Maria Angélica Simões Dornellas de Barros

A comparative study for the ion exchange of Fe(III) and Zn(II) on zeolite NaY

The uptake capacity of Fe(III) and Zn(II) ions in NaY zeolite was investigated. Experiments were carried out in a fixed bed column at 30 degrees C, pH 3.5 and 4.5 for Fe(III) and Zn(II), respectively, and an average particle size of 0.180 mm. In order to minimize the diffusional resistances the influence of flow rate on the breakthrough curves at feed concentrations of 1.56 meq/L for Fe(III) and 0.844 meq/L for Zn(II) was investigated. Flow rate of the minimal resistance in the bed according to mass transfer parameter were 2.0 mL/min for iron and 8.0 mL/min for zinc ions. Freundlich and Langmuir isotherm models have been used to represent the column equilibrium data. The iron dynamic isotherm was successfully modeled by the Langmuir equation and this mathematical model described well the experimental breakthrough curves for feed concentrations from 0.1 up to 3.5 meq/L. The zinc dynamic isotherm was successfully modeled by the Freundlich equation. This equilibrium model was applied to mathematical model. Experimental breakthrough curves could be predicted. Experiments were also carried out in a batch reactor to investigate the kinetics adsorption of the ions Fe(III) and Zn(II). Langmuir kinetic model fit well both experimental data.

Adsorption of Reactive Blue 5G Dye by Activated Carbon and Pyrolyzed Shale Oil Residue

This work was aimed at the study of the adsorption mechanism of Reactive Blue 5G dye on activated carbon derived from babassu shells and pyrolyzed oil shale residue. Experiments were undertaken employing a fixed bed reactor at 30°C using continuous systems. To minimize diffusional resistances, the influence of the flow rate was investigated via breakthrough curves at a feed concentration of 35 mg/l. Breakthrough curves for flows in the range 2–10 ml/min were carried out using bed height of 15.5 cm for activated carbon and 9.5 cm for pyrolyzed oil shale residue, with an inlet diameter of 1.01 cm. From the calculated mass-transfer parameters, it was shown that the minimum resistance to flow occurred at 4 ml/min for activated carbon and at 2 ml/min for pyrolyzed oil shale residue. It was concluded that the sizes of the pores in the adsorbents play an important role in the adsorption mechanism.

Kinetics and thermodynamics studies of silver ions adsorption onto coconut shell activated carbon

ABSTRACT The presence of silver in the natural water environment has been of great concern because of its toxicity, especially when it is in the free ion form (Ag+). This paper aims to study the adsorption kinetics of silver ions from an aqueous solution onto coconut shell activated carbon using batch methods. Batch kinetic data were fitted to the first-order model and the pseudo-second-order model, and this last equation fits correctly the experimental data. Equilibrium experiments were carried out at 30°C, 40°C, and 50°C. The adsorption isotherms were reasonably fit using Langmuir model, and the adsorption process was slightly influenced by changes in temperature. Thermodynamic parameters (ΔH°, ΔG°, and ΔS°) were determined. The adsorption process seems to be non-favorable, exothermic, and have an increase in the orderness.

A kinetic and equilibrium study of zinc removal by Brazilian bentonite clay

This paper aimed to study the removal of zinc using bentonite clay from the Northeastern Brazil, as an adsorbent. A study of the clay subjected to thermal and chemical treatment was performed in order to evaluate the optimization of the adsorption capacity of this material. For the evaluation of the kinetic equilibrium of the process, experimental tests were carried out in a finite bath system. The maximum amount of metal adsorbed was 0.151 mEq of metal per gram of calcined clay and 0.257 mEq of metal per gram of sodium saturated clay. The kinetic models of pseudo-first order, pseudo-second order and intraparticle diffusion were fitted to experimental data, and the pseudo-second order model provided the best result. The Langmuir and Freundlich models were used for the adsorption equilibrium analysis, and the Langmuir model provided the best fit for sorption isotherms. The physicochemical characterization of clay involved X-ray diffraction, scanning electron microscopy, chemical analysis by energy-dispersive X-ray spectroscopy, helium pyconometry and thermogravimetric analysis. The modified clay has potential use for removing Zn2+ ions replacing more expensive adsorbents, since good adsorption properties will be also associated with great availability and low cost.

Ecofriendly dyeing of silk with extract of yerba mate (Ilex paraguariensis)

Silk fabric was dyed with extract of roasted yerba mate (Ilex paraguariensis). Dyeing experiments were carried out at varying dyestuff concentration, temperature and pH. The influence of mordants, such as potassium alum and tannin, was investigated. The best results in dyeing were produced with 20 g L–1 of dyestuff concentration, pH 3 and temperature of 90℃. Mordants showed negligible influence. The kinetic study showed that the pseudo-second-order equation better represented experimental data, which is related to the chemisorption process as the rate-controlling step. The equilibrium data were easily adjusted by the Langmuir–Freundlich model, indicating the significant contribution of the chemisorption process in a monolayer followed by a multilayer physisorption. The thermodynamic study indicated that dye adsorption was spontaneous and endothermic.

