Sorção de cério em solo oxídico

Abstract

Currently the use of rare earth elements has become a necessity for its essentiality in several technologies, particularly in industry. In recent years, their effects have also been studied in agriculture, because these elements are present in many minerals in the soil, as well as in fertilizers and other soil amendments used in agricultural practices, especially phosphate fertilizers and phosphogypsum. In tropical soils, the use of phosphate fertilizers is critical and farmers, when applying such input, are also indirectly applying rare earth elements to the soil. The same occurs for phosphogypsum, an input that is also widely used in Brazilian agriculture and may contain high concentrations of cerium (Ce). With the focus of knowing better the contribution of this element in the soil -plant system, many researches have been directed towards this end. The biggest concern is to know how rare earth elements behave when they are applied to the soil. Within the rare earth elements, Ce is the most abundant and most abundant element in phosphate fertilizers as well, and is consequently the most indirectly applied in tropical agriculture. This present work evaluated the sorption and desorption behavior of Ce in a Red Latosol dystrophic typic (LVd) that has been managed with the use of different doses of phosphogypsum, using soils from three areas with different management of phosphogypsum (native area, area with 2 t ha -1 of phosphogypsum and area with 56 t ha -1 of phosphogypsum), in the same property. Soil samples were exposed to increasing concentrations of Ce during 72 hours, alternating 12 hours of shaking and 12 hours of rest. The Ce analyses were performed using ICP-OES and the values obtained were used to fit adsorption isotherms, assess the maximum adsorption capacity of the element and determine the quantities of Ce desorbed. The results showed that the Latosol studied presents high Ce adsorption capacity and low desorption capacity, with a maximum Ce adsorption capacity of 3555, 2419 and 3391 mg kg -1 Ce, for the three managements respectively. It is concluded that this adsorption capacity is related to soil factors such as pH, cation exchange capacity and soil organic matter content