Strategies to Improve Pore-Size Distribution Characterization of Activated Carbons Using CO 2

The pore-size distribution (PSD) of an activated carbon (AC) sample, which is obtained by molecular simulation using a specific probe gas, does not always reproduce the adsorptive behaviour of that sample with other gases. Moreover, different gases generate distinct distributions for the same AC. These facts go against the concept of PSD, which must be unique for a given sample, irrespective of the probe gas used. We analyzed adsorption isotherms of WV-1050 AC sample with nitrogen at 77 K, carbon dioxide at 298 K and methane at 303 K, yielding their respective PSDs, based on local isotherms database (kernels) generated through grand canonical Monte Carlo simulation. The PSD obtained for nitrogen and carbon dioxide was used (individually) to reproduce the three experimental isotherms and significant deviations were observed. By applying a volume normalization methodology, the isotherm fitting was significantly enhanced. Furthermore, a more realistic model of AC pores considering etched slit walls was tested to improve PSD similarity. The new model presented tends to unify the PSDs obtained from different probe gases evaluated

Molecular simulation of collection of methane isotherms in carbon material using all-atom and united atom models

In this study the performances of all-atom (AA) and united atom (UA) models (fitted and unfitted) of the methane molecule are evaluated for the description of adsorption isotherms on graphite surfaces and in a collection of graphitic slit pores. We simulated collections of isotherms using the grand canonical Monte Carlo method with an all-atom model and adjusted united atom models in graphene layers made up of discrete atoms of carbon. The collections of isotherms are used to determine the pore size distribution (PSD) of four activated carbon samples. We also investigated the sensitivity of the system to the cutoff and solid–fluid standard parameterization. It was found that the simulated AA model isotherm shape on the graphite surface is much more similar to the experimental data than the UA model isotherm. The cutoff had little influence on isotherm and different solid–fluid standard parameterizations change the PSD. We also found that despite presenting similar fitting with the experimental isotherms, the models presented distinct PSDs. The unfitted united atom model (UA1) suggested less plausible PSDs, while the all-atom (AA) and the fitted united atom model (UA2) model provided apparently more realistic estimates of the internal structure of microporous carbons.Fil: Lucena, Sebastião M. P.. Universidade Estadual Do Ceara; BrasilFil: Frutuoso, Luis F. A.. Universidade Estadual Do Ceara; BrasilFil: Silvino, Pedro F. G.. Universidade Estadual Do Ceara; BrasilFil: Azevedo, Diana C. S,. Universidade Estadual Do Ceara; BrasilFil: Toso, J. P.. Universidad Nacional de San Luis. Laboratorio de Ciencias de Superficies y Medios Porosos; ArgentinaFil: Zgrablich, Jorge Andres. Universidad Nacional de San Luis. Laboratorio de Ciencias de Superficies y Medios Porosos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis; ArgentinaFil: Cavalcante Jr, Célio L.. Universidade Estadual Do Ceara; Brasi

Nutrient status and organic matter content of newly-established peach orchards in central Portugal

Peach production is an important agricultural activity in the center of Portugal, which is the main region of stone fruit production. This region is characterized by hot and dry summers, that can actively accelerate the organic matter degradation and, thus, increase the susceptibility to erosion and decrease the soil capacity to retain nutrients. To evaluate the relationship of peach production activity and soil characteristics, a long-term project was installed based on 31 peach orchards covering the main peach production area. The main objective was to find out the influence of peach production activity on soil characteristics with special reference on organic matter content. Orchards were monitored since establishment, collecting soil samples at establishment time and after 4 years. Plant development was monitored annually by the evaluation of trunk cross-sectional area and nutrition status by foliar analysis at 100 to 120 days after blooming. Simultaneously, weed development in the row and inter-row was evaluated. Results indicated that peach orchards are very heterogeneous over the first years after planting. After 4 years from the initial 31 orchards, only 23 remained, corresponding to 26% of uprooting orchards, mainly related with Pseudomonas syringae complex incidence. In90% of the orchards the soil content in potassium was classified as high (100-200 mg kg-1; LQARS, 2006) and very high (>200mgkg1; LQARS, 2006). Nevertheless, according to nutritional analysis, the leaf potassium content was classified as low in 35% of the orchards, considering the reference interval of 2to 3% for this nutrient. Nitrogen leaf content was below reference interval in17% of the orchards, and in 22% was above this interval. All orchards use weed cover at inter-rows, mowed regularly. Weeds were controlled in rows using herbicides. Considering the 23 orchards, Organic Matter content increased 0.68% in the row and 0.18% in the interrow, after 4 years.info:eu-repo/semantics/publishedVersio