为避免在磷肥与锌肥配合使用过程中造成的营养元素被固定、有效性降低等问题,目前普遍采用螯合的方式将中微量元素保护起来。以焦磷酸钠作螯合剂,七水硫酸锌为原料,制备焦磷酸锌,以螯合锌含量为考核指标,研究了反应比、反应温度、溶液pH、无水乙醇的用量等因素对螯合反应的影响;在单因素实验的基础上采用4因素3水平的Box-Behnken响应面分析法,对螯合工艺进行优化。在无水乙醇用量为25 mL/g、反应比为1（0.1 mol/L的七水硫酸锌溶液与焦磷酸钠的体积质量比为18.8 mL/g）、反应pH为9、反应温度为30 ℃的条件下,制备的焦磷酸锌锌质量分数最高,达到17.92%,与预测值相对误差仅为0.3%。响应面法分析出各因子对焦磷酸锌含量的影响从大到小依次是反应pH、无水乙醇用量、反应比、反应温度,并采用红外光谱分析验证了焦磷酸锌的生成,螯合后焦磷酸钠中的P=O、P—H都参与了Zn²⁺的配位。

In order to avoid the problems caused by the fixation of nutrient elements and the decrease of availability during the application of phosphate fertilizer and zinc fertilizer,chelation is widely used to protect medium and trace elements at present.Sodium pyrophosphate was used as the chelating agent and zinc sulfate heptahydrate was used as raw material to prepare zinc pyrophosphate.Using chelated zinc content as an assessment index,the effects of reaction ratio,reaction temperature,solution pH,and the amount of ethanol on the chelation reaction were studied.Based on single factor experiments,boxbehnken response surface analysis at the four-factors and three-levels was used to optimize the chelating process.Under the conditions such as ethanol amount of 25 mL/g,reaction ratio of 1（the volume to mass ratio of 0.1 mol/L zinc sulfate heptahydrate solution to sodium pyrophosphate was 18.8mL/g）,reaction pH of 9 and reaction temperature of 30 ℃,the highest chelated zinc content about 17.92% was obtained,and the relative error between the measured value and the predicted value was only 0.3%.Response surface analysis showed that the influence of each factor on the chelated zinc in descending order was as follows：reaction pH,consumption of ethanol,reaction ratio and reaction temperature.Fourier transform infrared spectrometer（FT-IR） analysis verified the formation of zinc pyrophosphate,and P=O and P—H in sodium pyrophosphate were involved in the coordination of Zn²⁺.