Effect of Surface Deposition Coating with Aluminum Hydroxide on the Stabilization of Iron–Arsenic Precipitates

Iron–arsenic coprecipitate is a kind of solid waste produced in the treatment of arsenic-bearing wastewater from non-ferrous metallurgy. Stability of amorphous coprecipitates is usually poor if the Fe/As ratio is lower. In this study, the surface of coprecipitates was deposited with aluminum hydroxide with the aim to prevent the release of arsenic. The deposition experiments were carried out at normal temperature using Al2(SO4)3 solutions with pH between the range of 6.0–7.0. The characterization of the coated precipitates was investigated using SEM-EDS, TEM, XRD, FTIR, and BET. The stability experiment showed that the coated precipitates exhibit a higher release of arsenic than the coprecipitates without coating. The anion exchange might have taken place in the coated surface, and the release of arsenic may be a comprehensive result.