Enhanced adsorptive removal of ammonia nitrogen from wastewater by EDTA-2Na modified vermiculite

Ammonia nitrogen (NH3-N), a prevalent persistent and refractory pollutant in aqueous environments, compromises ecosystem structural integrity and poses potential risks to human health due to its long-term persistence. The development of efficient and cost-effective technologies for its removal is therefore imperative. In this study, a novel vermiculite-based adsorbent was fabricated through modification with ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), designated as E-V. Compared to natural vermiculite (NV), the modified adsorbent exhibits a significant enhancement in ammonia nitrogen adsorption performance. Specifically, the 0.3E-V variant achieved an adsorption capacity of 18.45 mg·g-1 with a maximum removal efficiency of 95%, representing a 50% improvement over NV. The adsorption process was well-described by the pseudo-second-order kinetic model and the Freundlich isotherm model, suggesting that chemical and multilayer adsorption are the dominant mechanisms. Furthermore, application of the intraparticle diffusion model indicated that the adsorption process is co-governed by intraparticle diffusion and liquid film diffusion. These results provide valuable insights into the potential of natural vermiculite for wastewater treatment.