Diols are key intermediate materials for polymers. Conventional distillation techniques for the separation of diols require a substantial energy input. Alternatively, in this paper we examine an adsorption technique to recover and separate diols. Silica gels modified by boronate were used as a selective adsorbent for diols. First, using potentiometric titration, we examined the number and pK(a) of the active site included in the gels. The values of the pK(a) of the boronate were larger than that of phenylboronic acid. From the adsorption experiments on the resin, we found that main adsorption mechanism was a complex formation between neutral boronic acid and the diols. A pH value smaller than pK(a) (=10) of boronate is desirable for the adsorption of diols. Silica gels modified by phenylboronic acid effectively adsorbed the hydrophobic diols. The adsorption capacity of vicinal and 1,3-diols were similar.