Mg Fe layered double hydroxide-graphene oxide nanocomposite adsorbents for arsenic removal

This paper presents a systematic investigation on the synthesis, structural characterization, and performance evaluation of a range of composite adsorbents of MgFe layered double hydroxide (LDH) with 2-dimensional graphene oxide (GO) for arsenic (As) removal from aqueous solutions. Synthesized through a co-precipitation method, the LDH-GO composites are featured with GO nanosheets loaded with LDH particles designed at different Fe/(Fe + Mg) molar ratios (x = 0.26, 0.42, and 0.60) and mass contents (20, 50, and 80 wt%). The composites have been comprehensively characterized for their structural, textural, and physicochemical properties. A systematic evaluation on their performance towards the batch adsorption of both As(III) and As(V) has been undertaken, with the aim of elucidating the relationships between their composition/structure and adsorption performance. Among them, LDH0.42‐80-GO20 with an optimum x value of 0.42 and an LDH content of 80 wt% shows the best overall performance with the highest maximum As(V) adsorption capacity (307 mg g‐1) and second highest maximum As(III) adsorption capacity (186 mg g‐1), which is attributed to its high surface area and high zeta potential. In particular, its enhanced zeta potential results from the strategic incorporation of Mg-based hydroxide known for high point of zero charge within the LDH structure, which improves its adsorption of As(V) often present in anion forms. Notably, the arsenic adsorption capacities of LDH0.42‐80-GO20 rival and even surpass those of some benchmark oxide- and hydroxide-based adsorbents reported to date. Consequently, this study offers insights into the rational design of high-capacity adsorbents for arsenic removal.