Simple synthesis and characterization of L-Cystine functionalized delta-FeOOH for highly efficient Hg(II) removal from contamined water and mining waste

L-Cystine functionalized delta-FeOOH nanoparticles (Cys-delta-FeOOH) were prepared by a cheap and straightforward method for using as an adsorbent of Hg(II) in aqueous solution. X-ray diffraction (XRD), attenuated total reflectance infrared spectroscopy (ATR-IR), and Raman spectroscopy confirmed that Cys-delta-FeOOH was successfully synthesized. Cys-delta-FeOOH with 14 nm crystal size, 34 m(2) g(-1) surface area, and 9 nm pore size were produced. The functionalization of the delta-FeOOH surface with cysteine decreases the point of zero charge of the iron oxyhydroxide from 8.4 in delta-FeOOH to 5.7 in Cys-delta-FeOOH, which is beneficial for the adsorption of Hg(II) near neutral pH. The maximum Hg(II) adsorption capacity of the delta-FeOOH and Cys-delta-FeOOH at pH 7 were found to be 35 mg g(-1) and 217 mg g(-1), respectively. The kinetics data were best fitted by a pseudo-second-order model, suggesting chemical adsorption on the surface and pores of Cys-delta-FeOOH nanoparticles. Finally, delta-FeOOH and Cys-delta-FeOOH filters were constructed for purifying mercury-contaminated water. The filters were highly efficient to treat mercury-contaminated water from a Brazilian river, reducing the concentration of mercury in water to values below the allowed limits by the current legislation. (C) 2018 Elsevier Ltd. All rights reserved.