Photocatalytic Degradation of Xylene by Carbon Quantum Dots/Clinoptilolite Composites

Abstract

In this work, a series of clinoptilolite composites decorated with carbon quantum dots (CQDs/clinoptilolite) with hierarchical pore structures was demonstrated that exhibits good photocatalytic performance for the removal of xylene. The technique for the attachment of carbon quantum dots to clinoptilolite was prepared by a hydrothermal method in this study. The structural features were confirmed by SEM, TEM, EDS, XRD, BET, XPS, and solid diffuse reflection measurements, while the degradation mechanism was investigated by adding a trapping agent into the nanocomposites. The introduction of CQDs promoted the separation of photogenerated electrons and holes as well as the generation of reactive radicals, which effectively improved the light utilization and even increased the degradation rate of xylene by 73% at the optimal state. The photocatalytic test was conducted under a different dwell time, catalyst dosage, initial concentration, and illumination intensity. The results showed that the degradation rate of xylene by the CQDs/clinoptilolite catalyst reached 97.4% under the optimal reaction conditions (the catalyst was Catalyst No. 2, the residence time was 90 s, the initial concentration was 2.5 g/m3, the light intensity was three lamps for irradiation, and the catalyst dosage was 0.05 g). In addition, the degradation efficiency of the CQDs/clinoptilolite photocatalyst still reached 78% after eight consecutive catalytic regeneration cycles. This work sheds new light on the degradation of xylene.

Gadolinium-Doped Carbon Nanoparticles with Red Fluorescence and Enhanced Proton Relaxivity as Bimodal Nanoprobes for Bioimaging Applications

“…The same lattice spacing was observed early for CDs and CNPs synthesized by MCW [16,18], HTS [20] or similar methods at about 180 • C and slightly higher temperatures [26]. It is interesting to note that the graphene-like interlayer distances have been preserved in Gd-doped CNPs similar to the results for catalytically active CD-based nanocomposites, which were highly doped with different impurities such as aluminum and tellurium [26,27]. It means that the incorporation of both light and heavy elements does not necessarily destroy the atomic order in CDs and CNPs.…”

“…A HR-TEM image of a selected CNP reveals atomic planes with a lattice spacing of 0.22 ± 0.01 nm (left inset in Figure 1A). This lattice parameter is close to the interatomic distance for the (0110) crystallographic plane of graphite [25] and it is corresponding to the in-plane periodicity in graphene-like nanosheets [26]. The same lattice spacing was observed early for CDs and CNPs synthesized by MCW [16,18], HTS [20] or similar methods at about 180 • C and slightly higher temperatures [26].…”

“…This lattice parameter is close to the interatomic distance for the (0110) crystallographic plane of graphite [25] and it is corresponding to the in-plane periodicity in graphene-like nanosheets [26]. The same lattice spacing was observed early for CDs and CNPs synthesized by MCW [16,18], HTS [20] or similar methods at about 180 • C and slightly higher temperatures [26]. It is interesting to note that the graphene-like interlayer distances have been preserved in Gd-doped CNPs similar to the results for catalytically active CD-based nanocomposites, which were highly doped with different impurities such as aluminum and tellurium [26,27].…”