Preparation And Performance Studies On Wheat Straw Cellulose-based Superabsorbent With The Function Of Release Nitrogen And Phosphorus Fertilizers

In this work, a novel wheat straw based semi-interpenetrating polymer networks (semi-IPNs) hydrogel with the function of release nitrogen and phosphorus fertilizers (WSC-g-PAA/PVA/NP) was prepared by the method of solution polymerization. During the synthesis, acrylic acid (AA) as a monomer was grafted onto the wheat straw cellulose (WSC) in the presence of initiator and crosslinker. The swelling properties and the fertilizer release behaviors of WSC-g-PAA/PVA/NP were investigated, the main contents and conclusions are as following:1. The single factor experiment was conducted to investigate the optimum synthetic condition of WSC-g-PAA/PVA/NP, and several modern analytical techniques, including infrared spectroscopy, scanning electron microcopy and elemental analysis were adopted to characterize WSC-g-PAA/PVA/NP. The results were as following:m(WSC):m(AA):m(PVA)= 1:10:2, the content of crosslinker was 0.40 wt%, the neutralization degree of AA was 75%. The WSC-g-PAA/PVA/NP synthesized under optimized condition showed excellent water absorbency of 198.5g/g in distilled water and 26.3g/g in 0.9wt% NaCl solution. The nitrogen and phosphorus contents of WSC-g-PAA/PVA/NP were 6.03% and 2.05%, respectively.2. The influences of particle sizes, salt solutions, ionic strength and pH changes on the swelling properties of WSC-g-PAA/PVA/NP were investigated. The product could hold more water in the pH range of 6.0-8.0. Effect of ions on swelling was observed in the order of Na+> K> Ca2+and Cl-> SO42-. The WSC-g-PAA/PVA/NP in solutions with low concentration swelled faster and held much more water compared to that with higher solution concentration. The swelling rates of small WSC-g-PAA/PVA/NP particles had an apparent raise than those of larger ones, and the smaller ones could hold a litter more water. The swelling behaviors of the product in various conditions were evaluated by Schott’s second-order swelling kinetics model, and the results indicated that this model could well assess the kinetics welling behaviors of WSC-g-PAA/PVA/NP. Besides, the adding of WSC-g-PAA/PVA/NP in soil could obviously improve the water-retention capacity of soil.3. The fertilizer release behaviors of WSC-g-PAA/PVA/NP were affected by particle size, salt solutions, ionic strength and various pHs. The fertilizers diffusion parameters of the product were assessed by a cubic form according to the diffusion coefficients in the kinetic equation. In neutral condition, nitrogen nutrient releases lower and phosphorus release faster, compared with conditions of strong acid or strong alkaline. The effect of cations on fertilizer release abide by the order of Na+> K+> Ca2+. The release rate of nitrogen and phosphorus fertilizer became faster with the higher ions concentration. The utilization of WSC-g-PAA/PVA/NP in soil could greatly reduce the leaching loss of nutrients, compared with traditional fertilizers.