KR-20260065548-A - Method and System for Aqueous-Based Polystyrene Recovery

Abstract

The present invention relates to a method for dissolving, separating, and recovering polystyrene (PS) in an aqueous system (freshwater or seawater) using limonene, a natural solvent, and a system for the same. The method includes the step of adding and dissolving limonene in an aqueous system in which polystyrene or a material containing it is dispersed, separating the mixture into layers by settling or centrifugation, and then vaporizing the limonene by heating to recover the polystyrene film formed on the water surface. According to the present invention, even low-concentration polystyrene at the level of 0.005% (w/v) can be recovered with an efficiency of over 90% under freshwater and seawater conditions, and by reusing the condensed recovered limonene, solvent consumption and environmental burden can be significantly reduced. In addition, by providing a recovery system consisting of a reactor, a limonene injection unit, a stirrer, a heating unit, a condensation unit, and a film recovery unit, process automation and continuous operation are possible, making it useful for marine microplastic recovery and polystyrene recycling industries.

Inventors

• 최명현
• 정인준
• 정혜민
• 김다니엘

Assignees

• 디컴포지션 주식회사

Dates

Publication Date

20260508

Application Date

20251029

Priority Date

20241029

Claims (12)

1. (a) a step of adding limonene to an aqueous phase in which polystyrene (PS) or a material containing the same is dispersed to dissolve the PS in the limonene phase; (b) a step of separating the aqueous phase and the limonene phase by allowing the mixture to stand at room temperature to induce phase separation or by centrifugation; (c) a step of heating to vaporize limonene; and (d) a step of recovering a polystyrene film formed on the water surface, Method for recovering polystyrene from water systems.
2. A method for recovering polystyrene according to claim 1, wherein the water system is fresh water or seawater.
3. A method for recovering polystyrene according to claim 1, wherein the concentration of polystyrene dispersed in the water system is 0.005% (w/v) or higher.
4. A method for recovering polystyrene in which, in the case of paragraph 2, the polystyrene concentration is 0.01% (w/v) or higher when the water system is seawater.
5. A method for recovering polystyrene according to claim 1, wherein the added concentration of limonene is 0.4 to 5.0% (v/v).
6. A method for recovering polystyrene according to claim 1, wherein stirring of the dissolution step (a) is performed at 100 to 200 rpm for 7 to 10 minutes.
7. A method for recovering polystyrene according to claim 1, wherein step (b) is performed by standing at room temperature for 1 to 10 minutes or centrifuging at 3,000 to 5,000 rpm for 5 to 15 minutes.
8. A method for recovering polystyrene according to claim 1, wherein the heating of step (c) is performed at 77 to 100 ℃ for 15 to 120 minutes.
9. A method for recovering polystyrene according to claim 1, wherein a polystyrene film is formed on the water surface between 10 and 60 minutes after the start of heating in step (c).
10. A method for recovering polystyrene according to claim 1, performed in a container made of glass, polypropylene (PP), or a metal material including stainless steel.
11. A polystyrene recovery system comprising: a reactor filled with a water system; an injection unit for injecting limonene into the water system; a stirrer for assisting in the dissolution of polystyrene; a heating unit for vaporizing limonene; a condensation unit for condensing and recovering the vaporized limonene; and a surface film recovery unit for recovering a polystyrene film formed on the water surface.
12. A polystyrene recovery system according to claim 11, further comprising a limonene recovery tank for storing condensed limonene.

Description

Method and System for Aqueous-Based Polystyrene Recovery The present invention relates to the field of waste plastic recovery and recycling technology, and more specifically, to a method for dissolving, separating, and recovering polystyrene (PS) under water conditions, such as fresh water or seawater, using limonene as a solvent, and a system for carrying out the same. The present invention relates to a method for recovering polystyrene in a water system by forming it into a film. Microplastics, including polystyrene, are difficult to physically separate in aqueous systems, and there are issues where recovery rates and quantitative accuracy decrease as concentrations decrease. Conventional methods such as filtration, centrifugation, and solvent extraction are highly dependent on equipment and involve complex processes; furthermore, quantitative reliability can be compromised due to interference from water quality factors such as salinity or organic matter. Therefore, there is a need for a technology that can induce stable film formation even at low concentrations through simple operations and simultaneously secure both recovery rates and quantitative accuracy by physically recovering the formed films. Polystyrene (PS) is a polymer material widely used in various industrial fields, such as packaging, containers, and electronic housings. However, polystyrene is difficult to biodegrade naturally and poses a problem by remaining in marine and terrestrial environments and accumulating in the form of microplastics. In particular, low-density materials such as expanded polystyrene (EPS) float on the water surface, making complete separation difficult using conventional mechanical recovery or solvent treatment methods. Conventional polystyrene recovery processes have primarily utilized dissolution and precipitation methods using organic solvents; however, most solvents present issues such as toxicity, flammability, and volatility, limiting their application in aquatic environments. Furthermore, efficient recovery has been difficult in environments containing salt, such as seawater, due to altered solvent distribution behavior. Accordingly, there is an increasing need for technology capable of stably dissolving and recovering polystyrene even under water conditions using environmentally friendly and biodegradable natural solvents. To solve these problems, the present invention aims to provide a new water-based polystyrene recovery technology capable of achieving high recovery efficiency while minimizing environmental burden by using limonene to dissolve and separate polystyrene in an aquatic environment (freshwater or seawater) and recovering the polystyrene film formed on the water surface during the vaporization process of limonene by heating. Figure 1 shows the appearance of a polystyrene film formed at a concentration of 0.1% (w/v) under fresh water (DW) conditions of Example 1. Figure 2 shows the appearance of polystyrene films formed at concentrations A (0.05%), B (0.025%), and C (0.005%), respectively, under fresh water (DW) conditions of Example 2. Figure 3 shows the appearance of a polystyrene film (or semi-solid film) formed at concentrations of A (0.5%) and B (0.2%) under seawater conditions of Example 5. Figure 4 is a photograph comparing the appearance of polystyrene films formed under fresh water (DW) and seawater (SEA water) conditions, respectively, in Example 8. FIG. 5 shows a schematic diagram of the polystyrene recovery system (100) of the present invention. Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. [A: Confirmation of PS film formation under freshwater conditions] Example 1. Confirmation of PS film formation under fresh water conditions 20 mL of distilled water (DW) was placed in a 100 mL beaker, and 0.1% polystyrene (PS) powder was added and sufficiently dispersed. After adding 4% (v/v) limonene, the mixture was stirred at approximately 50 °C until the PS powder was completely dissolved. After confirming the dissolution, the aqueous phase and the limonene phase were separated by centrifugation at 4000 rpm for 10 minutes. Subsequently, the limonene was vaporized by heating in a water bath for about 1 hour and 50 minutes under conditions of 77°C or higher, resulting in the formation of a continuous polystyrene film on the water surface. After removing residual moisture and drying, a polystyrene film was obtained. After the film formation was completed, it was recovered and completely dried, and the mass was measured after drying to calculate the recovery rate. Figure 1 shows the appearance of a polystyrene film formed at a concentration of 0.1% (w/v) under fresh water (DW) conditions. Under these conditions, a PS film