Nippon Soda Co., Ltd.

Takahashi Metal Industries Co., Ltd.

Toshiyasu Hirokawa

Nobuo Kimura

Tsuyoshi Noishiki

Yukiko Takahashi

Masato Amaike

Yuichi Tateishi

A method of selectively and efficiently adsorbing an anion such as a phosphate ion which adversely affect the environment when discharged without any treatment, or an anion which can be used beneficially when recovered, from waste water or a solution including such ion using an adsorbent. A method of adsorbing an anion of interest from an aqueous solution (A) containing the anion of interest and the other anion using an anion adsorbent, including performing at least (1) a step of contacting the aqueous solution (A) having a pH of 5.8 or less with the anion adsorbent to allow the anions to be adsorbed to the anion adsorbent, and then (2) a step of contacting water or an aqueous solution (B) having a pH of 5.2 to 11 with the anion adsorbent to desorb at least a part of the other anion adsorbed to the anion adsorbent from the anion adsorbent.

Adsorption method

Adsorbent particle includes iron oxyhydroxide as a main component, wherein 90% or more of volume of particle is constituted of a granular crystal having a crystal grain size of 20 nm or less or a columnar crystal having a width of 10 nm or less and length of 30 nm or less and particle has BET specific surface area of 250 m/g or more. Above adsorbent particle is produced by a method including a step of generating iron oxyhydroxide by adding base represented by YOH (wherein Y represents a monovalent atom or atomic group) to solution including at least one selected from trivalent iron compounds represented by FeX(wherein X represents a monovalent atom or atomic group other than OH) while adjusting pH to pH 3 to 6, wherein solution has total concentration of FeX, YOH and other electrolytes of 10% by mass or more at completion of the step.

Adsorbent particles

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Nagahama, Japan

Toshiyasu Hirokawa