• ISSN 1008-505X
  • CN 11-3996/S

微波合成法制备铁基双金属锌/钙 MOFs 的可行性及其养分缓控释性能研究

Microwave-assisted synthesis of iron-based bimetallic Zn/Ca MOFs: feasibility and nutrient slow-controlled release performance

    摘要
  • 摘要:
    目的 铁基金属有机框架(MOFs)在缓控释肥料领域具有广阔应用潜力。本研究采用微波辅助合成法制备铁基MOFs，并评估引入Ca 或 Zn 元素对其组成结构、养分释放特性及作物生长的影响，旨在推动多元中微量元素肥料的精准设计与农业应用。
    方法 以氯化铁、氯化锌、氯化钙、磷酸、草酸和尿素为原料，以水热法(20 h)制备了常规铁基 MOFs(SR)，通过微波合成仪在 165 min 内制备铁基 MOFs(WB1)，并在 WB1 基础上合成了Fe/Zn 基(WB2)和Fe/Ca 基(WB3)两种双金属MOFs。应用 X 射线衍射、傅里叶变换红外光谱、X 射线光电子能谱、扫描电子显微镜、Zeta 电位、热重分析和元素定量等手段对 4 种材料进行结构与组成表征，并通过静水溶出法评估其养分释放特性。探究4 种铁基 MOFs 在不同浓度下(0、10、100、1000 µg/mL)对水稻幼苗生长的影响。
    结果 水热法制备的 SR 中，N、P 和 Fe 养分含量分别为 2.94%、8.58% 和 24.15%，WB1 中 N、P 和 Fe 养分含量分别为 2.32%、5.89% 和 25.26%，WB2 中 N、P、Fe 和 Zn养分含量分别为 1.27%、1.37%、8.95% 和 15.83%，WB3 中 N、P、Fe 和 Ca 养分含量分别为 1.68%、3.18%、9.37% 和 9.88%。WB1 的结构和形貌与 SR 相似但稳定性降低，WB2 和 WB3 的结构稳定性显著下降，微观形貌呈不均匀块状晶粒，其中 WB3 晶粒最小。双金属铁基 MOFs 中铁配位仍占主导，但 Zn 或 Ca 的掺入导致结构和形貌发生部分改变，且WB3 受影响最为显著。微波合成的 MOFs 在 30 d 内 N、P、Fe 累积释放率较SR分别提高88.87%、287.87% 和 106.08%，WB2 和 WB3 的释放速率更高，最高为 19.6%，WB2 中 Zn 累积释放量和 WB3 中 Ca 累积释放量均超过了 SR 和 WB1 中 Fe 释放量。微波合成 MOFs 显著提高水稻幼苗的生物量，平均达 24.35%，其中 WB3 在 1000 µg/mL 浓度下对水稻生长的促进作用最强。
    结论 微波辅助合成铁基 MOFs 法不仅缩短了肥料合成时间，还引入了其他养分元素，导致结构和形貌发生了变化，但养分释放性能仍满足缓控释肥料标准要求，且增强了对水稻幼苗的促生效果，为定向开发新型铁基多元肥料提供了技术支撑。

     

    Abstract:
    Objective Iron-based metal-organic frameworks (MOFs) show great potential as controlled-release fertilizers. This study aimed to prepare iron-based MOFs via a microwave-assisted method and to evaluate the effects of incorporating Ca or Zn secondary and micro-elements on their composition, structure, nutrient release properties, and crop growth, thereby providing insights for the precise design and agricultural application of multi-nutrient micronutrient fertilizers.
    Method Conventional iron-based MOFs (SR) were prepared by hydrothermal method (20 h) using ferric chloride, zinc chloride, calcium chloride, phosphoric acid, oxalic acid and urea as raw materials. Iron-based MOFs (WB1) were prepared within 165 min by microwave synthesizer. Based on WB1, two bimetallic MOFs, Fe/Zn based (WB2) and Fe/Ca based (WB3), were synthesized. The structure and composition of these MOFs were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), eta potential analysis, thermogravimetric analysis (TGA), and elemental analysis. Their nutrient release characteristics were evaluated via static leaching tests. Finally, the effects of different concentrations (0, 10, 100, 1000 µg/mL) of these MOFs on the growth of rice seedlings were investigated.
    Result Hydrothermally synthesized SR contained approximately 2.94% N, 8.58% P, and 24.15% Fe, whereas microwave-synthesized WB1 exhibited 2.32% N, 5.89% P, and 25.26% Fe. WB2 demonstrated 1.27% N, 1.37% P, 8.95% Fe, and 15.83% Zn, while WB3 contained 1.68% N, 3.18% P, 9.37% Fe, and 9.88% Ca. Compared to SR, WB1 exhibited similar structure and morphology but lower stability. The stability of WB2 and WB3 decreased significantly, with their micro-morphology showing irregular granular crystals, among which WB3 had the smallest crystal size. Although iron coordination remained dominant in the bimetallic MOFs, the incorporation of Zn or Ca induced partial changes in their structure and morphology, with the changes being most pronounced in WB3. The microwave-synthesized MOFs achieved cumulative 30 d release rates of N, P, and Fe that were 88.87%, 287.87%, and 106.08% higher than those of SR, respectively, which showed the relatively faster release from WB2 and WB3 with the highest nutrients release rate of 19.6%. The microwave-synthesized MOFs significantly increased the biomass of rice seedlings by 24.35%, with WB3 at 1000 µg/mL showing the strongest growth-promoting effect.
    Conclusion Microwave-assisted synthesis of iron-based MOFs greatly reduces fertilizer preparation duration while enabling the integration of additional nutrient elements. Although structural and morphological alterations occur, nutrient release kinetics still could satisfy the criteria of controlled-release fertilizer. The targeted incorporation of Zn or Ca in the MOFs proved their fertilizer efficacy in promoting rice seedling growth, thereby the microwave-assisted synthesis of MOFs-based fertilizers containing multiple nutrients provides an alternative technical support for the tailored development of novel multi-nutrient iron-based MOFs fertilizers.

     

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