Waste plastic-derived NiO-MWCNT composite as visible light photocatalyst for degradation of methylene blue dye

Low-cost and visible light photocatalysts are essential to achieve industrial-scale photocatalysis. Towards this goal, waste-derived preparation of nanophotocatalysts can be an important direction. Herein, we report waste-derived preparation of nickel oxide–multiwall carbon nanotube (NiO-MWCNT) and its application for visible light photocatalysis to degrade methylene blue (MB) dye. NiO nanoparticle (size ~ 4 nm) was prepared by the coprecipitation method. NiO-MWCNT composite was prepared by thermocatalytic pyrolysis using NiO nanoparticle and high-density polyethylene (HDPE) waste plastic. The average length and diameter of MWCNT were found to be ~ 300 nm and 66 nm, respectively. The NiO-MWCNT composite photocatalyst is found to have a band gap of 3.02 eV along with characteristic CNTs X-ray diffraction (XRD) peak (26.12°), Raman D, G peaks. The decolorization% of MB dye is achieved up to 92.4% using NiO-MWCNT catalyst under 28 W light-emitting diode (LED) visible light within 1 h. The decolorization% for 1 Sun equivalent light exposure is found to be 87.45% within 1 h. A degradation pathway of MB dye has been proposed based on the ESI–MS data leading to the formation of different intermediate fragments of m/z 214, 193, 186, 167, 158, 150, 141, 125, 114, 109, and 102. The study will generate momentum in solar-based industrial-scale photocatalysis for pollutant management and other solar-based chemical transformations. Graphical abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.