Abstract: Iron(III)-arsenate coprecipitation is widely practiced for the removal and immobilization of arsenic from mineral processing solutions and effluents in hydrometallurgical industry. However, the role of gypsum in the fixation of arsenic in the coprecipitation process is still unknown. In this study, the gypsum generated during ironarsenate coprecipitation process was isolated by ascorbic acid leaching and the content of arsenic, the mass of the gypsum and the percentage of arsenic fixed by gypsum were determined. The effects of initial arsenic and sulfuric acid concentrations and Fe/As molar ratio were investigated. The results showed that the content and the percentage of arsenic fixed by gypsum increased significantly with the increase of coprecipitation pH. Raising the initial arsenic concentration of the starting solution would increase the arsenic content in gypsum. The generated gypsum contained lower content of arsenic at higher concentration of sulfuric acid or greater Fe/As molar ratios, but fixed higher percentage of arsenic from the starting solution. The findings in this work have important implications to a better understanding of the speciation of arsenic in the coprecipitates and their environmental risk assessments.

Key words: clipping, saline-alkali stress, nitrogen allocation, Leymus chinensis, compensatory growth