ZnO/AC recovered from PET bottles via pyrolysis for the hybrid treatment (adsorption/photocatalysis) of BB41 dye in aqueous media

Abstract

Plastic waste continues to increase on land and poses a critical danger to human life, which is why our contribution addresses this issue. Waste PET bottles were collected and subjected to pyrolysis to produce activated carbon, which was then doped with ZnO to form a ZnO/AC(PET) heterostructured composite. The deposition of ZnO nanoparticles on activated carbon was confirmed using different characterization techniques, such as SEM, XRD, and FTIR spectroscopy, which demonstrated the effectiveness of our doping method. High-performance ZnO/AC(PET) was used for the hybrid treatment of solutions synthetically colored with the textile dye blue basic 41. Adsorption and solar photocatalysis are the two techniques chosen in our study. The mass effect of the hybrid material and the effect of the initial concentration of the BB41 dye were evaluated. A maximum adsorption capacity of 561.80 mg g⁻¹ was recorded for ZnO/AC(PET) due to the pores present on the surface of the activated carbon. After the adsorption step, the treated solutions were further exposed to solar irradiation for a secondary treatment, achieving a removal efficiency of up to 94.44%. The process was optimized by identifying the model that best fits the experimental data and determining the main kinetic mechanism of the photocatalytic degradation of the BB41 dye using first and second-order models. The findings demonstrated that, given the high correlation coefficients, the first-order model offered the best match. This work highlights the valorization of PET waste into ZnO/activated carbon, which shows good affinity for BB41 dye and functions as both an adsorbent and a photocatalyst.