Selective NTA Removal from EDTA Solutions via Alkaline Adsorption
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Solution Overview
Problem
Existing methods fail to selectively remove nitrilotriacetic acid (NTA) salts from aqueous chelating agent compositions, particularly those containing EDTA, due to non-selective binding with ion-exchange resins and inefficiencies in adsorption processes, especially at varying pH levels and concentrations.
Innovation Solution
Treating aqueous chelating agent compositions at a pH of 7 to 12 with granular adsorbents, preferably activated carbons from coconut, wood, or hydrocarbon sources, in a sequential fashion to selectively remove NTA salts while retaining 95% or more of the chelating agents, using a combination of adsorbents to enhance removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ion-exchange resin is used for NTA removal, then NTA can be removed from aqueous chelating agent compositions, but the removal is non-selective and EDTA is also bound significantly
Solution Approach 1:
The patent changes the fundamental parameter of the separation mechanism from ion-exchange to adsorption. By using activated carbon and adjusting pH to alkaline conditions (pH 7-12), the process achieves selective NTA removal while EDTA remains in solution. The adsorption mechanism is less dependent on charge interactions and more on surface affinity and molecular structure, enabling selectivity where ion-exchange failed.
Solution Approach 2:
The patent introduces activated carbon as an intermediary substance with specific surface properties that mediate the separation between NTA and EDTA. The activated carbon surface acts as a selective mediator that preferentially adsorbs NTA through its porous structure and surface chemistry, while allowing EDTA to pass through unaffected.
2Quantity of substance
If activated carbon is used for NTA adsorption at low pH (pH 5.0), then NTA removal efficiency is maximized, but chelating agents are also removed and selectivity is lost
Solution Approach 1:
The patent changes the pH parameter from acidic (pH 5.0) to alkaline (pH 7-12). This parameter change fundamentally alters the adsorption behavior: at alkaline pH, NTA remains adsorbed on activated carbon while EDTA does not adsorb, achieving both high NTA removal and high chelating agent retention. The pH change modifies the surface charge and molecular conformation of both compounds, creating selective adsorption conditions.
3Quantity of substance
If smaller adsorbent particle size is used, then adsorption surface area increases and NTA removal improves, but separation efficiency and selectivity decrease
Solution Approach 1:
The patent changes the particle size parameter to a specific optimal range (0.3-4 mm) that balances surface area availability with separation efficiency. This intermediate particle size provides sufficient adsorption capacity while maintaining good flow characteristics and selectivity, avoiding the problems of both very fine particles (poor separation) and very coarse particles (insufficient surface area).
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 highly selective removal of NTA salts from various chelating agent streams, maintaining 99% or more of the chelating agents, and effectively reducing NTA content to below 1 wt.%, suitable for manufacturing and waste stream recycling.
Implementation Method 1
treating the aqueous compositions at a pH of from 7 to 12 with one or more adsorbent
Data Source
AI summary
The present invention provides simple methods for treating aqueous chelating agent compositions containing one or more nitrilotriacetic acid (NTA) salts with one or more adsorbents, such as activated carbon, two or more activated carbon adsorbent in sequential treatments, to remove the NTA without removing more than 5 wt. %, or more than 3 wt. % or, preferably, more than 1 wt. % of the chelating agent in the aqueous chelating agent compositions. The methods comprise treating aqueous chelating agent compositions having a pH of from 7 to 12 and can be carried out at from 10 to 110 C. The methods can be used to treat a wide range of aqueous chelating agent compositions having, for example, from 700 to 6000 ppm of NTA, such as waste streams.