This work consists in the use of a 3A zeolite (K-LTA) obtained by a process of exchange of sodium for potassium (4A zeolite), synthesized from Venezuelan kaolin for the removal of Pb (II) ions from aqueous solutions by batch process mode in order to consider its application in treating industrial wastewaters. The 3A zeolite was characterized for X-ray powder diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and scanning electron microscopy and energy dispersive X-ray microanalysis (SEM-EDX). The metal concentration in the equilibrium C e (mg•L −1) after adsorption with 3A zeolite was analyzed using flame atomic absorption spectrometry (FAAS). The influences of the solution pH, contact time, metal initial concentration and adsorbent dosage have been studied. The retention of metal occurring at pH values around 6.5 and the adsorption equilibrium was obtained at 60 min. The equilibrium process was well described by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir parameters q m (mg•g −1) and b (L•mg −1) (which are related to the sorption capacity and constant of sorption energy) obtained were 14.64 and 5.42 respectively. The Pb (II) experimental uptake was about 14.56 mg•g −1 , a little smaller than the theoretical one given by Langmuir isotherm model. The regression parameters and correlation coefficients (R) indicate that the adsorption data for Pb (II) removal fit better the Langmuir isotherm model. Moreover, 0 < 1/n < 1 (1/n is 0.13), indicating that adsorption of metal ions on the zeolite, is a favorable physical process. The application of removing of the metal lead from real samples was examined by industrial wastewater samples. For all samples, the percentage of recovery was found with accuracy of more than 98%. The present work suggests 3A zeolite used as a sorbent material with relatively low cost, obtained from Venezuelan raw material; it is a candidate for removal lead ion and probably other cationic heavy metal species from wastewater.

Palabras clave: residuo vegetal, pirólisis, isotermas, adsorción química RESUMEN En este trabajo se sintetizó carbón activado a partir del epicarpio de Attalea macrolepis y se evaluó como adsorbente para la remoción de iones Pb 2+ . El pH, la masa del adsorbente, el tiempo y la concentración inicial de plomo se evaluaron como pará-metros influyentes en el proceso de adsorción. Por otro lado, se evaluó el mecanismo de adsorción de los iones de plomo sobre el carbón activado usando los modelos de Langmuir, Freundlich y Dubinin-Radushkevich. Mediante espectroscopía infrarroja con transformada de Fourier en el material adsorbente se identificaron los grupos funcionales hidroxilos, carboxilatos, olefinas y anillos bencénicos. Por medio de microscopía electrónica de transmisión se evidenció una matriz de partículas aglomeradas heterogéneas de tamaño comprendido entre 149 a 185 nm. Las condiciones óptimas obtenidas para la remoción de 70 % de iones Pb 2+ (5 mg/L) fueron a pH 5, una masa de adsorbente de 150 mg, un tiempo de contacto de una hora, una agitación de 1500 rpm y un volumen de 25 mL. A partir de las isotermas se obtuvo una capacidad máxima de adsorción de 0.500 mg/g. La energía de adsorción calculada a partir del modelo de Dubinin-Radushkevich fue de 10.42 KJ/mol, este valor energético permite inferir que en el sistema carbón activado-iones Pb 2+ ocurre una adsorción química. Los resultados demuestran que el carbón activado producido con el epicarpio de Attalea macrolepis es un adsorbente alternativo de bajo costo y amigable con el ambiente para remover Pb 2+ de sistemas acuosos.

In this work, a flow injection analysis (FIA) method for the trace determination of lead, cadmium, nickel and cobalt in natural waters by formation of neutral chelates with ammonium pyrrolidine dithiocarbamate (APDC) was developed. The neutral chelates formed was retained in a mini-column packed with Linde type A zeolite (LTA) and type Y Faujasite zeolite (FAU) and then eluted with methyl isobutyl ketone (MIBK) to flame atomic absorption spectrometry (EAA) for its detection. Physicochemical characterization of this zeolite was carried out by Fourier Transform infrared spectroscopy and attenuated total reflectance (FTIR and IR-ATR), scanning electron microscopy and energy dispersive X-ray microanalysis (SEM-EDX) and X-ray power diffraction (XRD). Then, a FIA configuration was used with a column preconcentration system coupled to the detection system at room temperature (22?C). The detection limit and the relative standard deviation for 5 determinations of different solutions of Pb²⁺, Co²⁺, Ni²⁺ and Cd²⁺ for FAU and LTA zeolite were calculated. The sampling frequency ranged from 18-35 h^-1 and preconcentration factors from 21-250 were achieved, for a sample volume of 6 mL using 20 mg of sorbents, indicating a high retention of the analytes on the zeolites material. The recoveries obtained in natural waters samples were close to 100% for all ions metal using synthetic zeolites, confirming the applicability of the method. The isotherm models of Langmuir, Scatchard, Freundlich and Dubinin-Radushkevich were used to study the equilibrium data, indicating that successfully followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms at low metal ion concentration. The Freundlich parameter n varied between 0.35-1.01, whereas D-

Amorphous aluminophosphates nanoparticles with diameter sizes from 23 to 30 nm were used for the adsorption of lead ions (Pb 2+) in aqueous solutions. The materials were biosynthesized using Saccharomyces cerevisiae as a biological template. Adsorption studies were conducted using the batch method, employing 100 mg of the solid and 200 µg L-1 of lead ions. The quantitative determination of Pb 2+ was carried out by electrothermal atomic absorption spectrometry (ETAAS). The percentage of removal (EF), adsorption capacity q e (µg g-1) and removal coefficient Kd (mL g-1) averaged 40, 90 and 800, respectively. The results showed the potential of these materials for the adsorption of Pb 2+ ions, and that these materials are good candidates for use in the remediation of contaminated water.

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