Multilevel immobilized CNT/SCN purification beads and the removal efficiency over TCHCl/clay composite pollutant in the underwater environment

Abstract

Natural water bodies often contain a significant amount of suspended colloidal particles, which not only reduce water transparency but also have a high adsorption capacity for soluble pollutants. These composite pollutants can migrate rapidly with water flow, which are usually difficult to degrade and remove by traditional methods. Aiming at suspended contaminated waterbodies, this study introduced a multilevel loading method to prepare carbon nanotube/sulfur doped carbon nitride (CNT/SCN) composite photocatalytic purification beads. The surface of the obtained core-shell structured purification beads is loaded with CNT/SCN photocatalysts which exhibit three-dimensional conductive and porous characteristics. TCHCl was introduced as the target pollutant, and the removal efficiency of the composite purification beads under different water turbidity and hydrodynamic conditions were investigated. The results showed that during 15 h of degradation process, at the depth of 20 cm, with the flow rate of 0.015 m³/h and water turbidity of 10.3 NTU, the purification beads achieved a removal efficiency of 54.9% for tetracycline hydrochloride (TCHCl), which was 2.03 times higher than that of SCN purification beads. The three-dimensional porous structure of the surface exhibited excellent adsorption and trapping capabilities for suspended colloidal particles. The introduction of carbon nanotubes enhanced charge transfer ability of the surface layer and reduces the local charge accumulation effect caused by surface adsorption, which effectively enhances the adsorption of suspended colloid, and also significantly improved the degradation efficiency of TCHCl. This study provides a valuable insight for the engineering application of photocatalytic technology.