Ammonium Paratungstate Hydrate Crystallization via Continuous Re-extraction
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Solution Overview
Problem
Current processes for producing ammonium paratungstate hydrates and decahydrate suffer from low bulk density, high impurity levels, high energy consumption, and high process costs, with previous methods resulting in finely crystalline products that are difficult to purify and have low crystallization yields.
Innovation Solution
A continuous process involving re-extraction of a tungsten-loaded organic phase with an aqueous ammonia solution in a mixer-settler device, optimizing the NH3:W molar ratio, phase volume ratios, and stirring conditions to achieve direct crystallization of coarsely crystalline, highly pure ammonium paratungstate hydrate with high bulk density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional evaporation crystallization is used to produce ammonium paratungstate, then the process is simple, but the product has low bulk density (0.7-1.03 g/cm³) and fine crystalline morphology
Solution Approach 1:
The invention changes the crystallization parameters by controlling pH (7.0-7.4), temperature (0-25°C), and ammonia-to-tungsten molar ratio (3.6:1 to 50.1:1) during re-extraction to produce coarse crystals with bulk density of 1.7-2.1 g/cm³, resolving the contradiction between process simplicity and product quality
Solution Approach 2:
The invention implements continuous re-extraction followed by continuous crystallization in a controlled environment, maintaining optimal conditions throughout the process to consistently produce high-density coarse crystals without interrupting the production flow
2Manufacturing precision
If liquid-liquid extraction with amine-containing organic phases is used to purify tungsten, then impurity removal is effective, but APW x 10H2O formation deteriorates phase separation and product purity
Solution Approach 1:
The invention performs preliminary re-extraction of tungsten from the organic phase with ammonia solution to form ammonium tungstate, converting the tungsten into a form that precipitates as coarse APW crystals, thereby preventing the formation of fine APW x 10H2O crystals that would interfere with phase separation
Solution Approach 2:
The invention changes the chemical form of tungsten through controlled re-extraction and crystallization at specific pH and temperature conditions, transforming it from a state that forms fine interfering crystals to a state that forms coarse, easily separable crystals
3Quantity of substance
If re-extraction with high NH3:W molar ratio is used, then ammonium tungstate solution is formed, but crystallization yield is low (maximum 65%) and phase separation is slow
Solution Approach 1:
The invention optimizes the NH3:W molar ratio to a specific range (3.6:1 to 50.1:1) and controls pH (7.0-7.4) and temperature (0-25°C) to achieve both complete ammonium tungstate formation and high crystallization yield of coarse crystals with rapid phase separation
Solution Approach 2:
The invention monitors and controls the crystallization process parameters to ensure optimal conditions are maintained, achieving high crystallization yield and fast phase separation through controlled precipitation of coarse crystals
4Ease of manufacture
If conventional processes are used to produce ammonium paratungstate, then production is established, but energy consumption is high due to evaporation concentration
Solution Approach 1:
The invention implements continuous re-extraction and crystallization processes that eliminate the energy-intensive evaporation step, maintaining continuous operation to produce coarse APW crystals directly from solution
Solution Approach 2:
The invention changes the production approach from evaporation-based concentration to controlled crystallization at ambient or low temperatures, dramatically reducing energy consumption while producing high-quality coarse crystals
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process yields highly pure, coarsely crystalline ammonium paratungstate with high bulk density and improved crystallization yield, reducing energy consumption and process complexity while minimizing ammonia usage and impurities.
Implementation Method 1
a liquid-liquid extraction is carried out using amine-containing organic phases
Implementation Method 2
re-extracted by adding dropwise 5-29% NH3 solution
Implementation Method 3
The resulting APW product is finally filtered and dried
Implementation Method 4
APW x 10 H2O during slow evaporation of an ammonium tungstate solution made from WO3 and NH3 solution, emerges
Implementation Method 5
The purified solution is usually concentrated by evaporation, with APW ultimately crystallizing out
Implementation Method 6
phase separation during re-extraction
Data Source
Figure 1~2
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AI summary
A method for continuous production of ammonium paratungstate hydrates by back extraction of a tungsten-containing organic phase with an aqueous ammonia solution. It is possible to directly produce coarse crystalline ammonium paratungstate hydrates on back extraction by selection of suitable method parameters. The above crystallise in high purity and in high yield. The production method can be carried out in a simple and energy-efficient manner.