Abstract
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-R isotherm yields the sorption free energy E 8 kJ.mol-1 indicating psysisorption.
Highlights
The selective extraction and determination of heavy metals, especially some toxic ones, are still an intensively active research areas due to their biological mechanisms
On the other hand, comparing the FTIR-spectra of the obtained kaolin with the FTIR-spectra of Na-Linde type A zeolite (LTA) and Na-Faujasite zeolite (FAU) (Figure 4) one can appreciate differences between the bands of stretching vibrations and deformation of the H-O-H in the region of 3000 - 3700 cm−1 for the adsorbed molecular water which is located in the cavities of the LTA and FAU zeolites; and the band in 1650 cm−1 characterizes the signal stretching and angular deformation of the hydroxyl molecules of water of hydration of the zeolites
The bands in 1100 - 1050 cm−1 indicates the presence of Si-O and the crystallization bands appear in the zone of absorption 555 - 501 cm−1 which is assigned to the presence of structural double rings of LTA (D4R) and FAU (D6R) zeolites
Summary
The selective extraction and determination of heavy metals, especially some toxic ones, are still an intensively active research areas due to their biological mechanisms. The traditional methods for noble metals purification were precipitation and complexation procedure which needed large numbers of toxic acids and complexation agents, such as potassium or sodium cyanides that have negative impact on environment [1]. Analytical techniques such as inductively coupled plasma optical emission spectrometry (ICP-OES) [2], and inductively cou-. Flame atomic absorption spectrometry (FAAS) is the most widely used analytical method in this field due to its low cost, friendly operation, high sample throughput and good selectivity.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
