Desenvolvimento de sistema híbrido de cera de carnaúba e bentonita para liberação controlada de ureia.

Abstract

Approximately 70% of the applied urea fertilizer can be lost to the environment. This loss is due to the leaching, decomposition and volatilization of ammonia in soil, water and air. Through the coating (encapsulation), slow or controlled release technology can be used to reduce losses and increase urea efficiency. These fertilizers improve the absorption of nutrients by the plants through the synchronized release, significantly reducing their possible losses, either by leaching and/ or by volatilization. Thus, the objective of this work was to study the diffusional behavior of urea when associated with carnauba and/or bentonite wax (natural, sodium and organophilic), thus obtaining controlled release fertilizers. Hybrid coatings of carnauba wax and bentonite, with different proportions, encapsulated urea bars. The obtained samples were tested as a new model of controlled release nitrogen fertilizer. All the raw materials, as well as the hybrid coatings were characterized by the following techniques: laser grading, X-ray fluorescence (EDX), X-ray diffraction (XRD), thermal analysis (TG / DTG / DTA) and FTIR. Dissolution tests were carried out in aqueous medium and in soil column in order to verify if the dissolution of urea was influenced by the types of coatings. Aqueous and ground column dissolution tests revealed that the coatings of carnauba wax and bentonite (natural and sodium) were those which retained the urea longer. These studies allowed the design of a controlled release urea fertilizer system.