Akaganeite decorated graphene oxide composite for arsenic adsorption/removal and its proconcentration at ultra-trace level

Carboxylic graphene oxide (GO-COOH) is decorated with akaganeite (beta-FeOOH) to produce a beta-FeOOH@GO-COOH nanocomposite. The nanocomposite acts as an efficient adsorption medium for the uptake of arsenite and arsenate within a wide range of pH 3-10, providing high adsorption capacities of 77.5 mg g(-1) for As(III) and 45.7 mg g(-1) for As(V), respectively. Adsorption efficiencies of 100% and 97% are achieved for 5 successive operation cycles for the removal of 100 mu g L-1 As(V) and As(III) in 5 fresh portions of aqueous solution (1.0 mL for each) with 3 mg nanocomposite. After 20 successive adsorption cycles, removal efficiency of >80% is still maintained for both arsenate and arsenite. Further, a removal efficiency of >90% is obtained for 1000 mu g L-1 As(V) with 3 mg beta-FeOOH@GO-COOH for 5 successive adsorption cycles, and the presence of 2000-fold SO42-, NO3-, Cl- and Mg2+ pose no interfering effect. beta-FeOOH@GO-COOH also provides a promising medium for the preconcentration of ultra-trace inorganic arsenic. 1 mg of nanocomposite is used to adsorb 0.1-3.00 mu g L-1 As(V) in 4.0 mL solution, and the retained arsenate is recovered by 400 mu L of NaOH (2 mol L-1, containing 2.0% NaBH4), followed by detection with atomic fluorescence spectrometry. A detection limit of 29 ng L-1 is obtained for arsenate. This procedure is validated by analyzing arsenic in a certified reference material (GBW 09101b) and further applied for arsenic determination in water samples. (C) 2015 Elsevier Ltd. All rights reserved.