Studies on sorption isotherm models of ion exchange modified acrylic fibers

The sorption behavior, favorability, shape and thermodynamic parameters of Cu(II), Ni(II), Pb(II), and Fe(III) ions sorption onto the ion exchage acrylic fiber were studied by applying Langmuir, Freundlich, Dubinin‐Radushkevich and Redlich–Peterson models. Analytical studies from sorption isotherms proved that sorption process follows mono layer adsorption mechanism. Gibbs free energy was spontaneous for all interactions. The adsorption processes all exhibited endothermic enthalpy values and were accompanied by increasing in entropy. The activation energies for the sorption of metal ions on aminated acrylic fiber were at the same order of magnitude as the activation energy of ion exchange. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Moisture Sorption Isotherms of Domestic and Imported Milk Powders and Their Calculated Heat of Sorption

This experiment investigated the moisture sorption isotherms (MSI) of domestic and imported milk powders at 15, 25, and 35°C. The MSI of the milk powders showed sigmoid curves for all samples. Also, equilibrium moisture content (EMC) decreased with increasing temperature, and the monolayer moisture content of the domestic samples was higher than that of the imported samples. So, the heat of sorption was higher at low water activity, indicating that the required sorption energy of the domestic samples was lower than that of the imported samples. Accordingly, this experiment determined the optimal storage conditions for stability as well as the energy required for the drying process of domestic and imported milk powders.     

Heat of wood pyrolysis

The heat of pyrolysis of beech and spruce wood was investigated by means of a differential scanning calorimeter. Wide variations were found for the heat of the primary pyrolysis process, depending on the initial sample weight and on the conditions used in the measurements. However, reporting the heat of the primary pyrolysis process versus the final char yield resulted in a linear correlation. This strong dependency of the heat of wood pyrolysis on the final char yield, that is in turn highly sensitive to the experimental conditions, can explain the uncertainty of the data for the heat of wood pyrolysis reported in the literature. A possible explanation for the variability of the heat of wood pyrolysis depending on the final char yield seems to be an exothermic primary char formation process competing with an endothermic volatile formation process.     

Nanostructural characterization and sorption isotherm analysis of spray-dried date powder

Dates are naturally rich in antioxidants and other bioactive molecules. To enhance the shelf life and market value of these bioactive molecules, free flow spray-dried date powder was produced in a pilot scale spray drier. To better understand the rheological properties of the spray-dried date powder produced by different carrier materials (maltodextrin (MD) and gum Arabic (GA)), different drying temperatures (150 and 170°C) and different flow rates of the atomizer (25 and 40?mL/min), a microstructural characterization of the scanning electron microscopy images of the date powder was performed using the graphical user interface design environment and image analysis toolbox in MATLAB. Also, the fundamental rheological characteristics of deformation and flow of particulate solids (i.e., packing, permeability, and strength) were obtained using an advanced rheometer and helium pycnometer. The microstructural and rheological properties of the date powders were significantly affected by the processing conditions used in this study. The date powder produced with MD had smooth, regular-shaped spherical particles along with good agglomeration and packing characteristics. Date powder with GA had irregular-shaped relatively smaller particles with dented surfaces with poor agglomeration and packing properties. Moreover, the rheological quality of the date powders was inversely proportional to the temperature and flow rate. The Guggenheim–Anderson–de Boer model for sorption isotherms was a suitable fit for the date powder. The monolayer moisture content for gum Arabic was twice that of the maltodextrin carrier material, whereas the monolayer heat of sorption was higher for maltodextrins. Using maltodextrin as the carrier material and drying at 150°C with a flow rate of 25?mL/min produced a free flowing less caking product as depicted by the sorption isotherms.     

A comparison of isotherm and kinetic models for binary-solute adsorption to affinity membranes

Single-solute isotherms for pepsin (EC 3.4.23.1) and chymosin (EC 3.4.23.4) adsorption to affinity membranes were fitted using five of the most popular isotherm models. It was found that the single-solute Langmuir isotherm was the best two-parameter model, although the three-parameter models gave even better fitting. Experimental binary-solute adsorption isotherms were compared with four different types of binary-solute Langmuir models using the single-solute parameters. The results showed that the difference in the saturation capacities affected the adsorption equilibrium. Furthermore, three types of binary-solute Langmuir models were converted into the kinetic form and used to calculate the association rate constants of pepsin and chymosin from experimental data. The best-fitted rate constant values were found to be identical for different kinetic models. However, the model predictions of association curves were significantly influenced when the values of association rate constants were changed.     

