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.
Highlights
The current standard for the maximum contaminant level (MCL) of arsenic in drinking water recommended by the World Health Organization (WHO) is 10 mg LÀ1
Iron-based adsorbents have been extensively developed and showed good removal efficiency for arsenic species from water.[44]. Some adsorbents such as granular ferric hydroxide (GFH) and zero-valent iron have been produced on an industrial scale as commercial adsorbents.[45]
The results indicated that an increasing pH decreased the g-FeOOH and increased the Fe3O4/g-Fe2O3 content in the corrosion products of Nanoscale zero-valent iron (nZVI), enhancing the adsorption affinity of nZVI to As(V)
Summary
Arsenic element exists as oxides in the soil, sediments and water in many parts of the world and originates from both natural and anthropogenic activities. There are four chemical oxidation states for arsenic (À3, +3, 0, and +5) in Nature.[1] The most common arsenic compounds that naturally occur are arsenite (H3AsO3 – As(III)) and arsenate (HAsO42À – As(V)). Arsenic can release into the aquatic environments by natural processes such as dissolution of minerals by weathering, microbial activity, and complexation with natural organic materials.[11] On the other hand, anthropogenic activities, including industrial mining and metallurgical industries, combustion of fossil fuels, use of arsenic pesticides, herbicides, and crop desiccants, can result in arsenic contamination in soils and surface water.[12] The microorganism plays an important role in transformation of minerals or weathering of rocks in the geo-aqueous solution.
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