Evaluation of hydrophobicity/oleophilicity of kapok and its performance in oily water filtration: Comparison of raw and solvent-treated fibers

Kapok (Ceiba pentandra) fiber, an agricultural product, contains waxy material that contributes to its hydrophobic–oleophilic characteristics. Its performances, as untreated and solvent-treated fibers, in deep-bed filtration of oily water containing 2.5% diesel were assessed in this study. The solvents used were ethanol and chloroform. The filtration performance was assessed through measurements of column breakthrough time, filtration rate, filtrate quality, and the amount of oil retained by the filter column at breakthrough under a constant vacuum pressure. The kapok fibers, both at its natural state and after solvent treatments, demonstrated excellent oil/water separation and filtration, for which oil was retained while water was filtered through the kapok filter column. The filtrate quality, in terms of turbidity and percent oil removal, appeared to be unaffected by the solvent treatment of the kapok fiber. The oil removal efficiencies consistently exceeded 99%. However, the filter column packed with solvent-treated kapok fibers showed premature breakthrough of the oily influent and produced less filtrate than that by the untreated kapok. The filter column packed with the solvent-treated kapok also retained less oil compared to the untreated kapok, and as a result, a quarter of the filter pore volume was not wetted even after breakthrough. This could be the main cause for the premature breakthrough of the oily influent. Apparently, the solvent treatment for impurities removal could impair the oleophilicity/hydrophobicity of the kapok fibers which was crucial for the oily water separation and filtration.