Sodium alginate-g-poly(sodium acrylate) hydrogel for the adsorption–desorption of ammonium nitrogen from aqueous solution

A series of interpenetrating polymer network sodium alginate-g-poly(sodium acrylate) (PASA) hydrogels (PASA-1, PASA-3, and PASA-5) were prepared through the thermal radical polymerization. Fourier transform infrared spectroscopy results revealed that all the hydrogels had been prepared successfully. The effects of various amounts of sodium alginate (SA) on various properties were investigated. When increasing the amount of SA in PASA polymer, the number of pores increased but the size of poores decreased. In addition, PASA hydrogels presenting crosslinking qualities exhibited relatively low swelling in water. Finally, the synthesized hydrogels were tested as adsorbents for ammonium chloride (NH4Cl) solution. The PASA-1 hydrogel exhibited the highest ammonia nitrogen adsorption capacity (12.9 mg/g), which 21.1 % higher than that of the reference poly(sodium acrylate) (PANa) hydrogel (10.7 mg/g) under similar conditions. The synthesized PASA-1 hydrogel exhibited satisfactory reusability and maintained 87 % of its adsorption capacity after nine cycles of ammonium nitrogen adsorption–desorption.