LAUSR

In this work, zinc oxide coupled cadmium tungstate (ZnO-CT) was prepared as a nano-photocatalyst through a green synthesis route using lemon leaf extract and characterized based on diverse microscopic and spectroscopic techniques. To extend the practical application of the prepared nanocomposite (NC), its photocatalytic activity was investigated against Congo red (CR) dye under natural solar light irradiation. ZnO- CT nano-photocatalyst shows 97% photocatalytic degradation of the CR after 90 min of natural solar light irradiation with quantum yield of 1.16 × 10-8 molecules photon-1. The ZnO-CT NC has shown the enhanced photocatalytic degradation performance for Congo red relative to ZnO (70%) or CT (44%). According to the free radical trapping and quenching experiments, the photocatalytic activity of ZnO-CT NC should be driven efficiently by superoxide and hydroxyl radicals. The photocatalytic degradation kinetics for CR dye was also studied using the pseudo-first-order, diffusional, and Singh models. The successful functioning and greater photocatalytic activity of ZnO-CT NC nano-photocatalyst might be associated due to the presence of electron-withdrawing functional groups like acids (-COOH) and aldehydes (-CHO) on its surface. The photocatalytic degradation of Congo Red was enhanced by the presence of functional groups on ZnO-CT NC surface as they were able to efficiently prolong the recombination of charge carriers. The high stability ZnO-CT was also maintained with moderately low leaching rate of cadmium ions (∼2-5%).