Removal of arsenate and 17α-ethinyl estradiol (EE2) by iron (hydr)oxide modified activated carbon fibers

Abstract

Activated carbon fibers (ACF) were modified with iron (hydr)oxide and studied to determine their suitability to remove arsenate and 17α -ethinyl estradiol (EE2) from water. Two synthesis methods, one involving aqueous KMnO₄ pretreatment followed by Fe(II) treatment, and the other involving reaction with Fe(III) in an organic solvent followed by NaOH treatment, were used to produce modified ACF media containing 5.9% and 8.4% iron by dry weight, respectively. Scanning electron microscopy (SEM) and Electron dispersion X-ray (EDX) techniques indicated slightly higher iron content near the outer edges of the fibers. Pseudo-equilibrium batch test experimental data at pH = 7.0 ± 0.1 in 5 mM NaHCO₃ buffered ultrapure water containing ∼ 100 μ g(As)/L and ∼ 500 μ gEE2/L were fitted with the Freundlich isotherm model (q = K × C _E ^1/n ). The adsorption capacity parameters (K) were ∼ 2586 (μ gAs/gFe)(L/μ gAs)^1/n and ∼ 425 (μ gAs/gFe)(L/μ gAs)^1/n ), respectively, for the KMnO₄/Fe(II) and Fe(III)/NaOH treated media. The KMnO₄/Fe(II) media exhibited a lower adsorption capacity at 99% EE2 removal than did the Fe(III)/NaOH treated media (1.3 mgEE2/g -dry -media vs. 1.8 mgEE2/g -dry -media). The arsenate adsorption intensity parameters (1/n) for both modified ACF media were < 0.29, implying very favorable adsorption, which suggests that this type of media may be suitable for single point -of -use applications in which arsenic and organic co-contaminants require simultaneous removal and the depth of the packed bed is the key factor.

Keywords:

• Arsenic
• EE2
• activated carbon fibers
• adsorption
• water

Acknowledgments

The authors would like to thank Solmetex, A Division of Layne Christiansen, for its help with the synthesis protocols, and Kynol, Inc., for their donation of ACF.

Notes

∗(μ g As(V)/g dry media/(μ g As(V)/L)^1/n )

∗∗(μ g As(V)/g Fe/(μ g As(V)/L)^1/n)

∗∗∗from Badruzzaman et al.^{[ 19 ]}

∗∗∗∗from Sperlich et al.^{[ 9 ]}

^†at pH = 6, from Chen et al.^{[ 22 ]}

^‡at pH = 6.4, from Hristovski et al.^{[ 23 ]}