Arsenate and Arsenite Removal by Zerovalent Iron:  Kinetics, Redox Transformation, and Implications for in Situ Groundwater Remediation

Abstract

Batch tests were performed utilizing four zerovalent iron (Fe0) filings (Fisher, Peerless, Master Builders, and Aldrich) to remove As(V) and As(III) from water. One gram of metal was reacted headspace-free at 23 degrees C for up to 5 days in the dark with 41.5 mL of 2 mg L(-1) As(V), or As(III) or As(V) + As(III) (1:1) in 0.01 M NaCl. Arsenic removal on a mass basis followed the order: Fisher > Peerless Master Builders > Aldrich; whereas, on a surface area basis the order became: Fisher > Aldrich > Peerless Master Builders. Arsenic concentration decreased exponentially with time, and was below 0.01 mg L(-1) in 4 days with the exception of Aldrich Fe0. More As(III) was sorbed than As(V) by Peerless Fe0 in the initial As concentration range between 2 and 100 mg L(-1). No As(III) was detected by X-ray photoelectron spectroscopy (XPS) on Peerless Fe0 at 5 days when As(V) was the initial arsenic species in the solution. As(III) was detected by XPS at 30 and 60 days present on Peerless Fe0, when As(V) was the initial arsenic species in the solution. Likewise, As(V) was found on Peerless Fe0 when As(II) was added to the solution. A steady distribution of As(V) (73-76%) and As(III) (22-25%) was achieved at 30 and 60 days on the Peerless Fe0 when either As(V) or As(III) was the initial added species. The presence of both reducing species (Fe0 and Fe2+) and an oxidizing species (MnO2) in Peerless Fe0 is probably responsible for the coexistence of both As(V) and As(III) on Fe0 surfaces. The desorption of As(V) and As(III) by phosphate extraction decreased as the residence time of interaction between the sorbents and arsenic increased from 1 to 60 days. The results suggest that both As(V) and As(III) formed stronger surface complexes or migrated further inside the interior of the sorbent with increasing time.

Removal of arsenic from water by electrocoagulation

“…As(III) and As(V) removals by iron oxides normally behave differently at different pH (Edwards, 1994;Hering et al, 1996;Bose and Sharma, 2002). Su and Puls (2001) have reported that As(III) shows greater removal than As(V), and mixture of As(V) and As(III) showed intermediate removal by iron oxides. It has been reported that pH is an important operating factor influencing the performance of electrocoagulation process (Chen et al, 2000).…”

“…They reported that As(III) and As(V) normally behave differently in terms of pH on the adsorption on hydrous ferric oxides. Some investigators have reported that favorable adsorption of As(V) on to hydrous ferric oxides at pH < 7 (Farrell et al, 2001;Su and Puls, 2001), while others have reported more favorable adsorption of As(III) at pH > 7 (Jain et al, 1999) and equal amounts of As(V) and As(III) adsorption below pH 7 (Su and Puls, 2001). Therefore the adsorption capacities of As(III) and As(V) in electrocoagulation and chemical coagulation were investigated.…”

“…The commonly used technologies include coagulation and precipitation with iron and aluminum salts (Edwards, 1994;Hering et al, 1996), adsorption onto activated alumina, activated carbon and activated bauxite (Gupta and Chen, 1978), ion exchange and reverse osmosis (Clifford, 1999). Some recent treatment technologies based on oxidation and adsorption are green sand filtration (Christen, 2000), iron oxide coated sand (Joshi and Chaudhuri, 1996), manganese dioxide coated sand (Bajpai and Chaudhuri, 1999), ferruginous manganese ore (Chakravarty et al, 2002), ferrihydrite (Jain et al, 1999), clay minerals (Manning and Goldberg, 1997) and zero-valent iron (Fendorf et al, 1997;Farrell et al, 2001;Su and Puls, 2001). Coagulation, precipitation and other adsorption techniques such as, activated alumina, and activated carbon, have been found to be not as efficient for As(III) removal as for As(V) removal.…”

“…Recently arsenic removal by zero-valent iron has also been reported (Farrell et al, 2001;Krishna et al, 2001;Su and Puls, 2001). In this method, iron oxide produced due to corrosion of iron filings removed both As(III) and As(V) from the contaminated drinking water.…”

Calcite precipitation dominates the electrical signatures of zero valent iron columns under simulated field conditions

“…The zero valent iron (ZVI) permeable reactive barrier (PRB) is an in-situ technology for the remediation of heavy metals, chlorinated hydrocarbons and radioactive materials in groundwater (Gillham and Ohannesin, 1994;Gu et al, 1998;Su and Puls, 2001;Agrawal et al, 2002). Although encouraging treatment efficiency has been documented (Gu et al, 1998;Morrison et al, 2001;Su and Puls, 2003), reactions between ZVI and groundwater constituents causing ZVI corrosion and subsequent secondary mineral precipitation contribute to long term performance reduction of ZVI PRBs (Liang et al, 2003;Slater and Binley, 2003;Wilkin et al, 2003;Jin Suk et al, 2009).…”