Julio Cézar Balarini

In the present work, the study of the hexavalent chromium ions (Cr6+) extraction from synthetic feed solutions of K2Cr2O7, using liquid surfactant membrane technique (LSM) was carried out. The main goal of this work is to reduce this metal content in tannery effluents. The investigated operational parameters were: extractant, surfactant and modifier concentrations present in the membrane phase, permeation time and volumetric phase ratios. The studied system was constituted of an aqueous external phase containing K2Cr2O7 (feed phase); a membrane phase formed by tri-n-octylamine (extractant), ECA 4360 (surfactant), EXXSOL D225/275 (diluent) and 1- decanol (modifier); and an internal or receiving phase containing NaOH 10 g/L. Extractions higher than 97% were obtained, giving final chromium levels lower than 8 ppm of Cr6+ from feed solutions containing 350 ppm of this specie.

This work investigates the leaching kinetics of roasted zinc in aqueous solutions of sulphuric acid from an electrolytic zinc production plant. Parameters such as stirring speed, temperature, granulometry, and acid concentration were investigated aiming to model the experimental data according to the shrinking core and progressive conversion models. The kinetic study determined that leaching of the roasted concentrate follows the progressive conversion model and is controlled by the chemical reaction step, whose activation energy, enthalpy, and apparent entropy values are 13.45 kJ.mol‑1, 11.07 kJ.mol‑1 and -256.20 J.mol‑1.K‑1, respectively. The estimated value of the chemical reaction rate constant (ks) is 3.00 x 10-2 cm.s-1.

A great fraction of global iodine production involves the solvent extraction (SX) of iodine from mother liquors. Therefore, a green analytical method for the direct determination of molecular iodine in kerosene was developed and validated using UV–Vis molecular absorption spectrophotometry. Resublimed iodine (≥99.8%) was employed as the analyte, and industrial kerosene (Escaid™ 110) as the solvent. The method was optimized to account for the high reactivity and volatility of iodine, with careful handling, refrigeration, and ultrasonic-assisted dissolution to ensure accurate standard preparation. Validation was performed in accordance with Inmetro, ANVISA, and ASTM E2857 guidelines, assessing selectivity, linearity, working range, detection and quantification limits, recovery, and precision. A wavelength of 521 nm was selected based on the absorption spectrum, and linearity was demonstrated across 0.005–0.55 g·L⁻¹ with R² = 0.998. Recovery values ranged from 97% to 103%, and relative standard deviations were below 5%, confirming both accuracy and precision. The method exhibited negligible interference from potassium iodide, a potential contaminant in industrial processes, such as solvent extraction. Overall, the proposed approach is rapid, cost-effective, and environmentally friendly, providing a reliable tool for monitoring iodine in kerosene during SX processes and supporting process optimization at an industrial scale.

This study evaluated the performance of Saccharomyces yeast strains in fermenting traditional mead, meads with varying proportions of orange juice, and a formulation with orange juice and peels. Experiments at 25–30 °C used strains 71B-1122 and ICV-D47 (Lalvin) and Montrachet (Red Star). Fermentation kinetics were tracked via CO₂ release, and final products were analyzed for total reducing sugars (TRS), ethanol, pH, acidity, dry matter, and density. Tukey’s test was applied for statistical comparison. Lalvin 71B-1122 was later selected for batch fermentations with direct aeration and stepwise nutrient addition. Volatile acidity was also measured. Flask-scale experiments showed no significant differences in fermentation kinetics among strains. Musts with orange juice completed fermentation in 160–180 h, while honey-only musts did not. TRS conversion was higher in orange juice formulations (0.38–0.44), with similar dry matter and density. Orange juice musts had higher pH (3.51–3.73) and acidity (72.6–113.8 meq/L) than pure mead (pH 3.05–3.25; 58.2–60.2 meq/L), due to organic acids’ buffering capacity. Larger batch fermentations yielded beverages with higher ethanol content (10.5–12.6% v/v), yield (71.2–89.0%), and efficiency (82.8–96.4%), confirming the beneficial effect of optimized nutrient management and aeration on fermentation performance.

Visando ao melhor aproveitamento da própolis bruta, foram estudadas algumas condições operacionais para as extrações de própolis verde e de própolis vermelha, sendo a da verde em água e em solução alcoólica, e da vermelha apenas em solução alcoólica. A própolis verde apresentou baixos percentuais de umidade e de cera e elevada concentração de flavonoides, sendo classificada como própolis bruta Ultra Green. A própolis vermelha apresentou baixo teor de umidade, mas elevado percentual de ceras, que, apesar de alto, é considerado comum para este tipo de própolis. A concentração de formononetina na própolis vermelha foi determinada para extrações realizadas em quatro concentrações alcoólicas, sendo o melhor resultado obtido para a solução 80°GL. Porém, a maior quantidade de sólidos solúveis totais foi obtida para a solução a 90°GL. Na extração de própolis verde, as razões massa de própolis/massa total (própolis + solvente) (MP/MT) que levaram às maiores quantidades de sólidos solúveis totais foram a de 0,35 para extração em solução alcoólica 90°GL e a de 0,15 para a extração em água. Observou-se, ainda, que a extração em dois estágios (corrente cruzada) leva a um melhor aproveitamento da própolis bruta, sendo este aproveitamento mais acentuado para a própolis verde.