acid-induced demulsification versus alum and polyaluminium chloride coagulation for oil and turbidity removal from concentrated soybean oil-in-water emulsions

This study evaluated the treatment of concentrated soybean oil-in-water emulsions by acid-induced demulsification using hydrochloric acid (HCl) and by coagulation with polyaluminum chloride (PAC) and alum. The impact of chemical dose, pH, and settling time was examined to determine the effectiveness of each process in oil and turbidity removal. Acid treatment reduced turbidity by 97.1% through phase separation at low pH but was not sufficient to bring residual oil below discharge standards. PAC and alum both demonstrated strong pH- and dose-dependent removal behaviors, with optimal performance at pH 7 for PAC and pH 6 for alum. Among the tested systems, the maximum removal of oil and turbidity was observed using optimized alum coagulation in a two-stage process, achieving oil removal up to 82% and turbidity removal of over 96%, which outperformed HCl and PAC, especially for high-strength emulsions. These findings identify alum-based systems as the most effective conventional choice for high-percentage oil and turbidity removal in concentrated soybean oil emulsions.