Acid-Base Washing for Polyolefin VOC Removal
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Solution Overview
Problem
Current recycling methods for polyolefins, particularly polypropylene and polyethylene, face challenges in achieving high purity and quality due to contamination and poor mechanical properties, with existing methods for removing volatile organic compounds being energy-intensive and inefficient.
Innovation Solution
A process involving treatment with an aqueous solution of an inorganic oxoacid at a pH of 2.0 or lower, followed by a caustic solution at a pH of 7.0 or higher, to reduce hydrophobic and hydrophilic volatile organic compounds in recycled polyolefins, improving their mechanical and odor properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If aeration is used to remove volatile organic compounds from recycled polyolefin, then VOC content is reduced, but energy consumption increases significantly
Solution Approach 1:
The invention changes the chemical parameters of the treatment solution by adjusting pH levels (using acid at pH 2.0 or lower, then base at pH 7.0 or higher) to selectively remove different types of VOCs. This chemical parameter approach replaces the energy-intensive physical aeration process, achieving VOC removal through chemical reactions rather than thermal/oxidative aeration.
Solution Approach 2:
The invention replaces the mechanical/physical aeration system with a chemical treatment system using aqueous acid and base solutions. Instead of using mechanical aeration equipment to remove VOCs, the process uses chemical reactions with treatment solutions, substituting a mechanical removal process with a chemical extraction process that consumes less energy.
2Ease of manufacture
If recycled polyolefin is used directly, then production cost is reduced, but mechanical properties and odor performance deteriorate
Solution Approach 1:
The invention applies preliminary chemical treatment to recycled polyolefin before it is used in final applications. By pre-treating the material with acid and base solutions to remove VOCs and contaminants, the process ensures that the recycled material meets quality requirements before being incorporated into products, thereby maintaining mechanical properties and odor performance while still using cost-effective recycled content.
3Ease of manufacture
If recycled polyolefin is used directly, then production cost is reduced, but odor and taste performance deteriorate
Solution Approach 1:
The invention changes the chemical environment parameters by using acid treatment (pH 2.0 or lower) followed by base treatment (pH 7.0 or higher) to selectively remove odor-causing VOCs. This parameter-based chemical treatment approach removes hydrophobic functional group-containing VOCs and hydrophilic VOCs that cause odor and taste issues, while maintaining cost-effectiveness by using simple aqueous treatment solutions rather than expensive purification systems.
Data Source
AI summary
A process for reducing the hydrophobic functional group-containing volatile organic compound content and hydrophilic volatile organic compound content of recycled polyolefin comprising an acid washing step followed by an alkaline/neutral washing step.