Abstract: Provided is a method for regenerating a liquid to be treated, the method includes bringing a lactic acid adsorbent that contains a Mg—Al-based layered double hydroxide having Mg2+ and Al3+ as constituent metals, and an ammonia adsorbent having L-type zeolite, into contact with the liquid to be treated that contains lactic acid and ammonia, to remove lactic acid and ammonia in the liquid to be treated.

Abstract: A lactic acid adsorbent includes a layered double hydroxide that contains multiple metal hydroxide layers and also contains anions and water molecules held between the metal hydroxide layers. The anions include (i) an amino acid such as glutamine, (ii) a dipeptide constituted by one or two kinds of amino acids such as glutamine, (iii) a vitamin such as ascorbic acid 2-phosphate, (iv) a pH buffer such as MES, (v) a glucose metabolite such as pyruvic acid, or (vi) inorganic ions selected from a group including NO3? and Cl?.

Abstract: A lactic acid adsorbent includes at least one of a layered double hydroxide that contains multiple metal hydroxide layers and also contains anions and water molecules held between the metal hydroxide layers, or a layered double oxide that is an oxide of a layered double hydroxide. The metal hydroxide layers contain divalent metal ions M2+ and trivalent metal ions M3+, mole ratio (M2+/M3+) of the divalent metal ions M2+ to the trivalent metal ions M3+ in a layered double hydroxide is 1.9 to 3.6, and the mole ratio in a layered double oxide is 1.8 to 3.6.

Abstract: The ammonia adsorbent contains at least one substance selected from the group consisting of L-type zeolite, ferrierite, ZSM-5 type zeolite, strongly acidic cation exchange resin and Prussian blue type complex.

Abstract: The lactic acid adsorbent contains at least one substance selected from the group consisting of layered double hydroxide, layered double oxide, weakly basic anion exchange resin having a styrene-bound dimethylamino group, and a strongly basic anion exchange resin.