Sorption and recovery of heavy oils using carbonized fir fibers and recycling

Fibers extracted from fir trees (Abis sachalinensis Fr. Schm) and carbonized at either 380 or 900degreesC were found to have a high performance for sorption, recovery and recycling of heavy oils, even the viscous ones. Sorption capacity showed strong dependence on bulk density of carbonized fibers, suggesting the importance of the space formed among entangled fibers: 60-80 g/g for bulk density of ca. 6 kg/m(3) and 10-20 g/g for density of ca. 40 kg/m(3). The sorption capacity of carbonized fir fibers for a less viscous heavy oil was almost comparable to that of exfoliated graphite which was also reported to have high capacity. For viscous oil, however, carbonized fir fibers had higher sorption capacities than exfoliated graphite, particularly when the bulk densities are high. Less viscous heavy oil could be recovered by simple filtration under suction and the fibers could be reused for the sorption of oil, although the sorption capacity decreased with recycling. Their recycling performance was also strongly dependent on their bulk density: the sorption capacity of 6 kg/m(3) fibers after the eighth cycle became less than 60% from that of the first cycle, but for 35 kg/m(3) fibers it was more than 90%. Viscous oil could be recovered only by washing with n-hexane and also with less viscous oil. After washing the fir fibers could be reused for the sorption of oil. (C) 2002 Elsevier Science Ltd. All rights reserved.