Polybenzoxazine: A powerful tool for removal of mercury salts from water

A reusable macroporous polybenzoxazine resin with high specific surface area was prepared as sorbent material for the removal of mercury salts. For this purpose, allyl-functionalized bis-benzoxazine was cured in dimethyl sulfoxide by thermally activated ring-opening polymerization at 180 C for 3 d followed by a freeze-drying process. The porous structure of the resin was confirmed by SEM analysis and N₂ adsorption/desorption studies at 77.3 K. Among various metal ions, namely, Pb^II, Fe^II, Mn^II, Cu^II, Zn^II, and Cd^II, the porous polybenzoxazine resin exhibited a specific sorption behaviour towards Hg ^II. Mainly chemisorption and to some extent adsorption mechanisms were proposed for the observed high loading capacity of the resin. As evidenced by FTIR spectral analysis, the chemisorption is attributed to the coordination system formed between free OH and tertiary amino groups in the polybenzoxazine structure and Hg^II ions. It was also demonstrated that the porous polybenzoxazine can be regenerated simply by treatment with acids. The resin was recycled for up to seven cycles without any significant loss of activity, as proved by sorption and desorption experiments.