Estudo Do Comportamento Térmico Da Rocha Fonolito

Abstract

A mineralogia é um dos principais fatores na definição de rochas para aplicação na agricultura. A rocha fonolito, do município de Poços de Caldas -MG, possui um teor de K 2 O de 8,7% (m/m) e seu principal constituinte é o feldspato potássico. Estudos realizados com essa rocha in natura revelaram que o teor máximo de K liberado foi de cerca de 1% do K total, com a solução de Mehlich 1. Atualmente, rochas puras ou em misturas, após tratamentos químicos e/ou térmicos são estudadas com o intuito de aumentar a disponibilidade do K contido na rocha quando aplicada ao solo. Neste trabalho foi investigado o comportamento térmico da rocha fonolito, com o propósito de identificar as fases mineralógicas formadas com o aumento da temperatura. A rocha foi calcinada a 300; 600; 900; 1.000; 1.100 e 1.200 o C e analisada pelas técnicas de DRX, IV e MEV. A análise dos resultados revelou que em 600 o C não são observados os picos de difração da analcima, enquanto que, em 900 o C ocorre a formação de leucita. Nos ensaios de calcinação a 1.200 o C, foi obtido um produto amorfo, confirmando a perda total da estrutura cristalina do mineral. As fases obtidas, segundo a literatura, devem aumentar a disponibilidade do potássio como nutriente para as plantas. PALAVRAS-CHAVE:fonolito, comportamento térmico, fertilizante potássico. STUDY OF THERMAL BEHAVIOR OF PHONOLITE ROCK WITH PURPOSE TO FERTILIZER PRODUCTION ABSTRACTMineralogy is a major factor in the definition of rocks for use in agriculture. Phonolite rock, located in the Poços de Caldas plateau, southern Minas Gerais, has 7.4% (w/w) of K2O and its main constituent is feldspar. Studies with fresh rocks showed that top K released was about 1% of the total K, in Mehlich 1 solution. Currently, pure or mix rocks are studied after chemical and/or heat treatments, in order to increase the availability of K contained in the rock when applied to soil. In this study was investigated the thermal behavior of the phonolite for identify the mineralogical phases formed with increasing temperature. Rock samples were calcined at 300, 600, 900, 1.000, 1.100 and 1.200°C and analyzed by XRD, IR and SEM. At 600°C the diffraction peaks of analcime are not observed, while at 900°C occurs the formation of leucite. At 1.200°C was obtained amorphous materials that confirm total loss of crystal structure of the mineral. According literature, these structure changes are favorable for potassium availability as a nutrient for plants.

Silicate rocks as an alternative potassium fertilizer for upland rice and common bean crops

“…At the recommended rate (40 kg ha -1 K 2 O), KCl and K1 provided higher concentrations of the nutrient, whereas at two times the recommended rate (80 kg ha -1 K 2 O), the leaf K concentration was highest when K1 was used. On this topic, Teixeira et al (2015) suggested that melting at temperatures above 1,200 o C modifies the structure of the original mineral and should facilitate the release of the K + ion, which was bound to the structure of the minerals that constitute the rock. According to Duarte et al (2015) and Santos et al (2016), the calcination of silicate rocks with limestone or CaCl 2 at high temperatures increases the solubility of their minerals.…”

“…To have potential for use in agriculture, a mineral should present a high nutrient content, as well as bioavailability (Teixeira et al, 2015;Manning, 2018;Ciceri et al, 2019). Studies on the feasibility of rock powders as agricultural sources of K have been carried out since the 1970s and 1980s, and the sources were applied either in natura (Lopes et al, 1972;Eichler & Lopes, 1983;Ribeiro et al, 2010;Martins et al, 2015;Manning, 2018) or after some kind of solubilization process (Santos et al, 2016;Ciceri et al, 2017Ciceri et al, , 2019.…”

“…In Brazil, the steady increase in agricultural production and its dependence on the import of K fertilizers over long distances justify assessing rocks as K sources for agricultural use (Manning, 2018). An example of a mineral source with potential for use in agriculture is the phonolite rock (Mancuso et al, 2014;Martins et al, 2015;Teixeira et al, 2015), a silicate rock of volcanic origin, with 7-8% (w/w) K 2 O, whose main constituents are alkaline feldspar and feldspathoids (Teixeira et al, 2012(Teixeira et al, , 2015Tavares et al, 2018). Due to the high level of alkaline oxides, this rock is widely used as a flux by the ceramic industries (Andrade et al, 2005).…”

“…Due to the high level of alkaline oxides, this rock is widely used as a flux by the ceramic industries (Andrade et al, 2005). In addition to K, phonolite contains other elements, such as silicon, calcium, magnesium, and iron (Teixeira et al, 2012(Teixeira et al, , 2015Martins et al, 2015), which are also required by plants. Therefore, finely ground phonolite rock can also be used in agriculture, especially to supply K to plants (Mancuso et al, 2014;Martins et al, 2015;Tavares et al, 2018).…”

“…Therefore, finely ground phonolite rock can also be used in agriculture, especially to supply K to plants (Mancuso et al, 2014;Martins et al, 2015;Tavares et al, 2018). Some studies have also shown that thermal treatments, such as calcination or melting, can increase the available K in alkaline silicate rocks (Duarte et al, 2015;Martins et al, 2015;Teixeira et al, 2015;Santos et al, 2016;Ciceri et al, 2019). Moreover, these Cl-free sources may be interesting options for organic agriculture, where KCl is not allowed (Ciceri et al, 2017).…”