Carbon dots/silica nanoaggregates for highly efficient adsorption of alizarin red S and malachite green dyes

Carbon dot-based nanomaterials show great potential for environmental pollution control and remediation applications. Herein, carbon dots/silica nanoaggregates for dye adsorption were easily synthesized via a hydrothermal reaction of N-doped carbon dots with (3-aminopropyl)triethoxysilane. The composition and structure of the resulting nanoaggregates were characterized using TEM, SEM, FT-IR and XPS. The adsorbent exhibited ultrahigh adsorption capability for alizarin red S (1327 mg g(-1)) and malachite green (4091 mg g(-1)), outperforming most of the reported adsorbents. The effects of pH, adsorbent dosage, contact time and initial dye concentration on adsorption capacities have been investigated. The adsorption isotherms and kinetics were well fitted using the Langmuir and pseudo-second order models, indicating that monolayer adsorption and chemisorption of dye molecules occurred on the surface of carbon dots/silica nanoaggregates. The fabrication of carbon dots/silica nanoaggregates is simple, low-cost and eco-friendly, and it is easy to separate the material from water for recycling in practical applications. To the best of our knowledge, this is the first investigation into the application of carbon dots/silica nanoaggregates for the adsorption of organic dyes, which facilitates the development of carbon dot-based nanomaterials for environmental applications.