Liquid CO2 Soil Remediation for Fine-Grained Contaminant Removal
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Solution Overview
Problem
Current soil remediation technologies, such as thermal desorption and soil washing, are ineffective for fine-grained soils, environmentally hazardous, and costly, while solvent-based methods pose pollution risks and require extensive wastewater treatment.
Innovation Solution
The use of carbon dioxide in its gaseous or liquid form to alter the physical-chemical equilibrium of contaminated soils, promoting desorption and solubilization of contaminants through solubility changes, acid-base reactions, and volatilization, allowing for their extraction and subsequent biological or chemical degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal desorption is used to remediate contaminated soils, then contaminants can be removed through volatilization, but the process causes excessive dust production in fine-grained soils and requires high energy consumption
Solution Approach 1:
The patent changes the physical state parameter of carbon dioxide from gaseous to liquid phase through pressurization and cooling, enabling it to act as a solvent for contaminants rather than relying on thermal volatilization. This parameter change allows effective contaminant removal without high temperature heating, thus avoiding dust production and excessive energy consumption while maintaining reliability in fine-grained soils
Solution Approach 2:
The patent replaces the thermal field (heat-based thermal desorption) with a chemical field (liquid CO2 solvent action). Instead of using high temperature to volatilize contaminants, the liquid CO2 directly dissolves and extracts contaminants from the soil matrix through solubility mechanisms, eliminating the need for high energy input and preventing dust generation
2Adaptability or versatility
If solvent extraction is used to remove contaminants from soils, then all types of soil particle sizes can be treated, but the process introduces additional environmental pollution risks and requires extensive wastewater treatment
Solution Approach 1:
The patent uses liquid carbon dioxide as a temporary solvent that is subsequently evaporated and recovered. The CO2 is introduced in liquid form, performs the extraction function, then evaporates leaving no residual pollution. The gaseous CO2 can be captured and reused, eliminating the need for extensive wastewater treatment and avoiding the environmental persistence issues associated with traditional organic solvents
Solution Approach 2:
The patent exploits the phase transition of carbon dioxide from liquid to gas. Liquid CO2 is injected into the soil to extract contaminants, then it evaporates into gas phase, leaving no liquid waste. This phase transition mechanism enables effective contaminant removal while eliminating wastewater treatment requirements and reducing environmental pollution risks
3Productivity
If traditional remediation methods are applied to fine-grained soils, then treatment can proceed, but the processes become less effective and more complex
Solution Approach 1:
The patent changes the physical state of carbon dioxide to liquid phase and controls its temperature and pressure parameters to optimize solvent properties. By adjusting these parameters, the system achieves high effectiveness in fine-grained soils without requiring complex process modifications, maintaining simplicity while improving productivity
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
Carbon dioxide effectively removes organic contaminants from soils without causing environmental harm, reducing bacterial counts and enabling the reuse of treated soil, while being a cost-effective and safer alternative to existing methods.
Implementation Method 1
Carbon dioxide is highly water soluble and when dissolved in water determines the formation of carbonic acid
Implementation Method 2
The use of carbon dioxide in its gaseous or liquid form to alter the physical-chemical equilibrium of contaminated soils, promoting desorption and solubilization of contaminants through solubility changes, acid-base reactions, and volatilization
Implementation Method 3
promoting desorption and solubilization of contaminants
Data Source
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AI summary
The object of the invention is the application of carbon dioxide (CO2) at gaseous or liquid state in remediation of contaminated soils, sediments and aquifers. In particular the application is based on the exploitation of physical and chemical properties of carbon dioxide in promoting the desorption and/or dissolution of the organic and/or inorganic contaminants from soil/sediments matrices. The mechanisms of desorption and/or dissolution by carbon dioxide allows to obtain: - extraction and/or recovery of the contaminants; - transport of contaminants from deeper layers to more superficial layers of the soil; - availability of contaminants for subsequent removal processes (biological, chemical and/or physical processes). The application covers remediation systems in-situ, on-site and ex-situ. In case of in-situ treatment, the invention relates to the injection and/or diffusion of carbon dioxide in the saturated and/or unsaturated soil. Carbon dioxide can be injected into the ground in gaseous or liquid form. In case of on-site or ex-situ treatment, the invention relates to the injection/diffusion of carbon dioxide in excavated soil or dredged sediment, collected in heaps or sent to dedicated reactors. Carbon dioxide can be injected into the soil and sediments in gaseous or liquid form. In all cases, in-situ, on-site or ex-situ, carbon dioxide can be injected pure or mixed and/or combined with other inert, oxidants and/or reducing gases.