Preparation of Carbon nitride/Carbon dots/4A molecular sieve composite and evaluation of adsorption performance for Methylene Blue

Abstract The discharge of dye wastewater poses significant hazards to the ecological environment and human health. In this paper, a new composite material carbon nitride/carbon dots/4A molecular sieve (C₃N₄/CDs/4A) was prepared by using urea, citric acid and 4A molecular sieve to remove dyes from wastewater. The material was characterized by SEM, FTIR and XRD tests to prove the successful preparation of C₃N₄/CDs/4A. Compared with 4A molecular sieve, the C₃N₄/CDs/4A had a larger specific surface area of 164.54 m²/g. The C₃N₄/CDs/4A had great adsorption performance for methylene blue (MB), with the adsorption capacity of up to 44.34 mg/g. Adsorption isotherm and kinetic studies showed that the adsorption of MB on C₃N₄/CDs/4A followed Langmuir isotherm (R² = 0.999) and pseudo-second-order kinetic model (R² = 1). In addition, the C₃N₄/CDs/4A maintained almost the same adsorption amount for MB in the pH range of 5–11 and was less affected by temperature. Furthermore, the excellent thermal regeneration performance of C₃N₄/CDs/4A laid a foundation for its industrial application. This study provided a new method for treating refractory dye wastewater.