Sorption capacity of exfoliated graphite for oils-sorption in and among worm-like particles Original Research Article

Four exfoliated graphite (EG) samples with exfoliation volume ranging from 102.6 to 267.7 mL/g were prepared. The volume of worm-like particles before sorption was estimated by analyzing the area occupied by worm-like particles in slices cut from the EG block formed using paraffin. The results show that both the volume in worm-like particles, Vn, and that among them, Vm, increase almost linearly with increasing exfoliation volume. Their ratios to the total exfoliation volume are 25% and 75%, respectively. Sorption experiments show that the average volume shrinkage of each worm-like particle is less than 1% and independent of oil viscosity. This implies that the volume of worm-like particles is almost unchanged after oil sorption. Sorption capacity of individual worm-like particle and bulk EG for kerosene, vacuum pump oil, and heavy oil were examined. Measurements show that both the sorption capacities of the pores in and among worm-like particles increase with increasing exfoliation volume. The volume of oils sorbed inside worm-like particles does not vary as much as that sorbed among them. For the oil with low viscosity, such as kerosene, most of the oil is sorbed in worm-like particles. The space among worm-like particles plays a very important role in oil sorption when the viscosity is high. For example, the heavy oil sorbed among worm-like particles reaches 68% of the total sorption capacity of EG with an exfoliation volume of 267.7 mL/g.