Surfactant-assisted self-assembly and fractal evolution of the aluminosilicate species with insights into clinoptilolite nucleation and selective CO2/CH4 adsorption

The surfactant involvement in hydrothermal synthesis system of clinoptilolite (CP) is an effective strategy for regulating self-assemble of the aluminosilicate species. Herein, using cetyltrimethylammonium bromide (CTAB) as surfactant, the CTAB-assisted influences on nucleation behavior of CP were demonstrated via various characterizations. Especially, small angle X-ray scattering patterns were used to investigate the fractal structural evolutions of aluminosilicate species in their sol-gel phase. The results indicated that the primary building structural units with 8- and 10-membered rings appeared in the early induced stage gradually aggregated into the worm-liked particles with the prolonged crystallization time. Among them, the nucleation process was initiated by reorganization via the solution-mediated transport and thereafter appeared the pseudo-layered structures with the core (aluminosilicate species)-shell (CTAB) features at the liquid-solid interfaces. The irregulated lamellas with the heulandite structures increased in size of around 70 nm until reaching the maximum of 90 nm, then followed the occurrences of the re-dissolving and repaid growth. Especially, the lamellar nuclei growth showed the transformations from loose mass fractals to dense surface fractals with the extensions of the induced time. In which, the interfacial solvation layer thickness increased from 1.04 to 2.87 nm for CTAB-assisted CP, thicker than that (0.63–2.08 nm) for pure-CP. These demonstrations suggested that the additive CTAB in the induced stage inhibited the agglomeration of the aluminosilicate species and following growth of the crystal nuclei via the solvated attachments pathway. Finally, using the irregulated particle as an adsorbent, the CO 2 adsorption and CO 2 /CH 4 selectivity were preliminarily explored.