Carbothermal Synthesis of Carbon-supported Nanoscale Zero-valent Iron Particles for the Remediation of Hexavalent Chromium

Abstract

Nanoscale, zero-valent iron is a promising reagent for in situ reduction of a variety of subsurface contaminants, but its utility in full-scale remediation projects is limited by material costs. Iron nanoparticles (20-100 nm diameter) supported on carbon (C-Fe0) were synthesized by reacting iron salts, adsorbed or impregnated from aqueous solutions onto 80 m2/g carbon black, at 600-800 degrees C under Ar. Similar products were obtained by heating the reactants under air in a covered alumina crucible. X-ray powder diffraction patterns show that Fe3O4 particles are formed at 300-500 degrees C in the initial stage of the reaction and that these particles are reduced to a mixture of alpha- and gamma-Fe nanoparticles above 600 degrees C. When C-Fe0 was combined with carboxymethylcellulose in a 5:1 weight ratio in water, the resulting material had similar transport properties to previously optimized nanoiron/polyanion suspensions in water-saturated sand columns. At a 10:3 Fe/Cr mole ratio, C-Fe0 reduced a 10 ppm Cr(VI) solution to approximately 1 ppm within three days. The surface area normalized first-order Cr removal rate was 1.2 h(-1) m(-2) under these conditions. These results demonstrate that reactive nanoiron with good transport properties in water-saturated porous media can be made in a scalable process from inexpensive starting materials by carbothermal reduction.

Homogeneously Dispersed Zerovalent Iron Nanoparticles Supported on Hydrochar-Derived Porous Carbon: Simple, in Situ Synthesis and Use for Dechlorination of PCBs

“…18,19 For the composite FHC-400, two peaks at 35.40°and 62.35°appeared, indicating the presence of the spinel structure Fe 2 O 3.…”

Application of Stabilized Nanoparticles for In Situ Remediation of Metal-Contaminated Soil and Groundwater: a Critical Review

“…He and Zhao [14,18] synthesized highly soil-dispersible ZVI nanoparticles using food-grade starch and CMC as stabilizers. CMC, a modified polysaccharide with a pK a value of 4.3 [19], can effectively stabilize various metal or semiconductive nanoparticles through concurrent steric and electrostatic stabilization mechanisms [19,29]. At an Fe concentration of 0.1 g/ L and with 0.2 % (w/w) of CMC (M.W.=90,000), highly stable discrete ZVI nanoparticles were obtained with a hydrodynamic diameter of 18.6 nm (Fig.…”

“…To prevent ZVI agglomeration, modification of ZVI with various stabilizers, support materials, or dispersants has been investigated intensively. Hoch et al [29] synthesized a kind of carbon-supported nanoscale zero-valent iron particles (CFe 0 ) and then modified with CMC and polyacrylate (PAA) and found the modified particles can effectively remove Cr(VI) and are transportable through porous media.…”

Nucleic acid from beans extracted by ethanediamine magnetic particles

“…of EDAMPs further demonstrated that organics had been successfully bound onto the magnetic iron oxide nanoparticles, and mainly consisted of two typical stages, corresponding to 200°C and 600°C. The first sharp weight loss under high temperature probably corresponds to the loss of NH 3 converted from organics, the final loss may be due to the carbon-thermal reduction to form α-or γ-Fe (Hoch et al 2008).…”