Abstract
Grafting polymerization of acrylic acid (AA) was undertaken onto cellulose powder (Cell) in presence of potassium fulvate (KF) to produce semi-interpenetrating network structures. The grafting efficiency (GE) and grafting yield (GY) were studied as and indicated that the grafting process was not influenced in presence of KF. KF was expected to be incorporated into the cellulose backbone in the same course of the graft polymerization via polycondensation with groups from cellulose and monomer. The simultaneous graft polymerization of acrylic acid and polycondensation processes of all components allows formation of a more chemically active semi-interpenetrating network structure. Successful incorporation of KF to the network structure was predicted from fourier transform infrared spectroscopy (FTIR) while enhanced Cu2+ uptake confirmed the better chemical activity with respect to the same network prepared in absence of KF. Furthermore, the wide variation of the swelling potential as a function of the pH further corroborates the insertion of KF to the network structure. Imaging with scanning electron microscopy (SEM) indicated morphological alteration on the surface which might be related to the KF anchoring to the cellulose backbone. The developed superabsorbents showed increment in the water absorption both in distilled water and salted solutions as well. The newly developed superabsorbent was applied as a support for soil nutrients and their controlled release in soil was studied. The results proved efficiency of the superabsorbent to warrant appropriate release of the nutrients according to the time regulations set by European Committee of Normalization (ECN). Improved water retention was also an additional advantage.
Highlights
Crosslinked polymers with a network structure and high content of hydrophilic functional groups are denoted as hydrogels
Vinyl monomers were grafted onto polysaccharides in the presence of crosslinking agents to cause crosslinking of the grafted chains which leads to development of a network structure and this allows for advancing their properties [13, 14]
Cheap superabsorbents were fabricated by grafting of monomers such as acrylic acid and acrylamide onto varieties of backbones including starch [1517], cellulose [18,19,20], carrageenan [21], lignin [22, 23], chitosan [24,25,26], wheat straw [27,28,29], sugarcane bagasse [30], pineapple peel [31], salep [32] and guar gum [33]
Summary
Crosslinked polymers with a network structure and high content of hydrophilic functional groups are denoted as hydrogels. Humic acids were elaborated as constituents in the course of preparation of superabsorbing materials [36, 37] in order to elevate the biological activity and broaden their applications thanks to the multifunctionality of the incorporated humic materials These remarkable compensations of fulvic substances over similar humics lie beyond the suggestion of using them as candidates to replace the humics in formulations related to superabsorbents especially those prepared with target for use as devices for controlled release of soil nutrients. Employing a cellulose as backbone for grafting polymerization of acrylic acid in the presence of potassium persulfate (KPS) as an initiator and methylenebisacrylamide (MBA) as crosslinker while fulvic acid was employed for improving properties like water absorbency and retention, which is expected to contribute better in controlled release applications of NPK as soil nutrients
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