Preparation Of Controlled Release Fertilizer With Liquefied Waste Paper And Its Application On Oilseed Rape

Compared with the traditional water-soluble chemical fertilizers,coated controlled release fertilizer can significantly improve the utilization of fertilizers and reduce the environmental problems caused by leaching of fertilizers.However,the high cost of controlled release fertilizer and the difficult degradation of coated materials are important factors which hindered the application of controlled release fertilizer.Therefore,in view of the above two important issues,reducing the cost of coated controlled release fertilizer,selecting the biodegradable coating material has become a hot spot for the development of new fertilizer.The natural polymer in life such as waste paper,straw can be used for preparing bio-based degradable polymer coating materials with advantages of low cost,eco-friendly etc.Controlled release fertilizer coated by these materials has excellent controlled release properties.Therefore,this paper chose waste paper as the main raw material,the liquefaction scheme was optimized,the liquefied waste paper coating material was prepared,and the liquefied waste paper coated controlled release fertilizer was obtained by the drum coating process.The performance and microstructure of liquefied materials and coating materials were studied by Fourier transform infra-red spectroscopy(FTIR),thermogravimetric analysis(TGA)and scanning electron microscopy(SEM).The nutrient release performance and mechanism of controlled release fertilizers were studied by water extraction experiment.The effects of the applications of controlled-release fertilizer and the residual residue on the oilseed rape growth and soil were studied,and the degradation mechanism of residual coating was studied.The main results are as follows:(1)Optimal liquefaction condition were conducted through single factor test: when the ratio of liquid-to-solid was 10:1(solvent: waste paper,w/w),solvent ratio was 2:8(EG:EC,w /w),the liquefaction time was 1.5 h,and liquefaction temperature was 160 oC,the amount of catalyst was 3 % of liquefied agent(w/w),under this condition,the liquefaction rate of waste paper was the highest.At the same time,the nutrient release performance of coated controlled release fertilizer was evaluated by water extraction at 25 oC.It was found that the property of coated controlled release fertilizer was the best under the optimal conditions,and the nutrient release period was 84 d.(2)Through the FTIR analysis of waste paper,liquefied material,PAPI and PU,it can be seen that the waste paper decomposed during the liquefaction process and reacted with the liquefied agent to produce the polyhydric alcohols.The disappearance of the NCO group on PU indicated that the polyurethane has been synthesized through OH in liquefaction waste paper reacts with the NCO in the PAPI.(3)The effects of different molar ratios of hydroxyl groups-to-isocyanate groups on the properties of coating materials were studied.It was found that when the [OH] / [NCO] molar ratio was 1.05: 1,the obtained coating material had the best performance.From the SEM of the PCU,it can be seen that the membrane shell is in close contact with the urea,the surface of the coating material is uniform and smooth,the structure is dense and the membrane section had no pores and cracks.(4)The effect of the coating contents on the nutrient release performance of the controlled release fertilizer was studied.When the coating rate was 3 %,the nutrient release curve of the controlled release fertilizer appeared an inverted "L",the faster nutrient release of CRF,the shorter release period of CRF.When the coating rate reached 7 %,the nutrient release period of the fertilizer was 84 d,and the nutrient release curve displayed "S" type,which was consistent with the growth curve of the plant.(5)Degradation of residual coating by 6 and 12 months were studied by soil burial degradation test.It was found that the coating material was degraded and the degradation trend was more evident with the extension of test time.(6)The effects of the application of controlled release fertilizer and the residual coating on the growth?quality of oilseed rape and soil property were studied by potted plantation.It can be seen from the comparison that the application of controlled release fertilizer and residual coating not only increased the yield and quality of oilseed rape,but also improves the soil properties.