Abstract
The present study investigated the effects of Fe/SiO2 ratio (0.8−1.6) and cooling methods (quenching and cooling with furnace) on the stability of As in typical copper smelting slag (FeO−SiO2−Fe2O3−CaO−MgO−Al2O3). It was determined that iron silicate slag can achieve As vitrification. In addition, the lower Fe/SiO2 contributed to the immobilization and reduced the leaching toxicity of As. FTIR analysis showed that the increase of Fe/SiO2 caused to the depolymerization of the glass structure and promoted the formation of [AlO6]9− octahedra. XPS spectra of O1s and Si2p showed that the amount of non-bridging oxygen (NBO) in the melt increases with increasing Fe/SiO2. In addition, Al2p and As3d spectra indicate that the covalency between the As−O and Al−O bonds decreased with increasing Fe/SiO2 to accommodate glass depolymerization. For the slow-cooled slag, As was mainly enriched in the iron olivine phase, with a small fraction in the silicate matrix. The increase of Fe/SiO2 promoted the precipitation of iron olivine phase and thus the leaching concentration of As increased with the increase of Fe/SiO2.
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