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The firing parameters in ceramic masses incorporated with 0, 5, and 10 wt% of scheelite tailings were investigated. The ceramic masses were characterized by X-ray fluorescence, granulometric, mineralogical analysis, and Atterberg limits determination. The samples were obtained by uniaxial pressing (20 MPa), sintered at different temperatures (800, 900, and 1000 °C), and heating rates (5, 10, 15, and 20 °C∙min−1). Physical and mechanical tests (water absorption, apparent porosity, and flexural strength) and mineralogical tests were accomplished from the sintered samples. Natural aging tests were also carried out to assess carbonation resistance. For this, some samples were kept in an internal environment (inside the laboratory) for 3 months. The results showed a high content of calcium oxide in the scheelite tailings and a reduction in the plasticity index of the ceramic masses with the tailings addition. The best results were observed for the ceramic mass with 5% tailings. The best results were observed regarding the firing parameters for the temperature equal to 1000 °C, increasing the heating rate to 10 °C∙min−1 without compromising the material properties. The samples kept in an internal environment for 3 months showed a loss of physical and mechanical properties. Such behavior probably occurred due to the onset of the carbonation phenomenon.

Mineralogical and technological characterization of ceramic raw materials from a new deposit located at Caxias city, Maranhão State—Brazil, was accomplished to determine their potential as raw materials for the ceramics industry in northeastern Brazil. The ceramic raw materials were collected from three different locations on the site and characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), differential thermal analysis (DTA), and thermogravimetry (TG). The XRF analysis of the fraction < 2 μm revealed that most samples had SiO2 (35–51 wt%), Al2O3 (19–29 wt%), Fe2O3 (2–21 wt%), MgO (0.7 to 4.5 wt%) and K2O (0.9 to 5 wt%) as components. Quartz, kaolinite, illite, hematite and montmorillonite were the main mineral phases identified. DTA and TG analysis confirmed the mineral identification. The technological potential of the ceramic raw materials was investigated by: cation exchange capacity (CEC), plastic behavior (Atterberg Limits), linear shrinkage at 950 °C (LSF), flexural strength (FS), apparent porosity (AP), water absorption (WA) and bulk density (BD). The main experimental results—WA (9–17%), AP (19–31%), FS (2.0–23 MPa), and the Atterberg limits—indicated that the ceramic raw materials investigated have high potential to be used to develop mass for red or structured ceramics, such as bricks and roof tiles.

Alkali-activated materials (AAMs) were produced using residues from the red ceramic industry as a precursor, and sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium silicate (Na2SiO3) as alkaline activators. The effect of activators and curing conditions on physical-mechanical properties and durability were evaluated. The processing parameters (amount of water and consistency index) and the activation conditions (the activator contents and curing temperature) were defined based on an experimental design getting the flexural rupture module as the response. The durability behavior was evaluated by natural aging, accelerated aging (simulated rain test), exposure to the marine environment (salt fog), and acidic environments (HCl and H2SO4). The results showed that the NaOH- and KOH-activated samples exhibited inferior mechanical behavior than those activated with Na2SiO3. In the durability studies, due to leaching, there was a decrease in mechanical strength when samples are subjected to aggressive exposure conditions. However, the strength values are still higher than the minimum indicated for traditional ceramic applications.

This study presents the development of new eco-friendly mortar compositions containing kaolin residues (KR) and assesses their durability behavior. Firstly, the natural and calcinated kaolin residues (600 °C, 650 °C, 700 °C, 750 °C, and 800 °C) were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), granulometric analysis, and surface area. The kaolin residue calcinated at 800 °C was chosen to be added to new compositions of mortar because it presented the best pozzolanic performance. The aging tests accomplished in internal (Ei) and external (Ee) environments were applied in mortars with a mass proportion of 1:2:6 (cement + KR: lime: sand), in which the KR, calcinated at 800 °C, replaced the cement in the mass fraction of 0%, 5%, 10%, 15%, 20%, and 30%. The Ei was performed for 30, 60, 90, 180, and 360 days, and the Ee for 90, 210, 360, and 512 days. After the aging tests were completed, the mortar compositions containing KR were evaluated to determine their mineralogical phases (XRD), compressive strength (CS), and thermal behavior (DTA and thermogravimetry). In summary, the KR addition to the mortar compositions decreases the mechanical resistance to compression, however, mortars with a substitution of 10% and 20% presented resistance values within the minimum limit of 2.4 MPa established by ASTM C 270.

Tailing incorporation into mortars has been the subject of much research in recent years. Despite this, most of these studies did not investigate the harmful effects resulting from the exposure of such mortars to an environment containing aggressive agents. This work investigated the effects of perlite tailing addition into mortars containing cement CP V-ARI MAX and hydrated lime. The raw materials were subjected to chemical characterization (X-ray fluorescence (XRF)) and mineralogical (X-ray diffraction (XRD)), while the samples immersed in 1 N NaOH solution were characterized by XRD, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and compression strength (CS). The results showed the harmful effects of incorporating perlite tailings into the mortar investigated. Such a degradation was proven by linear expansion and compressive strength experiments accomplished in the samples after the test of resistance to an alkali–silicate reaction.

