In-situ Subsurface Decontamination via Alkaline Chelation
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Solution Overview
Problem
Conventional in-situ treatment methods for halogenated organic contaminants in clayey ground media are inefficient due to physical and chemical heterogeneities, leading to limited reagent contact and high reagent consumption, with existing methods being costly and environmentally impactful, especially concerning CO2 emissions.
Innovation Solution
A method involving drilling injection and extraction holes, injecting an alkaline aqueous solution with a cation, peroxide, and chelating agent to catalytically convert peroxides to oxidizing agents and hydroxide ions, which react with contaminants to form environmentally safe compounds, reducing permeability and releasing trapped contaminants through pressure transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional in-situ treatment methods are used to deliver reagents to halogenated organic contaminants in clayey ground media, then the treatment can be performed at the site, but the physical and chemical heterogeneities of the ground media limit reagent contact with contaminants, reducing treatment effectiveness
Solution Approach 1:
The patent changes the chemical parameters of the reagent by using alkaline conditions (high pH) to dissolve metal compounds in the clayey ground media, generating hydroxide ions that can effectively contact and react with halogenated organic contaminants. This parameter change enables the reagent to adapt to the heterogeneous ground media and effectively treat contaminants despite physical and chemical variations in the subsurface environment.
2Reliability
If large volumes of highly concentrated reagent solutions are administered to overcome limited reagent contact, then contaminant treatment coverage is improved, but the cost and environmental impact increase significantly
Solution Approach 1:
The patent employs a self-service mechanism where the alkaline reagent automatically dissolves metal compounds present in the clayey ground media, and the dissolved metals catalyze the decomposition of peroxides to generate hydroxide ions in situ. This self-generating system eliminates the need to administer large volumes of highly concentrated reagent solutions, as the active treatment agents are produced locally where needed, reducing both reagent consumption and environmental impact.
3Reliability
If oxidizing reagents are used to chemically oxidize organic contaminants, then contaminants are converted to environmentally safe constituents, but the oxidizing reagents can be unstable and short-lived, limiting their effectiveness
Solution Approach 1:
The patent applies preliminary action by first introducing an alkaline reagent that dissolves metal compounds in the ground media before the peroxide decomposition occurs. The dissolved metals are then available to catalyze peroxide decomposition, generating hydroxide ions that immediately react with contaminants. This preliminary preparation ensures stable and effective contaminant conversion without relying on unstable oxidizing reagents.
4Reliability
If in-situ chemical oxidation is performed to treat contaminants, then treatment can be conducted at the site, but the exothermic reactions and heat generation pose control problems and safety risks
Solution Approach 1:
The patent uses a self-service approach where the alkaline reagent dissolves metal compounds that catalyze peroxide decomposition, generating hydroxide ions that treat contaminants through nucleophilic substitution rather than highly exothermic oxidation. This mechanism provides better temperature control and safety while maintaining effective in-situ treatment capability.
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 reduces contaminant concentrations, minimizes reagent use, and produces environmentally friendly solid compounds like calcium carbonate, reducing CO2 emissions and improving treatment efficiency while maintaining safety and cost-effectiveness.
Implementation Method 1
treating the ground media for a time sufficient to have the chelating agent chelate the metal of the metal compound present in the ground media
Implementation Method 2
reacting the chelated metal with the peroxide to catalytically convert the peroxide to oxidizing agents and hydroxide ions
Implementation Method 3
catalytically convert the peroxide to oxidizing agents and hydroxide ions
Implementation Method 4
contacting the contaminants in the ground media with the hydroxide ions to convert the contaminants through nucleophilic substitution to environmentally safe, non-toxic compounds
Implementation Method 5
increasing the pressure of the reagent into the ground media, to diffuse the reagent further into the ground media
Implementation Method 6
transferring contaminants from the ground media to above a surface of the ground media through pressure transfer
Data Source
AI summary
A method of decontaminating ground media. The method includes drilling an injection hole into ground media to a depth at or below where contaminants are also present, drilling one or more extraction holes into the ground media in close proximity to the injection hole, injecting a reagent into the injection hole, treating the ground media for a time sufficient to have a chelating agent chelate a metal present in the ground media, reacting the chelated metal with a peroxide to produce hydroxide ions, contacting the reagent with the ground media to decrease its permeability, contacting contaminants in the ground media with the hydroxide ions to convert the contaminants to environmentally safe compounds, increasing the pressure of the reagent into the ground media, further reducing the permeability of the ground media to release trapped contaminants, and transferring contaminants from the ground media to above a surface of the ground media.