Preparation And Molecular Simulation Of Lignin Slow Release Fertilizer

With the rapid development of agricultural technology, slow release fertilizer is used widely.However, the application of agricultural fertilizers which can be absorbed by crops actually isvery limited, and most of them are lost due to the influence of self and external factors. This notonly reduce the utilization of fertilizers, but also bring serious environmental pollution. Therefore,how to improve fertilizer use efficiency in agriculture is an important issue to be solved at homeand abroad. Although there have lignin/urea complex slow release fertilizer product fromdifferent manufacturers on the market, there has been no strong theoretical support and guidancebehind the production of these commodities, which will undoubtedly limit the furtherdevelopment of lignin/urea slow release fertilizer, and we can find that there have been no relatedresearches on the interaction between lignin/lignosulfonate and fertilizer molecules from theatomic and molecular level studies at home and abroad. Therefore, it is absolutely necessary tocarry out computer simulation methods to study the molecular mechanism of interaction betweenlignin/lignosulfonate and urea molecules. Through molecular simulation, we study themechanism of urea molecules absorbed on lignin/lignosulfonate、the distribution of ureamolecules absorbed on different group sites, and the diffusion coefficient of urea molecules. Dueto the large molecular structure of the lignin, more complex system containing lignin willincrease difficulties in molecular simulation calculation, so we are also trying to develop ligninresearch of coarse grained model. To this end, our studies are divided into the following fiveaspects:(1) This article first prepared lignin/clay composites under different conditions byexperiments, SEM pictures of lignin/clay composite material prepared showed that sphere likeassembling structure of lignin had been transferred into honeycomb assembling structure withmore pores for hydrogen bonding between hydroxyl groups of both of the starting materials. thisrich pore structure of composite materials fertilizer have an effective sustained release with ureamolecules.(2) Through molecular simulations we study the adsorption mechanism of urea molecules onlignin molecules and distribution of urea on urea lignin structure of the surface of differentadsorption sites under different conditions.(3) Through molecular simulations we study the urea adsorption mechanism and distributionon lignosulfonate under different conditions, urea different adsorption sites on surface structure of lignosulfonate.(4) We choose guaiacyl lignin units as the object, make the system balanced by all atomicmolecular dynamics simulations. After that, we use coarse-grained model statistics bond lengthdistribution, the distribution of bond angles, dihedral angle distribution and radial distribution.The system calculates the bond stretching energy, angle bending energy and non-bondinginteraction energy. Then start the coarse-grained molecular dynamics simulations, and add theabove bond length stretching energy, angle bending energy and non-bond interaction energies,until the system reaches equilibrium, bond length coarse-grained statistical molecular dynamicssimulation of distribution, the distribution of bond angles, dihedral angle distribution and radialdistribution. And analyze the static and dynamic physical quantities of lignin polymer chain, toverify the validity and accuracy of the coarse-grained model.(5) We take research on the viscosity of polyacrylamide in polyacrylamide-clay-waterSystem by MD simulation. According to the simulation results, it can be found that the radius ofgyration of polyacrylamide in polyacrylamide-clay-water system is higher than that inpolyacrylamide-water. In addition, under the shear force, the radius of gyration of polyacrylamidein polyacrylamide-clay-water system is lower with the increasing temperature or high shear forceincreased. This research can help us better understand and predict the viscosity of polyacrylamidein hydrated clay layer on the molecular level, and provide theoretical reference on the research oflignin-clay-water complex systems.