Efficient photocatalytic degradation of emerging pollutants by green synthesized Prussian blue analogue nanocomposite

Worldwide consumption, toxicity, and bioaccumulation of paracetamol (PCM) and atenolol (ATL) has drawn attention of researchers over last decades. A small portion of these drugs is absorbed by human body and rest of them is excreted through urine and feces to the environment (water bodies and soil) which might result in negative impacts. Nanocomposite of chromium oxide coupled with zinc hexacyanocobaltates (Cr₂O₃@ZnHCC) was synthesized by a green-method using Sapindus mukorossi seed-extract for the removal of targeted drugs. Microscopic and spectroscopic analysis of Cr₂O₃@ZnHCC showed uniformly incorporated prisms into cubic structure having ~75 nm particle size. Well-characterized Cr₂O₃@ZnHCC and individuals (Cr₂O₃ & ZnHCC) were utilized for the degradation of PCM and ATL under direct sunlight and dark conditions. Highest degradation of targeted drugs (91%–94%) resulted at 20 mg L⁻¹ concentration of pollutant, 25 mg of catalyst dose, and pH ~ 7 under daylight exposure (5 h). First-order kinetics followed with a high adsorption capacity, X_m (13.4–14.5 mg g⁻¹) value was obtained to confirm the strong binding with the pollutants. Moreover, Cr₂O₃@ZnHCC substantially suppressed the half-life of targeted drugs (PCM: 0.6 h; ATL: 2.9 h) and converted them into safer-small metabolites as confirmed by liquid chromatography-mass-spectrometry analysis, and the reduction of carbon content was confirmed by total organic carbon analysis. The charge separation mechanism was assisted by UV reflectance and photoluminescence data. The synthesized green-nano photocatalyst displayed high reproducibility (up to 10th cycle), sensitivity, and stability during the degradation process which makes this a suitable candidate for industrial applications.