Calcium Fluoride Seeded Crystallization for Fluorine Wastewater Recovery
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Solution Overview
Problem
Existing methods for recovering fluorine from fluorine-containing wastewater face challenges such as complex process flows, difficulty in ensuring the quality of calcium fluoride recovery, and the risk of secondary pollution, with existing calcium fluoride products having low purity and high moisture content.
Innovation Solution
A method involving impurity removal, activation of calcium fluoride seed crystals, controlled addition of seed crystals and crystal growth promoters, and precise pH and temperature adjustments to produce large-particle calcium fluoride, ensuring homogeneous nucleation and avoiding heterogeneous nucleation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional chemical precipitation method is used to treat fluorine-containing wastewater, then fluorine removal is achieved, but the produced sludge has high water content and low purity calcium fluoride
Solution Approach 1:
The patent applies preliminary action by adding seed crystals before the main precipitation reaction occurs. This allows the calcium fluoride to nucleate and grow on the seed crystal surfaces rather than forming new particles, ensuring high purity from the start. The seed crystals are added to the wastewater before adjusting pH to initiate precipitation, which directs the precipitate to deposit on existing crystals rather than forming impure sludge.
Solution Approach 2:
The patent uses seed crystals as an intermediary substance to mediate the precipitation process. These seed crystals act as a template or mediator that guides the deposition of calcium fluoride, ensuring that the precipitate forms as high-purity crystalline material rather than amorphous sludge. The seed crystals intermediate between the reactants and the final product, controlling the crystallization process to achieve both removal efficiency and product purity.
2Reliability
If conventional flocculation precipitation method is used, then fluorine removal is achieved, but a large amount of sludge with high water content is produced
Solution Approach 1:
The patent applies preliminary action by adding seed crystals before the main precipitation reaction occurs. This allows the calcium fluoride to nucleate and grow on the seed crystal surfaces rather than forming new particles, ensuring high purity from the start. The seed crystals are added to the wastewater before adjusting pH to initiate precipitation, which directs the precipitate to deposit on existing crystals rather than forming impure sludge.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the pH value during precipitation. The pH is adjusted to a specific range (7-9) to optimize calcium fluoride precipitation while minimizing sludge formation. This parameter control ensures that the reaction produces compact, filterable crystals rather than voluminous sludge, reducing the quantity of waste material while maintaining removal efficiency.
3Loss of substance
If existing recovery methods are used, then fluorine recovery is attempted, but the process flow becomes complex and quality control becomes difficult
Solution Approach 1:
The patent applies segmentation by dividing the recovery process into distinct, manageable stages: (1) adding seed crystals, (2) adjusting pH to initiate precipitation, (3) aging the mixture, and (4) filtration and drying. Each stage is simple and well-defined, avoiding the need for complex multi-step processes. This segmented approach maintains fluorine recovery while keeping the process flow simple and quality control straightforward.
Solution Approach 2:
The patent uses seed crystals as an intermediary substance to mediate the precipitation process. These seed crystals act as a template or mediator that guides the deposition of calcium fluoride, ensuring that the precipitate forms as high-purity crystalline material rather than amorphous sludge. The seed crystals intermediate between the reactants and the final product, controlling the crystallization process to achieve both removal efficiency and product purity.
4Loss of substance
If existing recovery methods are used, then fluorine recovery is attempted, but secondary pollution risks increase
Solution Approach 1:
The patent applies blessing in disguise by converting the potential harm of waste sludge disposal into a benefit. Instead of producing harmful sludge that requires complex treatment and disposal, the process produces high-purity calcium fluoride crystals that can be directly filtered, dried, and reused. The precipitate becomes a valuable product rather than a pollutant, eliminating secondary pollution risks while achieving fluorine recovery.
Solution Approach 2:
The patent uses seed crystals as an intermediary substance to mediate the precipitation process. These seed crystals act as a template or mediator that guides the deposition of calcium fluoride, ensuring that the precipitate forms as high-purity crystalline material rather than amorphous sludge. The seed crystals intermediate between the reactants and the final product, controlling the crystallization process to achieve both removal efficiency and product purity.
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
The method achieves high-purity, large-particle calcium fluoride recovery with a simple process, meeting discharge standards and avoiding secondary pollution, while ensuring effective crystal growth and product quality.
Implementation Method 1
activating a seed crystal containing calcium fluoride
Implementation Method 2
adjusting a pH value of the reaction solution at a preset reaction temperature, and performing a stirring on the reaction solution, and then performing a settling
Implementation Method 3
adding the activated seed crystal to the pure fluorine-containing wastewater, and adding a calcium-containing regulator according to a preset calcium-fluorine ratio, and then adding a crystal growth promoter
Implementation Method 4
performing a settling, a filtering and a drying on the reaction solution to obtain the large-particle calcium fluoride
Data Source
Figure 1~2
Figure 3~4
AI summary
A method for recovering a large-particle calcium fluoride from a fluorine-containing wastewater according to some embodiments of the invention comprises: performing an impurity removal treatment on the fluorine-containing acidic wastewater to obtain a pure fluorine-containing wastewater; activating a seed crystal containing calcium fluoride to obtain an activated seed crystal; adding the activated seed crystal into the pure fluorine-containing wastewater, and adding a calcium-containing regulator according to a preset calcium-fluorine ratio, and then adding a crystal growth promoter at a preset mass ratio to obtain a reaction solution; and adjusting a pH value of the reaction solution at a preset reaction temperature, and performing a stirring on the reaction solution, and then performing a settling, a filtering and a drying on the reaction solution to obtain the large-particle calcium fluoride, wherein the addition amount of the activated seed crystal ranges from 5 times to 10 times a concentration of fluorine ions in the pure fluorine-containing wastewater.