无机盐工业

无机盐工业 ›› 2021, Vol. 54 ›› Issue (4): 48-51.doi: 10.11962/1006-4990.2020-0253

• 研究与开发 • 上一篇    下一篇

湿法磷酸选择性除杂制工业级磷酸二氢铵

王智娟   

  1. 曲靖师范学院化学与环境科学学院, 云南曲靖 655000
  • 收稿日期:2020-10-13 出版日期:2021-04-01 发布日期:2021-04-23
  • 作者简介:王智娟(1984— ),女,硕士,讲师,研究方向为磷化工;E-mail: boying2004@163.com
  • 基金资助:
    国家自然科学基金项目(21978153);云南省高校本科教育教学改革研究项目(JG2018198);曲靖师范学院教学成果奖培育项目(JPCGPY201801)

Fabrication of industrial grade ammonium dihydrogen phosphate via selective removal of impurities from wet-process phosphoric acid

Zhijuan Wang   

  1. Faculty of Chemistry and Environment Science, Qujing Normal University, Qujing 655000, China
  • Received:2020-10-13 Online:2021-04-01 Published:2021-04-23

摘要:

以湿法磷酸为原料, 通过氟化钠选择性沉淀金属离子, 使其以NaMgAl(F, OH)6·H2O和XMgAlF6(X=Na +、K +、NH4 +)非含磷沉淀析出, 再通氨中和制得工业级磷酸二氢铵。分析了氟化钠加入量对杂质脱除(Na、K、Al、Mg、Fe和Ca等金属阳离子)及液相氟残留的影响, 结果表明氟化钠与磷酸质量比(mNaF/m)为2.5%时, 效果较好, 此条件下制得的磷酸二氢铵纯度和五氧化二磷收率分别达到98.53%和86.2%。

关键词: 湿法磷酸, 磷酸二氢铵, 除杂

Abstract:

Ammonium dihydrogen phosphate with high purity can be used as water-soluble fertilizer, flame retardant, feed and food additives and recently it has been studied for preparation of phosphate optical glass, cathode materials for lithium batteries and nonlinear optical materials.Due to its broad application prospect in the fields of agriculture, fire protection, food and materials, the demand for high purity ammonium dihydrogen phosphate is increasing.High purity ammonium dihydrogen phosphate can be fabricated via thermal phosphoric acid and extraction-purified wet-process phosphoric acid route.The formerroute is simple and can get high quality of product, but it is restricted to the influence of resources, energy and environment.While the latter route is complex and needs large investment.Hence, more researchers focus on the direct preparing high purity ammonium dihydrogen phosphate with raw wet-process phosphoric acid.But the lower P2O5 yield of product(25%~40%)inhibited its development due to the formation of a large amount of phosphorus-containing precipitates(e.g., metallic phosphate) during ammoniation.Therefore, herein modified-process with sodium fluoride was used to selectively precipitate metalcations to compounds containing no phosphorus(e.g., (NH4x(Mg)y(Al)zF6(OH)6·2H2O, NaMgAlF6·XH2O, MgAl2F8, MgAlF5)before ammoniation and thus to promote P2O5 yield of the product.Meanwhile, the dosage of NaF was optimized.The influence of NaF on the XRD patterns and morphologies of precipitates, removal of cations and the residual fluoride content in phosphoric acid was analyzed.When mNaF/m(mass ratio of NaF to H3PO4 solution) was lower than 3.5%, precipitates mainly existed as NaMgAl(F, OH)6·H2O, XMgAlF6(X=K+or NH4 +).While mNaF/m was increased, the diffraction peaks intensity of NaMgAlF6 gradually increased.When mNaF/m was further increased to 6.0%, calcium-containing silicate or aluminate salts phases appeared.Significantly, the adding amount of NaF also influenced the filtration performance.The content of metal cations in phosphoric acid decreased with the increase of NaF content.When mNaF/m was 6.0%, the content of Mg, Al, Fe, K, Na and Ca was decreased to 0.029%, 0.002 7%, 0.012%, 0.014%, 0.018% and 0.037%, respectively.Albeit higher mNaF/m would result in higher removal efficiency of metal cations, the effect of NaF on the residual fluoride content in phosphoric acid was significant.When mNaF/m was in the range of 1.2%~2.5%, there were no obvious differences in residual fluorine content of phosphoric acid, but further increased to 5%, the residual fluorine content in phosphoric acid was sharply increased from 0.148% to 0.331%.Hence, balancing the removal efficiency of metal cations and residual fluorine content in phosphoric acid, mNaF/m was fixed at 2.5% for the following fabrication of ammonium dihydrogen phosphate.Ammonium dihydrogen phosphate with a purity of 98.53% was produced with a high P2O5 recovery ratio of 86.2% and low residual fluorine content of 0.23%, which met the class Ⅱ standard of industrial grade ammonium dihydrogen phosphate.

Key words: wet-process phosphoric acid, ammonium dihydrogen phosphate, removal of impurities

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