A superabsorbent polymer with slow-release phosphate fertilizer was prepared by esterification of polyvinyl alcohol (PVA) and phosphoric acid (H 3 PO 4 ), which was a slow-release fertilizer at the same time. The product's water absorbency (WA) was about 480 times its own weight if it was allowed to swell in distilled water at room temperature for 24 h. WA under various conditions, such as varying the reaction time, the amount of sodium carbonate (Na 2 CO 3 ), the reaction temperature, and the concentration of phosphoric acid ([H 3 PO 4 ]), were investigated and optimized. The optimal sample of the product was characterized by FTIR and elemental analysis. The results showed that phosphoric groups had grafted on PVA molecule chains, and the content of P 2 O 5 in the product was 31.2%. The water retention property and phosphate slow-release mechanism of the product were studied as well.
A slow-release NP compound fertilizer with superabsorbent and moisture preservation was prepared by carboxyl methyl starch, acrylic acid, ammonia, urea, diammonium phosphate, and so on. The effects of the amount of initiator, crosslinker, and the degree of neutralization of acrylic acid on water absorbency were investigated and optimized. The product was characterized by FTIR, ICP, and element analysis, and the results showed that the product contained 22.6% nitrogen element and 7.2% phosphor (shown by P 2 O 5 ) element. Its water absorbency was about 85 (g ⅐ g Ϫ1 ) times its own weight in tap water. We also investigated the water retention property of the product and the slow release behavior of N and P in the product. The results showed that the product had a good water retention capacity and slow release property. The mechanism of the release of N and P in water was also investigated.
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