Kinetic studies of dyes sorption from aqueous solutions onto the strongly basic anion-exchanger Lewatit MonoPlus M-600

The sorption of Tartrazine, Allura Red, Sunset Yellow and Indigo Carmine from aqueous solutions onto the strongly basic anion-exchanger (Lewatit MonoPlus M-600) of dimethylethanolamine functional groups and styrene–divinylbenzene matrix was investigated. The experimental data obtained at 50, 100, 200, 300 and 500 mg/dm³ initial concentrations at 20 °C were applied to the pseudo-first order, pseudo-second order and Weber–Morris kinetic models. The calculated sorption capacities (q_1,cal) and the rate constant of the first-order adsorption (k₁) were determined. The pseudo-second order kinetic constants (k₂) and capacities (q_2,cal) were calculated from the plots of t/q_t vs. t, 1/q_t vs. 1/t, 1/t vs. 1/q_t, q_t/t vs. q_t and 1/q₂ − q_t vs. t for type 1, type 2, type 3, type 4 and type 5 of the pseudo-second order expression, respectively.     

High capacity potassium-promoted hydrotalcite for CO2 capture in H2 production

This paper presents an experimental study for a newly modified K₂CO₃-promoted hydrotalcite material as a novel high capacity sorbent for in-situ CO₂ capture. The sorbent is employed in the sorption enhanced steam reforming process for an efficient H₂ production at low temperature (400–500 ^°C). A new set of adsorption data is reported for CO₂ adsorption over K-hydrotalcite at 400 °C. The equilibrium sorption data obtained from a column apparatus can be adequately described by a Freundlich isotherm. The sorbent shows fast adsorption rates and attains a relatively high sorption capacity of 0.95 mol/kg on the fresh sorbent. CO₂ desorption experiments are conducted to examine the effect of humidity content in the gas purge and the regeneration time on CO₂ desorption rates. A large portion of CO₂ is easily recovered in the first few minutes of a desorption cycle due to a fast desorption step, which is associated with a physi/chemisorption step on the monolayer surface of the fresh sorbent. The complete recovery of CO₂ was then achieved in a slower desorption step associated with a reversible chemisorption in a multi-layer surface of the sorbent. The sorbent shows a loss of 8% of its fresh capacity due to an irreversible chemisorption, however, it preserves a stable working capacity of about 0.89 mol/kg, suggesting a reversible chemisorption process. The sorbent also presents a good cyclic thermal stability in the temperature range of 400–500 °C.     

Fate of Tolyltriazoles and Nonylphenol Ethoxylates in Upflow Anaerobic Sludge Blanket Reactors

The fate of tolyltriazoles, nonylphenol and nonlyphenol ethoxylates during anaerobic treatment of ethylene glycol (EG) based wastewater during batch or continuous upflow anaerobic sludge blanket reactors was investigated. Equilibrium sorption studies indicated that there was minimal sorption of benzotriazole (BT), 5-methyl-1 H-benzotriazole (MeBT), and 5,6-dimethyl-1 H-benzotriazole (DiMeBT) to anaerobic granules. Nonylphenol (NP), a reported biodegradation product of NP ethoxylates, had a higher sorption capacity to anaerobic biomass and was described by the Freundlich isotherm. Batch serum bottle EG degradation experiments indicated that BT, MeBT, DiMeBT, and the nonionic NP ethoxylate surfactant Tergitol NP-4 had no significant effects on acidogenesis and methanogenesis at the concentration levels studied. Significant inhibition of acetoclastic activity was observed for the biodegradation intermediate NP at 100?mg/L, with acetic acid consumption rate at 38% of the controls. No evidence for anaerobic degradation of benzotriazole and its derivatives was observed for both batch and continuously fed anaerobic systems. Continuously fed anaerobic experiments provided evidence that indicated that anaerobic degradation of nonylphenol ethoxylates and the biodegradation intermediate NP occurred.     

Water sorption isotherms for lemon peel at different temperatures and isosteric heats

Lemon peel constitutes a potential source of dietary fiber to formulate new and healthier products, as well as a source of essential oils. The relationship between moisture content and water activity provides useful information for lemon peel processing, especially for drying and storage. Water sorption isotherms of lemon peel were obtained using a standardized conductivity hygrometer at four different temperatures (20, 30, 40 and 50 °C) and wide ranges of moisture content (5.381-0.002 kg water/kg dry solid) and water activity (0.984-0.106). One theoretical (GAB) and four empirical equations (Oswin, Henderson, Halsey and Ratti) were used for modelling sorption isotherms. After evaluating the models according to several criteria, the GAB model appeared as the best option. Isosteric heats of sorption were assessed from experimental sorption isotherm data using different methods.     

Separation of IPA/water mixtures by pervaporation: sorption and pervaporation results

Homogeneous membranes were prepared by blending polyvinyl alcohol (PVA) with polyacrylic acid (PAA) and furthermore the blend membrane is cross-linked covalently through an ester linkage formation between a hydroxyl group of PVA and carboxyl group of PAA. These membranes were evaluated for separation of azeotropic isopropyl alcohol (IPA)/water mixtures by pervaporation, that is, a vacuum applying membrane process. The overall and preferential sorption of IPA/water mixtures in cross-linked membranes were determined to investigate the influence of PVA/PAA ratio and of liquid mixture composition. Pervaporation characteristics were also determined as a function of PVA/PAA ratio and of the feed mixture composition. With increasing PAA content in the membranes, solubilities and fluxes decreased and selectivities increased. Because of polarity, water permeated preferentially through the membranes. Sorption results showed the same tendency as pervaporation results.     

