Luis M. Navas-Gracia

Rhodamine B removal with activated carbons obtained from lignocellulosic waste

By-products from the wax production process from carnauba palm (leaves), from the extraction of oil from macauba seeds (endocarp) and from pine nut production (shell) have been assessed for activated carbon production, using H3PO4 or CaCl2 for their chemical activation. The resulting activated charcoals have been thoroughly characterized by elemental and thermal analysis, X-ray diffraction, infrared spectroscopy, electron scanning microscopy and N2 adsorption behavior. Subsequently, their adsorption capacity for the removal of rhodamine B (RhB) from aqueous solutions has been evaluated by studying different parameters: contact time, pH, adsorbent dose, initial dye concentration and solution temperature. The adsorption of RhB followed Freundlichs model in all cases. Kinetic studies indicate that the pseudo-second order model can be used for describing the dynamics of the adsorption process. Thermodynamic parameters have also been evaluated, indicating its endothermic and spontaneous nature. Finally, a preliminary analysis of the impact of cellulose content in the carbon precursor materials has been conducted, by using a mixture of native cellulose with one of the lignocellulosic materials.

A kinetic study on microwave-assisted conversion of cellulose and lignocellulosic waste into hydroxymethylfurfural/furfural

Native cellulose, lignocellulosic materials from Brazil (carnauba palm leaves and macauba pulp and shell) and pine nut shell from Spain have been studied as substrates for the production of HMF and furfural in a conventional microwave oven. In order to promote the dissolution of native cellulose, several ionic liquids, catalysts, organic solvents and water doses have been assessed. The most suitable mixture (5mL of choline chloride/oxalic acid, 2mL of sulfolane, 2mL of water, 0.02g of TiO2 and 0.1g of substrate) has been chosen to conduct kinetic studies at different reaction times (5-60min) and various temperatures (120-200°C) and to evaluate the best conditions for HMF+furfural production according to Seamans model. The best production yields of HMF+furfural have been attained for native cellulose, with a yield of 53.24% when an ultrasonic pretreatment was used prior to a microwave treatment with stirring.

Polymeric Carbon Nitride Nanosheets

Polymeric carbon nitride was synthesized by polycondensation in a nitrogen flux using melamine cyanurate as a reagent and sulfuric acid as a catalyst. The product was polymeric-graphitic carbon nitride based on heptazine units. The carbon nitride was composed of nanosheet flakes. This synthesis method seems to be a suitable pathway toward carbon nitride graphene formation.

Synthesis of Chitosan Oligomers/Propolis/Silver Nanoparticles Composite Systems and Study of Their Activity against Diplodia seriata

The synthesis and characterization of composites of oligomeric chitosan with propolis extract which allow the incorporation of a third component (silver nanoparticles) are reported, together with their application in aqueous or hydroalcoholic solutions with a view to the formation of adhesive substances or nanofilms for the protection of vineyards against harmful xylophagous fungi. The antimicrobial properties of the association of the two biological products or those resulting from the incorporation of silver nanoparticles (NPs) are studied and discussed. The efficacy of the chitosan oligomers/propolis/silver NPs ternary system is assessed in vitro for Diplodia fungi. A preliminary study on the convenience of replacing propolis with gentisic acid is also presented.

Temperature and relative humidity estimation and prediction in the tobacco drying process using Artificial Neural Networks.

This paper presents a system based on an Artificial Neural Network (ANN) for estimating and predicting environmental variables related to tobacco drying processes. This system has been validated with temperature and relative humidity data obtained from a real tobacco dryer with a Wireless Sensor Network (WSN). A fitting ANN was used to estimate temperature and relative humidity in different locations inside the tobacco dryer and to predict them with different time horizons. An error under 2% can be achieved when estimating temperature as a function of temperature and relative humidity in other locations. Moreover, an error around 1.5 times lower than that obtained with an interpolation method can be achieved when predicting the temperature inside the tobacco mass as a function of its present and past values with time horizons over 150 minutes. These results show that the tobacco drying process can be improved taking into account the predicted future value of the monitored variables and the estimated actual value of other variables using a fitting ANN as proposed.

