Multilayer films of carboxymethylcellulose/zeolite as smart materials for macro and micronutrients delivery

Abstract

The scientific community has intensified studies on new materials in order to use their properties in the manufacture of enhanced efficiency fertilizers (EEF). These materials are attractive because they release essential nutrients to plants for a long period. This work aimed to obtain and characterize EEF structured in multilayer films based on natural zeolite (Ze) enriched with macro and micronutrients and carboxymethylcellulose (CMC). We evaluate Ze nutrient adsorption capacity, the kinetics, and the adsorption isotherms. The enriched Ze was incorporated into the CMC solution to obtain monolayer casting films and multilayer films containing macro in the inner and micronutrients in the outer layer (CMC-ZeMulti/CMC-ZeK/CMC-ZeMulti). Evaluation of the kinetic models of adsorption leads to observe the best fitting are pseudo-first-order for macro and pseudo-second-order for micronutrient. Langmuir isothermal model best fitted the experimental data, which corresponds to the process of forming a monolayer adsorbed on the surface of the Ze. Ze establishes a selectivity regarding the absorption of micronutrients (Cu > Zn > Fe > Mn) which is related to the physicochemical properties of the ions. Monolayer films released higher macronutrient percentage compared to multilayer mainly due to the competition of the ions and its longer diffusion path. But no ion release relationship for Ze-enriched (Mn < Zn < Fe < Cu) and CMC-films (Cu < Mn < Fe < Zn) with adsorption capacity was observed. In a comparison with commercial Basacote® material, a similar release of macro and micronutrients were observed for CMC-ZeMulti/CMC-ZeK/CMC-ZeMulti. These facts highlight the potential for commercial application in a more sustainable agricultural practices, due to the low cost, simplicity of production and ecologically viable formulation.