A Study of the Limitations to Spray Dryer Outlet Performance

The concept of the product moisture locus was tested in this work using a pilot-scale modified Niro spray dryer (diameter 0.8 m, height 2 m), where the residence time of the particles inside this spray dryer is lower compared with larger industrial spray dryers. The moisture contents of skim milk powder produced from spray drying skim milk (solids content 8.8% w/v) at different operating conditions, namely different swirl vane angles (0°, 25°, 30°), inlet air temperatures (170°C, 200°C, 230°C) and process fluid flowrates (1.4 kg h^-1, 1.6 kg h^-1, 1.8 kg h^-1), were compared with the predicted equilibrium moisture contents. In addition, the residence time of the particles was also increased in the spray dryer by decreasing the inlet air mass flowrate from 0.016 to 0.013 kg s^-1. The outlet moisture contents of the skim milk powder for all the 23 runs carried out in this work were within 0.4% of the equilibrium values. Thus, the skim milk powder particles were in close equilibrium with the gas inside the drying chamber. These equilibrium limitations are confirmed by other literature data (Boonyai, P. Comparative Evaluation of Soymilk Drying in a Spray Dryer and Spouted Bed of Inert Particles. M.Sc. Thesis. Asian Institute of Technology: Bangkok, Thailand, 2000; 90 pp; Harvie, D.J.E.; Langrish, T.A.G.; Fletcher, D.F. A computational fluid dynamics study of a tall-form spray dryer. Trans IChemE 2002, in press). The use of this finding to predict spray dryer performance is demonstrated by mass and energy balance calculations.     

锝在格列土上的吸附研究

用静态实验法研究了锝在格列土上的吸附行为，考察了葡萄糖，ＮａＯＨ和腐殖酸对锝在格列土上吸附比（Ｒｄ）的影响，结果表明，格列土比一般地表土（砂土，凝灰岩土等）对锝有更大的吸附比，微生物活动能够阻滞锝的迁移，腐殖酸对吸附的影响不大，ＮａＯＨ可以增加格列土锝的阻滞能力。     

碘（I~－）在水泥、氢氧化铁和岩盐中吸附行为的研究

采用放射化学法测定了ＡｇＩ在浓盐溶液中的溶解度。用间歇平衡实验研究了浓盐溶液中碘（Ｉ￣－）在水泥、氢氧化铁和天然岩盐中的吸附行为。研究结果表明，在以上三种吸附体系中，Ｉ￣－浓度为１０￣（－７）－１０￣（－４）ｍｏｌ／ｌ时，Ｉ￣－的吸附比（Ｒ＿ｄ）与吸附剂种类有关，与溶液中Ｉ￣－的平衡浓度（ｃ＿（ｅｑ））无关。Ｉ￣－在吸附剂上的浓度（ｃ＿ｓ）与其在溶液中的平衡浓度（ｃ＿（ｅｑ））的关系符合Ｆｒｅｕｎｄｌｉｃｈ方程。     

Moisture Adsorption Isotherms of Watermelon Seed and Kernels

The moisture adsorption isotherms of watermelon seeds and kernels from Citrullus lanatus Cv Mateera and Citrullus vulgaris Cv Sugar baby were obtained using standard static method with saturated salt solutions over a range of water activities from 0.113 to 0.92 at 20-60°C. The adsorption capacity of seeds decreased with the increase in temperature at constant water activity. Sorption models were used to explain the adsorption behavior involving water activity and moisture content (Type I) and also temperature (Type II). Oswin's models gave best fit among Type I with coefficient of determination of 0.953-0.995, standard error of 0.031-0.0571, mean relative error of 0.071-0.152, and scattered residual plots. Modified Oswin was the best fit model among Type II for the seeds and kernels of both the cultivars with coefficient of determination of 0.997-0.999, standard error of 0.151-0.255, mean relative error of 0.018-0.244, and scattered residual plots. The net isoelectric heat of adsorption, estimated from Clausius-Clapeyron decreased from about 27.0 to 0.5 kJ/mol in kernels and 18.0 to 0.5 kJ/mol in seeds of both the cultivars as the moisture content increased from 5 to 25% (dry basis).     

Influence of plasticizers on the water sorption isotherms and water vapor permeability of chicken feather keratin films

Biodegradable films from many protein sources have in recent decades attracted a lot of attention for their potential use in food protection because they have several advantages over synthetic films, including those related to the environment. The effects of type and concentration of plasticizers on microstructure, sorption isotherms and water vapor permeability (WVP) of films obtained from chicken feather keratin (CFK) were investigated. Keratins were extracted with an aqueous solutions of urea, 2-mercaptoethanol and surfactant. The protein was dosed and the maximum concentration achieved was 12 g/100 ml. The protein concentration in the keratin film solution was standardized at 7 g/100 ml for the preparation of the films by casting. The results showed that increasing the plasticizer concentration caused a decrease in barrier properties and favored water adsorption by the polymeric network, increasing the moisture content of the films. The monolayer moisture content was 8.76 times higher for films made with glycerol than films made without plasticizer and 12 times higher than films plasticized with PEG 4000. The same behavior was observed for the water solubility coefficient, which increased with increasing plasticizer concentration.