Methods of recovering furan dicarboxylic acid from mixed plastic waste streams

Abstract

The invention provides a method of recovering furan dicarboxylic acid (FDCA) from a mixed plastic waste stream comprising one or more polymeric materials that include one or more hydrolysable polymeric material and at least one of the one or more hydrolysable polymeric material is a polymeric material that comprises repeating units derived from FDCA, the method comprising: (i) providing an aqueous mixture of hydrolyzed products obtained by hydrolysis of the mixed plastic waste stream; (ii) precipitating FDCA from the aqueous mixture of step (i) with an inorganic acid and filtering the precipitated FDCA, thereby recovering FDCA, provided that when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the method further comprises an intermediate step (ia) before conducting step (ii): (ia) preferentially precipitating TPA from the aqueous mixture of step (i) with a weak acid and removing the precipitated TPA.

Description

[0001] METHODS OF RECOVERING FURAN DICARBOXYLIC ACID FROM MIXED PLASTIC WASTE STREAMS

[0002] FIELD OF INVENTION

[0003] The present invention provides methods of recovering furan dicarboxylic acid (FDCA) from mixed plastic waste streams.

[0004] BACKGROUND

[0005] The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

[0006] Biomass-derived polymers, such as polyethylene furanoate (PEF), are being introduced as renewable alternatives to petrochemical-based polyethylene terephthalate (PET). However, the linear lifecycle of plastics leads to resource overconsumption and waste generation, and PEF will face similar challenges. A linear lifecycle for PEF risks excessive use of biomass, agricultural land, and water resources. Furthermore, a linear lifecycle for PEF will contribute to waste generation similar to the current plastic waste crisis caused by petrochemical-derived plastics. Establishing circular lifecycles for plastics, including bioplastics, remains challenging due to the complexities in recycling mixed plastic waste. Given that PEF and PET are used in similar applications, mainly bottles and packaging materials, they are likely to enter the same waste streams. Physical separation of different plastics within a waste stream is unscalable and energy-intensive, which is one of the reasons for the limited effectiveness of current recycling efforts.

[0007] Furan-2,5-dicarboxylic acid (FDCA), the building block of PEF, is a valuable chemical with a rapidly growing global market driven by the demand for bio-based and sustainable materials. Ideally, FDCA would be recoverable in its purified form from waste plastic streams, enabling its reuse and contributing to the circular lifecycle of PEF. Achieving this requires technology that can selectively depolymerize PEF in the presence of other polymers, utilizing green solvents and scalable reagents. Such a solution should also enable the isolation of pure FDCA from depolymerized PEF while effectively separating it from other plastics and additives.

[0008] Although FDCA and correspondingly, PEF, are biomass-derived, saccharides are the feedstock used for their production. Thus, increasing demands of PEF as a potential replacement for PET would place increasing demands for these saccharide feedstocks, whichin turn competes with food supply. Thus, there is a need for improved / alternative methods to effectively and efficiently recycle PEF through recovery of FDCA, particularly in the presence of contaminants, for solving at least the above-mentioned problems.

[0009] SUMMARY

[0010] Aspects and embodiments of the current invention will now be described by reference to the following numbered clauses.

[0011] 1. A method of recovering furan dicarboxylic acid (FDCA) from a mixed plastic waste stream, where the mixed plastic waste stream comprises one or more polymeric materials that include one or more hydrolysable polymeric material and at least one of the one or more hydrolysable polymeric material is a polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA), the method comprising:

[0012] (i) providing an aqueous mixture of hydrolyzed products obtained by hydrolysis of the mixed plastic waste stream;

[0013] (ii) precipitating FDCA from the aqueous mixture of step (i) with an inorganic acid and filtering the precipitated FDCA, thereby recovering FDCA,

[0014] provided that when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the method further comprises an intermediate step (ia) before conducting step (ii):

[0015] (ia) preferentially precipitating TPA from the aqueous mixture of step (i) with a weak acid and removing the precipitated TPA.

[0016] 2. The method according to Clause 1 , wherein the aqueous mixture of step (i) is provided by subjecting the mixed plastic waste stream to hydrolysis conditions for a period of time.

[0017] 3. The method according to Clause 2, where the hydrolysis conditions involve an aqueous alkali hydroxide, optionally wherein the aqueous alkali hydroxide is one or both of sodium hydroxide and potassium hydroxide, further optionally wherein the aqueous alkali hydroxide is sodium hydroxide.

