Development of hollow δ-FeOOH structures for mercury removal from water

Abstract

δ-FeOOH, a magnetic iron oxyhydroxide, has a significant number of -OH groups on its surface. These provide an attractive platform for heavy metal species in contaminated water, giving it potential as an adsorbent. Its performance can be improved by increasing the number of active surface sites. δ-FeOOH hollow structures were synthesized on a mesoporous silica surface then treated with NaOH solution. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that structure synthesis was successful. δ-FeOOH, 5,27 nm, hollow crystals were produced with 63 m2 g−1 surface area and 20 nm average pore size. The point of zero charge was 4.72, which is beneficial for Hg(II) adsorption near neutral pH. The maximum Hg(II) adsorption capacity at pH 7 was determined as 89.1 mg g−1. The kinetics data were best fitted by a pseudo-second-order model with k2 equal 0,1151 g mg−1min−1. Finally, a nanomaterial filter was developed and used to remove mercury in water samples from a Brazilian river.