Impact of metal ions (Cr+6/Mn+7) loaded CaCO3 extracted from tap water for adsorption/ degradation of toxic pollutants under sunlight

Abstract

The present work involves the extraction and characterization of highly efficient CaCO3 from tap water. The resulting white powder was sintered at 900 °C and study for the adsorption/degradation of Rhodamine-B (RB) dye. After sintering at a higher temperature, it was found that CaCO3 was decomposed into CaO and Ca(OH)2 which results in the superior adsorption of RB dye relative to CaCO3 dried at room temperature. The degradation efficiency of CaCO3 was further enhanced by loading two metal ions (Cr+6, Mn+7) having different oxidation states. The as-prepared composites were characterized by different techniques i.e., dynamic light scattering, X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy (SEM) and UV-Visible spectrophotometer and examined for photocatalytic degradation of Rhodamine-B (RB) dye under sunlight. The average hydrodynamic size of bare CaCO3 (900 °C) found to be 0.63 µm which was increased to 1.34 µm and 1.48 µm after loading of Cr+6 and Mn+7 ions respectively. SEM images suggested the hierarchical morphology of CaCO3 and energy dispersive X-ray spectroscopy (EDS)-mapping also confirms the presence of Cr+6 and Mn+7 ions on the surface CaCO3. It was observed that Mn+7-CaCO3 (900 °C) shows higher degradation efficiency of RB dye under solar radiation relative to bare and Cr+6 loaded CaCO3 and exhibited a higher rate constant of 4.6 × 10-2 min-1.