Determination of Pb (II), Cu (II), Co (II), Mn (II), and Fe (III) by electrothermal atomization atomic absorption spectrometry after preconcentration with nanofibers

The results of sorption preconcentration of some heavy metal (HM) ions with their subsequent determination in natural and drinking water by electrothermal atomization atomic absorption spectrometry (ETAAS) are presented. The sorption and desorption (0.01 – 1 M HNO₃) of lead, copper, iron, cobalt and manganese ions from aqueous media on nanofiber samples obtained from polyacrylonitrile (PAN) with subsequent directed modification by 1.25 M NaOH solution upon heating (70°C) (PAN*) are studied and optimized. Nanofibers were obtained by capillary-free electroforming from solutions of PAN in dimethylformamide. This method is advantageous for the simplicity of equipment, high energy efficiency of nanofiber production, versatility and flexibility in controlling process parameters and allows production of nanomaterials with desired properties. The values of the extraction degree (95.8 – 99.5%) and selectivity coefficients for competing pairs of metal ions are calculated: в_Pb/Cu = 1.2; в_Pb/Co = 2.8; в_Pb/Mn = 3.2;в_Cu/Co = 1.7; в_Cu/Mn = 3.7; в_Co/Mn = 2.5. A comparative analysis of the sorption activity of the obtained nanofibers revealed that the character of lead, copper, cobalt and manganese ion sorption by nanofibers is non-selective at pH 6 – 8 and selective for iron (III) ions at pH  3. A technique of sorption-atomic absorption determination of the aforementioned metal ions in real objects with preliminary nanofiber concentration at the level of tenths and hundredths of MPC is proposed. Non-woven materials based on modified PAN are used as effective extractants of nanogram quantities of HM ions. The detection limits for heavy metal ions are 40 – 80 ng/dm³.

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