OPTIMIZATION AND KINETICS STUDIES OF THE DISSOLUTION OF DOLOMITE IN SULPHURIC ACID (H2SO4) VIA BOX-BEHNKEN EXPERIMENTAL DESIGN
Background: The recovery of any valuable component from dolomite as a double carbonate mineral depends on its dissolution efficiency. Aim: This study aimed to optimize and provide a simplified novel approach to the kinetics of dolomite dissolution in sulphuric acid solution using the Box-Behnken experimental design. Methods: The dolomite sample was dissolved in a sulphuric acid solution at seventeen different experimental conditions. The residue containing impurities was removed via filtration, while precipitation was carried out at the optimum conditions. Results and Discussion: The relationship between the independent and dependent variables best fits into the two-factor interaction model with a coefficient of determination of 0.9492, adjusted R² of 0.9187, and predicted R² of 0.7514. The total residual sum of 3x10-13 and adequate precision of 18.769 show that the predicted dissolution efficiency is much closer to the experimental values. The analysis of variance revealed that the individual effect of acid concentration, temperature, and dissolution time all positively contribute to the dissolution. The interactive effect of acid concentration with temperature and the interactive effect of temperature with dissolution time also positively influences the dissolution efficiency. Following the dissolution of dolomite in sulphuric acid, a white precipitate was formed at room temperature, which dissolved back at a temperature of 70 oC, agitation speed of 900 revolutions per minute, and within 10 minutes. A predictive approach using a two-factor interactive model was applied to generate the kinetic data. Conclusions: The established model equation is suitable for predicting dolomite dissolution in sulphuric acid. The application of the shrinking core model to the generated data shows that the reaction between dolomite and sulphuric acid is film diffusion control with a first-order reaction (0.6587) and activation energy of 27.5 KJmol-1k-1.
Read ArticleSURVEY ON KNOWLEDGE OF SEXUALLY TRANSMITTED INFECTIONS AND GONORRHEA: DO WE KNOW ENOUGH?
Background: Sexually Transmitted Infections (STIs) constitute an important group of infections with serious implications for public health. According to WHO, 1 million new contagions are produced daily, with more than 370 million new cases yearly. STIs can be originated from viruses, bacteria, fungi, or parasites. Regardless of their nature, they can be either cured or treated and controlled, but more importantly, they are preventable. Aims: The best tool to fight against STIs is prevention, which has a strong dependence on knowledge. This work aimed to assess the level of knowledge of society about STIs and gonorrhea. Methods: We conducted an online survey, covering a wide range of ages and levels of education, inquiring about areas such as origin, ways of contagion, prevention, associated diseases, and treatment of STIs and gonorrhea. We performed a statistical analysis of the answers. Results and Discussion: it was found that the general level of knowledge about STIs was independent of the age and level of education of the respondents. The respondent has shown better familiarity with prevention and contagion than with origin, diseases, and treatment. When the question was focused on gonorrhea, we found a lack in the cognizance of several points. Conclusions: Based on our findings, we conclude it is necessary to improve sexual education programs, starting at early ages but directed to all populations, particularly about gonorrhea.
Read ArticleCALCULATION FOR REDEMPTION OF COMPACT TESTING BY THE PROCTOR METHOD THROUGH NEWTON’S GRAVITATIONAL POTENTIAL ENERGY
Throughout this article, a study on the characteristics of the compaction test by the Proctor Method, regulated by ABNT NBR-7182, which is used to verify the degree of soil compaction, will be approached in order to broaden the discussion and raise points that demonstrate the urgent need to make it more accurate, efficient and safe. Through qualitative and quantitative research carried out by the authors of this article, it sought to collect data through a questionnaire for professionals in the field of geotechnics in the “Quadrilátero Ferrífero” region in Minas Gerais. In addition to other relevant data for the topic, it was raised that of the 22 professionals from the participating region, 72.7% of the total belief that the manual compaction test can be manipulated by an operator during the test execution, failing to generate results reliable, thus showing the importance of the proposed theme. In this way, we initially sought to correlate the Compaction Energy formula idealized by Ralph Proctor with Isaac Newton’s Gravitational Potential Energy formula and, through it, present the resizing, which may enable the construction of manual, semi-automatic human propulsion machines (not or making the automated ones that depend on electricity available to the market. In conclusion, from the mathematical calculations, it was possible to evidence the use of Newton’s Gravitational Potential Energy to constructnew equipment to carry out this test.
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