3.6. Dynamic oil retention
The oil retention capacity is an important parameter for evaluating the ability of the sorbents to retain the absorbed oil during transfer and handling operations. As shown in Fig. 5, RP, AP and SP demonstrate high oil retention ability that less than 30% of the absorbed oil is lost from the oil-saturated samples after 2 h. In this study, diesel drained out at a faster rate and achieved equilibrium sooner compared to lubricating oil. The phenomenon may be explained by previous study. Lim et al. found that the draining process could be due to two reasons (Lim & Huang, 2007). Firstly, it was the instantaneous dripping of oil from external surfaces of the kapok assembly; Secondly, the draining of extra-lumen liquids occurred because the capillary pressure was insufficient to hold the weight of the oil retained in the kapok assembly. The results imply that SP has good oil retention capacity.