CS-ZnO- CQDs Nanophotocatalyst for the Removal of AO۷:Modeling and Optimization

Azo compounds have long been recognized as the leading cause of death worldwide by releasing toxic and potentiallycarcinogenic compounds into the aqueous phase. Adsorption on activated carbon, ultrafiltration, reverse osmosis,coagulation by chemical agents, ion exchange on synthetic adsorbent resins, and adsorption are proposed methods forthe degradation of azo compounds in recent years; however, their efficiency is restricted due to their weakness incompletely removing pollutants. The use of semiconductor nanoparticles with ability to receive energy from opticalsources and lead to catalytic results is a promising approach to successfully remove azo compounds. Acid orange ۷(AO۷) is an azo dye with potential usefulness in hair and wool colouring. Nonetheless, causing thousands of humancasualties and irreparable damage to the environment by releasing toxic and potentially carcinogenic compounds intothe aqueous phase hamper the use of AO۷ as a colouring agent. The principal aim of this study was to augment AO۷degradation using chitosan (CS) – zinc oxide (ZnO)-carbon quantum dots (CQDs) photocatalyst under UV illumination.The inclusion of all components in the nanophotocatalyst was proved through the presence of all the characteristicpeaks of the components in the FTIR spectrum. The average diameters of CS-ZnO and CS-ZnO-CQDsnanophotocatalyst particles in the FESEM images were ۱۱۰.۷ and ۱۲۷.۴ nm, respectively. Zeta potential of CS-ZnOCQDsnanophotocatalyst was ۲۴.۸ mV, which shows the good stability of the nanophotocatalyst. The findings of thisstudy indicate that degradation efficiency in CS-ZnO-CQDs nanophotocatalyst was enhanced owing to the use of CQDsin the CS-ZnO. Study on the role of pH demonstrated that degradation efficiency increased with decreasing pH value.Study regarding the role of nanophotocatalyst dosage indicated that although degradation efficiency improved withincreasing catalyst dosage from ۰.۴ g/L to ۰.۶ g/L, we found that degradation efficiency decreased at larger amount.The optimum pH, catalyst dose, and AO۷ concentration for obtaining maximum degradation were ۴.۲, ۰.۶۵ g/L, and ۳۱ppm, respectively. The developed nanophotocatalyst is a promising photocatalytic platform with the potential toenhance the photodegradation of AO۷.

Keywords:

Acid orange ۷ , Nanophotocatalyst , Enhanced photocatalytic activity , Wastewater treatment