A comparison of desorption process of Chinese and Australian lignites by dynamic vapour sorption

Modified BET model and Do and Do (D.D.) model were chosen to interpret the desorption process of water on hard and soft lignites. The organic and inorganic hydrophilic sites were determined by X-ray photoelectron spectroscopy and X-Ray fluorescence spectroscopy. From the modified BET model, only a small part of hydrophilic sites (HSs) acted as effective primary sites due to space restraint, intramolecular hydrogen bond and maybe more than one hydrophilic site connecting with one water molecule. From the D.D. model, the total adsorption sites (S_t) of Loy Yang lignite (LY) is 18.7 mmol/g, which is higher than that of Shengli (SL) 17.0 mmol/g in spite of lower primary sites, and the saturation concentration of water (q_us) in the micropore of LY is 33.7 mmol/g, which is much higher than that of SL (12.5 mmol/g). So the high moisture-holding capacity of LY is mainly determined by the high S_t and q_us, and not the primary sites. The size of water clusters entering the micropores is 7 for SL and 6 for LY, which is related to relative location of HS. When dewatered, the higher total sites density and smaller water cluster size of LY both implied higher dewatering energy.     

A Cheap,Fast and Simple Way to Measure Sorption Isotherms of Granular Materials

ABSTRACT

A set-up and a method are described with which sorption isotherms of granular materials can be measured. The set-up uses a recirculating air flow through a fluidized bed of granular materials. The measuring procedure starts with drying the granular material completely. A known amount of water is added to the fluidized bed. At equilibrium between the amount of water in the granular material and the circulating air the air humidity is measured. The method is demonstrated using silica gel.     

Influence of humectants on the drying kinetics,water mobility,and moisture sorption isotherm of osmosed air-dried papaya

Papaya slices were sequentially soaked in 40, 50, and 60° Brix sucrose solutions. There was a higher water loss and solids gain when 60° Brix sucrose solution was partially substituted with 10% (w/v) sorbitol, 10% (v/v) glycerol, or invert sugar. The modified Henderson and Pabis model provided the best fit to experimental drying kinetics. Moisture sorption isotherm of all dried papaya, at 30 ± 2°C, was a type III with different curvature, revealing different sugar-binding ability towards water molecules. The Henderson model showed suitable fit to experimental desorption isotherm data. NMR water mobility revealed the better ability of glycerol to bind water than sucrose.     

A Cheap, Fast and Simple Way to Measure Sorption Isotherms of Granular Materials

A set-up and a method are described with which sorption isotherms of granular materials can be measured. The set-up uses a recirculating air flow through a fluidized bed of granular materials. The measuring procedure starts with drying the granular material completely. A known amount of water is added to the fluidized bed. At equilibrium between the amount of water in the granular material and the circulating air the air humidity is measured. The method is demonstrated using silica gel.     

Assessment of kinetic and isotherm models for competitive sorption of Cs+ and Sr2+ from binary metal solution onto nanosized zeolite

This study examined the sorption performance of synthesized nanosized zeolite for the elimination of Cs⁺ and Sr²⁺ cations in a binary metal system. The influence of pH, sorbent amount, temperature, and contact time was studied. The relationship between each of these parameters and the removal efficiency was investigated. An analysis of the rate data was performed using both pseudo-first- and second-order reaction models. The ranking of three equilibrium sorption isotherm models used (Redlich–Peterson, Langmuir, and Freundlich) with a variety of numbers of parameters was determined using the corrected Akaike’s information criterion. The results demonstrate that a pseudo-second-order model fits the sorption kinetic data better than a pseudo-first-order model. The isotherm model rank order that best described the data statistically was Redlich–Peterson?>?Langmuir?>?Freundlich for the cesium ions and Langmuir?>?Redlich–Peterson?>?Freundlich for the strontium ions. Our results revealed that the existence of Sr²⁺ caused a significant reduction of Cs⁺ sorption in the binary metal mixture according to a lumped parameter model and vice versa. The results show that the synthesized material’s surface had a relatively stronger affinity for Cs⁺ than for Sr^2+.     

Heat transfer and drying kinetics of tomato pulp processed by cast-tape drying

Cast-tape drying (CTD) is a process to dehydrate suspensions. This study evaluated the influence of heat source and forced air convection on the drying rate and temperature of tomato pulp during CTD. To this, a pulp thin layer was spread on a flexible support with its lower surface in direct contact with a heat source. Similar drying rates and evaporative capacities were observed for both flexible supports and heating media. Steam simplifies the temperature control and equipment construction. CTD is a suitable process for producing dried tomato pulp in short drying times, resulting from high evaporative capacity.     

Prediction of fire classification for wood based products. A multivariate statistical approach based on the cone calorimeter

Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd.     

Models for Sorption Isotherms for Foods: A Review

This article presents basic concepts related to the thermodynamics of sorption of water and measurement of sorption isotherm for food materials. A comprehensive review of the widely used sorption models is presented. Various statistical techniques used to ascertain the effectiveness of a model to describe the sorption data are discussed. It is anticipated that this article will provide useful information to researchers pursuing work on sorption behavior of food materials as well as modeling of drying processes.     

