Avaliação de óxidos mistos metálicos (Al2O3/Nb2O5) dispersos em matriz porosa de sílica como adsorvente de íons Cd2+ em sistema Fia

Abstract

In this work, a preconcentration method for Cd2+ ions using flow injection analysis (FIA) coupled with flame atomic absorption spectrometry (FAAS) was developed. In this system, Cd2+ ions are adsorbed onto a minicolumn packed with the adsorbent material based on modified silica with niobium (V) oxide and alumina (SiO2/Nb2O5/Al2O3) with further elution with 1.0 mol L-1 HCl. The synthesis of mixed oxide SiO2/Al2O3/Nb2O5 was carried out by sol-gel process. The characterization of the adsorbent was carried out using Scanning Electron Microscopy (SEM) and Infrared (IR). The experimental parameters associated to the system were studied by means multivariate analysis using 24 full factorial design and Doehlert matrix. The factors buffer concentration (Tris HCl = 0.09 mol L-1), preconcentration flow (5.0 mL min-1), pH (8.64) and adsorbent mass (100.0 mg) were optimized. The adsorptive capacity of the material was evaluated by adsorption isotherms, where the maximum adsorption was found to be 17.88 mg g-1. Studies were performed to verify which ions could interfere in the Cd2+ adsorption on SiO2/Al2O3/Nb2O5 adsorbent. The ions evaluated were SO42-, Cl-, Cu2+, Zn2+, Ni2+, Pb2+ in the ratio 1:1, 1:10 and 1:100 (m/m) analyte/interferent. The proposed method showed preconcentration factor of 18.44 times, consumption index of 1.08 mL, sample throughput of 14 h-1, concentration efficiency of 4.33 min-1 and limits of detection and quantification of 0.19 and 0.65 μg L-1, respectively.