Mitigation of Arsenic Pollution by using Iron-based Nano-adsorbents

Abstract

Inorganic and organic forms of arsenic (As) are naturally distributed in the biosphere. However, anthropogenic sources like mining and metallurgical processes are responsible for the enrichment of arsenic compounds in the environment. Specifically, inorganic forms of arsenic show acute health related issues on animals and human beings through polluting aqueous and terrestrial ecosystems. Adsorption is considered a promising treatment method to abate arsenic pollution in water due to its numerous admirable advantages. Natural materials, waste derived materials, carbon-based materials, nanostructured metal, metal compounds, etc., have been evaluated as adsorbents for the arsenic removal process. The present chapter exclusively focuses on nanostructured iron-based adsorbents for abatement of arsenite (AsO3− 3 or As(III)) and arsenate (AsO3− 4 or As(V)) contamination in water. Arsenic removal capacities of iron(III) oxides, iron(III, II) oxides, spinel ferrites, iron hydroxide, iron oxyhydroxides, iron carbonate, and zero-valent iron are described. Defect creation, metal ion doping, surface functionalization, adsorbent activation by oxidants, and composite formation are the important improvement strategies for iron-based adsorbents. Meanwhile, the effect of experimental conditions, including pH, temperature, contact time, and interfering ions on iron-based adsorbents, were also discussed. Arsenic adsorption on iron-based adsorbents happens through physisorption, chemisorption, ion exchange, and precipitation. Separation and regeneration of iron-based adsorbents after the adsorption equilibrium process were also outlined.