Multifunctional Iron-Humic Acid Fertilizer from Ball Milling Double-Shelled Fe-N-doped Hollow Mesoporous Carbon Microspheres with Lignite

Iron (Fe) chelated by water-soluble humic substances can effectively overcome plant micronutrient deficiencies. However, the traditional synthesis methods are often complex, expensive, and thus not applicable to large-scale industrial productions. In this work, an ecofriendly and multifunctional Fe-humic acid (HA) complex was successfully prepared through simply ball milling lignite with double-shelled Fe-N hollow mesoporous carbon microspheres (DS-Fe-NHC). The novel DS-Fe-N-HC was synthesized using a simple strategy and was first applied in activating HA from lignite by solid-phase ball milling to attain the water-soluble HA-iron fertilizer (WHIF). The physicochemical properties of the DS-Fe-N-HC nanocomposites and WHIF were systematically characterized by a series of techniques. A traditional Fe-HA complex is mainly obtained by mixing HA and iron ions, which has poor water solubility because HA is not activated. In comparison to samples prepared with other methods, WHIF contained more stable water-soluble HA. Furthermore, the as-obtained WHIF had higher amounts of proteins and amino sugar tannin as evidenced in FT-ICR MS analysis. Moreover, WHIF contributed to higher activities in chlorophyll content, height, steam diameter, and biomass of peanuts than other samples. The results demonstrate that WHIF is effective in reducing symptoms of iron deficiency in peanuts, which can be attributed to its iron-based compounds and water-soluble HA. The findings of this study provide a promising, cost-effective, and environmentally friendly solution to mitigate iron deficiency and promote the growth of peanuts for large-scale agriculture production.

Automated summary

The ecofriendly and multifunctional Fe-humic acid (HA) complex was successfully prepared using simply ball milling lignite with double-shelled Fe-N hollow mesoporous carbon microspheres (DS-Fe-NHC). The WHIF fertilizer obtained through this method showed higher stability of water-soluble HA and significantly promoted growth in peanuts by reducing iron deficiency symptoms. The results suggest a cost-effective and environmentally friendly solution for large-scale agriculture production.