Surface modified mesostructured iron oxyhydroxide: Synthesis, ecotoxicity, and application

Mesoporous iron oxide, particularly amine-functionalized FeO_x and FeO_x, was investigated for the removal of toxic heavy metal anions of arsenic and chromium from an aqueous solution. As a control experiment for these toxic compounds, adsorption tests were also performed on Fe₃O₄ as their counterpart bulk chemical. The mesostructures were confirmed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscopy (TEM). In addition, we prepared stock suspensions of meso-FeO_x, amine-functionalized meso-FeO_x and Fe₃O₄ particles, and compared their acute toxicity against Daphnia magna. The 24 h-EC₅₀ values of the amine-functionalized meso-FeO_x, meso-FeO_x and Fe particle suspensions used in this study were 1682, 2549 and 95 mg/L, respectively. Organism toxicity caused by spills of adsorbents can be negated when the amine-functionalized meso-FeO_x, up to 1500 mg/L, is used as the adsorbent for heavy metal treatment. The adsorption of arsenic and chromium by the three adsorbents were examined, and different adsorption models were used to describe the equilibrium and kinetic data. The amine-functionalized meso-FeO_x adsorbent was found to give the maximum adsorption capacities for arsenic and chromium (33.51 and 25.05 mg/g, respectively). This research gives promising results for the application of modified meso-FeO_x as an adsorbent of toxic heavy metal anions from aqueous solutions.