Scalable synthesis of SWCNT via CH4/N2 gas: The effects of purification on photocatalytic properties of CNT/TiO2 nanocomposite

Single-walled carbon nanotubes (SWCNT) were synthesized by a catalytic CVD method over Mo–Fe–MgO and Mo-Fe-Al2O3 catalysts. A systematic investigation was carried out for the purification of SWCNTs by using 20 methods including different acids, acid concentrations, temperatures, and treatment times. The method of consecutive HCl treatment, air oxidation, and second time HCl treatment was successful for the purification of SWCNTs. The purification was effective in the removal of the catalyst support, embedded metal catalysts and non-nanotube carbon materials from the as-synthesized SWCNTs. Effects of purification of SWCNTs on the photocatalytic activity of CNT-based nanocomposites were then studied. The composite SWCNT/TiO2 containing 15 wt% purified SWCNT was synthesized which showed the maximum photocatalytic activity in the degradation of the dye rhodamine B under optimized conditions. The photocatalytic activity of the composite pure-SWCNT/TiO2 was much higher than those of non-purified-SWCNT/TiO2 and neat TiO2. Overall, this work could clarify the scalable synthesis of SWCNTs, an effective purification method for SWCNTs prepared by CCVD and the purity effect on the photocatalytic activity of CNT-based nanocomposites for wastewater treatment. [Display omitted] •Single-wall carbon nanotubes were synthesized via a large-scale strategy of CCVD method.•A systematic study was achieved for the purification of the synthesized SWCNT over FeMo/Al2O3 and FeMo/MgO catalysts.•More than 20 methods were examined for the purification of SWCNT.•The purified SWCNTs provided high improvement on the photocatalytic efficiency of the SWCNT/TiO2 composite.