Facile preparation of graphitic carbon nitride nanosheet/agar composite hydrogels for removal of tetracycline via the synergy of adsorption and photocatalysis

Abstract

Graphitic carbon nitride (g-C₃N₄) nanosheet/agar composite hydrogels were prepared by sol–gel phase transition of agar. In the composite hydrogels, agar was advantageous for promoting the adsorption capacity, while the g-C₃N₄ nanosheet was beneficial to enhancing the degradation ability. The composite hydrogels showed good removal ability for tetracycline by the synergistic effect of adsorption and photocatalytic degradation. The best removal ability of the composite hydrogel was about 1.4 times that of the pure g-C₃N₄ nanosheet. Active species capture experiments showed that h⁺, ˙O₂⁻ and ˙OH played a crucial role in the tetracycline degradation. Compared with the bulk g-C₃N₄/agar composite hydrogel, the g-C₃N₄ nanosheet/agar composite hydrogel exhibited a much higher photocatalytic activity for tetracycline degradation due to suppressive recombination of electrons and holes. The present research provided new insight for facile fabrication of composite hydrogels with enhanced removal ability for antibiotics.