Abstract This paper discussed the synthesis of LTA zeolite from Pinheiro clay (PIN) aiming for adsorption of CO2. To obtain the LTA-PIN zeolite, the PIN was submitted to acid treatment, followed by calcination and hydrothermal treatment. These treatments promoted the reorganization of the crystalline structure of the PIN, leading to the LTA-PIN zeolite with 95.79% purity confirmed by XRD, SEM, XRF, and FTIR results. The performance of the LTA-PIN zeolite was similar to the one of the standard LTA zeolite. The CO2 adsorption by the zeolites could be properly described by the pseudo-second-order kinetic and Freundlich isotherm models, suggesting that physisorption was the main mechanism responsible for the deposition of CO2 at the surface of the zeolites. According to regeneration results, LTA-PIN zeolite can be reused five times without significant loss of CO2 adsorption capacity, contrary to the 12% reduction in CO2 adsorption capacity presented by the LTA-standard zeolite.

Resumo Falsa pega é a denominação dada ao enrijecimento prematuro anormal do cimento em poucos minutos após a adição de água. Alguns fatores podem ocasionar falsa pega no cimento Portland CPI-S-32, por exemplo, concentração de álcalis no cimento, formação de alita (C3S) com baixa reatividade e temperatura e tempo de armazenamento do cimento nos silos. O aumento da temperatura causa a desidratação do sulfato de cálcio di-hidratado formando o hemi-hidrato (CaSO4.0,5H2O) ou anidrita (CaSO4), que causa a falsa pega. Assim, neste trabalho foi avaliada a influência da temperatura de armazenamento do clínquer (100, 105, 110, 120 e 130 °C) combinada com o tempo de armazenamento do cimento (30, 60 e 120 min) no comportamento de falsa pega do CPI-S-32. Foi verificado que temperatura de armazenamento acima de 110 °C e tempo de armazenamento acima de 60 min são condições que favorecem a falsa pega do cimento CPI-S-32. Análises físico-químicas, TG/DTG, FRX e DRX foram utilizadas como análises complementares aos ensaios de falsa pega do CPI-S-32.

Abstract The false setting is when cement stiffens prematurely in a few minutes after adding water. Some variables could cause false setting in CPI-S-32 Portland cement, for example, alkali concentration in the cement, the formation of alite (C3S) with low reactivity, and cement storage temperature and time in silos. Temperature increases cause calcium sulfate dihydrate to dehydrate, forming hemihydrate (CaSO4.0.5H2O) or anhydrite (CaSO4), which causes the false setting. In this study, the influence of cement storage temperature (100, 105, 110, 120, and 130 °C) combined with the cement storage time (30, 60, and 120 min) in a silo was studied regarding the CPI-S-32 false setting behavior. It was verified that temperatures above 110 °C and storage time above 60 min are conditions that favor the false setting of CPI-S-32 cement. Physicochemical analysis, TG/DTG, XRF, and XRD were applied as complementary analyzes for the false setting assays of CPI-S-32.

Resumo O sulfametoxazol (SMX) é um antibiótico amplamente usado no tratamento de doenças e infecções e é frequentemente detectado em ecossistema de águas superficiais. Assim, este trabalho avaliou a capacidade de remoção deste antibiótico de sistemas aquosos utilizando argila Pirangi (PIR) do estado de Sergipe (Brasil). Amostras de argila Pirangi foram tratadas termicamente a 100, 400 e 600 °C e posteriormente modificadas com surfactante catiônico HDTMA. A modificação realizada baseou-se na organização em camadas da argila mineral possibilitando intercalação de surfactante catiônico, atribuindo caráter hidrofóbico à argila. A argila Pirangi tratada termicamente a 100 °C organofílica (org-PIR-100) apresentou maior capacidade máxima de adsorção de 27,3 mg.g-1 com remoção de 90% do SMX em 100 min e pH 6, seguindo o modelo de pseudossegunda ordem e isoterma de Langmuir. As argilas foram caracterizadas por FRX, FTIR, DRX, TG/DTG e BET, confirmando que as moléculas do surfactante foram incorporadas na superfície da argila e que a org-PIR-100 apresentou potencial para o uso em filtros de estações de tratamento de água.

Abstract Sulfamethoxazole (SMX) is a widely-used antibiotic in human and veterinary medicine for treating diseases and infections and is often detected in the surface water ecosystem. Thus, this study evaluated the capacity of removing SMX from aqueous systems using Pirangi clay (PIR) from the state of Sergipe (Brazil). Pirangi clay samples were treated at 100, 400 and 600 °C and modified with hexadecyltrimethylammonium (HDTMA) cationic surfactant. The modification process used was based on the layered organization of the mineral clay, allowing the intercalation of cationic surfactant, giving a hydrophobic character to the clay. The Pirangi clay treated at 100 °C and modified with HDTMA (org-PIR-100) showed adsorption capacity of 27.3 mg.g-1 with 90% removal of the SMX in 100 min and pH 6, following the pseudo-second-order model and Langmuir isotherm. Different characterization methods were employed to characterize the clays, such as XRF, FTIR, XRD, thermogravimetric analyzes (TG/DTG) and BET method, confirming that the surfactant molecules were incorporated on the clay surface and that org-PIR-100 showed potential for use in water treatment plant filters.