Improved Adsorption and Photocatalytic Degradation of Methyl Orange by Onion-like Nanocarbon/TiO2 Nanocomposites

Abstract

Waste cooking oil, a known environmental pollutant, has been used as a precursor for the synthesis of onion-like nanocarbons (OLNCs) using flame pyrolysis. The OLNCs were added to TiO2 to form TiO2/OLNC nanocomposites through hydrothermal treatment. The TiO2/OLNCs ratio was varied by increasing the mass of the OLNCs (10, 20, 30, and 50 mg), while the mass of TiO2 (100 mg) was kept constant at C to TiO2 molar ratios of 1:2, 1:4, 1:6, and 1:10, respectively. The surface area of the photocatalysts increased with an increase in the mass of OLNCs. The nanocomposites were applied in the photocatalytic degradation of methyl orange. The photocatalysts showed a degradation efficiency trend of TC-10 > (99.9%) TC-20 > (90%) TC-30 > (81%) TC-50 > (70%) TiO2 (44%) in 120 min. A similar trend was observed from the first-order kinetic rate data. The degradation efficiency of methyl orange was improved by adding 5% H2O2 (99.9%) in 30 min. The OLNCs were responsible for increased photocatalytic activity due to a high adsorption efficiency compared to pure TiO2. The OLNCs acted as an electron acceptor, while the TiO2 acted as an electron donor. The enhanced catalytic behavior was achieved by hindering the recombination of e−/h+ in the composite and increasing the adsorption capability of TiO2.