Zircon-Type CaCrO4 Chromite Nanoparticles: Synthesis, Characterization, and Photocatalytic Application for Sunlight-Induced Degradation of Rhodamine B

The degradation of organic dye pollutants is a criticalenvironmentalissue that has garnered significant attention in recent years. Toaddress this problem, we investigated the potential of CaCrO4 chromite (CCO) as a photocatalyst for the degradation of cationicand anionic dye solutions under sunlight irradiation. CaCrO4 was synthesized via a sol-gel auto-combustion route and sinteredat 900 & DEG;C. The Rietveld refined XRD profile confirmed the zircon-typestructure of CaCrO4 crystallized in the tetragonal unitcell with I41/amd space group symmetry.The surface morphology of the sample was investigated by field emissionscanning electron microscopy (FESEM), which revealed the polyhedraltexture of the grains. Energy-dispersive X-ray spectroscopy (EDX)and X-ray photoelectron spectroscopy (XPS) studies were carried outto analyze the elemental composition and chemical states of the ionspresent in the compound. Fourier transform infrared (FT-IR) spectroscopyanalysis revealed the vibrational modes corresponding to the tetrahedraland dodecahedral metal oxide bonds. The optical band gap was approximatedto be in the range of 1.928 eV by using the Tauc relation. The CaCrO4 catalyst with different contents (5, 20, 35, and 50 mg) wasinvestigated for its photocatalytic performance for the degradationof RhB dye solution under sunlight irradiation using a UV-Visspectrometer over the experimental wavelength range of 450-600nm. The degradation efficacy increased from 70.630 to 93.550% for5-35 mg and then decreased to 68.720% for 50 mg in 140 minunder visible light illumination. The comparative study demonstratesthat a higher degradation rate was achieved for cationic than anionicdyes in the order RhB > MB > MO. The highest deterioration (93.80%)was achieved for the RhB dye in 140 min. Equilibrium and kinetic studiesshowed that the adsorption process followed the Langmuir isothermand pseudo-second-order models, respectively. The maximum adsorptioncapacity of 21.125 mg/g was observed for the catalyst concentrationof 35 mg. From the cyclic test, it has been observed that the synthesizedphotocatalyst is structurally and morphologically stable and reusable.The radical trapping experiment demonstrated that superoxide and hydroxylradicals were the primary species engaged in the photodegradationprocess. A possible mechanism for the degradation of RhB has beenproposed. Hence, we conclude that CaCrO4 can be used asan efficient photocatalyst for the remediation of organic dye pollutantsfrom the environment.