Network interpenetrating slow-release nitrogen fertilizer based on carrageenan and urea: A new low-cost water and fertilizer regulation carrier

Modern agriculture presents new requirements of low cost, high water retention and degradability for superabsorbent and slow-release fertilizers. In this study, carrageenan (CG), acrylic acid (AA), N, N '-methylene diacrylamide (MBA), urea and ammonium persulfate (APS) were used as raw materials. A kind of high water absorption, water retention, nitrogen slow release and biodegradable carrageenan superabsorbent (CG-SA) was prepared by grafting copolymerization. The optimal CG-SA was obtained with a water absorption rate of 680.45 g/g by orthogonal L18(3)7 experiments and single-factor experiments. The water absorption behavior of CG-SA in deionized water and salt solution were studied. The CG-SA was characterized before and after degradation by FTIR, SEM. The nitrogen release behavior and kinetic characteristics of CG-SA were investigated. In addition, CG-SA degraded 58.33 % and 64.35 % in soil at 25 °C and 35 °C after 28 days. All the results indicated that the low-cost and degradable CG-SA can achieve simultaneous slow release of water and nutrients, which is expected to be widely used as a new water-fertilizer integration technology in arid and poor areas.

Characterization and drug delivery characters of nanocomposite hydrogels based on gamma-radiation copolymerization of poly (vinyl pyrrolidone) (PVP)/sodium alginate (AG)/silver NPs

Nanocomposite hydrogels were prepared by gamma-radiation copolymerization of poly (vinyl pyrrolidone) (PVP)/sodium alginate (AG) in the presence of silver nanoparticles (Ag NPs). The effect of irradiation dose and Ag NPs content on the gel content and swelling characters of PVP/AG/Ag NPs copolymers was investigated. In addition, the structure-property behavior of the copolymers was characterized by IR spectroscopy, thermogravimetric analysis (TGA) and x-ray diffraction (XRD). The drug uptake-release characters of PVP/AG/silver NPs copolymers, taking Prednisolone as a model drug, were studied. The study showed that the appropriate dose of gamma irradiation to achieve homogeneous nanocomposites hydrogel films and the highest swelling in water was 30 kGy, regardless of composition. The introduction of Ag NPs up to 5 wt % improved the physical properties and enhanced the drug uptake-release characters.

Environmentally Friendly Fertilizers Based on Starch Superabsorbents

Superabsorbents starches (SASs) were synthesized and characterized starting from native corn starch, bitter cassava and sweet cassava by graft copolymerization with itaconic acid. Additionally, their swelling behavior was studied both in water and in buffer solutions with different pHs and saline solutions. Their applicability was tested as environmentally friendly fertilizers in the absorption and release of urea, potassium nitrate and ammonium nitrate at different concentrations of fertilizers. The values of swelling at the equilibrium (H^∞) in water and different media of the graft copolymers demonstrated their superabsorbent capacity, polyelectrolyte behavior, and smart response to environmental stimuli. The percentage of fertilizer absorbed and released from the SASs was a function of the initial concentration of the fertilizer in the medium. The loading and release of SASs were depended on the initial concentration of the fertilizer in the medium as well as the nature, structure, and morphology of the starch used.