选择性磷酸沉淀分离铬铁的新工艺

针对酸性水溶液中铬铁分离难题，基于Fe3+还原预处理，提出选择性磷酸沉淀铬分离铬铁的方法。研究沉淀剂Na₃PO₄用量、溶液初始pH值、反应温度及保温时间等对铬铁分离的影响，所得较优工艺条件为:溶液初始pH值为2.0，按PO₄3-/Cr3+摩尔比0.375的量加入Na₃PO₄，90 ℃保温60 min。在上述条件下，铬沉淀率可达98.53%，铁沉淀率仅1.42%，分离效果理想。实验还证明，该方法适用于较宽的铁浓度范围，而且Cu2+、Zn2+、Ni2+及Cl-等杂质离子对选择性沉铬无明显干扰。该方法为含铬物料的铬分离提取提供了一条新的可选途径。 

A new process for separation of chromium from iron by selective phosphate precipitation

The selective phosphate precipitation process is proposed for the effective Cr/Fe separation in acidic solutions after the pretreatment of Fe3+reduction. The effects of dosage of Na3PO4 as the precipitant, the initial pH, reaction temperature and time on Cr/Fe separation are experimentally studied. The optimal conditions are determined as follows: initial pH of 2.0, PO43-/Cr3+molar ratio of 0.375, reaction temperature of 90 ℃, reaction time of 60 min. Under the above conditions, the precipitation of Cr is achieved as 98.53 %while that of Fe is only 1.42 %. This new process is proved to be applicable to a wide range of Fe concentration of the solutions and the impurities, such as Cu2+, Zn2+, Ni2+and Cl-have no obvious effects on the selective precipitation of Cr, which provides a new alternative process for the separation and resourcelization of Cr from Cr-containing materials.