Unraveling the Chemical Transformation Pathway of Palm Oil Mill Effluent in Removing Sulfate via Synthesized Natural Earth‐Compound Coagulant

ABSTRACT This study unravels the intermolecular mechanistic degradation of palm oil mill effluent (POME) in sulfate removal, utilizing a distinctive coagulant derived from naturally abundant limestone (CaCO 3 ), which was activated into calcium hydroxide [Ca(OH) 2 ] through calcination and exothermic reactions. Sulfate was reduced from POME by 88.76% with the optimal conditions (pH 5, 200 g/L Ca(OH) 2 dosage, and 135 min settling time) with strong correlation ( r = 0.8237) and statistically significant ( p = 0.0064) of Pearson's correlation. Scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDX) revealed an ideal morphology and elemental composition with reduction of 4.4753 m 2 /g surface area in Ca(OH) 2 to slurry. Kinetic studies evaluated that sulfate removal at 4400 mg/L strongly followed the second‐order model with a high coefficient of determination ( R 2 = 0.9883). Analysis using Fourier‐transform infrared spectroscopy (FTIR) and gas chromatography–mass spectrometry (GC–MS) detected the formation of 2‐isopropyl‐5‐methyl‐1‐heptanol (C 11 H 24 O). Overall, this study demonstrates the potential of Ca(OH) 2 from CaCO 3 as an efficient material for POME additional treatment, helping reduce VOCs and improve the value of industrial wastewater.