Seleninic acid adsorption material

Provided is an adsorbent which is produced using a low-environmental-load material as a raw material and which selectively and efficiently adsorbs seleninic acid. A seleninic acid adsorbent according to the present disclosure contains a cellulose derivative (I) having a repeating unit represented by formula (I). In the formula, Ra represents a hydrogen atom or a group represented by formula (a-1) or a group represented by formula (a-2). In the cellulose derivative, at least one of all Ra contained in the cellulose derivative is a group represented by formula (a-1) or a group represented by formula (a-2). 本发明提供一种以低环境负荷材料为原料来制造，选择性且高效地吸附亚硒酸的吸附材料。本公开的亚硒酸吸附材料包含具有下述式(I)所示的重复单元的纤维素衍生物(I)。式中，Ra为氢原子、或下述式(a-1)所示的基团或下述式(a-2)所示的基团。需要说明的是，纤维素衍生物所含的全部Ra中，至少一个为下述式(a-1)所示的基团或下述式(a-2)所示的基团。