Optimization of Sibipiruna activated carbon preparation by simplex-centroid mixture design for simultaneous adsorption of rhodamine B and metformin.

The present paper reports the application of augmented simplex-centroid mixture design to obtain a high BET surface area activated carbon using as reactants KOH, K2CO3 and K2C2O4. The optimum mixture composition was 2.51 g of KOH, 0.49 g of K2CO3 and absence of K2C2O4, generating an optimized AC (ACop) with SBET value equals to 1984 m2 g-1. The results herein obtained show that low amounts of K2CO3 can catalyze the pore development in the presence of KOH, increasing the surface area. Furthermore, the fractal dimensions of ACop are greater than 2.72, indicating the material has a complex pore structure with irregularities self-similar upon variations of resolution, as seen by SEM images. The TPD curves showed that the ACop has different oxygenated molecular fragments, which agrees with the pHPZC value (5.05). The ACop was applied in the adsorption of rhodamine B (RhB) and metformin (Met) in both binary and monocomponent systems. The simultaneous adsorption at 30 °C reveals that the adsorption capacity of RhB is 630.94 mg g-1, while for Met the value is 103.83 mg g-1.

Biodiesel production by free fatty acid esterification using Lanthanum (La3+) and HZSM-5 based catalysts.

In this work the use of the heterogeneous catalysts pure (LO) and sulfated (SLO) lanthanum oxide, pure HZSM-5 and SLO/HZSM-5 (HZSM-5 impregnated with sulfated lanthanum oxide (SO4(2-)/La2O3)) was evaluated. The structural characterization of the materials (BET) showed that the sulfation process led to a reduction of the SLO and SLO/HZSM-5 surface area values. FTIR showed bands characteristic of the materials and, FTIR-pyridine indicated the presence of strong Brønsted sites on the sulfated material. In the catalytic tests the temperature was the parameter that most influenced the reactions. The best reaction conditions were: 10% catalyst, 100°C temperature and 1:5 m(OA)/m(meOH) for LO, SLO, SLO/HZSM-5 and 10% catalyst, 100°C temperature and 1:20 m(OA)/m(meOH) for HZSM-5. Under these conditions the conversions were: 67% and 96%, for LO and SLO, respectively and 80% and 100%, for HZSM-5 and SLO/HZSM-5, respectively. All catalysts deactivated after the first use, but the deactivation of SLO/HZSM-5 was smaller.

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.