Models for Sorption Isotherms for Foods: A Review

This article presents basic concepts related to the thermodynamics of sorption of water and measurement of sorption isotherm for food materials. A comprehensive review of the widely used sorption models is presented. Various statistical techniques used to ascertain the effectiveness of a model to describe the sorption data are discussed. It is anticipated that this article will provide useful information to researchers pursuing work on sorption behavior of food materials as well as modeling of drying processes.     

Removal of divalent nickel from aqueous solution using blue-green marine algae: adsorption modeling and applicability of various isotherm models

Adsorption of Ni(II) onto blue-green marine algae (BGMA) is investigated under batch condition. Under optimum experimental conditions, the initial Ni(II) metal ion concentration is varied from 25 to 250 ppm and the maximum adsorption capacity of BGMA is found to be 42.056 mg/g. The optimum pH, biomass loading, and an agitation rate on maximum removal of Cu(II) ion are found to be 6, 2 g, and 120 rpm, respectively. 24 h of contact time is allowed to achieve equilibrium condition. All the experiments are carried out at room temperature. The equilibrium experimental data infer that the isotherm is L-shaped. It is the indication of no strong competition between solvent and Ni(II) to occupy the active sites of BGMA. Also, it indicates that the BGMA has a limited sorption capacity for adsorption of Ni(II). The experimental data are tested with various isotherm models; subsequently, the mechanism of adsorption is identified and the characteristic parameters for process design are established. Fritz–Schlunder-V isotherm model is highly significant in establishing the mechanism of adsorption of Ni(II) under the conditions employed in this investigation followed by Freundlich. The q_max of 41.89 mg/g obtained by this model indicates its relevance more precisely with experimental data.     

Flame spread measurements on wood products using the ASTM E 1321 LIFT apparatus and a reduced scale adaptation of the cone calorimeter

Flame spread experiments were conducted in an ASTM E 1321 lateral ignition and flame transport (LIFT) apparatus and a reduced scale ignition and flame spread test (RIFT) adaptation of the cone calorimeter. Wood‐based products were tested and a flame spread model was applied to the results to obtain the flame spread parameter and the minimum heat flux required for flame spread. The materials used were plywood, medium density fibreboard, hardboard, two‐particle board products, Melamine (Melteca) covered products with two types of wood substrate along with New Zealand grown Rimu, Beech, Macrocarpa and Radiata Pine. The RIFT gave comparable results to the LIFT for several of the materials investigated. There appeared to be an effective limit on suitable materials that can be successfully tested in the RIFT to those that have a minimum flux for flame spread of less than 7kW/m². This limitation was due to the rapid decay of the heat flux profile along the sample and the lower resolution dictated by the smaller size of the RIFT apparatus. It was found that the limit on the minimum heat flux for flame spread was approximately equivalent to a minimum ignition flux of 18kW/m². Copyright © 2009 John Wiley & Sons, Ltd.     

Simulation Model for the Model-Based Control of a Biofuel Dryer at an Industrial Combined Heat and Power Plant

The primary aim of this article is to present a simulation model for a bark dryer integrated into a combined heat and power plant. The same model can be used for the model-based control of the dryer. The secondary aim is to evaluate how useful the control is from an economic point of view. Results show that the final fuel moisture content can be stabilised by controlling the drying temperature(s). On the other hand, the deviation in final bark moisture decreases even when the dryer has no control at all. Net incomes resulting from drying increase in most cases compared to dryers without control. The need for control cannot be justified on economic grounds.     

Optimized design of wastewater treatment systems: Application to the mechanical pulp and paper industry: I. Design and cost relationships

Four different end-of-pipe waste-treatment processes applicable to mechanical pulp and paper manufacture were modelled. Calculated costs for an average mill were capital $34–$44 million, operating cost $3.5–$6 million/year and discounted (10 years) $60–$85 million. Compared with mill reported values, capital and operating costs of activated sludge treatment (AST) were higher by 17 and 29%, respectively; those for aerated stabilization basin (ASB) were higher by 27 and 180%. Major variables affecting the costs were BOD and TSS levels and the wastewater-to-pulp ratio. It was concluded that ASB is more economical than AST and that anaerobic treatment plus AST could be advantageous at high BOD levels.     

Simulation Model for the Model-Based Control of a Biofuel Dryer at an Industrial Combined Heat and Power Plant

The primary aim of this article is to present a simulation model for a bark dryer integrated into a combined heat and power plant. The same model can be used for the model-based control of the dryer. The secondary aim is to evaluate how useful the control is from an economic point of view. Results show that the final fuel moisture content can be stabilised by controlling the drying temperature(s). On the other hand, the deviation in final bark moisture decreases even when the dryer has no control at all. Net incomes resulting from drying increase in most cases compared to dryers without control. The need for control cannot be justified on economic grounds.