Anion Removal from Wastewater via pH-Controlled Extraction
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Solution Overview
Problem
Current wastewater treatment technologies are costly and inefficient in removing selenate, sulfate, and nitrate ions from mine-affected water, particularly when these ions are present together, as they often interfere with each other's removal processes.
Innovation Solution
A method involving the use of an organic phase composition containing a quaternary amine and a weak organic acid to selectively extract and separate nitrate, sulfate, and selenate ions from wastewater through staged pH-controlled processes, allowing for their subsequent purification and compliance with environmental regulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wastewater treatment technologies are used to remove anions, then treatment effectiveness is achieved, but treatment cost increases significantly
Solution Approach 1:
The patent employs pH control as a key parameter to enable selective extraction of different anions. By adjusting pH levels, the process optimizes the extraction efficiency of nitrate, sulfate, and selenate ions at different stages, achieving effective anion removal while reducing treatment costs through targeted rather than blanket treatment approaches.
2Reliability
If multiple anions are present in wastewater, then comprehensive treatment is required, but ion interference reduces removal efficiency
Solution Approach 1:
The patent divides the anion removal process into multiple sequential extraction stages, each targeting specific anions. The first stage removes nitrate ions, the second stage removes sulfate ions, and the third stage removes selenate ions. This segmentation eliminates ion interference by treating each anion type in isolation at optimized pH conditions, thereby achieving both comprehensive removal and high separation efficiency.
Solution Approach 2:
The patent performs preliminary removal of nitrate ions before treating for sulfate and selenate ions. This preliminary action prevents nitrate from interfering with subsequent sulfate and selenate extraction processes, ensuring that each subsequent stage operates under optimal conditions for its target anion, thus maintaining high separation efficiency throughout the comprehensive treatment process.
3Reliability
If a treatment train of multiple technologies is used, then ultimate treatment goal is achieved, but process complexity increases
Solution Approach 1:
The patent employs a single organic extractant system that performs multiple functions across different pH stages. The same organic phase is used to selectively extract nitrate, sulfate, and selenate ions by simply adjusting pH levels, eliminating the need for multiple different treatment technologies. This multi-functionality achieves comprehensive anion removal while maintaining relatively simple process equipment and operations.
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 method effectively separates and removes nitrate, sulfate, and selenate ions, enabling further purification and reducing treatment costs by optimizing the pH-dependent behavior of the quaternary amine and weak organic acid to maximize ion separation and recovery, thereby meeting environmental standards.
Implementation Method 1
contacting the primary aqueous solution with an initial organic phase composition in a primary stage to form a first mixture... wherein the initial organic phase composition comprises a quaternary amine and a weak organic acid... The organic phase preferentially absorbs nitrates in the water
Implementation Method 2
the pH of the second mixture is higher than the pH of the first mixture... the pH of the third mixture is higher than the pH of the second mixture... optimizing the pH-dependent behavior of the quaternary amine and weak organic acid to maximize ion separation
Implementation Method 3
separating the first mixture to obtain a nitrate-depleted and selenate-rich raffinate and a nitrate-containing organic phase... separating the second mixture to remove sulfate present in the nitrate-containing organic phase... separating the third mixture to obtain a nitrate-rich aqueous strip solution and a secondary organic phase composition
Data Source
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AI summary
Methods for removing anions from an aqueous solution include contacting the aqueous solution with an initial organic phase composition in a primary stage to form a first mixture, the initial organic phase composition including a quaternary amine and a weak organic acid; separating a nitrate-depleted raffinate from the first mixture; mixing the remaining organic phase (now containing nitrate) with a first basic solution to obtain a second mixture; separating an aqueous phase sulfate-containing scrub solution from the second mixture; mixing the remaining organic phase with a second basic solution to form a third mixture; and separating the third mixture into an aqueous phase nitrate-rich solution and a secondary organic phase composition. The secondary organic phase composition can be recycled. The raffinate, the sulfate-containing scrub solution, and the nitrate-rich solution can then be further processed.