Enhanced photocatalytic degradation of chrysene by Fe2O3@ZnHCF nanocubes

Abstract

Chrysene is a high molecular weight polycyclic aromatic hydrocarbon and priority pollutant due to its persistent nature and toxicity. Ecological concern of this emerging contaminant calls for low-cost and efficient removal practices. Recently, doped or coupled nanomaterials with advanced characteristics are fascinating. Therefore, we have synthesized crystalline nanocubes (∼100 nm) of Fe2O3@ZnHCF nanocomposite using plant extract of Azadirachta indica and subsequently used it for degradation of chrysene. Under sunlight, a rapid initial exponential decrease in concentration of chrysene over time revealed high photo-activity of doped Fe2O3@ZnHCF because of remarkably improved surface area (343.436 m2 g−1) and band gap energy (2.18 eV). At optimum catalyst dose (25 mg) and neutral pH photodegradation of chrysene (2 mg L−1) up to 92% followed first order kinetics and Langmuir isotherms. Comparing with constituents, doped nanocubes (Xm = 45.45 mg g−1) were more effective for degradation as revealed by three to six times greater adsorption of chrysene than ZnHCF (Xm = 16.22 mg g−1) and Fe2O3 (Xm = 7.348 mg g−1). Moreover, it reduced the t1/2 value of chrysene (0.54 h) manifolds than that of Fe2O3 (t1/2 = 23.41 h) and ZnHCF (t1/2 = 8.66 h) nanoparticles. GC–MS results revealed the presence of smaller and safer by-products like malealdehyde, propionic acid and but-2-ene-1,2,4-triol that are formed by oxidation of chrysene by OH radical. Catalysts were also found reusable for ten cycles without significant loss in activity. Overall, Fe2O3@ZnHCF nanocubes might be believed to be a promising photocatalyst for environmental protection by virtue of greater active sites, high surface activity, low band gap with charge separation and semiconducting nature.