High-capacity hydrogel polymer composite adsorbent for nitrate and phosphate removal from water

The presence of nitrate and phosphate in water is of serious concern since these contaminants are responsible for short- and long-term health and ecological problems. For instance, nitrate can cause methemoglobinemia in infants and result in the production of nitrosamines, which can be carcinogenic. Meanwhile, trace amounts of phosphate (< 1 ppm) in treated wastewater from municipalities and industries are often responsible for eutrophication of bodies of water. In this study, we propose simultaneous removal of nitrate and phosphate using a chitosan-based adsorbent. The adsorbent was fabricated by crosslinking chitosan (CS) with polyethyleneimine (PEI), an amine-rich polymer. Results showed that the resulting adsorbent (CS-PEI-GLA) is effective in removing nitrate and phosphate from water. Adsorption capacity derived from Langmuir isotherm was found to be 416.6 mg g-1 and 238.1 mg g-1 for nitrate and phosphate, respectively. Simultaneous removal of nitrate and phosphate from real water samples using CS-PEI-GLA was found to be more effective compared to commercial materials. Furthermore, the adsorbed nitrate and phosphate can be recovered using dilute amounts of acid or base.