γ-FeOOH and γ-FeOOH decorated multi-layer graphene: Potential materials for selenium(VI) removal from water

The development of robust, cost-effective remediation technologies of selenium uptake from ground and surface water is challenging and at the same time urgently needed. The present study provides a new, facile synthesis protocol for lepidocrocite (gamma-FeOOH) nanoflakes and lepidocrocite decorated on mull-layered graphene (gamma-FeOOH-MLG) and their possible application for Selenate [Se(VI)] ions removal from drinking water. The morphological and structural properties of gamma-FeOOH were studied by using different techniques. There is a limited data on the adsorption of Se(VI) ions onto the 2D gamma-FeOOH nanosheets. This work delineates adsorption mechanism and merits of incorporating graphene for enhancing adsorbent's potential for selenium removal from contaminated water. The extraordinary electronic and textural properties of graphene sheets make it a physical support to stabilize gamma-FeOOH nanoflakes, substantially improving adsorption capacities and kinetics besides strengthening particle stability. Maximum adsorption capacity of gamma-FeOOH and gamma-FeOOH-MLG samples estimated by Langmuir adsorption isotherms observed to be similar to 40.09 and similar to 83.44 mg/g, respectively. The adsorption mechanism of Se(VI) to the surfaces of adsorbents was found to be monolayer and of chemisorption in nature. The pH dependence experiments showed that gamma-FeOOH exhibited maximum adsorption capacity at a pH close to the PZC 5.97 (+/- 1), which are in suitable for real ground water conditions.