Pyridine is a recalcitrant organic compound present in industrial wastewater that causes severe effects on the environment and the health of living beings, as it is considered a toxic, mutagenic, teratogenic, and carcinogenic agent. Therefore, this research explored the efficacy of a zinc oxide catalyst, doped with platinum nanoparticles and supported alumina through the precipitation method, for the photocatalytic degradation of pyridine using a fluidized bed reactor. A Box–Behnken experimental design was used to analyze the effect of the pH (4–10), the pyridine concentration (20–300 ppm), and the amount of catalyst (20–100 g). The X-ray diffraction (XRD) characterization results confirmed the hexagonal structure of the zinc oxide and the successful incorporation of platinum. Scanning electron microscopy (SEM) revealed a nano-bar morphology upon catalyst doping, favoring the photocatalytic activity. Pyridine removal of 57.7% was achieved under the following conditions: a pH of 4, 160 ppm of pyridine, and 100 g of catalyst. The process followed a pseudo-first-order model, obtaining the reaction constant k₁ = 1.943 × 10⁻³ min⁻¹ and the adsorption constant k₂ = 1.527 × 10⁻³ L/mg. The results showed high efficiency and stability of the catalyst in the fluidized bed reactor for pyridine degradation, especially under acidic conditions, representing a promising technological alternative for treating industrial wastewater contaminated with N-heterocycles such as pyridine.

The degradation of pyridine, considered one of the most polluting heterocycles used in industries, was performed. A fluidized bed photocatalytic reactor (FBR) with the cata-lyst Pt-ZnO/Al₂O₃ synthesized by precipitation and wet impregnation was used for its removal. FTIR, XRD, and SEM characterization were performed on the catalyst. The analyses confirmed the hexagonal structure of ZnO (average crystal size: 53.18 nm), the successful incorporation of Pt (increase to 57.21 nm), and a nano-rods morphology in Pt-ZnO favoring the photocatalytic activity. The kinetics followed the pseu-do-first-order model (R² > 0.95), obtaining a value of k1 = 1.943 × 10-3 min-1 (reaction constant) y k2 =1.527× 10-3 L/mg (absorption constant), reaching pyridine removal of 57.7% at conditions (pH 4, 160 ppm pyridine, 100 g catalyst), validating the efficiency of the RFL to improve mass transfer and catalytic exposure. With the results obtained, it was demonstrated that the Pt-ZnO/Al₂O₃ catalyst possesses high stability and poten-tial for the treatment of industrial wastewater contaminated with N-heterocycles.

The production of microalgae biomass has a high cost due to the composition of the culture medium; therefore, the cultivation of Arthrospira (Spirulina) platensis using carbon dioxide (CO2) and whey could be considered an effective method of obtaining microalgae biomass while reducing greenhouse gas emissions and a sustainable solution for the treatment of dairy industry wastewater. As a result, the microalgae biomass produced has the potential to become a valuable source of energy (biodiesel), food (for humans or animals), and other compounds such as vitamins and pigments. According to circular economy and development practices, this paper aimed to investigate the growth of Arthrospira platensis biomass using CO2 and whey as a substitute for culture medium. The effects of different whey dilution and culture conditions on biomass productivity, nutrients, and chemical oxygen demand (COD) removal were examined in batch experiments. The results show that the highest biomass production (3.31 g·L-1) was achieved in 19-day experiments using a modified Schlösser culture medium with 500 mL CO2 as a carbon source. In the cultures with whey, removal of organic load percentages of 89.16%, 98.88%, and 97.76% was reached on the tenth day in the cultures with 1, 5, and 9 g COD·L-1, respectively. The highest lipid content of 7.07 g lipids 100 g-1 biomass was reached using 500 mL of CO2 as a carbon source, demonstrating that subjecting the culture to a nutrient deficit causes an accumulation of lipids as long as there is light and CO2 available.

Whey, a high-volume by-product of the dairy industry, is a valuable substrate for biotechnological valorization that presents an environmental challenge. This study aimed to investigate the kinetic and rheological behavior of Kluyveromyces marxianus during lactic acid fermentation using deproteinized whey by varying initial lactose (35 and 50 g L-1) and inoculum (3 × 106 and 10 × 106 cells mL-1) concentrations and working volumes (0.6 and 0.9 L), through a full factorial (23) experimental design. Growth kinetics, lactose consumption, and lactic acid production were modeled using the Gompertz, Luedeking-Piret, and Pirt models. Rheological behavior was obtained using the Ostwald-de Waele power-law model. A rheokinetic model that integrates biomass growth with fluid properties was proposed. The results showed that high lactose and low inoculum levels significantly improved lactic acid yield (0.285 g g-1) and productivity (0.116 g L-1 h-1). Strong statistical interactions were identified between inoculum and substrate levels. The rheokinetic model demonstrated strong correlations between the consistency coefficient and the rheological behavior index, as well as microbial growth (correlation coefficient (R2) > 0.92), providing a predictive tool that eliminates the need for destructive measurements.