Uniformly dispersed FeOOH nanoparticles supported on alumina-carbon nanosheets for Cr(VI) removal

Abstract

The mesoporous alumina-carbon nanosheets supported FeOOH nanoparticles were prepared by a facile and cost-effective hydrothermal synthesis for Cr(VI) removal in the wastewater, based on the affinity and selectivity of FeOOH and the accelerated mass transfer of nanosheet structure. The prepared nanoparticles with a small size of 2–5 nm were uniformly dispersed over the alumina-carbon nanosheets, attributed to the metal interaction and mesoporous confinement. The acid property after the introduction of alumina induced a positive charge on the surface of the adsorbent, which could enhance the adsorption of negatively charged metal ions. The Cr(VI) removal efficiency with the Al/Fe ratios showed a similar volcano curve. When Al/Fe ratio was around 3.3 and pHpzc was about 7.1, the adsorbent exhibited the best Cr(VI) removal efficiency of 99.4 %, owing to a large specific surface area, and small nanoparticle size, combined with abundant moderate-strong acid content of 294.5 μmol NH3 g−1.The Langmuir model could describe the adsorption process well, and the kinetic data was consistent with Pseudo-second-order. The thermodynamics revealed that the reaction process was spontaneous and endothermic. The adsorbent maintained a high removal efficiency of more than 80 % after running for five cycles and kept over 95 % under ionic co-existence and natural water conditions. Therefore, this study provides a new insight into the rational construction of efficient adsorbents with low-cost Cr(VI) removal.