Separation and Determination of Fe(III) and Fe(II) in Natural and Waste Waters Using Silica Gel Sequentially Modified with Polyhexamethylene Guanidine and Tiron.

Svetlana Didukh,Vladimir Losev,Nikolay Maksimov,Anatoly Trofimchuk,Elena Borodina,Olga Zaporogets

doi:10.1155/2017/8208146

Abstract

Silica gel, sequentially modified with polyhexamethylene guanidine and pyrocatechin-3,5-disulfonic acid (Tiron), was suggested for sorption separation and determination of Fe(III) and Fe(II). It was found that quantitative extraction of Fe(III) and its separation from Fe(II) were attained at pH 2.5–4.0, while quantitative extraction of Fe(II) was observed at pH 6.0–7.5. An intensive signal with g = 4.27, which is characteristic for Fe(III), appeared in EPR spectra of the sorbents after Fe(II) and Fe(III) sorption. During interaction between Fe(II) and Tiron, fixed on the sorbent surface, its oxidation up to Fe(III) occurred. Red-lilac complexes of the composition FeL3 were formed on the sorbent surface during sorption regardless of initial oxidation level of iron. Diffuse reflectance spectrum of surface complexes exhibited wide band with slightly expressed maxima at 480 and 510 nm. Procedures for separation and photometric determination of Fe(III) and Fe(II) at the joint presence and total Fe content determination as Fe(II) in waste and natural waters was developed. The limit of detection for iron was 0.05 μg per 0.100 g of the sorbent. The calibration graph was linear up to 20.0 μg of Fe per 0.100 g of the sorbent. The RSD in the determination of more than 0.2 μg of Fe was less than 0.06.

Highlights

Element speciation, including determination of various oxidation states of the elements, in environmental objects is an important challenge of analytical chemistry
Natural waters contain iron in oxidation states +2 and +3, and Fe(III) content is much higher than Fe(II) content at that
Maximum recovery (≥98%) of Tiron from solution of 0.16 mM L−1 by SiO2-polyhexamethylene guanidine hydrochloride (PHMG) sorbent was attained at pH of 3.0–7.5 (Figure 2, 100 (1)

Summary

Introduction

Element speciation, including determination of various oxidation states of the elements, in environmental objects is an important challenge of analytical chemistry. Colorless sorbents are preferred to be used for sorptionphotometric determination of Fe(III) and Fe(II) From this point of view silica based sorbents modified with colorless organic reagents which can form colored complexes with iron ions are very promising. Examples of such reagents include Tiron (4,5-dihydroxybenzene-1,3-disulfonic acid), which forms colored complex compounds with Fe(III) [25, 26]. Procedures for separate sorptionphotometric determination of Fe(III) and Fe(II) from one sample of water and sorption-photometric and test-method for determination of the total iron content as Fe(II) in natural waters were developed

Experimental

Results and Discussion

Conclusion