Masks thermal degradation as an alternative of waste valorization on the COVID-19 pandemic: A kinetic study.

The COVID-19 pandemic generated a new dynamic around waste management. Personal protective equipment such as masks, gloves, and face shields were essential to prevent the spread of the disease. However, despite the increase in waste, no technical alternatives were foreseen for the recovery of these wastes, which are made up of materials that can be valued for energy recovery. It is essential to design processes such as waste to energy to promote the circular economy. Therefore, techniques such as pyrolysis and thermal oxidative decomposition of waste materials need to be studied and scaled up, for which kinetic models and thermodynamic parameters are required to allow the design of this reaction equipment. This work develops kinetic models of the thermal degradation process by pyrolysis as an alternative for energy recovery of used masks generated by the COVID-19 pandemic. The wasted masks were isolated for 72 h for virus inactivation and characterized by FTIR-ATR spectroscopy, elemental analysis, and determinate the higher calorific value (HCV). The composition of the wasted masks included polypropylene, polyethylene terephthalate, nylon, and spandex, with higher calorific values than traditional fuels. For this reason, they are susceptible to value as an energetic material. Thermal degradation was performed by thermogravimetric analysis at different heating rates in N2 atmosphere. The gases produced were characterized by gas chromatography and mass spectrometry. The kinetic model was based on the mass loss of the masks on the thermal degradation, then calculated activation energies, reaction orders, pre-exponential factors, and thermodynamic parameters. Kinetics models such as Coats and Redfern, Horowitz and Metzger, Kissinger-Akahira-Sunose were studied to find the best-fit models between the experimental and calculated data. The kinetic and thermodynamic parameters of the thermal degradation processes demonstrated the feasibility and high potential of recovery of these residues with conversions higher than 89.26% and obtaining long-chain branched hydrocarbons, cyclic hydrocarbons, and CO2 as products.

The effect of the chemical composition on the sensory characterization of Ecuadorian coffee.

The study aims to test if Ecuadorean coffee's symbolic and material contents agree with the instrumental analysis and grading protocols. We studied the relationship between the chemical composition and the organoleptic characteristics of eight non-specialty and six specialty coffee samples. Firstly, the study addresses the grading following the Specialty Coffee American Association (SCAA) method. The second stage focuses on the qualitative composition of the coffee brews employing GC-MS and caffeine concentrations using HPLC. Then, we employed statistical tools such as Cohen's concordance coefficients, dissimilarity dendrograms, and linear correlations between the chemical compounds in the beverage and the attributes' scores. The grading panel consisted of 6 semi-trained-testers who would assess if the primary cultural capital can provide a criterion to identify specialty coffee. The variety of compounds allowed the evaluators to distinguish between commercial and specialty coffees. However, the composition analysis identified molecules that would imply greater gradation in the tasting, a prevision that was not reflected in the results. Finally, we confirmed that basic training could create cultural capital to distinguish non-specialties from specialty coffees through their chemistry and organoleptic attributes.

Natural zeolite as a chromium VI removal agent in tannery effluents.

This study concerns Cr(VI) removal using zeolites in a batch system for tannery effluent. In the initial stage, natural zeolite (ZN) and synthetic zeolite (ZS) were characterized, obtaining a Si/Al ratio of 4.64 and 1.60, and with predominant clinoptilolite and faujasite phases, the surface area of 9.34 and 25.82 m2/g and cation exchange capacity of 84.05 and 188.72 meq/100 g, respectively. Subsequently, ZN and ZS were activated with HCl and NaOH. Through preliminary tests, with a solution of K2Cr2O7, it was determined that the highest Cr(VI) removal for both, ZN and ZS, was with NaOH activation, obtaining 82 and 56% removal, respectively. According to Ecuadorian regulations, the Cr(VI) concentration exceeds the maximum permissible limits on the tannery effluent. For this effluent, it was determined that the highest Cr(VI) removal, 45%, is obtained with 1 g of ZN activated with NaOH and 100 mL of effluent. With ZN-NaOH, removal tests were carried out in a fixed bed with 5, 10, and 20 g of natural zeolite. The natural zeolite also has chromium removal capacity in the bed system, achieving similar removals to those obtained in the batch experiments, but decreasing the treatment time. Thus, both natural and synthetic zeolites can remove Cr(VI) in tannery effluents, achieving this effluent with permissible limits.