Abstract
Arsenic (As) is considered one of the most serious inorganic pollutants, and the wastewater produced in some smelters contains a high concentration of arsenic. In this paper, we purified the high-concentration arsenic solution with red mud and Fe3+ synergistically. In this system, arsenite anions reacted with Fe(III) ions to form ferric arsenite, which attached on the surface of red mud particles. The generated red mud/Fe1−x(As)x(OH)3 showed a better sedimentation performance than the pure ferric arsenite, which is beneficial to the separation of arsenic from the solution. The red mud not only served as the carrier, but also as the alkaline agent and adsorbent for arsenic treatment. The effects of red mud dosage, dosing order, pH, and molar ratio of Fe/As on arsenic removal were investigated. The efficiency of arsenic removal increased from a pH of 2 to 6 and reached equilibrium at a pH of 7. At the Fe/As molar ratio of 3, the removal efficiency of arsenic ions with an initial concentration of 500 mg/L reached 98%. In addition, the crystal structure, chemical composition, and morphological properties of red mud and arsenic removal residues (red mud/Fe1−x(As)x(OH)3) were characterized by XRD, XPS, X-ray fluorescence (XRF), SEM-EDS, and Raman spectroscopy to study the mechanism of arsenic removal. The results indicated that most of the arsenic was removed from the solution by forming Fe1−x(As)x(OH)3 precipitates on the red mud surface, while the remaining arsenic was adsorbed by the red mud and ferric hydroxide.
Highlights
Arsenic (As) is considered one of the most serious inorganic pollutants, and the most abundant and potential inorganic carcinogen [1,2]
Ramanasspectroscopy study was done by forming arsenite a red mud (XRF), surface.SEM-EDS, The red mud the carrier to to improve the mechanism of arsenic removal
The pH adjustment caused by red mud or by NaOH has no significant effect on arsenic removal
Summary
Arsenic (As) is considered one of the most serious inorganic pollutants, and the most abundant and potential inorganic carcinogen [1,2]. Minerals 2020, 10, 583 solution with the concentration of arsenic being less than 100 mg/L occurs by the adsorption of iron oxides, such as ferrihydrite, goethite, and ferric oxyhydroxide gel [23–25]. Several researchers have reported formationarsenic of ferric arsenite acidic solutions with high concentrations of arsenic [26]. The removal arsenite-bearing solution withstructure the concentration arsenic highly alkaline solid waste discharged from alumina production, and approximately. Red mud was widely explored for its potential to remove arsenic from water. Ramanasspectroscopy study was done by forming arsenite a red mud (XRF), surface.SEM-EDS, The red mud the carrier to to improve the mechanism of arsenic removal. The effects of red mud dosage, dosing order, pH, and a molar ratio of Fe/As on arsenic removal were investigated. The concentrated sulfuric acid (H2SO4), iron sulfate (Fe2(SO4)3), sodium hydroxide (NaOH), and
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