Composite Fiber Based on Sisal Fiber and Calcium Carbonate

The impregnation of a raw sisal fiber in a saturated solution of calcium hydroxide generated a fiber coated by a remarkable quantity of calcium carbonate and calcium oxide. However, some detachments of the inorganic coating were observed at microscopic level, and interstices in the external walls, filled by the precipitated material, were less visible than in raw fiber. Additionally, some fiber components have been removed by the preliminary sodium silicate washing. The final composite exhibited more amorphous characteristics than the original raw fiber, as well as its mechanical behavior was very similar to an elastomeric material with more homogeneous mechanical properties than the original raw fiber.

Seasonal and sex-related variations in serum steroid hormone levels in wild and farmed brown trout Salmo trutta L. in the north-west of Spain.

Serum steroid profiles were investigated in order to evaluate the potential use of circulating sex steroid levels as a tool for sex identification in brown trout. Changes in the serum concentrations of testosterone (T), progesterone (P), 17-β-estradiol (E2), and cortisol (F) in wild and farmed mature female and male brown trout, Salmo trutta L., were measured in each season (January, May, July, and October) in six rivers and four hatcheries located in the north-west of Spain. Serum cortisol levels in farmed brown trout were significantly higher and showed a seasonal pattern opposite to that found in wild trout. Because levels of the hormones under study can be affected by disruptive factors such as exposure to phytoestrogens (which alters the hypothalamic-pituitary-gonadal axis) and infection with Saprolegnia parasitica (which alters the hypothalamic-pituitary-adrenal axis), both factors are taken into account.

Hygienization and control of Diplodia seriata fungus in vine pruning waste composting and its seasonal variability in open and closed systems

After the ban on sodium arsenite, waste management alternatives to the prevalent burning method, such as the hygienization and biodegradation in solid phase by composting, are required for the pruned material from grapevines affected by various fungi. In this work the dynamics of a fungus associated with vine decay (Diplodia seriata) during the composting process of a mixture of laying hen manure and vine pruning waste (2:1w/w) have been investigated in an open pile and a discontinuous closed biodigester. Through the optimization of the various physical-chemical parameters, hygienization of the infected waste materials was attained, yielding class-A organo-mineral fertilizers. Nevertheless, important differences in the efficiency of each system were observed: whereas in the open pile it took 10days to control D. seriata and 35 additional composting days to achieve full inactivation, in the discontinuous biodigester the fungus was entirely inactivated within the first 3-7days. Finally, the impact of seasonal variability was assessed and summer temperatures shown to have greater significance in the open pile.

Simulation of macauba palm cultivation: an energy-balance and greenhouse gas emissions analysis

ABSTRACT The expansion of the production and use of bioenergy is one of the most efficient mechanisms to reduce greenhouse gas (GHG) emissions. Nevertheless, the environmental impact of the production processes for many raw materials remains unexplored. Several studies have pointed to macauba palm as a promising species for biofuel production in the tropics, but investigations on the environmental benefits of its cultivation have not been reported so far. In this work, an analysis of macauba production system in terms of GHG emissions and CO2 uptake has been conducted for a productive cycle. The energy conversion efficiency per unit area of land has been put in relationship with crop productivity and related to the dilution effect of production inputs. Simulation results estimate GHG emissions of 180 Mg CO2eq·ha-1 and a CO2 fixation ranging from 796 to 1137 Mg CO2eq·ha-1. The net energy balance would reach 512.3 GJ·ha-1 and energy efficiency would be 24.2 GJ·GJ-1. These results suggest that macauba would outperform traditional energy crops such as sugarcane, oil palm, sunflower, corn or jatropha in terms of efficiency. The domestication and exploitation in extensive farming of this species as an agroforestry crop, although still at an early stage, has a bright future.

The Spatial Low-Pass Filtering as an Alternative to Interpolation Methods in the Generation of Combine Harvester Yield Maps

Interpolation techniques are usually employed in the yield maps generation. In this article, a method based in spatial low-pass filtering is presented and compared with interpolation techniques. The method consists in the application of low-pass filters typically used for image processing. The yield map is constructed in a similar way to a Digital Elevation Model (DEM), except for the fact that heights represent crop quantities.