In-situ construction of morphology-controllable flower-shaped lignin-derived carbon/ZnO composite for efficient photocatalytic degradation of organic dyes

Abstract

The emission of organic pollutants from the dye industry and medical treatment represents a significant threat to the quality of water resources and human health. The development of green, environmentally friendly and efficient photocatalysts for the removal of organic pollutants from the environment is of paramount importance in addressing these issues. Flower-like lignin-derived carbon (LC)/zinc oxide (ZnO) composites with controllable morphology were synthesized via a direct precipitation method. In this study, alkali lignin was employed as an anionic active agent to alter the molecular arrangement on the liquid surface during the synthesis reaction and to reduce the surface tension between mixtures, thereby forming a special stacked morphology, which was then used for the highly efficient removal of methylidene blue (MB) and tetracycline hydrochloride (TCH) in water under different light conditions. The formation mechanism of LC/ZnO and the degradation characteristics under different reaction conditions were investigated. The loading of LC can form composites with large specific surface area and rich porous structure. In addition, with the help of lignin, the morphology of ZnO was changed from a rod-like structure to a lamellar structure, and LC could effectively reduce the band gap of ZnO, which could improve the electron transfer rate in the photocatalytic process. The ·O₂⁻ and ·OH radicals generated under photoexcitation promoted the decomposition of pollutants. This study presents a simple, economical, and scalable method for the application of photocatalysts and explores new ways for the high-value application of industrial lignin.