Lime neutralization and coprecipitation of As(Ⅴ) with iron(Ⅲ) are regarded as the most effective and economical method for the removal and immobilization of arsenic from mineral processing solutions and effluents and widely used in hydrometallurgical industry.However, the effect of gypsum crystallization during the coprecipitation process on arsenic removal is still unknown.This work investigated the incorporation of arsenate into gypsum during the crystallization process at various pH.XRD, FTIR and SEM were employed to characterize the coprecipitated solids.