Evaluación de la eficiencia de encapsulación de urea en alginato de calcio y su tasa de liberación

Abstract

Nitrogen is one of the main constituents of various vital compounds of living beings, therefore, it is one of the most important nutrients in the fertilization of crops; more than 50% of the total fertilizers used worldwide correspond to nitrogen fertilizers, among these, urea stands out, due to the large proportion of nitrogen it contains (46%), additionally, it is a product of easy access by the farmer due to its low value in the market. When urea nitrogen fertilizer is used in agricultural crops and it comes into contact with water, a cycle with different phases begins; first, hydrolysis, where ammonium ions (NH4 +) are produced and second, nitrification, where ammonium is converted into nitrates (NO3-) by oxidation, these compounds and ammonium ions are the nitrogen forms available to plants. However, when there is an excess of nitrates and ammonium in the crop, these are not fully utilized and are lost in the environment through leaching, volatilization and denitrification processes. Various mechanisms have been reported in the scientific literature that aim to improve the efficiency of use of this nutrient in the soil, but a considerable reduction of nitrogen compounds from urea has not been reported, which generate various environmental problems such as soil acidification, loss of ions such as calcium and potassium, nitrate mobility in water and NOx volatilization. One way to control the release of compounds is through microencapsulation, this technology has gained great interest in different areas of study; it is widely used in the food industry, as well as in the pharmaceutical industry. In this way, different materials have been used for this purpose; This is the case of alginate, a natural polysaccharide polymer extracted from brown algae, which, through an external (ionic) gelation process, becomes a gel in the presence of a divalent calcium ion. This material has optimal and attractive characteristics for use as an encapsulant due to its biocompatibility, low toxicity, inertia, low cost and high encapsulation efficiency. Encapsulation efficiency can be defined as the final amount of the component to be encapsulated that results inside the capsule compared to the initial amount used in the encapsulation process. There are different variables that can affect said efficiency: the oily phase, the surfactant, the agitation speed, the product content, among others. In this research, the efficiency will be evaluated with the following variables of interest: the size of the capsule and the concentration of calcium alginate.