Enhanced sonophotocatalytic degradation of phthalate acid ester using copper-chromium layered double hydroxides on carbon nanotubes and biochar

Abstract

Layered double hydroxides (LDHs) are lamellar and stable nanocatalysts driven by visible light. They have received much attention in the context of advanced oxidation processes. Their catalytic performance is remarkably restricted owing to undesired aggregation and the possibility of electron-hole recombination. To address these issues, we engineered carbon-nanotube (CNT)-and biochar (BC)-based CuCr LDH nanocomposites via a facile hydrothermal method. The synthesized nanocomposites were physically and chemically characterized using various methods. The performances of the BC-CuCr LDH and CNT-CuCr LDH nanocomposites were compared during the sonophotocatalytic degradation of dimethyl phthalate. With 1.5 g L-1 of BC-CuCr LDH, complete degradation of dimethyl phthalate was achieved within 25 min under 50 W light intensity and 150 W ultrasound irradiation with a synergy factor of 14. The critical roles of the hydroxyl and superoxide radicals were confirmed by the addition of several inhibitors. Ultimately, six possible intermediates generated during the sonophotocatalytic process were identified using gas chromatography-mass spectrometry (GCMS).