The combination of biocompatible polymers and ceramics shows great promise in the development of composites with suitable mechanical properties for dental applications. In an attempt to further expand this research line, Al2O3 commercial powders (Vitro-ceram, Alglass, In-ceram) were sintered at 1400 °C for 2 h and infiltrated with poly(methyl methacrylate) for potential use in dental prostheses. The infiltration was performed using a homemade apparatus under a pressure of 7 bar for 6 and 12 h. The microstructure (studied using a scanning electron microscope), Archimedes density, 3-point bending flexural strength and Vickers hardness of the prepared composites were assessed and quantitatively compared. In general, microstructural analyses showed ceramic- and polymer-based interpenetrating network in all materials. The preforms infiltrated for 12 h showed superior properties, among them, the Vitro-ceram-based composite also demonstrated a near-zero open porosity and optimum mechanical characteristics. Specifically, its density, strength and hardness were 2.6 ± 0.07 g/cm3, 119.3 ± 5.0 MPa and 1055.1 ± 111.0 HV, respectively, passing the acceptance criteria of ISO 6872 and making it suitable for consideration as a metal-free structure for dental crowns and fixed partial prostheses until three anterior units.

Ceramic nanofibers have been shown to be a new horizon of research in the biomedical area, due to their differentiated morphology, nanoroughness, nanotopography, wettability, bioactivity, and chemical functionalization properties. Therefore, considering the impact caused by the use of these nanofibers, and the fact that there are still limited data available in the literature addressing the ceramic nanofiber application in regenerative medicine, this review article aims to gather the state-of-the-art research concerning these materials, for potential use as a biomaterial for wound healing and bone regeneration, and to analyze their characteristics when considering their application.

In this study, we develop ceramic formulations based on quartzite and scheelite tailings collected from mining companies in the northeast of Brazil (Rio Grande do Norte State). New ceramic samples (27 wt% of kaolin, 29 wt% of plastic clay, 11 wt% of quartzite tailing, and 0&ndash, 8 wt% scheelite tailing) were uniaxially pressed in two steps (20 MPa and 50 Mpa for 20 s), dried at 110 &deg, C for 24 h, and sintered at 1150 &deg, C, 1200 &deg, C, and 1250 &deg, C. The main mineralogical phases (mullite, quartz, calcite, and anorthite) of the sintered samples were identified using X-ray diffraction (XRD). After evaluation of the physical-mechanical properties (water absorption, linear shrinkage, apparent porosity, and flexural strength), it was observed that the incorporation of scheelite tailing by up to 8 wt% did not significantly alter the properties of samples sintered at all temperatures. Our results indicate that the new ceramics formulations developed have strong potentials in manufacturing sustainable materials such as ceramic tiles and porcelain stoneware.

The efficiency of acid treatment on natural calcium bentonite (natural bentonite) for anionic dye adsorption was investigated using methyl orange (MO) as a probe. Additionally, adsorption experiments were accomplished between the natural bentonite, acidified bentonite, and a cationic dye (methylene blue, MB). Acid functionalization in natural bentonite (RF) was carried out with HCl and H2SO4 acids (RF1 and RF2, respectively). The samples were characterized by chemical analysis, mineralogy, particle size, and thermal behavior with the associated mass losses. The adsorption efficiency of MO and MB dyes was investigated by the effects of the initial concentration of adsorbate (Ci) and the contact time (tc). The acid treatment was efficient for increasing the adsorption capacity of the anionic dye, and the Qmaxexp values measured were 2.2 mg/g, 67.4 mg/g e 47.8 mg/g to RF, RF1 e RF2, respectively. On the other hand, the acid functionalization of bentonite did not significantly modify the MB dye adsorption. The Sips equation was the best fit for the adsorption isotherms. Thus, we found that the acid-functionalized bentonite increases the anionic dye adsorption by up to 8000%. The increased adsorptive capacity of acidified bentonite was explained in terms of electrostatic attraction between the clay surface and the dye molecule.

The inadequate discharge of effluents from different sources without prior treatment can impact the characteristics of soil and water, which reflect serious environmental problems. Advanced oxidative processes (AOP) appear as a viable alternative for environmental remediation, including wastewater treatment. Herein, &alpha, MoO3 and &alpha, Fe2O3 semiconductors were synthesized at low temperature by a Pechini-based method and then applied in photocatalysis. The catalytic efficiency was performed under visible light toward the degradation of an organic persistent pollutant (Rhodamine B dye, RhB), commonly present in industries wastewater. The results indicated that the synthesized &alpha, MoO3 or &alpha, Fe2O3 photocatalysts presented a pronounced activity and promoted an efficient RhB degradation after 15 min of reaction. &alpha, MoO3 had a degradation efficiency of 93% and 98%, while &alpha, Fe2O3 showed 67% and 100% RhB degradation without and with the addition of H2O2, respectively. These results suggest that the synthesized oxides have high oxi-reductive capacity, which can be used for a fast and effective photodegradation of RhB and other organic persistent pollutants to minimize environmental impacts.