Characterization of water hyacinth cellulose-g-poly(ammonium acrylate-co-acrylic acid)/nano-hydroxyapatite polymer hydrogel composite for potential agricultural application

Polymer nano-composite was prepared by grafting partially neutralized acrylic acid onto swollen cellulose isolated from water hyacinth in the presence of nano-hydroxyapatite (nano-HA) using N,N-methylene-bisacrylamide (MBA) as the cross-linker and ammonium persulphate (APS) as the free radical initiator. Water absorption tests showed an increase in swelling ratio of the copolymer with increased nano-HA content to value of 120 g/g at 2.5% w/v above which it declined. FTIR spectrum of nano-composite revealed grafting of the monomer (acrylic acid/ammonium acrylate) onto cellulose and nano-HA. Transmission electron microscopy (TEM) images of nano-HA synthesized in the presence of Triton X-100 (non-ionic surfactant) displayed rod-shaped agglomerates and nano-particle dispersion within the copolymer matrix. Energy dispersive X-ray (EDX) spectra revealed the constituents of nano-composite to be mainly C, O, Ca and P, while N was not detected by this method. X-ray diffractograms (XRD) of cellulose grafted copolymer showed a more amorphous structure relative to that of dry water hyacinth cellulose and also presence of crystalline nano-HA within the copolymer. This polymer nano-composite could be beneficial in agriculture in aiding moisture retention as well as a source of P which occurs through microbial degradation of cellulose grafted copolymer and solubilization of nano-HA. (C) 2019 The Author(s). Published by Elsevier B.V.