Plastic Mixture Oxidation for Selective Flotation Separation
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Solution Overview
Problem
Current methods for separating plastics in waste, such as those from RBA, WEEE, and household waste, face challenges due to the hydrophobic nature of plastics, which makes selective separation by flotation difficult, and existing treatments are either inefficient or toxic, limiting the recovery of plastics like PVC and POM.
Innovation Solution
A method involving a mixture of plastics being treated with a potassium permanganate solution under microwave irradiation, followed by washing with sulfuric acid and hydrogen peroxide, and then subjected to flotation with air or nitrogen bubbles to modify surface hydrophobicity/hydrophilicity, allowing for selective separation of plastics like PVC and POM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional flotation methods are used to separate plastics, then the process is simple, but the hydrophobic nature of plastics prevents selective separation
Solution Approach 1:
The patent applies parameter changes by modifying the surface chemical properties of plastics through oxidation treatment. Specifically, it changes the surface chemistry from hydrophobic to hydrophilic by introducing polar groups (carboxyl, hydroxyl, carbonyl) via controlled oxidation with potassium permanganate, enabling selective separation during flotation based on altered surface properties rather than inherent hydrophobicity
Solution Approach 2:
The patent employs strong oxidants (accelerated oxidation) by using potassium permanganate as the oxidizing agent to modify plastic surfaces. The oxidation process creates hydrophilic surface groups that enable selective flotation separation, transforming the surface properties of plastics to achieve the desired separation efficiency
2Manufacturing precision
If toxic reagents are used to modify plastic surfaces, then selective separation is achieved, but environmental harm increases
Solution Approach 1:
The patent applies the principle of using cheap, environmentally benign reagents that can be easily disposed of or degraded. Potassium permanganate is used as the oxidizing agent, which, while strong, is not permanently toxic and can be managed through controlled application and subsequent washing, replacing the need for more harmful reagents in the process
Solution Approach 2:
The patent converts the potentially harmful effect of strong oxidation into a beneficial outcome. The oxidation process, which could be seen as destructive to the plastic structure, is instead harnessed to create the desired hydrophilic surface properties for separation. The controlled oxidation transforms a harmful chemical action into a useful surface modification technique
3Manufacturing precision
If existing oxidation methods are used, then surface modification is achieved, but the process is inefficient for mixed plastic waste
Solution Approach 1:
The patent applies local quality by selectively oxidizing specific plastic types within the mixture based on their differential reactivity. Different plastics in the mixture are oxidized to different extents depending on their chemical structure and surface mobility, creating local variations in surface properties that enable selective separation. This allows the single oxidation step to produce multiple distinguishable surface states for different plastic types
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 process effectively modifies the surface properties of plastics, enabling their selective separation by flotation, increasing the recovery of purified plastic fractions and reducing the carbon footprint by avoiding toxic reagents and improving the recycling of previously unsatisfactory waste materials.
Implementation Method 1
The invention relates to a method for modifying the surface properties of a mixture of plastics by oxidation
Implementation Method 2
A method involving a mixture of plastics being treated with a potassium permanganate solution under microwave irradiation
Implementation Method 3
a step of fractionation, by flotation with air or nitrogen bubbles in a liquid medium, of the mixture of plastic pieces
Data Source
Figure 1
Figure 2
AI summary
Method for processing a mixture of plastics by controlled oxidation A method for separating at least one type of plastic fragments from a mixture of plastic fragments comprising at least two different types of plastics selected from the group consisting of PP, PC, PVC, ABS, POM, PET, ABS-PS and ABS-PC; said method making it possible to obtain a fraction which is enriched with at least one of said at least two different types of plastics in relation to the proportion by weight of said at least one type of plastic in said mixture of plastic pieces; said method comprising the following steps: a) bringing into contact said mixture of plastic pieces with an aqueous solution, which is saturated or non-saturated, of potassium permanganate; b) irradiating said mixture with microwaves in the presence of said aqueous solution of potassium permanganate at an irradiation power of 0.3 to 6 kW for 0.5 to 6 minutes; c) a step of washing the mixture of plastic pieces using a solution in a mixture of sulphuric acid and hydrogen peroxide; d) a step of fractioning the mixture of plastic pieces, by floating said mixture of plastic pieces in a liquid medium, in order to obtain at least a first fraction and a second fraction; and e) a step of recovering at least one of said fractions. Figure 1.5