Packed Bed Column for Adsorption of Arsenic on Mixed-Valent Iron [Fe(II)-Fe(III)] Oxide Synthesized from Industrial Waste

Abstract

Hundreds of millions of people in the world regularly intake groundwater that has a high-risk arsenic level. In several parts of Asia, the arsenic concentration reaches up to 1,000 μg/L, which is above the drinking water standards of the World Health Organization (10 μg/L). The present study discusses the arsenic removal from groundwater using a mixed-valent iron [Fe(II)-Fe(III)] oxide, commonly known as magnetite. Mixed-valent iron [Fe(II)-Fe(III)] oxide particles were synthesized from iron oxide waste that was obtained from the steel industry. Six column reactors were operated based on different operational variables, such as amount of adsorbent, particle size, initial arsenic concentration, empty bed contact time (EBCT), and flow rate. Four columns were continuously operated for 44 days, and two columns were operated for 80 days. The adsorption profile was maintained well for all the reactors with more than 98% arsenic removal efficiency from influent water. The shorter breakthrough curve was achieved for the columns operated with a higher influent arsenate concentration as compared with the columns operated with a low influent arsenate concentration. Moreover, the longer breakthrough curve was achieved for the column packed with a higher quantity of adsorbent. The column operated with a low EBCT and high flow rate resulted in the earlier breakthrough because arsenate ions did not get adequate time to bind at the adsorption sites and, subsequently, excited the column before it reached the state of equilibrium.