Sorption Isotherms and Drying Characteristics of Tomato Peel Isolated from Tomato Pomace

Tomato peel was separated from pomace by sedimentation and dried in cabinet and fluidized-bed dryer at 50–70°C using 4–12 kg/m²tray load. The drying of tomato peel took place under the falling rate period and the drying behavior was well described by Page's model with coefficient of determination greater than 0.99 and standard error of 0.003–0.016. A fluidized-bed dryer was much more efficient than a cabinet dryer to dry tomato peel. The moisture adsorption isotherms of tomato peel were obtained by equilibrating above saturated salt solutions of known a _w (0.113–0.92) at 20–60°C. The data were analyzed using fifteen sorption models based on coefficient of determination, standard error, and residual plots. Modified Henderson was the best model for tomato peel with coefficient of determination >0.99, standard error <0.210, and a scattered residual plot. The net isostearic heat of sorption, estimated using the Clausius-Clapeyron equation, was 0.74–23.23 kJ/mol at 2.0–2.5% moisture content (dry basis).     

PREDICTION OF PINEAPPLE SORPTION ISOTHERMS USING THE ROSS EQUATION

ABSTRACT

A mathematical prediction of pineapple sorption isotherms was developed using Ross, Norrish and Henderson equations. The prediction considered to have the pineapple average composition oflhe main solutes: sucrose, glucose, fructose, citric acid, malic acid, NaCI, KC1 and cellulose as non-solute. Water activity of individual sugars and organic acids was obtained by Norrish's equation and for the two salts by Raoult's Law. Solute solubility at different temperatures was taken into account. Predicted isotherms were compared with the experimental isotherms obtained in laboratory at 30, 35, 40 and 45° C and with the isotherms reported in literature at 30 and 45° C. The generalized correlation coefficients ( r² ) between predicted and experimental isotherms were in the range of 0.8 - 0.98.     

Modern hybrid sorbents – New ways of heavy metal removal from waters

The possibility of hybrid ion exchanger (HIX) application in the simultaneous removal of heavy metal ions such as Cr(VI), Cu(II) and Zn(II) as well as Cd(II) and Pb(II) was presented. The ion exchanger in question combines the unique properties of hydrated metal oxides with the mechanical and thermal stability of synthetic ion exchangers. The kinetics of the sorption process of Cr(VI), Cu(II) and Zn(II) as well as Cd(II) and Pb(II) in the presence of Cl⁻, NO₃⁻ and SO₄²⁻ as well as EDDS (ethylenediaminedisuccinic acid) was also analyzed. Additionally, the effect of initial concentration, phase contact time and pH was also studied. Taking into account the possibility of its application on a large scale, the parameters of the adsorption process were estimated based on the linear form of the Langmuir and Freundlich isotherms.     

INTERFACIAL ADSORPTION OF 2-HYDROXY-5-NONYLBENZOPHENONE OXIME IN STATIC AND VIGOROUSLY STIRRED DISTRIBUTION SYSTEMS

ABSTRACT

The interfacial adsorption of 2-hydroxy-5-nonylbenzo-phenone oxime (LIX65N) at a n-heptane/water interphase was examined under static and vigorously stirred conditions, varying the aqueous pH from 2 to 12. In static systems, the pH and the concentration dependences of the interfacial tension were analysed on the basis of the Gibbs equation. The acid dissociation equilibrium at the interface was evaluated. In vigorously stirred systems, the interfacial adsorption was observed as a reversible, reproducible decrease of the organic phase concentration in response to stirring. A Langmuir isotherm was applicable for the adsorption of neutral LIX65N in acidic condition. The greater adsorption of the anionic form of LIX65N occurring in alkaline condition required an alternative isotherm.     

Moisture sorption isotherms of two varieties of millet

Moisture sorption isotherms of EX-BORNO and SOSAT C88 millets at temperature range of 30–70 °C and water activity range of 0.07–0.98 were determined using the static gravimetric method. The sorption isotherms of both millet varieties decreased with increasing temperature, exhibited type II behaviour according to BET classification and hysteresis having loop size increasing with increasing temperature. This is as a result of the hard nature of the millet varieties. The moisture sorption and the data fitted well with Modified Henderson, Modified Halsey, Modified Oswin and Modified GAB models. The constants of the equations used in fitting were determined by non-linear regression analysis when the models were compared using the standard error of estimate, mean relative percent deviation, fraction explained variation and residual plots. The Modified Oswin model gave the best fit for the whole set of data. The study has provided information and data useful in large scale drying and processing of millet which have remained at the traditional level despite the importance of the drought resistance crop in poverty alleviation.     

