Abstract: The invention provides a heterocycle-substituted aromatic compound represented by the following Formula (I). In Formula (I), one of R2, R3, and R4 is Ry at a meta- or para-position with respect to Rx, R1, R2, R3, R4 and R5 not including Ry each independently representing a hydrogen atom, a substituted or unsubstituted aliphatic group having 1 to 30 carbon atoms, or a sulfonate group, where R1, R2, R3, R4 and R5 not including Ry are not hydrogen atoms all together; Rx and Ry each independently represent the following heterocyclic substituent, R6 and R7 in the heterocyclic substituents each independently representing a hydrogen atom or methyl group, and A representing a five-membered or six-membered heterocyclic group containing at least one nitrogen atom.

Abstract: Disclosed is a boron removal method which can remove boron from boron-containing water satisfactorily by using a small amount of a chemical agent, and which generates small amount of precipitate. Also disclosed is a boron-removing agent which is easy to handle and has excellent boron-adsorption ability. A xerogel of an organic polymeric compound having a cis-type diol structure and a water-soluble salt of an alkaline earth metal are added to a boron-containing water under alkaline conditions.