Synthesis And Performances Of Coco Peat Based Superabsorbent Composite

In this paper, coco peat was used as the raw material. A series new kind of superabsorbent based on coco peat was prepared and their swelling performances were studied. The main findings were as follows:the coco peat powder / poly acrylic acid-acryl amide hybrid superabsorbent were prepared by means of solution polymerization reaction using coconut husk powder as matrix material, N, N,-methylenebisacrylamide(MBA) as cross-linking agent and sodium persulfate as initiator. The optimum conditions showed that the ratio(wt) of cellulose to monomer mass was 1/8, the degree of neutralization 70%, the initiator content 0.7%(referred to the monomers), and the cross-linker content 0.2%(referred to the monomers). The water absorbency of as-obtained composite superabsorbent materials was about 273 g/g for water, and about 43g/g for saline solution. The structure of the poly acrylic acid-acryl amide/coconut husk powder was characterized by FT-IR and SEM. The model of Fickian Scott, first-order swelling kinetic and Scott second-order swelling kinetic were used to simulate the kinetic swelling property of the polymers, respectively. The results showed that the pervasion of water into the SAP followed by the Fickian diffusion, and the kinetic swelling processes was coincided with Scott first-order swelling kinetic. The polymers have the superior reusability and holding-water capacity.A series of superabsorbent hydrogel composites were prepared via the ultraviolet irradiation copolymerization of acrylic acid monomer and coco peat cellulose in the presence of the cross-linker trimethylolpropane trimaleate. The obtained optimized products were characterized by FT-IR and SEM. The effects of different cross-linker level, the amount of coco peat and reaction time on water absorbency were studied, respectively. The samples synthesized under the optimal condition exhibited the maximum swelling value of 523.09 g/g in distilled water and 40.52 g/g in 0.9 wt % NaCl solution. The swelling behaviors of the superabsorbent hydrogel composites were relied on the pH of external solution and the concentration of salt solution. Besides, the effect of ions species on swelling was in the order: Na+ > Ca2+ > Fe3+ and the superabsorbent hydrogel composite displayed better p H-responsiveness and reversible on-off switching characteristics in pH 2.2 and 7.2 aqueous solutions. Urea, as an agrochemical model, was loaded into the superabsorbent hydrogel composites to supply with nitrogen nutrient. The results exhibited that urea loading percentage was dependent on the concentration of urea aqueous solutions and the release of urea from loaded samples in water followed a non-Fickian mechanism.A novel superabsorbent polymer(MAH-CPD@ADH-g-PAA) was synthesized through grafting-poly acrylic acid and maleic anhydride onto the surface of adipic acid dihyfrazide-modified-natural coco peat powder with the presence of cross-linker and initiator. The structure and morphology of thus-produced products were characterized by Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM). In contrast, after fixation of ADH molecular onto the surface of MAH-CPD substrate, the MAH-CPD@ADH had a higher value of degree of substitution than that of parallel MAH-CPD under identical reaction conditions. The swelling equilibrium of the MAH-CPD@ADH-g-PAA samples under the optimal conditions achieved to about 470.02 g/g in distilled water, 350.19 g/g in tap water and 61.03 g/g in 0.9% NaCl solution, respectively. The dynamic water uptake behavior of MAH-CPD@ADH-g-PAA fitted well with the pseudo-second-order kinetic model. The effects of the salt concentration and cations type on water absorbency were examined further and the results showed that the swelling behaviors of the superabsorbent polymer were significantly sensitive to the concentration of salt solution and cation type. The influence of the temperature and centrifugal force on the water retention capacity indicated that the MAH-CPD@ADH-g-PAA were more sensitive to pressure than to temperature. It was believed that the MAH-CPD@ADH-g-PAA superabsorbent products could have potential industrial applications, especially in agriculture and horticulture usage.