Sorption isotherms of Brazil nuts

ABSTRACT Knowledge of the water sorption phenomenon in Brazil nut seeds will allow proper handling of this product, especially with regard to adequate conditions for safe storage. Thus, the present study aimed to determine the sorption isotherms (desorption and adsorption) of Brazil nuts, fitting different mathematical models to the experimental data, as well as to examine the hysteresis effect. To obtain the sorption isotherms, the static method was employed at temperatures of 25, 35, 45 and 55 °C and air relative humidities varying from 10 to 80%. The psychrometric conditions of the air were acquired with the aid of acid solutions and specific saturated saline left inside desiccators with the samples. It was verified that for a given isotherm, the equilibrium moisture content of Brazil nuts increases with water activity increment. In addition, at a constant water activity, equilibrium moisture content decreases with temperature increase. The Copace, Henderson and Oswin are the models that best describe the hygroscopicity of the Brazil nut seed for both the adsorption and desorption processes. Hysteresis was more pronounced at lower temperatures and higher values of water activity. The moisture content value for storage at temperatures less than 55 °C, without the risk of fungal development, must be lower than 8.2% (d.b.).

Removal of Ciprofloxacin from of Pharmaceutical Wastewater by Adsorption on SiO2 Nanoparticle

The removal of Ciprofloxacin (CFX) on SiO2 nanoparticle was performed as a function of initial CFX concentration, contact time at fixed pH and adsorbent dose and characterized using scanning electron microscopy (SEM) and Brunauer Emmett Teller (BET) surface area. Amount of CFX uptake increased with increasing contact time and decreased concentration of initial CFX. Adsorption behavior was well described by pseudo second-order kinetic model. It was observed that equilibrium dye uptake significantly increased from 49.01 to 174.58 mg/g when initial CFX concentration increased from 25 to 100 mg/L. Experimental data were well fitted to Langmuir, Freundlich and Temkin and Dubinin-Radushkevich (D–R) models. Three different error functions were conducted to find better model to describe the experimental data. The lower values of error functions exhibited that Langmuir model was more suitable for the adsorption of CFX, which implied a homogeneous sorption phenomenon.

Fluoride Removal from Groundwater by Technological Process Optimization

Fluoride removal from aqueous solutions was studied using nanofiltration and sorption techniques which have always been best key ways to deal with water contaminated by fluoride. In this presented work, we were firstly interested on fluoridated rejected water overcoming the drawback of RO membrane process of groundwater treatment plant in Baltic region (Kretinga, Lithuania). Opoka sorbent has shown effective results of fluoride sorption with efficiency higher than 77 %. In order to understand the sorption phenomenon and to validate the results obtained, we have applied experimental data on Freundlich and Langmuir isotherms which allow us to determine isotherms parameters (KF; 1/n and KL; qmax) and to confirm the experiment. Because of the unacceptable tariff of drinking water treated by RO, defluoridation with nanofiltration method is proposed in this study as a solution which can replace reverse osmosis technique. For that, tests of nanofiltration for fluoride removal were carried out at laboratory scale by using nanofiltration flat sheet membranes (NF270 and NF90).

Research on Fluoride Removal from Membranes Rejected Water

The excess of fluoride in water intended for human consumption can cause some problems in health of consumers from concentrations over than 1.5 mg/L. A detailed study has been carried out for the removal of fluoride from concentrated rejected water overcoming the drawback of membrane processes by using sorption techniques. Opoka mineral which is a natural sorbent and polonite have been chosen and valorized in this present work as fluoride sorbents for rejected water by membranes of the water treatment plant. These sorbents have been selected in order to reduce the treatment cost and to meet the standards of rejected water especially in term of fluoride. Opoka sorbent and polonite have shown effective results for fluoride removal from rejected water with efficiency over than 77%. In order to understand the sorption phenomenon and to validate the results with sorbents, we have applied experimental data on Freundlich Isotherm and SEM microscopic technique.

Adsorption with chemical reaction in porous catalyst pellets under alternate concentration fields. Uniform temperature case

The work concerns the dynamic behaviour of a porous, isothermal catalyst pellet in which a simultaneous chemical reaction, diffusion and adsorption take place. The impact of the reactant adsorption onto the pellet dynamics was evaluated. A linear isotherm and a non-linear Freundlich isotherm were considered. Responses of the pellet to sinusoidal variations of the reactant concentration in a bulk gas were examined. It was demonstrated that the dynamics of the pellet is significantly affected both by accounting for the adsorption and by the frequency of the bulk concentration variations. The sorption phenomenon causes damping of the concentration oscillations inside the pellet and damping of its effectiveness factor oscillations. Depending on the frequency of the concentration oscillations in the bulk, the remarkable oscillations can involve an entire volume of the pellet or its portion in the vicinity of the external surface.

Sorption of a Xenobiotic Contaminant in Clean and Petroleum-Contaminated Soil: Roles of Water and Xenobiotic Size

Environmental Context.Soil uptake of xenobiotics (e.g. pesticides) can be a complex phenomenon where it is useful to distinguish readily reversible sorption from longer-term retention. A scheme for doing this using fluorescence detection is presented here, along with application to uptake of a model compound in clean and oil-contaminated soils. Both the wetting of the soil and the size of the xenobiotic seem to be important. The present data concern uptake. Desorption is expected to exhibit dependencies on similar factors. The data have implications for understanding persistence. Abstract.Description of sorption of xenobiotics (e.g. pesticides) into soils requires identification of at least two kinetic components. In the present work, the distinction between ‘labile’ (readily reversible) and ‘non-labile’ (not reversible) uptake was extended, introducing a fluorescence-based method using 9-anthracenepropionic acid as a probe molecule. Study of clean, oil-contaminated wettable, and water-repellent oil-contaminated soils has given new perspectives into the role that water plays in xenobiotic uptake. Non-labile uptake is unimportant in the water-repellent soils; however, non-labile components are observed in both clean and wettable oil-contaminated samples, supporting earlier suggestions that water plays a role in non-labile uptake processes. A soil pre-exposed to water exhibited different labile sorption behavior from one where xenobiotic was added simultaneously with water to an air-dried soil. The comparatively rapid non-labile component of uptake (3 days) of 9-anthracenepropanoic acid by a clean soil contrasted with much longer times in earlier studies of 2,4-D and atrazine. This pointed to another factor influencing the sorption phenomenon. Literature data supports a suggestion that the non-labile component of xenobiotic sorption may be more strongly influenced by the size of the xenobiotic than by the structure (e.g. polarity) of the xenobiotic or soil composition.