Kinetic and equilibrium studies of hydrophilic and hydrophobic rice husk cellulosic fibers used as oil spill sorbents

In this work, rice husk cellulosic sorbents are produced by both chemical and biological pretreatment. The results indicate that the sorbent pretreated by sodium hydroxide (NaOH) and hydrogen peroxide (H2O2) contains up to 87.75% cellulosic concentration. Acetylated sorbents produced from both NaOH/H2O2 and Aspergillus flavus pretreated rice husks are compared with raw rice husk and non-acetylated rice husk sorbents for oil sorption capacities. By plotting oil uptake capacity against contact time, the optimum theoretical sorption capacity of acetylated chemical pretreated rice husk sorbent is 28.2 g/g RMG 386 after 15 min dripping. The sorption data shows that the modified rice husk sorbents achieve saturation after only 3-5 min of contact with both RMG 386 marine diesel and corn oil. The experimental data of acetylated chemical pretreated rice husk sorbent is analyzed using the pseudo-first order, the pseudo-second order and the intraparticle diffusion models. The model results indicate that the pseudo-second order model accurately correlates with the oil sorption data. In terms of the equilibrium isotherm analysis, the Freundlich model provides the best fit to the experimental data. As a result, the acetylated rice husk sorbent has shown to significantly outperform the non-acetylated sorbent with a high oleophilic and hydrophobic capacity with up to 19.66 g/g RMG 386 oil uptake capacity compared to 8.26 g/g by the non-acetylated rice husk sample in an aqueous medium. (C) 2015 Elsevier B.V. All rights reserved.