Kinetics,equilibrium and thermodynamics studies of arsenate adsorption from aqueous solutions onto iron hydroxide

This paper reports the equilibrium, kinetics and thermodynamic studies of arsenate adsorption onto freshly precipitated iron hydroxide. Adsorption of arsenate onto iron hydroxide depends on arsenate concentration, contact time and temperature. The intrapartical diffusion model indicates that both the film and intrapartical diffusion control arsenate adsorption on iron hydroxide. The values of activation energies (E_a) indicate the chemical nature of adsorption accompanied by diffusion controlled processes as the rate limiting step. The endothermic nature of the adsorption process suggests that adsorption reaction consumes energy. The negative values of ΔS^# can be assigned to decreased randomness at the solid liquid interface.     

Plasma grafting montmorillonite/iron oxide composite with β-cyclodextrin and its application for high-efficient decontamination of U(VI)

β-Cyclodextrin (CD) was grafted onto montmorillonite/iron oxides to prepare a novel magnetic CD/MMT/iron oxide composite by low-temperature plasma technology, and applied to remove U(VI) from aqueous solutions. The sorption irreversibility was attributed to inner-sphere binding of U(VI) on CD/MMT/iron oxide surface sites. The thermodynamic parameters indicated that the sorption of U(VI) on CD/MMT/iron oxide was an endothermic and spontaneous process. The maximum sorption capacity of U(VI) on CD/MMT/iron oxide was considerably higher than that of U(VI) on other reported materials. The CD/MMT/iron oxide can be potentially used as a cost-effective material for the purification of actual U(VI)-bearing effluents.     

The influence of binder content on the water transport properties of waterborne acrylic paints

Diffusion coefficients and sorption isotherms of water in waterborne acrylic paint films and in the pure binder of the paints have been measured by gravimetric sorption. Solubility of water was found to enhance with the increased binder content in the paint films while the diffusivity of water decreased significantly. Sorption isotherms in the paint and pure copolymer films were correlated with the Flory Huggins theory and ENSIC model, respectively. Fickian diffusion was observed in both types of films and the kinetic data were best correlated with a numerical model which takes into account the concentration dependency of the diffusion coefficient and the dimensional change of the film due to sorption. It was concluded that the utilization of a simplified analytical solution may lead to significant errors in the estimation of diffusivities.     

Multivariate analysis of a biologically activated carbon (BAC) system and its efficiency for removing PAHs and aliphatic hydrocarbons from wastewater polluted with petroleum products

The efficiency of a biologically activated carbon system for treating wastewater polluted with petroleum products was examined and the effects of process parameters on its efficacy were evaluated. In each experiment 17 alkylated and 19 non-alkylated polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs, C₁₀–C₄₀) were extracted using semipermeable membrane devices from wastewater before and after treatment. The acquired data during experiments were analyzed using principal component analysis (PCA). The treatment system robustly removed dissolved PAHs across the studied ranges of the process parameters, providing overall removal efficiencies of 96.9–99.7% for the sum of 36 PAHs. However, the major contributor to their removal was sorption rather than biodegradation, and despite the general efficiency of the process there was up to a 9-fold range in the sums of quantified PAHs in the effluents between experiments. Combinations of long process contact time (24 h) with high temperature (24 °C) and moderate oxygen concentration (6–7 mg O₂ L⁻¹) resulted in good removal of bioavailable PAHs. The removal of TPHs was more dependent on biological activities during the wastewater treatment, and consequently more dependent on the process parameters. In addition, small but significant proportions of PAHs were volatilized and released during the wastewater treatment.     

AN EXPERIMENTAL EVALUATION OF THE GOVERNING MOISTURE MOVEMENT PHENOMENA IN THE PAPER COATING PROCESS. I. THEORETICAL ASPECTS

The most important issue when coating paper is the modelling of the moisture movement in the coating process, since the water movement pattern is strongly connected to binder movement and the final structure of fibres and coating colour, which in turn affects the final printing properties of the paper. Therefore, we are now studying a novel laboratory method to determine the dynamic water movement in a hygroscopic porous media, i.e. the liquid movement in the paper coating process. The experimentally determined physical properties yield information relevant to the mass and energy balances of a real paper coating process. We have also studied the widely used Lucas-Washburn capillary suction theory in combination with the build-up of a filter-cake in the coating colour. The study shows, that the water loss from the coating colour into a hygroscopic material can be well explained by applying vapour diffusion into the base paper as the governing mass transfer mechanism.