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Biomethane generated from renewable sources can be used as a renewable fuel to achieve ambitious targets for biofuels. The development of adsorption-based technologies for purification of biogas requires knowledge of adsorption equilibria and kinetics of pure gases on a specific adsorbent material. In this work, we have measured adsorption equilibria of CO2, CH4, and N2 at (299, 323, 348, 373, and 423) K over a pressure range between (0 and 700) kPa on a carbon honeycomb monolith. The adsorption capacity of the activated carbon honeycomb monolith was CO2 > CH4 > N2. The multisite Langmuir model was employed to fit the data of the pure gases offering the possibility of direct prediction of multicomponent adsorption equilibria. The diffusion of single gases in the microporous structure of the activated carbon honeycomb monolith was studied by diluted breakthrough experiments. The experiments were performed over the same temperature range [(303 to 423) K]. A simplified 1D mathematical model was employed in the description of the adsorption phenomenon. The data reported in this work allows modeling of adsorption processes such as pressure swing adsorption (PSA) and temperature swing adsorption (TSA).

Water vapor needs to be removed from many industrial streams using, for example, adsorption processes. Equilibrium and kinetic data are essential for the design of these adsorption processes. In this work, the adsorption equilibrium isotherms of water vapor were measured at 303 K by a gravimetric system on three commercial adsorbents, an activated carbon, an activated alumina, and a zeolite. The zeolite sample presented the highest capacity at low relative pressures, while at pressures near saturation the higher amount adsorbed was obtained on the alumina sample. The experimental points obtained for the activated carbon and the zeolite were fitted with the Virial isotherm while the n-layer BET equation was used in the fitting of the alumina data. The adsorption kinetics was evaluated through the analysis of breakthrough curves obtained at the same temperature for different feed humidity values. The fixed bed behavior was described using an isothermal model that includes axial dispersion and external (film model) and internal (homogeneous LDF model) mass transfer resistances. The homogeneous diffusivity values were determined by adjusting the model to the experimental data.

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Due to an increase in water consumption in the industrial sector and within the Brazilian population, surface water that receives wastewater from industries, domestic sewage, agricultural industries, and sewage treatment stations can pollute water bodies when not properly treated. The water quality has been linked to catchment characteristics and intensity of agricultural activities. Thus, the aim of this study was to monitor the cytotoxic potential of the water of the Quatorze River, located in the town of Francisco Beltrão, Paraná, Brazil, along its route in the rural area, using the root meristematic cells of Allium cepa L. as a bioindicator. The results showed that the water at points 2, 3, and 4 were not cytotoxic because the rates of A. cepa cell division were unaltered. Point 1 had presented a mitotic index that was statistically larger than the negative control, indicating that this water contained substances with mitogenic capacity, as demonstrated by elevated values in chemical oxygen demand (COD) and biochemical oxygen demand (BOD). However, the mitotic index values decreased along the route of the river (point 1 to point 4), possibly indicating a mechanism of self-purification, despite having received other sources of pollution. Thus, the results of this study show that the water of the Quatorze River should undergo periodic environmental monitoring at different times of the year, including cytotoxicity analysis, to evaluate the principal sources of contamination to maintain the quality of the river water and, consequently, to maintain human health and equilibrium of the entire ecosystem.

The global process of heterogeneous photocatalytic oxidation can be described in consecutive steps of mass transfer, adsorption, reaction and desorption. Although such a deseription normally only considers the reactions in the aqueous solution, some compounds are degraded by photogenerated holes in the surface of the solid. In this work, the photocatalytic degradation of a leather dye, Direct Black 38, was studied as a model compound to elucidate the steps during the photocatalytic degradation. The mass transfer coefficients were evaluated through the description of the adsorption kinetics using the film and pore diffusion model. The equilibrium of adsorption was described according to the Langmuir model. Under irradiation, the degradation of the dye was measured and a pseudo-first order kinetic law was used to depict the reaction. The Weiz-Prater criterion was used to determine the rate controlling step of the reaction with the result that no diffusion limitations for the reaction existed. The characterization of the solid after adsorption and after desorption showed the presence of the reaction's intermediate species.

The evaluation of photonic efficiency in heterogeneous photocatalysis remains elusive because the number of absorbed photons is difficult to assess experimentally. The photonic efficiency of heterogeneous photocatalytic reactors depends on the reactor geometry, irradiation source, and photocatalyst properties. In this work, the relative photonic efficiency of heterogeneous photocatalytic reactors to degrade an azo dye was evaluated using phenol as the standard system. The experimental tests were carried out in a batch reactor under different conditions of pH, catalyst dosage, initial concentration, and ultraviolet (UV) lamps. The kinetics of disappearance of both phenol and azo dye were studied using the initial rate method and were described according to the Langmuir-Hinshelwood (L-H) kinetic model. It was observed that the relative photonic efficiency depends on the adsorption/desorption properties of the photocatalyst.

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