Facile preparation of amine-rich polyamidoamine (PAMAM) gel for highly efficient removal of Cr(VI) ions

The development of high-performance adsorbent towards toxic Cr(VI) ions is highly desired. Herein, we present a polyamidoamine (PAMAM) gel with porous structure and multiple amine groups for highly efficient removal of Cr (VI) ions. The gel is prepared in a single step based on the crosslinking reaction between the PAMAM and the epichlorohydrin. The adsorption property of resulted PAMAM gel towards toxic Cr(VI) ions was evaluated systematically with respect to the solution pH, NaCl, temperature, contact time, and initial concentration of Cr(VI) ions. At relatively low concentration of Cr(VI) ions (≤200 mg/L), the PAMAM gel exhibited very high removal efficiency (≥99.32%) towards Cr(VI) ions. The adsorption rate is fast and could reach equilibrium within about 60 min. The maximum adsorption capacity of PAMAM gel could reach as high as 267.4 mg/g. Furthermore, the adsorption data fitted well with the pseudo-second order kinetic model and Langmuir isotherm. After adsorption, the Cr(VI) ions-adsorbed PAMAM gel could be easily collected by filtration and the PAMAM gel presented nice desorption capability. Moreover, it still showed high adsorption capacity (202.15 mg/g) for Cr(VI) ions even after five cycles.