A novel oxygen-deficient core–shell ZA@ZnO1-X nanocomposite for enhanced degradation of multiple polyaromatic hydrocarbons

Abstract

Persistent organic pollutants such as polyaromatic hydrocarbons (PAHs) are one of the emerging micropollutants present in several industrial effluents. Being trace refractory organics, its treatment by conventional method is very challenging. Thus, we report a novel core–shell zeolite A@oxygen-deficient ZnO (ZA@ZnO1-X) nanocomposite for degradation of PAHs mixture containing fluorene, phenanthrene, and anthracene. The hierarchical structure helps to reduce the recombination of photogenerated electron and holes pair, thereby availing more active species for photodegradation. The enhanced photodegradation efficacy is due to the synergistic effect of oxygen-defect sites in ZA@ZnO1-X and photoactive species. Core-shell ZA@ZnO1-X shows improved catalytic properties with a band gap value of 2.65 eV lower than the sole ZnO nanosheet (3.03 eV). The porous shell of the ZnO1-X structure provides an enhanced adsorption site and fully utilizes photon energy (visible light) with no aggregation because of ZA support. The maximum photocatalytic degradation is achieved by optimizing reaction parameters of 96%, 95.1%, and 93% of fluorene (0.02436 min−1), phenanthrene (0.02421 min−1), and anthracene (0.02102 min−1), respectively in 2 h at neutral pH and catalyst load 1 g/l. The primary active species responsible for PAHs degradation is h+, followed by HO•, O2•- radicals analyzed by quenching experiment. The degradation intermediates, and degraded products analysis by GC–MS gives a plausible general reaction pathway of PAHs and reveals primary intermediate is a phthalate derivative. Finally, the regeneration of active catalytic sites in the ZA@ZnO1-X photocatalyst shows its stability and reusability over five consecutive cycles.