Gypsum is a high-volume by-product of hydrometallurgical arsenic removal using the Fe(III)-As(V) coprecipitation technique. However, the role of gypsum in As fixation during the Fe(III)-As(V) coprecipitation process and the potential risk of As-bearing gypsum are still not well known. In this study, the fixation of As by gypsum was quantitatively investigated as a function of the initial As and H₂SO₄ concentrations, Fe/As molar ratio, pH, and neutralization mode. Column leaching tests were also performed to evaluate the potential risk of Fe(III)-As(V) coprecipitates. The results showed that the gypsum isolated from Fe(III)-As(V) coprecipitates by ascorbic acid (VC) treatment could fix up to 4.5 % of the total As in the system at pH 8 in fixed-pH mode. The gypsum produced in fixed-pH mode contained a significantly higher concentration of As than that produced in acid-alkaline neutralization mode. The column leaching tests showed that a faster leaching rate could enhance the release of As from Fe(III)-As(V) coprecipitates. It seems that the presence of gypsum could prevent the release of As from Fe(III)-As(V) coprecipitates. Linear combination fits of the As and Fe K-edge XANES spectra suggested that As was likely to occur as adsorbed As and yukonite in VC-isolated gypsum.

石膏是使用Fe（III）-As（V）共沉淀技术去除湿法冶金砷的大量副产品。然而，在Fe（III）-As（V）共沉淀过程中，石膏在As固定中的作用以及含As的石膏的潜在危险仍不为人所知。在这项研究中，作为初始As和H ₂ SO ₄的函数，对石膏对As的固定作用进行了定量研究。浓度，Fe / As摩尔比，pH和中和模式。还进行了柱浸试验，以评估Fe（III）-As（V）共沉淀物的潜在风险。结果表明，在固定pH模式下，通过抗坏血酸（VC）处理从Fe（III）-As（V）共沉淀物中分离出的石膏可固定高达4.5％的系统中总As。在固定pH模式下产生的石膏比在酸碱中和模式下产生的砷浓度高得多。柱浸出试验表明，更快的浸出速率可以增强As从Fe（III）-As（V）共沉淀物中的释放。似乎石膏的存在可以阻止As从Fe（III）-As（V）共沉淀物中释放出来。As和Fe K的线性组合拟合边XANES光谱表明，在VC隔离石膏中，As可能以吸附的As和约克沸石的形式出现。