A new method for removing dispersed carbon nanotubes from aqueous solution by nanoporous biosilica (frustule)

Abstract

In this paper, we propose a new method for removing dispersed carbon nanotubes (CNTs) from an aqueous solution by nanoporous biosilica (frustule) as an adsorbent. UV–vis spectra clearly showed that more than 90 % of the CNTs were adsorbed onto the surface of frustule when frustule was mixed with the CNT dispersion. In particular, adsorption was more effective in an acidic solution than in a basic solution or in pure water. In addition, methylene blue (MB) was adsorbed onto the surface of the frustule in similar fashion as the CNTs. This suggests that electrostatic interaction may be an important factor in determining the adsorption capacity. The CNTs adsorbed onto the surface of the frustule were easily removed from the solution by centrifugation. On the other hand, when we employed diatomite instead of frustule, the adsorption ratio of CNTs was less than 20 % even though diatomite is widely used as an adsorbent. Our results demonstrated for the first time that using frustule as an adsorbent to removing CNTs is effective and simple.