title: Immobilization mechanisms of arsenate in iron hydroxide sludge stabilized with cement.
abstract: Leaching tests, Fourier transform infrared spectroscopy (FTIR), extended X-ray absorption fine structure (EXAFS) spectroscopy, and thermodynamic modeling were performed to investigate arsenate [As(V)] immobilization mechanisms in iron hydroxide sludge stabilized with cement. The sludge from a groundwater remediation site in Tacoma, WA was mixed and immobilized with premixed cement to reach cement-to-sludge ratios of 2.5, 3.3, 5, 10, and 20 (wt premixed cement/wt dry sludge). The EXAFS analysis determined that As(V) formed bidentate mononuclear complexes on the iron hydroxide surface in the sludge. The adsorbed As(V) had a characteristic FTIR band at 830 cm(-1). Cement treatment converted the adsorbed As(V) to calcium arsenate precipitate with a FTIR peak at 860 cm(-1). The chemical forms of the As(V) were incorporated in an adsorption triple layer model (TLM) to describe the leaching behavior of As(V) in a pH range between 3 and 12. Cement treatment significantly reduced arsenic mobility because of the formation of the sparingly soluble calcium arsenate.
authors: Center for Environmental Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA.
authors: Chuanyong
authors: C
authors: Jing
authors: George P
authors: GP
authors: Korfiatis
authors: Xiaoguang
authors: X
authors: Meng
mesh_terms: D001149:Arsenates / Q000737:chemistry; D001151:Arsenic / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry; D003252:Construction Materials; D005290:Ferric Compounds / Q000737:chemistry*; D008962:Models, Theoretical; D012037:Refuse Disposal / Q000379:methods*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D001149:Arsenates; D017610:Calcium Compounds; D005290:Ferric Compounds; C021024:ferric hydroxide; C045817:calcium arsenate; D001151:Arsenic