Fig. 1. Schematic illustration of current work: (a) catalytic pyrolysis of waste PE; (b) fabrication of graphene-CNT aerogel; (c) adsorption test.

Fig. 2. Effects of protectant type on phase formation (a) and the yield of CNTs (b) in samples resulted from 2 h pyrolysis at 873 K with 0.50 wt.% Co(NO3)2 catalyst precursor.

Fig. 3. SEM images of the samples whose XRD-patterns and yields of CNTs are given in Fig. 2:(a) without protectant, None; (b) oleylamine, OAm; (c) ISOBAM-104, ISOBAM; (d) polyvinylpyrrolidone, PVP; (e) hexadecyl trimethyl ammonium bromide, CTAB; (f) sodium dodecyl benzene sulfonate, SDBS.

Fig. 4. TEM (a, b) and HRTEM images (c, d) of CNTs prepared at 873 K for 2 h using 0.50 wt.% Co(NO3)2 as a catalyst precursor and OAm as a protectant (ROAm = 6).

Fig. 5. Compression process under a 100.0 g load (a), standing on a Setaria viridis (b), WCA measurement (c), and Cyclic compressibility (d) of a ~4.0 cm3 graphene-CNT aerogel prepared with a CNT/GO mass ratio of 5:5 and a solid content of 0.2 wt.%.

Fig. 6. XRD patterns (a) and Raman spectra (b) of the commercial graphene oxide (GO), as-obtained CNTs, and graphene-CNT aerogel prepared with a CNT/GO mass ratio of 5:5 and a solid content of 0.2 wt.%.

Fig. 7. SEM images of pure graphene aerogel (a) and graphene-CNT aerogel (b) prepared with a CNT/GO mass ratio of 5:5 and a solid content of 0.2 wt.%.

Fig. 8. TEM (a), HRTEM (b, c) images and selected area electron diffraction (SAED) pattern (d) of the graphene-CNT aerogel prepared with a CNT/GO mass ratio of 5:5 and a solid content of 0.2 wt.%.

Fig. 9. Absorption capacities (Q) for toluene, paraffine, vegetable oil and phenoxin (b), and recyclability for the adsorption of paraffine under adsorption-squeezing cycles (c) of the graphene-CNT aerogel prepared with a CNT/GO mass ratio of 5:5.