Abstract: The purpose of the present disclosure is to provide a method for regenerating a highly water-absorbing polymer that has been deactivated by an acid, the method enabling formation of a highly water-absorbing recycled polymer having predetermined water absorption properties. The regeneration method according to the present disclosure is configured as follows. This method regenerates a highly water-absorbing polymer that has been deactivated by an acid into a highly water-absorbing recycled polymer having predetermined water absorption properties.

Abstract: A method of recovering urine-derived nutrient salts from a used absorbent article containing urine, includes: immersing the used absorbent article in an aqueous solution containing a calcium compound to deactivate a superabsorbent polymer; using a sieve to separate a solid-liquid mixture yielded by the deactivation into a first fraction containing the constituent materials of the absorbent article, and a second fraction containing an aqueous solution containing the calcium compound and nutrient salts, and nutrient-salt-containing sediment that has passed through the sieve; producing nutrient-salt-containing sediment using a HAP method; and adjusting the pH of the aqueous solution in contact with the nutrient-salt-containing sediment to within a range of 5.6-7.0, dissolving at least some of a calcium compound other than hydroxyapatite in the sediment, and increasing the hydroxyapatite content of the sediment.

Abstract: A method enabling a used superabsorbent polymer recovered from used absorbent, etc., to be readily and inexpensively recovered without using acids or alkalies. The used superabsorbent polymer is treated with an aqueous solution of a multivalent metal salt such as calcium chloride, etc., the superabsorbent polymer treated with the aqueous solution of a multivalent metal salt is treated with an aqueous solution of an alkali metal salt such as sodium chloride, etc., the superabsorbent polymer treated with the aqueous solution of an alkali metal salt is washed with water, and the superabsorbent polymer washed with water is then dried.

Abstract: A method enabling a used superabsorbent polymer recovered from used absorbent, etc., to be readily and inexpensively recovered without using acids or alkalies. The used superabsorbent polymer is treated with an aqueous solution of a multivalent metal salt such as calcium chloride, etc., the superabsorbent polymer treated with the aqueous solution of a multivalent metal salt is treated with an aqueous solution of an alkaline metal salt such as sodium chloride, etc., the superabsorbent polymer treated with the aqueous solution of an alkaline metal salt is washed with water, and the superabsorbent polymer washed with water is then dried.