Effect of Na and K on crystallization and their precipitation behavior during APT preparation from AMT solution

IF 4.6 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

International Journal of Refractory Metals & Hard Materials Pub Date : 2025-09-09 DOI:10.1016/j.ijrmhm.2025.107438

Liming Zhang, Leiting Shen, Qiusheng Zhou, Tiangui Qi, Zhihong Peng, Guihua Liu, Xiaobin Li

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引用次数: 0

Abstract

Understanding the precipitation behavior of impurities Na and K during crystallization is fundamental to produce high-quality ammonium paratungstate (APT). Based on the proposed near-equilibrium technology of APT preparation via employing ammonium metatungstate (AMT) solution as an intermediate, this study systematically investigated the impact of impurities Na and K on ammoniating crystallization. The results demonstrated that impurities Na and K significantly affected the phase and the morphology of crystalline product, but had a weak influence on crystallization efficiency. Na and K entered the product in the form of (NH₄)₈Na₂[H₂W₁₂O₄₂]·12H₂O and (NH₄)₈K₂[H₂W₁₂O₄₂]·4H₂O, respectively. Specifically, crystalline products were primarily hexagonal sheet crystals of (NH₄)₈Na₂[H₂W₁₂O₄₂]·12H₂O at 40 °C, and cubic crystals of (NH₄)₁₀[H₂W₁₂O₄₂]·4H₂O and (NH₄)₈K₂[H₂W₁₂O₄₂]·4H₂O at >70 °C. During ammoniating crystallization, element K was more readily precipitated than Na under optimized conditions. The mechanism of ammoniating crystallization with impurities Na and K was concluded as the transformation of metatungstate ion to paratungstate ion and the combination of paratungstate ion with NH₄⁺, K⁺ or Na⁺ to precipitate low-solubility paratungstates. Compared to evaporation crystallization mainly used in current industry, Na and K were less likely to enter the product during ammoniating crystallization.

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在AMT溶液中制备APT时，Na和K对结晶和沉淀行为的影响

了解杂质Na和K在结晶过程中的析出行为是生产高质量仲钨酸铵的基础。本研究基于提出的以偏钨酸铵（AMT）溶液为中间体制备APT的近平衡工艺，系统研究了杂质Na和K对氨化结晶的影响。结果表明，杂质Na和K对结晶产物的物相和形貌有显著影响，但对结晶效率的影响较小。Na和K分别以（NH4）8Na2[H2W12O42]·12H2O和（NH4）8K2[H2W12O42]·4H2O的形式进入产物。具体而言，结晶产物主要为（NH4）8Na2[H2W12O42]·12H2O的六角形片状晶体，以及（NH4）10[H2W12O42]·4H2O和（NH4）8K2[H2W12O42]·4H2O的立方晶体。在氨化结晶过程中，优化条件下K元素比Na元素更容易析出。杂质Na和K的氨化结晶机理为偏钨酸盐向仲钨酸盐转化，仲钨酸盐与NH4+、K+或Na+结合沉淀低溶解度的仲钨酸盐。与目前工业上主要采用的蒸发结晶相比，在氨化结晶过程中Na和K进入产品的可能性较小。

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来源期刊

$International Journal of Refractory Metals & Hard Materials$

International Journal of Refractory Metals & Hard Materials 工程技术-材料科学：综合

CiteScore

7.00

自引率

13.90%

发文量

236

审稿时长

35 days

期刊介绍： The International Journal of Refractory Metals and Hard Materials (IJRMHM) publishes original research articles concerned with all aspects of refractory metals and hard materials. Refractory metals are defined as metals with melting points higher than 1800 °C. These are tungsten, molybdenum, chromium, tantalum, niobium, hafnium, and rhenium, as well as many compounds and alloys based thereupon. Hard materials that are included in the scope of this journal are defined as materials with hardness values higher than 1000 kg/mm2, primarily intended for applications as manufacturing tools or wear resistant components in mechanical systems. Thus they encompass carbides, nitrides and borides of metals, and related compounds. A special focus of this journal is put on the family of hardmetals, which is also known as cemented tungsten carbide, and cermets which are based on titanium carbide and carbonitrides with or without a metal binder. Ceramics and superhard materials including diamond and cubic boron nitride may also be accepted provided the subject material is presented as hard materials as defined above.