Visible light photocatalytic degradation of cyanide using Au–TiO2/multi-walled carbon nanotube nanocomposites

• MWCNT/Au–TiO2 were used for photocatalytic oxidation of cyanide.
• Photocatalytic oxidation of cyanide was dependent on wt% of MWCNT, reaction time, and weight of catalyst.
• Catalyst re-use revealed the present photocatalyst remain effective and active after five cycles.

Au–TiO2 nanocatalyst-supported multi-walled carbon nanotubes were effectively prepared by the sol–gel modified technique. The Au–TiO2/MWCNT nanocomposite was used to remove cyanide by photocatalytic oxidation under visible light irradiation. The Au–TiO2/MWCNT nanocomposite photocatalyst was characterized by XRD, TEM, UV–vis, and BET techniques. Results revealed the nanoparticles TiO2 and Au were well dispersed into MWCNT. Addition of Au and MWCNT can eliminate recombination pairs of electron holes in the Au–TiO2/MWCNT nanocomposite. Also, the presence of the MWCNT in the Au–TiO2/MWCNT nanocomposite transfers absorption of TiO2 from the UV region to visible region of the spectrum. The optimum weight ratio of MWCNTs:TiO2:Au was 0.06:1.0:0.10, which resulted in experimental performance photocatalyst oxidation of about 100% of the cyanide in a solution of 100 mg/L over 40 min, with 1.2 g/L of catalyst used.

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