A convenient strategy is proposed for improving the oil-absorbing performance of Calotropis gigantea fiber (CGF) by a simple immersion procedure that takes seconds ("instant") in an ethanolic solution of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES). The fabricated CGF shows a roughed surface with the water contact angle of 130, and with further combination of its intrinsic large lumen, this treated fiber PFOTES-CGF shows a remarkable improvement in oil absorbency, with an increase percentage of 52.2% for soybean oil, 22.0% for engine oil and 112.2% for kerosene, respectively. Owing to its hydrophobic-oleophilic property, the PFOTES-CGF can selectively collect oil spills from water with fast absorption kinetics, high absorption capacity and good recyclability, and also can be used for construction of a gravity-induced separation system for subsequent oil-water separation. This facile approach can be further applied to kapok fiber and proved to be very efficient in improving its oil-absorbing performance. Due to the abundance and biodegradability, upgrading this fiber via versatile methods may further explore its potential as an attractive alternative for oily wastewater treatment. (C) 2016 Elsevier B.V. All rights reserved.