The purpose of the present disclosure is to provide a method for producing pulp fibres for saccharification from the pulp fibres of used sanitary items, said pulp fibres for saccharification having low lignin contents distributed within a narrow range, and enabling the production of pulp fibres for saccharification having superior saccharification properties. The production method according to the present disclosure is characterised by comprising the following: a step for supplying a mixed solution (51) containing pulp fibres and highly-absorbent polymers sourced from used sanitary items to a treatment tank (31) via a mixed-solution supply port (32); a step for supplying an ozone-containing gas (53) to a treatment solution (52) within the treatment tank (31) via an ozone-containing-gas supply port (43); a step for lifting the ozone-containing gas (53) whilst lowering the pulp fibres and highly-absorbent polymers within the treatment tank (31), thereby bringing the ozone-containing gas (53) into contact with the pulp fibres and highly-absorbent polymers, and forming pulp fibres for saccharification from the pulp fibres; and a step for discharging the treatment solution (52) via a treatment-solution discharge port (33). The method is further characterised in that the pulp fibres for saccharification have lignin contents of 0.1% or less.

The purpose of the present invention is to provide a method which is for producing pulp fibers for cellulose nanofiberization from pulp fibers of used sanitary products, and which can produce pulp fibers for cellulose nanofiberization that have low lignin content and a low distribution thereof and that have excellent cellulose nanofiberization properties. This method is described below. The method is characterized by involving: a step for supplying, from a mixed solution supply port (32) to a treatment tank (31), a mixed solution (51) which contains superabsorbent polymers and pulp fibers derived from used sanitary products; a step for supplying an ozone-containing gas (53) from an ozone-containing gas supply port (43) to a treatment solution (52) inside of the treatment tank (31); a step in which, by raising the ozone-containing gas (53) while lowering the superabsorbent polymers and pulp fibers in the treatment tank (31), the ozone-containing gas (53) is brought into contact with the superabsorbent polymers and the pulp fibers, and pulp fibers for cellulose nanofiberization are formed from the pulp fibers; and a step for discharging the treatment solution (52) from a treatment solution discharge port (33), wherein the pulp fibers for cellulose nanofiberization have a lignin content of less than or equal to 0.1 mass %.

A method for manufacturing terephthalic acid includes the following operations: providing a raw material, in which the raw material includes a first raw material including polyethylene terephthalate; performing a depolymerization reaction on the first raw material to form a depolymerization product, in which the depolymerization product includes disodium terephthalate; performing a decolorization process on the disodium terephthalate to form decolorized disodium terephthalate and precipitated sludge; separating the decolorized disodium terephthalate and the sludge; and forming terephthalic acid from the decolorized disodium terephthalate after separating the decolorized disodium terephthalate and the sludge.

A method for manufacturing terephthalic acid includes the following operations: providing a raw material, in which the raw material includes a first raw material including polyethylene terephthalate; performing a depolymerization reaction on the first raw material to form a depolymerization product, in which the depolymerization product includes disodium terephthalate; performing a decolorization process on the disodium terephthalate to form decolorized disodium terephthalate and precipitated sludge; separating the decolorized disodium terephthalate and the sludge; and forming terephthalic acid from the decolorized disodium terephthalate after separating the decolorized disodium terephthalate and the sludge.

Systems and methods are provided that involve a subcritical water reaction to recycle the cellulose and polyester components of waste cotton and cotton/polyester blend textiles that would otherwise be discarded or disposed of. Specifically, the disclosed methods provide for treatment of the waste textiles to produce advanced materials including cellulose and terephthalic acid (TPA) with a low environmental impact. The cellulose and TPA that are produced are of a high quality allowing for production of regenerated cellulose and regenerated polyethylene terephthalate (PET) suitable for fiber spinning and textile applications.

Systems and methods are provided that involve a subcritical water reaction to recycle the cellulose and polyester components of waste cotton and cotton/polyester blend textiles that would otherwise be discarded or disposed of. Specifically, the disclosed methods provide for treatment of the waste textiles to produce advanced materials including cellulose and terephthalic acid (TPA) with a low environmental impact. The cellulose and TPA that are produced are of a high quality allowing for production of regenerated cellulose and regenerated polyethylene terephthalate (PET) suitable for fiber spinning and textile applications.

A method for manufacturing terephthalic acid includes the following operations: providing a raw material, in which the raw material includes a first raw material including polyethylene terephthalate; performing a depolymerization reaction on the first raw material to form a depolymerization product, in which the depolymerization product includes disodium terephthalate; performing a decolorization process on the disodium terephthalate to form decolorized disodium terephthalate and precipitated sludge; separating the decolorized disodium terephthalate and the sludge; and forming terephthalic acid from the decolorized disodium terephthalate after separating the decolorized disodium terephthalate and the sludge.

A method for manufacturing terephthalic acid includes the following operations: providing a raw material, in which the raw material includes a first raw material including polyethylene terephthalate; performing a depolymerization reaction on the first raw material to form a depolymerization product, in which the depolymerization product includes disodium terephthalate; performing a decolorization process on the disodium terephthalate to form decolorized disodium terephthalate and precipitated sludge; separating the decolorized disodium terephthalate and the sludge; and forming terephthalic acid from the decolorized disodium terephthalate after separating the decolorized disodium terephthalate and the sludge.

A process for chemically recycling polyethylene terephthalate (PET) which utilizes a microwave absorber to optimize glycolytic depolymerization of PET via microwave irradiation. The method of chemically degrading PET to its reactive intermediate, bis(2-hydroxyethyl) terephthalate (BHET), is carried out by: (a) combining PET with ethylene glycol and a catalytic system comprising a catalyst and a microwave absorber to produce a heterogeneous reaction mixture; and then (b) heating by microwave irradiating the reaction mixture to a temperature sufficient to produce a reaction product comprising BHET. The BHET monomer then can be purified and re-polymerized to form new, virgin PET.

A process for chemically recycling polyethylene terephthalate (PET) which utilizes a microwave absorber to optimize glycolytic depolymerization of PET via microwave irradiation. The method of chemically degrading PET to its reactive intermediate, bis(2-hydroxyethyl) terephthalate (BHET), is carried out by: (a) combining PET with ethylene glycol and a catalytic system comprising a catalyst and a microwave absorber to produce a heterogeneous reaction mixture; and then (b) heating by microwave irradiating the reaction mixture to a temperature sufficient to produce a reaction product comprising BHET. The BHET monomer then can be purified and re-polymerized to form new, virgin PET.