Performance and application of EDTA modified carbon nitride in adsorbing ammonia nitrogen in fish ponds

Objective To prepare modified carbon nitride with enhanced performance in adsorbing ammonia nitrogen in fish ponds.

Method Carbon nitride (s-C₃N₄) with basic adsorption capacity was prepared by co-heating of melamine and sodium bicarbonate using the thermal condensation method, and then s-C₃N₄ was further modified by disodium ethylene diamine tetraacetic acid (EDTA-2Na) to obtain modified carbon nitride (EDTA-s-C₃N₄). Scanning electron microscope (SEM), X-ray diffraction (XRD), BET surface area, and Zeta potential were used to characterize the materials.

Result The specific surface area of EDTA-s-C₃N₄ was as high as 17.7012 m²/g, and the surface potential was −19 mV. It had excellent adsorption performance for ammonia nitrogen in fish ponds with the removal rate of 72% at pH=7.5. The adsorption process conformed to quasi-second-order kinetics, and the maximum adsorption capacity estimated by Langmuir isothermal model fitting was 24.2131 mg/g. After five cycles of regeneration, EDTA-s-C₃N₄ still had a removal rate of 60% for ammonia nitrogen. The toxicity evaluation proved that EDTA-s-C₃N₄ was safe and non-toxic to zebrafish.

Conclusion EDTA-s-C₃N₄ has good removal effect on ammonia nitrogen in fish ponds. It is safe and non-toxic, and has good practicality.