Preparation of a MWCNT/ZnO nanocomposite and its photocatalytic activity for theremoval of cyanide from water using a laser

Abstract

Nano-zinc oxide (n-ZnO) was loaded onto multi-walled carbon nanotubes (MWCNTs) via ahydrothermal process. Here pure n-ZnO used for loading was synthesized by thepulsed-laser ablation technique while MWCNTs were used as received. The synthesizedMWCNT/ZnO nanocomposites were characterized using x-ray diffraction, field emissionscanning electron microscopy, high resolution transmission electron microscopy and Fouriertransform infrared spectrometry. A model has been proposed for the structuralnature of the alignment of ZnO on the surface of MWCNTs. The photocatalyticactivity in the removal of highly toxic substances like cyanide (CN) was carried outin a special reactor using pulsed 355 nm UV generated by the third harmonicof an Nd:YAG laser. In order to understand the cyanide removal process, thestudy was carried out at different laser irradiation times, incident laser energies,pH of the solution and dosage of the MWCNT/ZnO nanocomposite. The studydemonstrated that the CN removal process by MWCNT/ZnO composite has higherphotocatalytic activity than pure n-ZnO and MWCNTs alone. The mechanism for thedegradation using MWCNT/ZnO has been schematically explained. It was noticed thatthe oxidation process activity is affected by the pH of the solution, and after20 min of UV laser irradiation, approximately 90% of CN had been degraded.