Carbon Quantum Dot-Titanium Doped Strontium Ferrite Nanocomposite: Visible Light Active Photocatalyst to Degrade Nitroaromatics

Abstract

The synthesis of carbon quantum dots (CQDs) from agricultural waste is a promising approach for waste valorization. In the present work, CQDs were synthesized using sugarcane bagasse as a carbon precursor. The nanocomposite of CQDs with trimetallic strontium–titanium ferrite was synthesized with an ultrasonication approach. The structural, magnetic and optical features of the synthesized nanocomposite and pristine NPs were studied using different analytical techniques. The TEM micrograph of the nanocomposite reveals the distribution of CQDs (8–10 nm) along with the agglomerated ferrite NPs. To validate the results, the photocatalytic efficiency of the nanocomposite, NPs and CQDs was comparatively studied for the photodegradation of nitroaromatic pollutants viz. p-nitrophenol, martius yellow and pendimethalin under visible-light irradiation. A nanocomposite having a 2:1 w:w ratio of CQDs and Sr0.4Ti0.6Fe2O4.6 displays an excellent photocatalytic performance, with the degradation efficiency ranging from 91.2 to 97.4%, as compared with 65.0–88.3% for pristine NPs and CQDs. These results were supported by band gap and photoluminescence analyses. The promising photocatalytic potential of the nanocomposite over the pristine CQDs and ferrite NPs could be ascribed to the increased specific-surface area (101.3 m2/g), lowering in band gap coupled with fluorescence-quenching which facilitated the transfer of photoinduced charge carriers. The impact of parameters affecting the photocatalytic process viz. pH, catalyst dose and contact time was also investigated. On the basis of quenching and gas chromatography-mass spectrometry (GC-MS) studies, plausible degradation pathways were proposed. The results highlight the broad potential of designing substituted ferrite-CQDs-based nanocomposites as reusable and visible-light-driven photocatalysts.