Novel Quaternary Ammonium Functionalized Cellulosic Materials for Nitrate Adsorption from Polluted Waters

This study investigated the ability of waste-derived cellulose materials to remove nitrate from water through adsorption processes. First, a variety of cellulosic waste materials were screened to quantify their adsorptive ability to remove nutrients from water. Due to the low adsorption capacity and frequent leaching of nitrate observed in raw materials, quaternary ammonium functionalization was then employed. Materials were functionalized by adding cationic groups to the biowaste materials to form novel ion exchange adsorbents containing naturally derived biopolymers and/or whole natural fibres with improved nitrate binding capacity. Results revealed that adsorbents originating from high cellulose waste materials can be successfully used to remove nitrate from water. Significant nitrate was removed by functionalized flax and cellulose, of comparable treatment efficiency to a commercial polystyrene-based material used in drinking water filters. Adsorption of nitrate on flax and cellulose based materials was best characterized by the Sips isotherm, reaching maximum sorption capacity of 234.8 and 240.5 mg/g, respectively. This suggests that the interactions between adsorbents and nitrate are more complex than ion exchange alone and can involve other mechanisms, such as dipole/ion force. The kinetics of NO₃^- adsorption was described well by the pseudo-first order model. The ability to remove nitrate via adsorption from polluted drinking water and freshwaters by re-purposing waste materials aligns strongly with sustainability principles and supports several sustainable development goals (SDGs) including clean water and sanitation.