Mineralogical characterization of natural clays from Brazilian Southeast region for industrial applications

Abstract

Characterization studies of clays are often performed to identify possible markets for these materials. Bearing this in mind, two samples of natural clays from the Southeast region of Brazil were studied. Conventional techniques of characterization were used. Granulometric analysis and determination of cationic exchange capacity of these clays were also performed. Nitrogen adsorptiondesorption measurements were used to determine the Brunauer-Emmett-Teller specific surface area, and Barrett-Joyner-Halenda and t-plot pore size analysis were carried out. The results obtained were similar for the two clays. Both present high clay fraction (above 80 wt%) composed of illite, kaolinite and quartz minerals. Stratified illite-smectite structures were also observed. Traces of calcite were detected in one of the clay samples, while traces of montmorillonite were observed in the other sample. These results were corroborated by the low cationic exchange capacity values obtained for both clays. These clays showed good adsorptive properties, evidenced by their specific surface areas, with predominantly mesoporous structures and slit-like pores. According to their features, these clays have potential use as adsorbents to replace more expensive materials due to their easy availability and low cost. Keywords: characterization techniques, clay minerals, natural clays. Resumo

Characterization of raw and thermally treated Nigerian kaolinite-containing clays using instrumental techniques

“…The hysteresis of the adsorption isotherms of the raw and thermally treated clays in Fig. 3 corresponds to H3 hysteresis pattern, which suggests that their pores are narrow and slit-shaped having average pore diameter of 118-213 Å for the raw clays and 125-187 Å for the thermally treated clays as shown in Table 1 [36].…”

“…The t-plot micropore areas decreased from the raw clays to the thermally treated clays except for ROD and TOD in Table 1. Furthermore, the values of the micropore areas were smaller than the external surface areas except for RIJ and RIS, indicating that the external surface area was the major active surface for the clays [36].…”

“…According to International Union of Pure and Applied Chemistry (IUPAC), the adsorption-desorption isotherms of the raw and thermally treated clays correspond to Type IV isotherm in Fig. 3, these isotherms are illustrated by a limited uptake over a series of high relative pressure and a hysteresis loop [36][37][38]. The first part of the adsorption isotherms in the range of low relative pressures (0.02-0.7) was due to monolayer-multilayer adsorption, while the second section was associated to adsorption by capillary condensation in the mesopores [36,37].…”

Caracterização de argilas de novos jazimentos situados em Parelhas/RN, Brasil, visando aplicação na indústria cerâmica

“…A composição química das amostras de argilas A, B e C é apresentada na Tabela 1. A partir dos resultados observa-se que as argilas são compostas principalmente por óxido de silício (SiO 2 ), com teores variando entre 45,13 a 58,65% sendo maior na argila C. Com relação ao teor de alumina (Al 2 O 3 ), que representou o segundo maior componente das argilas, identificou-se que os teores variaram entre 16,81% a 39,19%, sendo maior na argila A. Estes resultados foram similares com outros trabalhos encontrados na literatura [3,10,[21][22][23]. A relação SiO 2 /Al 2 O 3 foi aproximadamente 3:1 para as amostras, exceto para amostra A, que apresentou relação aproximada de 1:1.…”

“…As argilas são materiais encontrados na natureza, bastante abundantes, de baixo custo de extração e processamento e altamente versáteis, além de ser, historicamente, o principal insumo utilizado na indústria de cerâmica vermelha [1][2][3]. Os materiais de cerâmica vermelha possuem um amplo campo de aplicação, sobretudo, na construção civil, como blocos de vedação e estruturais, telhas, tijolos, manilhas, agregado para concreto leve dentre outras inúmeras aplicações [4][5][6].…”