A critical review on arsenic removal from water using iron-based adsorbents

Abstract

Intensive research efforts have been pursued to remove arsenic (As) contamination from water with an intention to provide potable water to millions of people living in different countries. Recent studies have revealed that iron-based adsorbents, which are non-toxic, low cost, and easily accessible in large quantities, offer promising results for arsenic removal from water. This review is focused on the removal of arsenic from water using iron-based materials such as iron-based nanoparticles, iron-based layered double hydroxides (LDHs), zero-valent iron (ZVI), iron-doped activated carbon, iron-doped polymer/biomass materials, iron-doped inorganic minerals, and iron-containing combined metal oxides. This review also discusses readily available low-cost adsorbents such as natural cellulose materials, bio-wastes, and soils enriched with iron. Details on mathematical models dealing with adsorption, including thermodynamics, kinetics, and mass transfer process, are also discussed. For elucidating the adsorption mechanisms of specific adsorption of arsenic on the iron-based adsorbent, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) are frequently used. Overall, iron-based adsorbents offer significant potential towards developing adsorbents for arsenic removal from water.

Fig. 1. The geochemical cycles of arsenic in Nature.

Fig. 2. A typical method for the removal of high concentrations of arsenic from water.

Fig. 3. Scheme of the laboratory iron oxy-hydroxides' production.

Fig. 4. TEM images of the (a) “blank”, (b) “ex situ”, and (c) “in situ” samples and (d) particle size distribution of all three studied systems derived from the statistical processing of TEM images. Note: “Blank” sample formed after addition of ferrate(vi) only to deionized water, “in situ” sample formed after simultaneous addition of ferrate(vi) and an As(v)-containing compound to deionized water, and (iii) “ex situ” sample formed after addition of ferrate(vi) to deionized water and followed by an addition of As(v)-containing compound.

Fig. 5. The schematic diagram of iron oxides deposited on poly(styrene-divinylbenzene) (St/DVB) matrix.

Fig. 6. (A) Light microscope photograph of SBA (45×); (B) SEM images of SBA and (C) light microscope photograph of HFO/SBA adsorbent (45×); (D) SEM images of HFO/SBA adsorbent.

Fig. 7. Mechanism of arsenic adsorption on magnetite nanoparticles in anaerobic water and air-enriched water.

Fig. 8. The schematic diagram of the adsorption of As(iii) species on nZVI particles.

Fig. 9. Schematic mechanism of As(v) adsorption on Mg–Fe–CO₃²⁻-LDHs.