Adsorbent dispersion and adsorption method

The purpose of the present invention is to provide an anion-adsorbent dispersion that comprises an iron oxyhydroxide nano-dispersion that is stable and that does not contain a component derived from an auxiliary component. This anion-adsorbent dispersion is formed by dispersing, in a solvent, particles that have an iron oxyhydroxide as a main component and that have an average particle diameter d50 of 2 μm or less. The iron oxyhydroxide is preferably β-iron oxyhydroxide. In addition, the average diameter d50 of the particles that have an iron oxyhydroxide as a main component is preferably 0.2 μm or less.