A novel zero-valent iron/titanium tannate composite for deep removal of nitrogen from water

Nitrogen pollution poses a significant threat to aquatic ecosystems, necessitating the deployment of effective water treatment strategies to mitigate its levels. Given the scarcity of traditional nitrogen adsorbents in the water treatment sector, this study explored the potential of titanium tannate, a metal-phenolic network (MPN) material, as a carrier for nitrogen removal. Specifically, a novel composite material, zero-valent iron/titanium tannate (nZVI/Ti-TA), was synthesized through a liquid-phase reduction reaction method and subsequently assessed for its nitrogen removal efficacy in batch experiments. The results showed that nZVI/Ti-TA is a dual-functional composite, exhibiting both adsorption and reduction capabilities. The optimal preparation parameters were determined to be a mass ratio of Ti-TA to FeSO₄•7H₂O of 1:1.5 and a molar ratio of NaBH₄ to FeSO₄•7H₂O of 8. Furthermore, the composite exhibited a broad pH application range, maintaining stable performance across a pH range of 4 to 9. Additional parameters, such as nitrogen concentration, adsorbent dosage, and the presence of ions, also influenced the treatment outcomes. Specifically, higher nitrogen concentrations and lower adsorbent doses resulted in a higher adsorption capacity. Conversely, higher concentrations of ions like SiO₃²⁻, CO₃²⁻, and K⁺ inhibited nitrogen separation. However, the composite demonstrated promising results in treating inorganic and organic nitrogen in real wastewater samples. In model solutions, inorganic nitrogen could be completely removed, while in field applications such as domestic wastewater, the total nitrogen removal rate exceeded 95 %. The primary mechanisms underlying nitrogen removal were the dual functions of adsorption by Ti-TA and reduction by nZVI. The adsorption process was primarily governed by hydrogen bonding and electrostatic interactions. Overall, this study introduces a novel composite material for effective removal of nitrogen, offering a promising solution to the pressing issue of nitrogen pollution in aquatic ecosystems.