Preparation And Performance Of MOF-based Slow-release Fertilizer

Excellent adsorbents were prepared based on the excellent adsorption properties of metal-organic framework materials（MOFs）by combining with natural polymers.It was used to adsorb ammonium salts and phosphates to fabricate composite water-retaining slow-release fertilizers（SRFs）,which is expected to solve the problems of low fertilizer utilization rate,water eutrophication,atmospheric environmental pollution and sustainable development in agricultural production.1.A hybrid aerogel（CMC/Gelatin/MOF（Cu）@biochar）was prepared via a simple and effective freeze-drying method,using carboxymethyl cellulose（CMC）,gelatin and MOF（Cu）@biochar as raw materials.The NH₄Cl-loaded aerogel was used as the slow-release nitrogen fertilizer（SRNFs）.The cumulative release rate of SRNFs in the soil within the 30th day was 79.4%.Fertilizer release behaviour is determined by the synergistic mechanism of non-Fickian diffusion and cation exchange.2.Iron-filled MOF-Al-based hydrogels（SA@Fe@MOF-Al）was prepared from sodium alginate（SA）,ferric chloride（Fe Cl₃）and MOF-Al,and used as an adsorbent to adsorb H₂PO₄^-in wastewater.The P-enriched SA@Fe@MOF-Al was used as the water-retaining slow-release P-fertilizer.The maximum adsorption capacity of the hydrogel for H₂PO₄^-was 103.09 mg/g,and the adsorption reached equilibrium within30 min.Meanwhile,the thermodynamic results confirmed that the adsorption was exothermic and spontaneous.The adsorption kinetics results show that the adsorption process of the hydrogel was suitable for the pseudo-first-order model and the Langmuir model.The slow-release P-fertilizer prepared after adsorbing H₂PO₄^-had excellent slow-release and water retention properties.3.Poly（N-isopropyl acrylamide-co-acrylamide）-coated Alg-g-BMOF（Fe/Mg）（PABMOF）was fabricated in ionic liquids microemulsion（[Bmim]PF₆/TX-100/water）as nano-reactor.Efficient reclamation phosphate by PABMOF for temperature-responsive slow-release P-fertilizer.The temperature-responsive SRFs（TRSRFs）displayed excellent slow-release property.The water-holding and water-retention capacity of soil with TRSRFs addition of 2wt%were74.3%and52.13%within 30th day,respectively.Moreover,the release behavior of TRSRFs in water show that the cumulative release rate（Cr%）were 81.4%at 45℃and 97.6%at25℃within 172h,which displayed the excellent temperature-responsive property.In this paper,three kinds of slow-release fertilizers with excellent slow-release and water-retention properties were prepared by using three different MOFs as the matrix.Among them,CMC/Gelatin/MOF（Cu）@biochar loaded with ammonium chloride is used to prepare SRFs by freeze-drying method,which was simple and efficient;SA@Fe@MOF-Al and PABMOF adsorbing H₂PO₄^-,which could reduce its negative impact on the environment.Meanwhile,P-enriched SA@Fe@MOF-Al and PABMOF were reused as SRFs,which have potential applications in sustainable agriculture.