[0018] 4. The method according to Clause 3, wherein the aqueous alkali hydroxide is provided in an amount in excess relative to a total molar amount of repeating units present in the one or more hydrolysable polymeric material, such as from 1.5 molar equivalent to 3 molar equivalent relative to the total molar amount of repeating units present in the one or more hydrolysable polymeric material.5. The method according to any one of Clause 2 to Clause 4, wherein the hydrolysis is conducted at a temperature from 15°C to 150°C, such as from 20°C to 120°C, such as about 20°C, about 100°C and about 120°C, and optionally, a pressure of about 1 atm.

[0019] 6. The method according to Clause 5, wherein:

[0020] when the temperature is about 120°C, the period of time is from 1.5 hour to 4 hours, such as about 2 hours; and

[0021] when the temperature is about 20°C, the period of time is from 60 to 84 hours, such as about 72 hours.

[0022] 7. The method according to any one of the preceding clauses, wherein the inorganic acid is one or more selected from a group consisting of hydrochloric acid, sulfuric acid and nitric acid, optionally wherein the inorganic acid is hydrochloric acid.

[0023] 8. The method according to any one of the preceding clauses, wherein the inorganic acid is provided at a concentration of 0.5M to 5M, such as about 2M and added to the aqueous mixture of step (i) at a volume of from 50% v / v to 300% v / v relative to the volume of the aqueous mixture of step (i), such as from 60% v / v to 275% v / v relative to the volume of the aqueous mixture of step (i), such as about 60% v / v or about 275% v / v relative to the volume of the aqueous mixture of step (i).

[0024] 9. The method according to any one of the preceding clauses, wherein when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the weak acid is one or both of acetic acid and formic acid, optionally wherein the weak acid is acetic acid.

[0025] 10. The method according to any one of the preceding clauses, wherein when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the weak acid is added to the aqueous mixture of step (i) during the intermediate step (ia) at a volume of from 3% v / v to 10% v / v relative to the volume of the mixture provided in step (i), such as about 5% v / v relative to the volume of the mixture provided in step (i).

[0026] 11. The method according to any one of the preceding clauses, wherein the method is conducted in the absence of one or more of a catalyst and an organic solvent.12. The method according to any one of the preceding clauses, wherein:

[0027] the polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA) is a FDCA co-polymer, such as polyethylene furanoate (PEF); and

[0028] when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the polymeric material that comprises repeating units derived from terephthalic acid (TPA) is a TPA co-polymer, such as polyethylene terephthalate (PET).

[0029] 13. The method according to any one of the preceding clauses, wherein the mixed plastic waste stream further comprises one or more selected from a group consisting of polyamide 66 (PA66) and polylactic acid (PLA), or co-polymers thereof, or blends thereof.

[0030] 14. The method according to any one of the preceding clauses, wherein the mixed plastic waste stream further comprises a polyolefin selected from one or more of a group consisting of polyethene and polypropylene, or co-polymers thereof, or blends thereof, optionally wherein the method further comprises separating the polyolefin from the aqueous mixture of hydrolyzed products after subjecting the mixed plastic waste stream to hydrolysis conditions.

[0031] 15. The method according to any of the preceding clauses, wherein the yield of FDCA is above 60%, such as above 70%, such as above 80% based on the theoretical weight of FDCA in the polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA).

[0032] BRIEF DESCRIPTION OF DRAWINGS

[0033] FIG. 1 is schematic representation of the isolation of pure FDCA from a mixed plastics stream according to an embodiment of the present invention.

[0034] FIG. 2 is a photograph of mixed plastics (top: PEF, left: PET, right: PA66, bottom: PLA) used for the isolation of FDCA according to Example 1 of the present disclosure.

[0035] FIG. 3 includes the1H NMR spectra of FDCA obtained from pure PEF depolymerization (top) and from mixed plastics depolymerization (bottom) according to Example 1 of the present disclosure.

