Avaliação do uso de um resíduo de isolamento térmico a base de silicato de cálcio na agricultura

Abstract

This study aimed at evaluating the agronomic, technical and environmental feasibility of the destination of solid waste based on calcium silicate, from slabs of thermal insulation on overheated pipes from REDUC (Duque de Caxias Refinery), as an agricultural input. In this sense, three tests were conducted, which are presented in the following chapters. In the first chapter laboratory tests were performed for physical and chemical characterization of the residue, preconizing the parameters required by the Brazilian legislation, and also using two limestones and a slag of steel. There was an incubation test at different doses of corrective materials, evaluating after 90 days the chemical attributes related to soil acidity. Therefore, it was found out that the hydrossilicate has potential as a soil acidity corrective, allows for addition of significant amounts of Si, with no major changes in soil pH, and presents low levels of toxic heavy metals. In the second chapter, an experiment was carried out to measure granulometry and the influence of transition-metal impurities in determining the neutralization power (NP) was evaluated. Moreover, the reactivity rates of granulometric fractions were determined in two soils, classified as Ultisols and Alfisols. The methodology used to determine the granulometry was not appropriate to the hydrossilicate, hence it is necessary to reduce the mass of the sample and increase time of agitation. The NP determination by the traditional methodology through acid-base titration, for materials that present high levels of transition metals in their composition, underestimates the NP in such materials. In more coarse fractions, ABNT 10 to 20 and ABNT 20 to 50, the physical nature of the material conditions greater influence on their reactivity, so three classes of particles for the limestone (10 to 20) (20 to 50) and (< 50) can be admitted, with different rates of reactivity, respectively on the average of the two soils, 21%, 44% and 59%. For the slag studied, two classes of size fractions (10 to 20 and <20) can be admitted, with distinct reactivity, respectively on the average of the two soils, 50% and 64%. However, the hydrossilicate showed high reactivity in all the studied fractions, there was only one class of response (<10) with reactivity average of 69% in the two soils. In the third chapter, an experiment in pot was conducted to evaluate the effect of the localized application of calcium hydrossilicate, with the planting fertilization in the development of rice and the soil fertilization area. To accomplish that, specific pots were used (Pot ZZ), which enable radial sampling around the fertilizer application track with metal cylinders, sampled up to 1cm; 1 to 1.5 cm, 1.5 to 2 cm and 2 to 3 cm of radius from the center of the fertilizer application track. A rice fertilization was carried simulating a plantation in a line in the field, where the planting fertilization was varied with NPK or PK, with and without two doses of hydrossilicate digging the super triple (ST) fertilizer granules in the form of pellets. The rice plants have been grown for 45 days. With the localized application of calcium hydrossilicate in planting fertilization there was a decrease in acidity generated by ST, in the mobility of P from ST, in the absorption of P by rice, and in the number of senescent leaves.