Optimizing the use of natural and synthetic magnetites with very small amounts of coarse Fe(0) particles for reduction of aqueous Cr(VI)

Box-Behnken experimental design for chromium(VI) ions removal by bacterial cellulose-magnetite composites

“…At very low pH values and at pH higher than 4, the removal efficiency decreases. Our results are in agreement with other experimental studies of chromium removal using magnetic nanoparticles or bioadsorbents[27,35,36]. FromFig.7the surface plot indicates that the initial Cr(VI) concentration and the ratio solidliquid are not significant variables for the removal efficiency, if the pH is at its optimum value.…”

Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature

“…An recent study has investigated the Cr(VI) reduction performance of synthetic and natural magnetites of different particle size and found that only the finest magnetite show considerable Cr(VI) reduction yields. Mechanochemical mixing of the finer magnetites with 5% micron-sized Fe 0 increases dramatically their reductive reactivity despite the fact that the same quantity of Fe 0 added by itself reduces negligible amounts of Cr(VI) [378]. Biogenic MNPs synthesized by the Fe(III)-reducing bacterium Geobacter sulfurreducens, has been tested for the potential to remediate alkaline Cr(VI) contaminated waters associated with chromite ore processing residue (COPR).…”

Laboratory synthesis of goethite and ferrihydrite of controlled particle sizes

“…According to Guo and Barnard (2013) there are 14 species of iron oxides, ten of which occur in nature, the most abundant being goethite (α-FeOOH), hematite (α-Fe 2 O 3 ) and magnetite (Fe 3 O 4 ), followed by ferrihydrite [Fe 10 O 14 (OH) 2 ] (Michel et al, 2007), maghemite (γ-Fe 2 O 3 ) and lepidocrocite (γ-FeOOH). These iron oxides are responsible for the mobility and fate of numerous chemical species in soils and aquatic environments through adsorption processes, particularly onto goethite and ferrihydrite (Maji et al, 2008;Swedlund et al, 2009;Villalobos and Antelo, 2011) or through adsorption followed by reduction mechanisms as is the case of susceptible species on magnetite (Villacís-García et al, 2015).…”