Electronic-Grade HF and Nitric Acid Recovery via Salt-Assisted Distillation
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Solution Overview
Problem
Existing methods fail to effectively separate and regenerate high-purity hydrofluoric acid and nitric acid from waste acid solutions containing hydrofluoric acid, nitric acid, and water, due to the formation of azeotropes, limiting their application and economic benefits.
Innovation Solution
A method involving the use of alkali metal salts to break azeotropes in waste acid solutions, followed by distillation and condensation treatments, to obtain high-purity electronic grade hydrofluoric and nitric acids, with recycling of residual salts to enhance efficiency and reduce environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods (sulfuric acid treatment, vacuum evaporation, ion exchange, solvent extraction, electrodialysis) are used to treat waste acid solution, then the treatment process can be performed, but high-purity hydrofluoric acid and nitric acid cannot be effectively separated and regenerated due to azeotrope formation
Solution Approach 1:
The patent introduces alkali metal salts (such as lithium chloride, potassium chloride, or sodium chloride) as intermediary substances to break the azeotrope between hydrofluoric acid and water. These salts act as mediators that alter the vapor-liquid equilibrium relationship, enabling effective separation of hydrofluoric acid from the waste acid solution through distillation, thereby achieving high-purity recovery that conventional methods cannot accomplish.
Solution Approach 2:
The patent changes the chemical composition parameters of the waste acid solution by adding alkali metal salts, which modifies the azeotropic composition and boiling point characteristics. This parameter change allows the system to operate outside the constrained azeotropic region, enabling distillation to produce hydrofluoric acid with purity exceeding 99%, thus resolving the limitation of conventional methods.
2Manufacturing precision
If alkali metal salts are added to break azeotrope and perform distillation treatment, then high-purity hydrofluoric acid can be obtained, but the process complexity and number of steps increase
Solution Approach 1:
The patent combines multiple functions into a single distillation process: the alkali metal salts simultaneously break the azeotrope and serve as boiling point elevators, while the distillation tower performs both separation and concentration in one operation. This merging of functions achieves high-purity hydrofluoric acid production without requiring multiple sequential treatment steps, thereby reducing overall process complexity.
Solution Approach 2:
The patent recycles the alkali metal salts from the distillation residue back into the waste acid solution for continuous azeotrope breaking. This recovery and reuse eliminates the need for continuous addition of fresh salts and reduces waste disposal requirements, simplifying the overall process while maintaining high-purity product output.
3Loss of substance
If conventional treatment methods are used, then resource waste occurs and environmental pollution increases, but the treatment cost and energy consumption are not significantly reduced
Solution Approach 1:
The patent utilizes the phase transition (vaporization and condensation) of hydrofluoric acid during distillation to achieve separation and concentration in one step. By operating at controlled temperatures and pressures, the process efficiently transitions hydrofluoric acid from liquid to vapor and back to condensed liquid form, minimizing energy consumption while achieving high-purity recovery and reducing waste.
Solution Approach 2:
The distillation process is designed to be self-sufficient, where the heat of vaporization released during condensation can be partially recovered and reused to preheat the incoming waste acid solution. This self-service approach reduces external energy input requirements and minimizes overall energy consumption while effectively preventing resource waste and environmental pollution.
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
Achieves high recovery rates (>99% for hydrofluoric acid and >95% for nitric acid) and purity (49±0.5% for hydrofluoric acid and 70±0.5% for nitric acid), suitable for recycling in high-tech electronics manufacturing, while minimizing waste and energy consumption.
Implementation Method 1
alkali metal salts containing an alkali metal fluoride salt and an alkali metal nitrate salt are introduced into the waste acid solution to break azeotrope of hydrofluoric acid and water
Implementation Method 2
a first distillation treatment is performed in a vacuum environment to obtain a hydrogen fluoride vapor
Implementation Method 3
a first distillation treatment is performed in a vacuum environment
Implementation Method 4
the purified hydrogen fluoride vapor is subjected to a first condensation treatment
Implementation Method 5
the first distillation residue mixture obtained in step (A) is subjected to a first evaporation treatment in a vacuum environment, such that partial water and nitric acid are evaporated therefrom
Data Source
AI summary
A method for preparing electronic grade inorganic acids includes: introducing alkali metal salts into a waste acid solution containing hydrofluoric acid, nitric acid and water to obtain hydrogen fluoride vapor, and a distillation residue mixture containing nitric acid, water and the alkali metal salts; subjecting the first distillation residue mixture to evaporation treatment, and then introducing an alkali earth metal nitrate salt into the resultant nitric acid/water mixture followed by distillation treatment so as to obtain nitric acid vapor; and removing mist droplets in the hydrogen fluoride and nitric acid vapor, followed by condensation treatment and concentration adjustment so as to obtain electronic grade hydrofluoric acid and nitric acid.