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基于RSM的土壤原位测量参比电极制备优化与评估

Optimization and Evaluation of Preparation of Reference Electrodes for In-situ Soil Measurement Based on RSM

  • 摘要: 农用电化学原位监测Ag/AgCl参比电极存在氯离子泄漏风险,探讨通过新型液态金属纳米纤维复合毡改进柔性参比电极稳定性,利用响应面分析方法(RSM)确定材料制备工艺对参比电极稳定性的影响趋势,获取优化方案并进行可行性验证。试验结果表明,液态金属纳米纤维复合毡制备主影响因素包括纺丝收集距离、纺丝混液质量配比和拉伸次数,影响程度依次降低;收集距离和拉伸次数对参比电极稳定性的耦合作用显著;当制备参数方案为质量比为1∶5、收集距离为19 cm、拉伸次数为1 150次时,参比电极稳定性最优,平均相对误差不大于4.4%;自制柔性Ag/AgCl参比电极,将其应用于土柱硝态氮和pH值监测原位测量,16 d的连续监测过程中硝态氮与pH值测试数据与离线商用电极测量值的绝对误差、相对误差和均方根误差分别小于5.55 mg/L、7.2%、1.98 mg/L和0.21、2.8%、0.17,参比电极持续提供稳定参考基准,保障了两工作电极与外检数据间良好的一致性,证明了自制Ag/AgCl参比电极在土壤农化分析中的可行性。

     

    Abstract: Aiming at the potential change caused by chloride leakage of Ag/AgCl reference electrode in in-situ soil monitoring, a flexible Ag/AgCl reference electrode modified with liquid metal fiber mat was prepared. The influence of preparation parameters of liquid metal fiber mat on the potential stability of the reference electrode was studied and the parameters were optimized. In order to improve the stability(reduce the standard deviation(s)), one solution parameter and four process parameters were selected for single factor test. Finally, three key factors were selected, namely the mass ratio of polystyrene(styrene-block-butadiene-block-styrene)(SBS) to 1, 2-dichloroethane, the collection distance of electrospun fibers and the number of tension required for activation electrode. Then based on Box-Behnken principle, the 3-factor and 3-level response surface optimization experiments were carried out. The results showed that the order of influence was as follows: collection distance, mass ratio and drawing numbers. The coupling effect of collection distance and drawing number was significant. When the mass ratio was 1∶5, the collection distance was 19 cm, and the drawing number was 1 150 times, the model prediction results were better, and the average relative error of the verification set was no more than 4.4%, indicating that the parameter optimization model was reliable. In addition, the flexible Ag/AgCl reference electrode was prepared based on the optimal parameters and applied to the soil column nitrate nitrogen and pH monitoring test. The absolute error between the nitrate nitrogen detection results and the commercial electrode measurements was less than 5.55 mg/L, the relative error was less than 7.2%, and the root-mean-square error was 1.98 mg/L. The absolute and relative errors between the pH test results and the commercial electrode measurements were less than 0.21, less than 2.8%, and the root-mean-square error was only 0.17. At the same time, the data of the two groups of flexible electrodes were consistent with that of commercial electrodes.

     

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