[0036] DESCRIPTIONThe present inventors have developed a method for selectively recovering pure furan dicarboxylic acid (FDCA) from a physical mixture of mixed plastics comprising polyethylene furanoate (PEF) and other polymeric materials, including hydrolysable polymers such as polyethylene terephthalate (PET), polylactic acid (PLA) and polyamide 66 (PA66) and non-hydrolysable polymers such as polyethylene (PE) and polypropylene (PP) (see FIG. 1 for a schematic representation according to an embodiment of the invention). The present invention is particularly useful for separating PEF from PET because of their shared applications in for example, bottles and packaging. The present method is simple, scalable and involves mild conditions (e.g., room temperature to 120°C, 1atm) without the use of catalysts and toxic organic solvents / reagents (the present method uses water as a solvent). Advantageously, the method solves the long-standing obstacle of having to physically sort mixed plastics prior to chemical recycling i.e. , the present method recovers pure FDCA directly from a mixed plastic waste stream in high yield (e g., 80% or higher yield). Furthermore, FDCA is valuable component of PEF and hence, the present invention will be useful for circularity of FDCA.

[0037] In addition, the present inventors have surprisingly found that, when present, TPA can be preferentially precipitated before FDCA and hence, separated from FDCA in an aqueous mixture despite FDCA having a higher pKa than TPA (FDCA pKa1 = 4.38, pKa2 = 5.85, vs TPA pKa1 = 3.54, pKa2 = 4.34). Without wishing to be bound by theory, it is believed that while FDCA actually gets protonated first, TPA has a stronger lattice energy than FDCA and thus, equilibrium is shifted towards TPA being protonated and precipitated prior to FDCA. To achieve this, a weak acid (such as acetic acid) may be used to allow for this proton exchange between FDCA and TPA to occur and the selective precipitation of TPA prior to FDCA instead of coprecipitation of both TPA and FDCA which will be difficult to separate and purify. Therefore, the ability to selectively remove TPA from FDCA is contrary to what a skilled person in the art would expect from theory (that FDCA having higher pKa should precipitate before TPA) - this phenomenon will not be obvious to the skilled person who has not actually done the experiments.

[0038] Thus, in a first aspect of the invention, there is provided a method of recovering furan dicarboxylic acid (FDCA) from a mixed plastic waste stream, where the mixed plastic waste stream comprises one or more polymeric materials that include one or more hydrolysable polymeric material and at least one of the one or more hydrolysable polymeric material is a polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA), the method comprising:

[0039] (i) providing an aqueous mixture of hydrolyzed products obtained by hydrolysis of the mixed plastic waste stream;(ii) precipitating FDCA from the aqueous mixture of step (i) with an inorganic acid and filtering the precipitated FDCA, thereby recovering FDCA,

[0040] provided that when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the method further comprises an intermediate step (ia) before conducting step (ii):

[0041] (ia) preferentially precipitating TPA from the aqueous mixture of step (i) with a weak acid and removing the precipitated TPA.

[0042] In embodiments herein, the word “comprising” may be interpreted as requiring the features mentioned, but not limiting the presence of other features. Alternatively, the word “comprising” may also relate to the situation where only the components / features listed are intended to be present (e.g. the word “comprising” may be replaced by the phrases “consists of” or “consists essentially of’). It is explicitly contemplated that both the broader and narrower interpretations can be applied to all aspects and embodiments of the present invention. In other words, the word “comprising” and synonyms thereof may be replaced by the phrase “consisting of” or the phrase “consists essentially of” or synonyms thereof and vice versa.

[0043] The phrase, “consists essentially of’ and its pseudonyms may be interpreted herein to refer to a material where minor impurities may be present. For example, the material may be greater than or equal to 90% pure, such as greater than 95% pure, such as greater than 97% pure, such as greaterthan 99% pure, such as greater than 99.9% pure, such as greater than 99.99% pure, such as greater than 99.999% pure, such as 100% pure.

[0044] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a compound” includes mixtures of two or more such compounds, reference to “a composition” includes mixtures of two or more such compositions, and the like.

[0045] As used herein, the term “mixed plastic waste stream” may include any polymeric material including hydrolysable polymeric materials such as polyethylene furanoate (PEF), polyethylene terephthalate (PET), polylactic acid (PU\) and polyamide 66 (PA66) and non-hydrolysable polymeric materials such as, but not limited to, polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polypropylene (PP) and non-hydrolysable polymeric materials such as a polyolefin (e.g. polyethylene and polypropylene).

