Physicochemical and sorption characteristics of Malaysian Ceiba pentandra (L.) Gaertn. as a natural oil sorbent

Ceiba pentandra (L.) Gaertn (kapok) is a natural sorbent that exhibits excellent hydrophobic–oleophilic
characteristics. The effect of packing density, the oil types and solvent treatment on the sorption characteristics
of kapok was studied in a batch system. Oil sorption capacity, retention capacity, entrapment
stability and kapok reusability were evaluated. Based on SEM and FTIR analyses, kapok fiber was shown to
be a lignocellulosic material with hydrophobic waxy coating over the hollow structures. Higher packing
density at 0.08 g/ml showed lower sorption capacity, but higher percentage of dynamic oil retention, with
only 1% of oil drained out from the test cell. Kapok remained stable after fifteen cycles of reuse with only
30% of sorption capacity reduction. The oil entrapment stability at 0.08 g/ml packing was high with more
than 90% of diesel and used engine oil retained after horizontal shaking. After 8 h of chloroform and alkali
treatment, 2.1% and 26.3% reduction in sorption capacity were observed, respectively, as compared to
the raw kapok. The rigid hollow structure was reduced to flattened-like structure after alkali treatment,
though no major structural difference was observed after chloroform treatment. Malaysian kapok has
shown great potential as an effective natural oil sorbent, owing to high sorption and retention capacity,
structural stability and high reusability.