Plant axillary stem gall extract mediated bioengineered CuO nanoprisms as robust and reusable catalyst for photocatalytic and catalytic degradation of water pollutants

Abstract

The current work explains the synthesis of bioengineered CuO nanoprisms using axillary stem gall extract of the Ziziphus mauritiana plant. The photocatalytic and catalytic reduction potential of bioengineered CuO nanoprisms was analyzed for the photo-mineralization of methylene blue (MB) organic dye under exposure to visible light and catalytic reduction of 4-nitrophenol (4-NP) in the presence of NaBH4 solution. The biogenic CuO nanoprisms were characterized using XRD, FTIR, FESEM, EDS, and UV–Vis. spectroscopic techniques. The mean crystallite size of CuO nanoprisms was estimated to be 34.24 nm while the band gap energy value was found to be 1.47 eV. 99.21 % of MB dye was photo-mineralized within 70 min of visible light illumination at pH=5 and 30 mg of catalyst whereas 4-NP was almost completely reduced to 4-AP within 5 min in the presence of bioengineered CuO (NPs). The data of photo-mineralization of MB dye and catalytic reduction of 4-NP well agreed to the pseudo-first-order kinetics with the rate constant values of 63.86 × 10−3 and 0.8439 min−1, respectively. The reactive species entrapping studies revealed that •OH radicals were the key active species affianced in the photo-mineralization of MB dye. Photostability and reusability tests established that only a 9 % decline in the dye degradation efficiency of bioengineered CuO was observed after the fifth cycle of reuse under visible light irradiation.