Abstract:

In the process of wet-process phosphoric acid leaching, the product phosphoric acid appears black due to the incomplete carbonization of some organic matter. A novel type of catalytic oxidation wet-process phosphoric acid purification technology was proposed in this work. During the leaching process, the oxidant (H₂O₂) and catalyst (MnO₂) was added to form the peroxides such as ·OH and HO₂· in the transformation process, which can enhance the removal rate of organic matter and strengthen the leaching rate of phosphate rock. The different reaction conditions that affected the leaching rate of wet-phosphoric acid and the removal of organic matter were investigated. The results indicated that 96.9% of phosphate rock were leached under the optimum conditions of H₂O₂ dosage 0.08 ml/g, MnO₂/P mass ratio of 0.04, 80℃ and for 40 min. At the same time, the TOC remove rate reached 79%. The analysis mechanism showed that H₂O₂ will form H₃PO₄ · H₂O₂ peroxide with H₃PO₄ in the solution, and MnO₂ will react with it like Fenton to generate a large amount of ·OH, and then fully oxidized the black organic matter into CO₂ and H₂O. Organic matter “wrapped” on the surface of the phosphate rock is broken by ·OH, which promoted the leaching of phosphoric acid and enhanced the removal of organic matter.

Key words: wet-process phosphoric acid, black organic matter, catalytic oxidation

摘要：

在湿法磷酸浸出过程中由于部分有机物碳化不彻底，使产品磷酸呈现黑色。本文提出了一种新型的催化氧化湿法磷酸净化技术，即在湿法磷酸浸出过程中引入氧化剂（H₂O₂）及催化剂（MnO₂），基于转化过程中形成的·\mathrm{O}\mathrm{H}和\mathrm{H}{\mathrm{O}}_{\mathrm{2}}·等过氧化物实现对有机物的去除与浸出过程的强化。重点考察不同反应条件对湿法磷酸浸出率及有机质去除的影响。结果表明，浸出时间为40 min、反应温度为80℃、H₂O₂用量为0.08 ml/g、催化剂与磷矿的质量比为0.04时，磷矿浸出率可达96.9%；同时测定得到的TOC去除率达到79%。分析机理可得，H₂O₂会与溶液中的H₃PO₄形成H₃PO₄·H₂O₂过氧化物，MnO₂与之发生类Fenton反应，产生大量·\mathrm{O}\mathrm{H}，进而将黑色有机物充分氧化为CO₂和H₂O，打破有机物对磷矿颗粒表面的“包裹”，促进磷酸的浸出和有机物的去除。

关键词: 湿法磷酸, 黑色有机物, 催化氧化