Adsorption of ammonium and phosphate by feather protein based semi-interpenetrating polymer networks hydrogel as a controlled-release fertilizer

Abstract

A new feather protein-grafted poly(potassium acrylate)/polyvinyl alcohol (FP-g-PKA/PVA) semi-interpenetrating polymer networks (semi-IPNs) hydrogel was produced through graft copolymerization with FP as a basic macromolecular skeletal material, acrylic acid as a monomer and PVA as a semi-IPNs polymer. The adsorption of ammonium and phosphate ions from aqueous solution using the new hydrogel as N and P controlled-release fertilizer with water-retention capacity was studied. The effects of pH value, concentration, contact time and ion strength on NH ₄⁺ and removal by FP-g-PKA/PVA semi-IPNs hydrogel were investigated using batch adsorption experiments. The results indicated that the hydrogel had high adsorption capacities and fast adsorption rates for NH ₄⁺ and in wide pH levels ranging from 4.0 to 9.0. Kinetic analysis presented that both NH ₄⁺ and removal were closely fitted with the pseudo-second-order model. Furthermore, the adsorption isotherms of hydrogel were best represented by the Freundlich model. The adsorption–desorption experimental results showed the sustainable stability of FP-g-PKA/PVA semi-IPNs hydrogel for NH ₄⁺ and removal. Overall, FP-g-PKAPVA could be considered as an efficient material for the removal and recovery of nitrogen and phosphorus with the agronomic reuse as a fertilizer.

Keywords:

• ammonium
• phosphate
• semi-IPNs hydrogel
• adsorption
• controlled-release fertilizer

Acknowledgements

The authors are grateful for financial support from National Natural Science Foundation of China (21007034), Natural Science Foundation of Shandong Province (ZR2010EQ031) and Universities Innovation projects of Jinan City.