Cationic polymer flocculation optimization using a central composite design for color, polyphenols, and UV ₂₅₄ removal fro

Abstract

Wastewater from vegetable oil refineries (VORW) is heavily loaded with oils, greases, and phenolic compounds that are harmful to aquatic life and human health and requires effective treatment before discharge. This study reports the first use of the cationic polyacrylamide C8035 as a flocculant for VORW, applied after a low‐cost natural flotation pretreatment, and optimizes the process using response surface methodology. The effects of pH, flocculant concentration, and stirring time on the removal of color, aromatic organic matter (UV _254nm ), and polyphenols were investigated through jar tests. The raw effluent contained 168 mg/L of polyphenols and exhibited UV _254nm and color absorbances of 2.993 and 3.97 (dilution factor 10). Natural flotation alone removed 86.33% of polyphenols, 77.32% of color, and 61.91% of UV _254nm , while the subsequent flocculation step substantially improved performance. Analysis of variance confirmed that the quadratic models were highly significant ( R ²  = 0.948–0.980, adjusted R ²  = 0.90–0.96, p  < 0.0001) and reliable for prediction. Under the optimal conditions (pH 8, 20 mg/L flocculant, and 20 min stirring), removal efficiencies reached 98.27% for color, 88.82% for UV _254nm , and 83.27% for polyphenols, in close agreement with model predictions. These results demonstrate that C8035‐based flotation–flocculation is an efficient, low‐cost, and scalable approach for VORW treatment.