[0046] In certain embodiments, the aqueous mixture of step (i) may be provided by subjecting the mixed plastic waste stream to hydrolysis conditions for a period of time. As will be appreciated,when the mixed plastic waste stream is subjected to hydrolysis, the hydrolysable polymeric materials (e.g., PEF, PET, PLA and PA 66) will be broken down into their respective soluble monomeric components while the non-hydrolysable polymeric materials (e g., PE and PP) will not be hydrolyzed which are easily separated from the former by any suitable means (e.g., filtration).

[0047] In certain embodiments, the hydrolysis conditions may involve an aqueous alkali hydroxide. Any suitable aqueous alkali hydroxide may be used. In certain embodiments, the aqueous alkali hydroxide may be one or both of sodium hydroxide and potassium hydroxide. In certain exemplary embodiments, the aqueous alkali hydroxide may be sodium hydroxide.

[0048] Any suitable amount of the aqueous alkali hydroxide may be used. In certain embodiments, the aqueous alkali hydroxide may be provided in an amount in excess relative to a total molar amount of repeating units present in the one or more hydrolysable polymeric material, such as from 1.5 molar equivalent to 3 molar equivalent relative to the total molar amount of repeating units present in the one or more hydrolysable polymeric material.

[0049] The hydrolysis may be conducted at any suitable temperature and pressure. In certain embodiments, the hydrolysis may be conducted at a temperature from 15°C to 150°C, such as from 20°C to 120°C, such as about 20°C, about 100°C and about 120°C, and ata pressure of about 1 atm.

[0050] The term “about” as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, within 1%, within 0.5%, within 0.1%, within 0.05%, within 0.01%, within 0.005%, or within 0.001% of a stated value or of a stated limit of a range, and includes the exact stated value or range.

[0051] The hydrolysis may be conducted for any suitable period of time as determined by the skilled person based on their knowledge of the field and whether the hydrolysis has been deemed completed or not. In one example, when the temperature is about 120°C, the period of time may be from 1.5 hour to 4 hours, such as about 2 hours. In another example, when the temperature is about 20°C, the period of time may be from 60 to 84 hours, such as about 72 hours.

[0052] Any suitable inorganic acid may be used. In certain embodiments, the inorganic acid may be one or more selected from a group consisting of hydrochloric acid, sulfuric acid and nitric acid. In certain exemplary embodiments, the inorganic acid may be hydrochloric acid.Any suitable amount of the inorganic acid be used. In certain embodiments, the inorganic acid may be provided at a concentration of 0.5M to 5M, such as about 2M and added to the aqueous mixture of step (i) at a volume of from 50% v / v to 300% v / v relative to the volume of the aqueous mixture of step (i), such as from 60% v / v to 275% v / v relative to the volume of the aqueous mixture of step (i), such as about 60% v / v or about 275% v / v relative to the volume of the aqueous mixture of step (i).

[0053] As demonstrated in the present disclosure, the present method is particularly useful in separating FDCA from a polymeric material that comprises repeating units derived from terephthalic acid (TPA) by selectively precipitating TPA with a weak acid.

[0054] Any suitable water-soluble weak acid (e.g., with a pKa of from 3 to 5) may be used. In certain embodiments, when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the weak acid may be one or both of acetic acid and formic acid. In certain exemplary embodiments, the weak acid may be acetic acid.

[0055] Any suitable amount of the weak acid may be used. In certain embodiments, when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the weak acid may added to the aqueous mixture of step (i) during the intermediate step (ia) at a volume of from 3% v / v to 10% v / v relative to the volume of the mixture provided in step (i), such as about 5% v / v relative to the volume of the mixture provided in step (i).

[0056] The method may be conducted in the absence of one or more of a catalyst and an organic solvent. As will be appreciated, organic solvents may be considered toxic to the environment when disposed indiscriminately.

[0057] In certain embodiments, the polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA) may be a FDCA co-polymer, such as polyethylene furanoate (PEF).

[0058] In certain embodiments, when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the polymeric material that comprises repeating units derived from terephthalic acid (TPA) may be a TPA co-polymer, such as polyethylene terephthalate (PET).As mentioned hereinbefore, the present method is useful for recovering FDCA from a mixed plastic waste stream which may contain other hydrolysable polymeric materials besides PET. Thus, in certain embodiments, the mixed plastic waste stream may further comprise one or more selected from a group consisting of polyamide 66 (PA66) and polylactic acid (PLA), or co-polymers thereof, or blends thereof. As will be appreciated, the products of the hydrolysis of these hydrolysable polymeric materials (i.e., hexamethylene diamine and adipic acid and / or lactic acid) are very soluble and remain dissolved in the aqueous mixture when FDCA (and TPA, when present) is being precipitated and removed.

