Composite of amorphous silica encapsulated urea as a slow-release fertilizer

Abstract

Composite of amorphous silica encapsulated urea as a slow-release fertilizer has been performed. Amorphous silica was obtained from dealumination of natural clay by the reflux method using HCl 6M. Encapsulation composite was prepared with amorphous silica mass variations of 0.50; 0.75; 1,00; 1.50; and 2.00 g. The preparation of encapsulation composite aimed to study the effect of amorphous silica mass on compressive strength and water absorption of composite. The XRD data showed that the dealumination process was successfully prepared by the formation of an amorphous diffraction pattern. The dealumination process was also supported by EDX data that indicated a decrease in the percentage of Al atomic weight from 11.29 to 0.36%. The optimum compressive strength and water absorption results were obtained at amorphous silica mass of 0.75 g with values of 5.40 MPa and 42.60%, respectively. The kinetics model followed the pseudo-second order for urea as a control and Korsmeyer-Peppas for composite of amorphous silica encapsulated urea with rate values of 0.847 mg⁻¹ hour⁻ⁿ and 0.012 mg⁻¹ hour⁻¹, respectively.