The present invention provides a method which, in the process of manufacturing recycled pulp fibers from a mixture of pulp fibers and a high water-absorption polymer, enables efficient manufacturing of the recycled pulp fibers while properly removing the high water-absorption polymer from the pulp fibers. This method comprises: a supply step (S19-2a) for supplying an aqueous solution containing a mixture (98) to a driving fluid supply port (DI) of an ejector (107) and simultaneously supplying, to a suction fluid supply port (AI) of the ejector, a gaseous substance (Z2) which is capable of degrading a high water-absorption polymer so as to make the degraded polymer dissolvable; and a treatment step (S19-2b) for discharging, from a mixed fluid discharge port (CO) of the ejector that is connected to a lower part of a treatment tank (105), a mixed liquid, which is formed when the aqueous solution and the gaseous substance are mixed within the ejector, into a treatment liquid (P2) within the treatment tank, so as to lessen the high water-absorption polymer in the mixture.

The purpose of the present disclosure is to provide a recovery method for an organic acid. The recovery method makes it possible to efficiently recover an organic acid that is included in a deactivating aqueous solution that includes excrement. This recovery method has the following features. A method for recovering an organic acid that deactivates a highly water-absorbent polymer that is included in used absorbent articles, the method being characterized by including: a deactivation step (S1) in which the highly water-absorbent polymer is immersed in a deactivating aqueous solution that includes an organic acid and has a prescribed pH and the highly water-absorbent polymer is deactivated; a highly water-absorbent polymer removal step (S2) in which the deactivated highly water-absorbent polymer is removed from the deactivating aqueous solution; a pH adjustment step (S3) in which the deactivating aqueous solution is adjusted to a prescribed pH; a concentration step (S4) in which the deactivation step (S1), the highly water-absorbent polymer removal step (S2), and the pH adjustment step (S3) are repeated using deactivating aqueous solution that has gone through the pH adjustment step (S3) and the organic acid in the deactivating aqueous solution is concentrated; and an organic acid recovery step (S6) in which the organic acid is recovered from the deactivating aqueous solution.

The purpose of the present invention is to provide a recycled pulp fiber manufacturing method with which it is possible to easily obtain recycled pulp fibers containing less of a high water-absorption polymer without requiring any mechanical equipment such as an ozone generation apparatus. This method is for manufacturing recycled pulp fibers from used sanitary goods including pulp fibers and a high water-absorption polymer, and is characterized by comprising: an inactivation step (S1) for immersing a sanitary goods constituent material in an acid-containing aqueous solution so as to inactivate the high water-absorption polymer; a high water-absorption polymer degradation step (S3) for generating chlorine dioxide by adding a chlorine dioxide generating material, which is capable of generating chlorine dioxide through reaction with an acid, to the acid-containing aqueous solution that has undergone the inactivation step (S1), and then degrading the inactivated high water-absorption polymer using said chlorine dioxide; and a recycled pulp fiber recovery step (S4) for recovering the recycled pulp fibers from the acid-containing aqueous solution that has undergone the high water-absorption polymer degradation step (S3).

A recycled pulp that is reusable sanitary products is efficiently manufactured by recovering pulp fiber from used sanitary products containing the pulp fiber and a polymer absorbent. The method of the present invention comprises: a step applying a mechanical force to the used sanitary products in an aqueous solution containing a polyvalent metal ion or an acidic aqueous solution with a pH of 2.5 or lower and thus degrading the used sanitary products into the pulp fiber and other materials; a step separating the pulp fiber from the mixture of the pulp fiber and other materials that has been formed in the degradation step; and a step treating the pulp fiber thus separated with an ozone-containing aqueous solution with a pH of 2.5 or lower.

A recycled pulp that is reusable sanitary products is efficiently manufactured by recovering pulp fiber from used sanitary products containing the pulp fiber and a polymer absorbent. The method of the present invention comprises: a step applying a mechanical force to the used sanitary products in an aqueous solution containing a polyvalent metal ion or an acidic aqueous solution with a pH of 2.5 or lower and thus degrading the used sanitary products into the pulp fiber and other materials; a step separating the pulp fiber from the mixture of the pulp fiber and other materials that has been formed in the degradation step; and a step treating the pulp fiber thus separated with an ozone-containing aqueous solution with a pH of 2.5 or lower.

In this method of producing recycled fibers by removing superabsorbent polymers from fibers containing superabsorbent polymers, recycled fibers are efficiently produced while the superabsorbent polymers are suitably removed from the fibers. This method produces recycled fibers from a mixture of fibers and superabsorbent polymers. This method involves a continuous treatment step (S36) in which, in a treatment tank (31) having a treatment solution that can dissolve superabsorbent polymers, superabsorbent polymers are dissolved while a mixed solution (51) that contains water and fibers containing superabsorbent polymers is continuously supplied at a first flow rate, and the treatment solution (52) containing the removed fibers is continuously discharged to outside of the treatment tank at a second flow rate.

The purpose of the present invention is to provide a method for producing recycled pulp fibers such that articles using the recycled pulp fibers can easily achieve a uniform whiteness and users are not prone to feel psychological resistance to articles using the recycled pulp fibers. 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 multiple types of 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 the pulp fibers are bleached to form recycled pulp fibers; and a step for discharging the treatment solution (52) from a treatment solution discharge port (33), wherein the recycled pulp fibers have a 0-10 YI with respect to a standard white plate.

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 recycled pulp that is reusable sanitary products is efficiently manufactured by recovering pulp fiber from used sanitary products containing the pulp fiber and a polymer absorbent. The method of the present invention comprises: a step applying a mechanical force to the used sanitary products in an aqueous solution containing a polyvalent metal ion or an acidic aqueous solution with a pH of 2.5 or lower and thus degrading the used sanitary products into the pulp fiber and other materials; a step separating the pulp fiber from the mixture of the pulp fiber and other materials that has been formed in the degradation step; and a step treating the pulp fiber thus separated with an ozone-containing aqueous solution with a pH of 2.5 or lower.