Organic-inorganic hybrid hydroquinone bridged V-CdS/HAP/Pd-TCPP: A novel visible light active photocatalyst for phenol degradation

Abstract

In the present study a novel V doped CdS-HAP-HQ-Pd-TCPP photocatalytic nanocomposite has been synthesized and applied to degrade phenol from contaminated wastewater. The self-photo-corrosion of the CdSQDs was prevented by immobilizing with a photo-induced hole scavenger like hydroxyapatite (HAP) which also prevents its agglomeration in the aqueous medium. Further to enhance the visible light absorption efficiency a palladium-tetra (carboxyphenyl) porphyrinphotosensitizer (Pd-TCPP) has been incorporated in the nanocomposite. For the first time, CdSQDs were doped with Vanadium as well as Pd-TCPP photosensitizer was grafted onto the surface of V doped CdSQDs-HAP through the application of hydroquinone (HQ) bridging molecule that prevent the desorption of photosensitizer from photocatalyst and also facilitates easy charge transfer due to the presence of conjugated π electronic structure. The morphological and structural characterizations of the synthesized nanocomposite were performed by FTIR, XRD, UV–Vis DRS, FE-SEM, EDS, and PL analysis. Results revealed that almost 98% of phenol and 95% toxicity removal was accomplished at 50 mgl−1 of influent phenol by the V doped CdS-HAP-HQ-Pd-TCPP nanocomposite in 120 min which is superior to many reports in the literature. Among the different free radicals generated by the nanocomposite OH radicals played the predominant role in removal of phenol. The experimental data on removal of phenol by the nano-compositewas very well fitted with a pseudo-first-order kinetics model. The estimated value of apparent rate constant (Kapp) of the V doped CdS-HAP-HQ-Pd-TCPP photocatalytic system was 5.3 times higher than that of CdSQDs. Thus, the V doped CdS-HAP-HQ-Pd-TCPP photocatalytic system can be employed as an alternative method for the treatment of phenolics wastewater.