仿生型水基共聚物包膜尿素改性机理及其养分释放特征

Modification mechanism of biomimetic water-based copolymer coated urea and its nutrient release characteristics

水基共聚物包膜尿素控释期较短,通过仿生改性技术提升水基共聚物包膜尿素养分控释期并明确其养分释放特征是实现其在农业生产中应用的重要影响因素。为了探究仿生型水基共聚物包膜尿素的改性机理及养分释放特征,本研究采用壳聚糖、淀粉和聚乙烯醇合成的水基共聚物膜材料为原料,通过纳米二氧化硅和1H,1H,2H,2H-全氟癸基三甲氧基硅烷对其进行仿生改性并制备仿生型水基共聚物包膜尿素。探究不同温度和土壤水分条件下仿生型水基共聚物包膜尿素养分释放的动力学和热力学特性,并结合扫描电镜、能谱分析、热稳定性分析、原子力电子显微镜,探究其养分释放机理。试验结果表明,仿生改性后水基共聚物包膜尿素的缓释效果显著提升,42 d氮素累积释放率比水基共聚物包膜尿素降低了7.23%。此外,通过一级动力学方程探讨了仿生型水基共聚物包膜尿素的动力学和热力学释放特性,结果表明:随着土壤含水量的增高,活化能Ea逐渐减小;吉布斯自由能变量ΔG>0、熵变ΔS>0、焓变ΔH<0表示包膜尿素在土壤中的释放不是一个独立的系统,与土壤环境发生了热量交换,并明确了土壤温度和含水量与养分释放间的关系。此外,还通过仿生改性前后膜材官能团结构特征、表面微观结构、表面元素变化及热重分析等手段明确了其养分释放机制。

The controlled release period of water-based copolymer-coated urea is relatively short.Using biomimetic modification technology to improve the nutrient controlled release period of water-based copolymer-coated urea and clarify the nutrient release characteristics are important influencing factors for its application in agricultural production.In order to explore the nutrient modification and release mechanism of biomimetic modified water-based copolymer coated urea,this study used water-based copolymer membrane materials synthesized from chitosan,starch and polyvinyl alcohol as raw materials,and nano-silica and 1H,1H,2H,2H-perfluorooctyltriethoxysilane were modified and the biomimetic modified water-based copolymer coated urea was prepared.The kinetic and thermodynamic characteristics of nutrient release of biomimetic modified water-based copolymer coated urea under different temperature and soil moisture circumstances were explained,and its nutrient release was made clear through scanning electron microscopy,energy spectrum analysis,thermal stability analysis,and atomic force electron microscopy mechanism.The test results showed that the sustained release effect of water-based copolymer-coated urea was significantly improved after biomimetic modification,and the cumulative nitrogen release rate in 42 days was 7.23%lower than that of water-based copolymer-coated urea.In addition,the kinetic and thermodynamic release characteristics of the biomimetic modified water-based copolymer coated urea were matched through the first-order kinetic equation.The results showed that the activation energy Ea gradually decreased with the increase of soil moisture content;Gibbs free energy changeΔG>0,entropy changeΔS>0,enthalpy changeΔH<0,which means that the release of coated urea in the soil is not an independent system,but heat exchanges with the soil environment,and it is clear of the relationship between soil temperature,moisture content and nutrient release rate.In addition,the nutrient release mechanism was clarified by means of the structural characteristics of the functional group of the membrane material before and after the biomimetic modification,surface microstructure,surface element changes,and thermogravimetric analysis.