Highly efficient and ultrafast removal of Cr(VI)in aqueous solution to ppb level by poly(allylamine hydrochloride) covalently cross-linked amino-modified graphene oxide.

We herein report a facile strategy to prepare poly(allylamine hydrochloride) cross-linked amino-modified graphene oxide (PAH-ASGO) by Schiff-base reactions. The resulting PAH-ASGO exhibited a maximum adsorption capacity of 373.1 mg/g for Cr(VI), which was nearly 9 times higher than that of pure graphene oxide, exceeding that of most GO-based materials previously reported. More significantly, PAH-ASGO can effectively diminish the Cr(VI) concentration from 9.9 mg/L to the extremely low level of 0.004 mg/L within 10 s, far below the maximum allowable level of Cr(VI) (0.05 mg/L) in drinking water. In addition, the adsorbents still displayed excellent removal efficiency of 91.8% after 10 cycles. Considering the broad diversity, we developed also a magnetic PAH-ASGO/Fe3O4 adsorbent by a simple cross-linking reaction to achieve rapid separation of PAH-ASGO from their aqueous solution. Finally, the PAH-ASGO was successfully utilized to treat the actual industrial effluent.