[0059] The present method is also useful for recovering FDCA from a mixed plastic waste stream which may contain non-hydrolysable polymeric materials. Thus, in certain embodiments, the plastic waste stream may further comprise a polyolefin selected from one or more of a group consisting of polyethylene and polypropylene, or co-polymers thereof, or blends thereof. As will be appreciated, these non-hydrolysable polymeric materials will not be hydrolyzed when mixed plastic waste stream is subjected to hydrolysis conditions and are easily separated by any suitable means (e.g., filtration). As such, in certain embodiments, when the mixed plastic waste stream further comprises a polyolefin, the method may further comprise separating the polyolefin from the aqueous mixture of hydrolyzed products after subjecting the mixed plastic waste stream to hydrolysis conditions.

[0060] As demonstrated in the present disclosure, the present method can recover FDCA in a high yield. In certain embodiments, the yield of FDCA is above 60%, such as above 70%, such as above 80% based on the theoretical weight of FDCA in the polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA). In certain exemplary embodiments, the yield of FDCA is 80% or above based on the theoretical weight of FDCA in the polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA).

[0061] Further aspects and embodiments of the invention will now be discussed by reference to the following non-limiting examples.

[0062] EXAMPLES

[0063] MaterialsPolyethylene furanoate (PEF) resin pellets (viscosity = 0.795 dl_ / g) were obtained from Zhengzhou Alfa Chemical. Polyethylene terephthalate (PET) resin pellets (viscosity = 0.828 mPa s) were purchased from BLDpharm. Nylon 66 (PA66) resin pellets, polypropylene (PP) resin pellets (Mn = 5,000; Mw = 12,000), and low-density polyethylene (LDPE) resin pellets (melt index = 25 g / 10 min at 190 °C / 2.16 kg) were obtained from Sigma-Aldrich. Polylactic acid (PLA) resin pellets were purchased from NatureWorks (Ingeo 3052D). Sodium hydroxide pellets and glacial acetic acid were also obtained from Sigma-Aldrich and used without further purification.

[0064] Example 1: Depolymerization of PEF

[0065] NaOH pellets (0.65 g, 16 mmol) were dissolved completely in 3 ml_ of water, followed by the addition of polyethylene furan-2,5-dicarboxylate (PEF) resin pellets (1.0 g, 5.5 mmol based on repeating CgHeOs unit). The mixture was then heated at 120 °C for 2 hours. After 2 hours, the mixture was cooled to room temperature, and HCI (2M, 8.25 ml_) was added. A white precipitate of FDCA formed and was collected by suction filtration.

[0066] Yield: 686 mg, 80 %

[0067] Example 2: Depolymerization of PEF + PET + PA66 + PLA mixture

[0068] NaOH pellets (1.3 g, 32 mmol) were dissolved completely in 6 mL of water, followed by the addition of PEF resin pellets (1.0 g, 5.5 mmol based on CgHeOs unit), polyethylene terephthalate (PET) resin pellets (1.0 g, 5.2 mmol based on C10H8O4 unit), polyamide / nylon 66 (PA66) resin pellets (1.2 g, 4.7 mmol based on C12H22N2O4 unit) and polylactic acid (PLA) resin pellets (0.4 g, 5.5 mmol based on C3H4O2 unit) (see FIG. 2). The mixture was then heated at 120 °C for 2 hours. After 2 hours, the mixture was cooled to room temperature, and 20 ml of water and 1.4 ml of AcOH is added. Remaining polymer and terephthalic acid were removed via suction filtration, then HCI (2M, 16.5 mL) was added to the filtrate. A white precipitate of FDCA formed and was collected by suction filtration.

[0069] Yield: 711 mg, 82 %

[0070] FIG. 3 includes the1H NMR spectra of FDCA obtained from pure PEF depolymerization (top) and from mixed plastics depolymerization (bottom), confirming purity of the FDCA isolated using the present method of recovering FDCA.