Competing Ion Exchange of Zn2+ and Fe3+ in NaY Zeolite

This study was aimed at investigating the equilibrium and interactive effects of binary solutions containing Zn+2 and Fe+3 ions in fixed-bed columns of NaY zeolite. To calculate the dynamic equilibrium through isotherms, experiments were carried out in a fixed-bed column. Reagent-grade ZnCl2 and FeCl3·6H2O solutions were mixed with deionized water to prepare the feed solutions with total ion concentrations in the range of 0.5–5.0 meq/ℓ. Experiments were then carried out using Fe3+ and Zn2+ ions in the following concentration ratios: 0.75:0.25, 0.50:0.50 and 0.25:0.75. The experimental equilibrium data were then described using Langmuir-type models (binary Langmuir model, Langmuir-type model, Jain and Snoeyink model, and noncompetitive Langmuir model) as well as ion exchange model. Results of our analysis revealed that NaY zeolite has a higher affinity for Zn2+ than Fe3+ ions. The equilibrium data were best fit to the Langmuir-type model. Zn2+ ions are removed through an ion-exchange process while the Fe3+ ions may be preferentially adsorbed onto the already exchanged zeolitic sites. This equilibrium model was then applied to a dynamic mathematical model. We describe the equilibrium in this model by assuming the binary Langmuir-type model and mass transfer in the zeolite based on the linear driving force model.

Ion Exchange Fundamentals and New Challenges

Ion exchange is a stoichiometric phenomenon commonly used in water treatment as an end-of-pipe technique. Such process is highly influenced by mass transfer conditions and may be modeled by adsorption equations. Although widely applied in industries its theo‐ ry has not been completely understood and depends on the exchanger characteristics. Moreover, competitive systems may add complexity and decrease removal efficiency and exchanger selectivity mainly in dynamic systems. In this chapter some general theory was presented and some detailed examples involving alginate biopolymer, bonechar and zeolite in single and competitive systems were discussed in batch and continuous state.

Determination of the maximum retention of cobalt by ion exchange in h-zeolites

This work aimed to determine the maximum content of cobalt that can be incorporated by ion exchange in zeolites H-USY, H-Beta, H-Mordenite, and H-ZSM-5. To reach this goal, batch isotherms at 75oC were constructed after addition of zeolite samples in flasks filled with cobalt nitrate solution. The equilibrium data were fitted to Langmuir, Freundlich, and Toth adsorption isotherm models. Langmuir was the best model for zeolites H-Beta, H-Mordenite, and H-ZSM-5, whereas experimental data for H-USY were better fitted to the Freundlich isotherm model. From the isotherms, it was possible to determine the maximum cobalt exchange level (qmax) that can be incorporated in each zeolite through ion exchange. In this sense, H-USY presented the highest qmax value (2.40 meq/gzeol), while H-ZSM-5 showed the lowest one (0.64 meq/gzeol). These results also show the influence of the zeolite framework related to the channel system, pore opening, presence of cavities and secondary porosity and SiO2/Al2O3 ratio (SAR) on the maximum capacity and behavior of cobalt ion exchange in protonic zeolites.

Study of wool dyeing with natural dye extracted from chamomile flowers

ABSTRACT In this study, wool fabric was dyed with chamomile flower. The influence of the pH, temperature, dyestuff concentration, and mordant on the adsorption was evaluated. The use of mordants caused no difference in dye uptake and the nonmordanted fabric showed good wash fastness. The fit of the kinetic model of pseudo-second order and the Langmuir-Freundlich isotherm indicated that the dyeing is related to the chemisorption process, although the physisorption cannot be neglected. The values from −9.34 to −12.30 (J mol−1) for ΔG° and 41.50 (J mol−1) for ΔH° indicated that dye adsorption was spontaneous and endothermic.

Zeolites as Potential Structures in Obtaining Jet Fuel Through the Fischer‐Tropsch Synthesis

Due to the constant expansion of the aviation sector, the global air industry has performed the search for alternative fuels to petroleum‐derived aviation kerosene, which present low emission of greenhouse gases and other pollutants, in addition to supplying the engines and aircraft already in operation using the existing distribution infrastructure. Thus, one alternative that has been studied is the synthetic kerosene derived from gasification processes followed by Fischer‐Tropsch synthesis. Several features seem to be crucial in controlling product selectivity in the aviation fuel range, among them are the zeolitic support, acidity, and promoters. Therefore, the effect of these parameters in the Fischer‐Tropsch synthesis is discussed in this chapter and, finally, the zeolitic catalysts that, according to the literature, have significant potential in obtaining synthetic aviation fuel are evidenced.