Highly efficient sorption and immobilization of gaseous arsenic from flue gas on MnO2/attapulgite composite with low secondary leaching risks

Abstract

Some sorbents have been developed for arsenic (As) compounds capture from flue gas . However, most of the conventional sorbents have cost constraints and can cause secondary pollution due to the leaching of arsenic after use. To solve this problem, a new and highly efficient adsorbent for gaseous arsenic was successfully developed in this paper with excellent immobilization performance and low-cost. A series of Mn-supported attapulgite (ATP) composites were fabricated, characterized, and investigated for arsenic capture. The modification of ATP with Mn not only considerably enhanced the adsorption efficiency but also stabilized the adsorbed As in the spent sorbents. SO 2 in flue gas promoted the adsorption performance through As-sulfate binding, whereas NO was beneficial for the oxidation of As(III) to As(V) on the surface of Mn-modified ATP. The incorporation of Mn with ATP generated abundant hydroxylate (OH − ) from hydration and accelerated the formation of As-sulfate compounds, which was beneficial for physical encapsulation . The results of the toxicity characteristic leaching procedure and sequential extraction test revealed that adsorbed As could be considerably immobilized by the sorbent with low leaching ability. Mn modification changed more As into inert fractions and consequently inhibited release from spent sorbents, which considerably reduced the risks of secondary pollution. The developed composite can be potentially used as a new efficient sorbent for gaseous arsenic capture in flue gas. • Manganese modification effectively enhanced the capacity of ATP for gaseous arsenic removal in flue gas. • Trivalent arsenic was oxidized into pentavalent arsenic during the process. • Manganese oxides facilitated the transformation of adsorbed-arsenic on Mn-ATP from leachable fraction to inert fraction.