Bio-based epoxy modified with nano-SiO2 and organosilicon for controlled-release urea

Nearly 100 million tons of spent mushroom substrates (SMS) are discarded annually in China, which causes a series of environmental pollutants. To improve the nitrogen (N) use efficiency of and to shift dependence away from petroleum-based products, a novel bio-based epoxy coated urea was successfully developed. The bio-based epoxy coating was synthesized from the liquefied SMS and bisphenol-A diglycidyl ether. Subsequently, both nano-SiO2 and organosilicon were employed to modify the bio-based epoxy and increase its hydrophobicity. Water absorption, ammonium adsorption, and water contact angles of the bio-based epoxy coatings were investigated. The nutrient release behaviors of the bio-based epoxy coated urea in water were also investigated and the modification mechanisms were explored by Fourier transform infrared, scanning electron microscopy-energy-dispersive X-ray spectroscopy and thermogravimetric analysis. The results revealed that the hydrophobic ability of the nano-SiO2 and organosilicon dual modified bio-based epoxy coated urea coating was significantly enhanced and that its nutrient release longevity was increased to 56 days. Therefore, this work demonstrated that bio-based epoxy coated urea with superior release characteristics exhibited great potential in modern agricultural applications.