Hollow carbon fiber sponges have been synthesized through the pyrolysis of bulk crude catkins which are ultralow-cost, hollow carbon fibers. The sponges exhibited a high sorption capacity for organic solvents and oils and excellent recyclability.

Due to their light weight and recyclable value, carbon nanotube-based materials have been widely used as adsorbents for oils and organic pollutants. The discovery and research of a novel approach to prepare carbon nanotube-based adsorbents with excellent performance is still required urgently. In this paper, we used a modified microfluidic device to construct a kind of three-dimensional (3D) magnetic porous multi-walled carbon nanotube bead and utilized them to adsorb oils and organic solvents floating on or under the water. In the preparation process, acidified multi-walled carbon nanotubes (MCNTs), watersoluble ferroferric oxide nanoparticles (Fe 3 O 4 ) and water-soluble submicron polystyrene microspheres can improve their dispersion stability and uniformity in microfluidic droplets. In addition, polystyrene microspheres as the hard template can not only supply abundant porous structures but also stabilize the morphology of composite droplets during the solidification. The measurement data indicated that magnetic porous multi-walled carbon nanotube beads (MCNTBs) had adsorption capability (up to 6-18 times their own weight) for oils and organic solvents with 6 times recyclability, and they can serve as a kind of promising adsorbent.

In this paper, magnetic porous graphene/multi-walled carbon nanotube beads (MPGCBs) were fabricated by a modified capillary microfluidic device. Polystyrene (PS) microspheres not only served as the hard templates to form uniform macropores, but were also beneficial for keeping the stability of spherical architecture. In the process of solidification, both graphene oxide (GO) and acidified multi-walled carbon nanotubes (aMWCNTs) enriched with carboxyl functional groups can form stable and uniform dispersion in the droplets. After the calcination treatment, the composite beads had excellent water resistance and robust mechanical properties. Moreover, due to the addition of the Fe 3 O 4 nanoparticles, the beads also possessed the advantage of flexible operation, which can facilitate oriented movement and recycling of the absorbents, and promoted the collection and recovery of the useful pollutants. These multifunctional MPGCBs with interconnected macroporous structures showed high absorption capacity (up to 8-25 times their own weight) for various kinds of oils and organic solvents, relatively high separation efficiency and long-term recycle stability in the oil/water mixture separation process.