Claims

CLAIMS1. A method of recovering furan dicarboxylic acid (FDCA) from a mixed plastic waste stream, where the mixed plastic waste stream comprises one or more polymeric materials that include one or more hydrolysable polymeric material and at least one of the one or more hydrolysable polymeric material is a polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA), the method comprising:(i) providing an aqueous mixture of hydrolyzed products obtained by hydrolysis of the mixed plastic waste stream;(ii) precipitating FDCA from the aqueous mixture of step (i) with an inorganic acid and filtering the precipitated FDCA, thereby recovering FDCA,provided that when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the method further comprises an intermediate step (ia) before conducting step (ii):(ia) preferentially precipitating TPA from the aqueous mixture of step (i) with a weak acid and removing the precipitated TPA.

2. The method according to Claim 1, wherein the aqueous mixture of step (i) is provided by subjecting the mixed plastic waste stream to hydrolysis conditions for a period of time.

3. The method according to Claim 2, where the hydrolysis conditions involve an aqueous alkali hydroxide, optionally wherein the aqueous alkali hydroxide is one or both of sodium hydroxide and potassium hydroxide, further optionally wherein the aqueous alkali hydroxide is sodium hydroxide.

4. The method according to Claim 3, wherein the aqueous alkali hydroxide is provided in an amount in excess relative to a total molar amount of repeating units present in the one or more hydrolysable polymeric material, such as from 1.5 molar equivalent to 3 molar equivalent relative to the total molar amount of repeating units present in the one or more hydrolysable polymeric material.

5. The method according to any one of Claim 2 to Claim 4, wherein the hydrolysis is conducted at a temperature from 15°C to 150°C, such as from 20°C to 120°C, such as about 20°C, about 100°C and about 120°C, and optionally, a pressure of about 1 atm.

6. The method according to Claim 5, wherein:when the temperature is about 120°C, the period of time is from 1.5 hour to 4 hours, such as about 2 hours; andwhen the temperature is about 20°C, the period of time is from 60 to 84 hours, such as about 72 hours.

7. The method according to any one of the preceding claims, wherein the inorganic acid is one or more selected from a group consisting of hydrochloric acid, sulfuric acid and nitric acid, optionally wherein the inorganic acid is hydrochloric acid.

8. The method according to any one of the preceding claims, wherein the inorganic acid is provided at a concentration of 0.5M to 5M, such as about 2M and added to the aqueous mixture of step (i) at a volume of from 50% v / v to 300% v / v relative to the volume of the aqueous mixture of step (i), such as from 60% v / v to 275% v / v relative to the volume of the aqueous mixture of step (i), such as about 60% v / v or about 275% v / v relative to the volume of the aqueous mixture of step (i).

9. The method according to any one of the preceding claims, wherein when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the weak acid is one or both of acetic acid and formic acid, optionally wherein the weak acid is acetic acid.

10. The method according to any one of the preceding claims, wherein when the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the weak acid is added to the aqueous mixture of step (i) during the intermediate step (ia) at a volume of from 3% v / v to 10% v / v relative to the volume of the mixture provided in step (i), such as about 5% v / v relative to the volume of the mixture provided in step (i).

11. The method according to any one of the preceding claims, wherein the method is conducted in the absence of one or more of a catalyst and an organic solvent.

12. The method according to any one of the preceding claims, wherein:the polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA) is a FDCA co-polymer, such as polyethylene furanoate (PEF); andwhen the one or more polymeric materials further comprises a polymeric material that comprises repeating units derived from terephthalic acid (TPA), the polymeric material thatcomprises repeating units derived from terephthalic acid (TPA) is a TPA co-polymer, such as polyethylene terephthalate (PET).

13. The method according to any one of the preceding claims, wherein the mixed plastic waste stream further comprises one or more selected from a group consisting of polyamide 66 (PA66) and polylactic acid (PI_A), or co-polymers thereof, or blends thereof.

14. The method according to any one of the preceding claims, wherein the mixed plastic waste stream further comprises a polyolefin selected from one or more of a group consisting of polyethene and polypropylene, or co-polymers thereof, or blends thereof, optionally wherein the method further comprises separating the polyolefin from the aqueous mixture of hydrolyzed products after subjecting the mixed plastic waste stream to hydrolysis conditions.

15. The method according to any of the preceding claims, wherein the yield of FDCA is above 60%, such as above 70%, such as above 80% based on the theoretical weight of FDCA in the polymeric material that comprises repeating units derived from furan dicarboxylic acid (FDCA).

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