Studies On Preparation And Properties Of Cellulose-based Slow-release Fertilizers With Water Retention

Water resources and fertilizers are two important factors for crop growth.Water-retaining agent is a kind of super absorbent composite material with three-dimensional network structure,which can absorb and retain water.It can obviously enhance the drought resistance of crop,effectively reduce the frequency of irrigation,and significantly improve the quality of crop.Slow-release fertilizers can greatly improve the utilization rate of fertilizers nutrients,reduce water eutrophication,soil compaction and other environmental pollution problems,and improve crop yield and quality.Therefore,this study was devoted to the preparation of a water-retaining slow-release fertilizer which can not only retain water but also slowly release nutrients.But the traditional water-retaining agent was mostly synthesized by polyacrylic acid with high cost and non-degradable.In the study,natural renewable and biodegradable cellulose materials such as waste paper and corn straw were used as raw materials to develop two cellulose-based slow-release fertilizers with low cost,degradability,good water-retention and excellent slow-release performance.1.Waste paper cellulose was used as the main raw material to prepare cellulose-based water-retaining slow-release fertilizers.Firstly,waste paper cellulose was prepared through deinking treatments.Under the action of acrylic acid,crosslinker and initiator,cellulose-based water-retaining slow-release fertilizers were prepared by graft copolymerization.The structure and morphology of WPC-g-PAA/NPK were analyzed and characterized by FTIR,XRD,SEM,TGA and EDS.The effects of different components and environmental factors on the water absorbency of WPC-g-PAA/NPK were studied.The water-retention capacity?thermal stability?water-holding capacity?swelling capacity?slow-release behavior and its kinetics of WPC-g-PAA/NPK were studied in detail.The results showed that waste paper cellulose and compound fertilizer were successfully grafted onto the polymer,the thermal stability of WPC-g-PAA/NPK was improved by 74.2?(T_5%),the surface structure of WPC-g-PAA/NPK was compact,the element distribution was uniform,the water-retention capacity was increased by 39.1%and the swelling capacity of WPC-g-PAA/NPK was good,the kinetics of WPC-g-PAA/NPK could be evaluated by Schott's second-order swelling kinetics model.Moreover,WPC-g-PAA/NPK has excellent slow release property.The slow-release kinetics of WPC-g-PAA/NPK could be explained by Ritger-Peppas model.These studies indicated that cellulose-based water-retaining slow-release fertilizers from waste paper have broad application prospects in agriculture and horticulture.2.Corn straw cellulose-based water-retaining slow-release fertilizers were successfully prepared by solution polymerization that is the most mature technology at present,using corn straw,acrylic acid and acrylamide as the main raw materials under the combined action of initiator and crosslinking agent.The structure and morphology of WSC-g-AA/AM/Urea were analyzed by FTIR?TGA?EDS?SEM and XRD.Then water absorbency and thermodynamic properties of WSC-g-AA/AM/Urea were studied.The swelling kinetics of WSC-g-AA/AM/Urea was studied,and the effect of different components and environmental on water absorbency were analyzed.The results showed that the thermal stability of WSC-g-AA/AM/Urea was significantly improved with the addition of urea,and the T_5%of the sample was increased by 98.8?.The SEM displayed that the surface of the sample was density.It was observed by EDS that all elements were evenly distributed on the surface of the sample.The Schott's second-order swelling kinetics model could be used to evaluate the swelling kinetics of WSC-g-AA/AM/Urea,which proved that the sample had strong swelling ability.In addition,it was found that WSC-g-AA/AM/Urea had higher water absorbency in medium with neutral?pH=7?,weak base?10>pH>7?,low ion concentration and low cation valence at 25?.These data provided a reference for the wide application of cellulose-based water-retaining slow-release fertilizers from corn straw in agriculture and horticulture.