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Geopolymers are chemically bonded ceramics formed at room temperature and obtained using aluminosilicates and alkali activators. Geopolymers have found applications beyond construction, such as in wastewater treatment and ceramics. This research aims to develop geopolymers using coal mining waste (CMW) for various purposes. The waste used in this study was obtained from the Barro Branco layer in companies located in southern Santa Catarina/Brazil. The waste was thermally treated at 900 °C for 160 min, followed by grinding and characterization using X-ray fluorescence spectroscopy, X-ray diffraction, and particle size analysis. Geopolymeric samples were produced using 60 wt% waste, 25 wt% sodium silicate, and 15 wt% 10 M NaOH. The specimens were divided into three groups and cured using different methods. The results showed that thermal curing enhanced waste reactivity, reduced curing time, and improved compressive strength. However, long-term submersion curing decreased compressive strength due to sodium leaching, reducing reactivity. [ABSTRACT FROM AUTHOR]

The article presents a study that evaluates the firing properties of plastic clay, kaolins, from Pantano Grande, Brazil. It explores the method of the study that observes the technological characterization of the clay in the temperature range from 1200 to 1400 Celsius. The result of the study indicates the complete characterization of the related clay and highlights its potential applications in the ceramic industry.

The transportation of mineral coal ash in trucks with open top load compartments is inefficient, harmful to the environment, and costly. One solution to this problem is to utilize highly concentrated aqueous suspensions (paste) transportation systems, through steel pipes assisted by hydraulic pumping. In this study, coal ash (both fly ash and bottom ash), produced at a typical coal power plant (South Brazil), was utilized at different formulations, with mixtures of fly ash, bottom ash, and water (65%-70% solids content). These ash-bearing pulps were characterized in terms of their chemical and mineralogical composition, suspension pH that varied with the presence of Ca-bearing minerals, particle size distribution, and rheological behavior. Ash samples were distributed in fine, mean, and coarse sizes, facilitating the particles packing, diminishing voids, and contributing to the formation of paste with good consistency. The ash suspensions (32% water content) did not show compression strength and were plastically deformed after 48 hours of water addition. This behavior indicates that there were no chemical reactions, or pozzolanic activity, and that the particle interactions were mainly due to electrostatic forces and dispersions forces. [ABSTRACT FROM AUTHOR]

Coal ash from Candiota thermoelectric power plant in southern Brazil is a waste generated in great amount. Current estimates indicate that coal ash production is likely to reach 2.000.000 tons per year. Of this total, only 10% are commercialized, so the price of this material is very low. In this work, it was investigated the use of coal ashes in a composition of refractory insulating brick. In coal combustion process, fly ashes and bottom ashes are generated. Bottom ashes are formed by partially fused ashes that precipitate to the bottom of the boiler, due to their coarser particle size. Therefore, it was analyzed fly ash addition in a refractory body and the addition of bottom ashes, partially replacing chamote (calcinated clay). The results showed that the effect of the ash is small in the fired materials. In terms of technological characterization, the bricks formulates with coal ash were considered suitable to commercial brick standards. Density and thermal conductivity of the refractory bricks with coal ashes had revealed to be similar the commercial products. Then, the use of ash is economical attractive and technical feasible. [ABSTRACT FROM AUTHOR]

The rapid increase in thermal power generating capacity in Brazil has resulted in the production of huge quantities of brown coal of high ash content. Current estimates indicate that coal ash production in Brazil is likely to reach 4 million tons per year by 2005. In view of the need to burn this type of fuel to the maximum possible extent, a rational use of coal is vitally important. However, the coal from Candiota (a coal mine in southern Brazil) contains calcium-bearing compounds that damage equipment, causing process stoppages; this coal may become cost ineffective unless the noncombustible material and its content is controlled. This article reports on the results of the comminution characteristics of coal combustion feed and of industrial tests, which demonstrate the urgent need for optimizing particle size distribution to preclude the presence of calcareous material. Hard calcium-based minerals display a crushing behavior that differs from coal particles, requiring their screening and elimination from the feed. Examples of the overall situation, screening optimization, and the beneficiation process at the Candiota power plant are discussed in terms of fragmentation, particle size analysis, type of screen, and economic benefits. [ABSTRACT FROM AUTHOR]

Background: The mental health (MH) burden on healthcare practitioners (HCPs) is emerging as a significant cost of the pandemic, although few studies have compared the MH of HCPs in different countries., Methods: A link to an online survey was posted in the Spring of 2020 which included questions regarding perceived impact of the pandemic; current MH symptom severity and impairment was evaluated using validated scales., Results: Overall, 1315 individuals (74% female, mean age: 42.9 + 16.4) in Canada, the United States, Brazil and Italy completed the survey. Nearly 26% met diagnostic thresholds for GAD and MDD; Italian respondents reported the lowest rates of disorder. Except for Canada, non-HCPs in each country reported higher symptom severity than HCPs. Amongst the HCPs, Canadian HCPs reported the highest rates of anxiety and depression as well as increases in alcohol and cannabis use, lower levels of perceived emotional support and more worry about themselves or their loved ones contracting COVID-19., Conclusion: Despite key infrastructural and COVID-19 mortality differences between the countries, the MH effects appeared to be quite similar. HCPs, with the exception of Canada, reported less impact on their mental health compared to the general population, suggesting resilience in the face of adversity.Key pointsRates of current mental health disorders were similar across Canada, the USA and Brazil but lower in Italy, yet much higher than pre-pandemic ratesNon-Healthcare Practitioners (HCPs) reported significantly higher severity on all MH scales in the overall sample. This was consistent within the USA, Brazil and Italy, however in Canada, HCPs reported higher anxiety, depression and stress symptom severity compared to Canadian non-HCPs.Canadian HCPs reported significantly higher anxiety and depression symptom severity than all other countriesCanadian HCPs also reported significantly greater increases in alcohol and cannabis use, lower levels of perceived emotional support and more worry about themselves or their loved ones contracting COVID-19 compared to HCPs in the other countries.

The main purpose of this work was the investigation of the immobilization of chromium ion present in the ash from the incineration of chromium-tanned leather shavings (ACS) by means of vitrified ceramic bodies. To achieve the immobilization samples were initially produced adding soda-lime glass to ACS. After that, new formulations were produced with the addition of pure oxides, TiO(2) and MgO, to the soda-lime glass and ACS sample. These samples were conformed by pressing and fired in an eletrical furnace, at temperatures of 750, 800, 950 and 1000 degrees C. The ceramic bodies were evaluated with respect to their physical properties and mineralogical composition by X-ray diffraction and energy dispersive spectroscopy (EDS) mapping. The chromium immobilization was characterized by leaching tests according to Brazilian Regulations (NBR 10005). The results confirmed the immobilization of the chromium ion within the allowed limits of Brazilian Regulations, NBR 10004 (5mg/L), with the use of glass and vitrification/densification agents such as titanium and magnesium oxides.