Study On Preparation Of Coal Based Humic Acid Urea And Its Leaching And Slow Release Effect

Humic acid（HA）is an important way for the clean utilization of lignite,and the use of HA and urea can improve the utilization efficiency of urea.The action law of HA and urea has not yet reached a consistent scientific conclusion,and the role of HA and urea and the efficient utilization of urea humic acid（HAU）fertilizer still need to be further explored.In this thesis,the optimal preparation conditions for the preparation of HAU fertilizer by water-solvent method were explored using lignite HA as raw material,and the interaction between HA and urea was analyzed by FTIR and XPS.Based on HAU mixed fertilizer and attapulgite clay（PAL）as the carrier,the HAU mixed fertilizer was molded and applied to obtain the best conditions for molding,and the adsorption capacity of the carrier PAL on urea was explored.Humic acid（PHA）was extracted by alkaline acid precipitation,and PHA and urea were used as raw materials to obtain the optimal preparation conditions of humic acid urea（PHAU）mixed fertilizer:400 g/L,material ratio 0.2,reaction temperature80°C,reaction duration 2 h.Humic acid（OHA）prepared by hydrogen peroxide oxidation was used as raw material to extract urea humic acid（OHAU）to compare and analyze the action law between HA and urea.The nitrogen content of PHAU increased from 1.41%to 6.2%of PHA.The original PHA contained a large number of oxygen-containing functional groups such as carboxyl carbonyls,and the relative content of carboxyl groups decreased and the relative content of carbonyl groups increased after the reaction.In PHAU,N is mainly present in the form of amide N and imine N.The change in OHAU is consistent with PHAU,but N in OHAU is mainly in the form of imine.Combined with elemental analysis,nuclear magnetic and other characterization data,the PHAU molecular model was constructed,and the molecular formula was C₄₆H₆₁O₂₅N₅.The energy minimization optimization of PHAU molecular configuration was carried out and the infrared spectrum was calculated.The infrared spectra are basically the same as the experimental spectra.The carrier PAL was modified and the adsorption capacity of PAL on urea was explored.The modification removes most of the structural water,zeolite water and carbonate impurities in PAL,and the surface structure of PAL is rougher after modification,which increases the contact area between PAL and solution.The adsorption results of PAL and modified PAL on urea showed that the modification made PAL have better adsorption capacity.The equilibrium adsorption time of PAL for urea was 180 min,and the equilibrium adsorption capacity was 7.93 mg/g.The equilibrium adsorption time of modified PAL for urea was 240 min,and the equilibrium adsorption capacity was 10.75 mg/g.According to the adsorption kinetics and isotherm fitting results,the adsorption process of modified PAL on urea is more in line with the quasi-secondary kinetics and Freundlich isotherm model.The adsorption of urea by modified PAL is a multilayer adsorption process including physical adsorption and chemical adsorption.Using modified PAL as the carrier,the PHAU mixture obtained by the reaction of PHA and urea was molded and applied.The optimal molding conditions are:binder（acetate starch）;Binder addition（2%）;Add water（10%）;Forming pressure（800 N）;The material ratio（1:1）,the molded fertilizer prepared under this condition has a urea loss rate of 48.93%after 11 consecutive rinses,showing a very good ability to resist leaching loss.In pot tests,molded fertilizers also showed better slow-release properties.This thesis has a total of 46 figures,16 tables,and 102 references.