Sustainable production of nitrogen-doped carbon quantum dots for photocatalytic degradation of methylene blue and malachite green

Abstract

Empty fruit bunches (EFB) are the most abundant source of agricultural wastes in Malaysia but with limited applications. Due to their high content of carbon, oxygen and hydrogen, EFB can potentially be used to produce carbon-based nanoparticles. This study introduces a sustainable route to fabricate nitrogen-doped carbon quantum dots (NCQDs) through hydrothermal treatment using lignin that was extracted from EFB as a raw material. The NCQDs showed blue fluorescence under a UV lamp owing to their excellent optical properties. The optical properties of NCQDs remained unchanged after several hours of UV-light exposure and over eight months of storage, indicating an outstanding reactivity and stability. The average particle size of NCQDs was found to be 3.6 nm. The NCQDs degraded 97 % of methylene blue and 98 % of malachite green within 180 min and 120 min of sunlight irradiation, respectively. The photocatalytic degradation rate of these dyes followed first-order kinetics based on the Langmuir-Hinshelwood model. This research demonstrates an attractive way of producing a highly efficient photocatalyst towards the photocatalytic degradation of organic dyes in water treatment.