Potential of modified iron-rich foundry waste for environmental applications: Fenton reaction and Cr(VI) reduction

Simultaneous removal of aniline, antimony and chromium by ZVI coupled with H2O2: Implication for textile wastewater treatment

Aniline, antimony (Sb) and chromium (Cr) are typical and regulated co-contaminants in textile wastewater, but their removal was often investigated individually. In this work, simultaneous removal of aniline, Sb and Cr by ZVI coupled with H₂O₂ was studied. With the dosage of 0.5 g L^-1 ZVI and 2 mM H₂O₂, aniline, Sb and Cr can be removed completely at pH 3. Experiment with iso-propanol as the radical scavenger confirmed that OH derived from Fenton reaction accounts for aniline degradation, but not for Sb and Cr removal. H₂O₂ accelerated Fe(0) corrosion and generated the nanoscale iron(hydro)oxides. Aniline was degraded by OH first and then the degradation products were removed by iron(hydro)oxides via adsorption and co-precipitation. Both Fe(0) and iron(hydro)oxides were responsible for Sb and Cr removal, yet iron(hydro)oxides were identified as the major contributor. X-ray photoelectron spectroscopy analysis demonstrated that Sb and Cr were removed mainly as the states of Sb(III) and Cr(III). The real textile wastewater investigation confirmed that ZVI coupled with H₂O₂ can eliminate aniline, Sb and Cr effectively, which has important implications for the advanced treatment of textile wastewater.

Use of iron and bio-oil wastes to produce highly dispersed Fe/C composites for the photo-Fenton reaction

This work describes the synthesis, characterization, and application of an active heterogeneous photo-Fenton system obtained from two different wastes, i.e., laterite (an iron mining waste) and the acid aqueous fraction (AAF) from bio-oil production. AAF with high acidity (ca. 3 mol_H+ L^-1) and organic concentration (25 wt.%) obtained from biomass flash pyrolysis was used for the efficient extraction of Fe³⁺ from laterite waste. After extraction, the mixture Fe³⁺/AAF was dried and treated at different temperatures, i.e., 500, 650, and 800 °C, to obtain Fe/C reactive composites. Mössbauer, XRD, TG, elemental analyses, and SEM/EDS showed the presence of highly disperse Fe oxide nanoparticles at 500 and 650 °C and Fe⁰ particles in the material obtained at 800 °C with carbon contents varying from 74 to 80 %. The three composites were tested as heterogeneous catalysts in the photo-Fenton reaction for the oxidation of the model dye contaminant methylene blue, showing high activities at neutral pH.

Controlled formation of reactive Fe particles dispersed in a carbon matrix active for the oxidation of aqueous contaminants with H₂O₂

In this work, reactive iron nanoparticles dispersed in a carbon matrix were produced by the controlled thermal decomposition of Fe(3+) ions in sucrose. During the sucrose decomposition, the Fe(3+) ions are reduced to form iron nanometric cores dispersed in a porous carbonaceous matrix. The materials were prepared with iron contents of 1, 4, and 8 wt.% and heated at 400, 600, and 800 °C. Analyses by X-ray diffraction, Mössbauer spectroscopy, magnetization measurements, Raman spectroscopy, termogravimetric analyses, BET surface area, scanning, and transmission electron microscopy showed that at 400 °C, the materials are composed essentially of Fe3O4 particles, while treatments at higher temperatures, i.e., 600 and 800 °C, produced phases such as Fe(0) and Fe3C. The composites were tested for the oxidation of methylene blue with H2O2 by a Fenton-type reaction and also H2O2 decomposition, showing better performance for the material containing 8 % of iron heated at 400 and 600 °C. These results are discussed in terms of Fe(2+) surface species in the Fe3O4 nanoparticles active for the Fenton reaction.

Reactive porous composites for chromium(vi) reduction applications based on Fe/carbon obtained from post-consumer PET and iron oxide

By using post-consumer PET waste and iron oxide (Fe₂O₃), novel porous magnetic Fe/carbon composites for environmental applications have been obtained by a very simple process.

Co2+-loaded periodic mesoporous aluminum phosphonates for efficient modified Fenton catalysis

Periodic mesoporous aluminum phosphonates exhibit high uptake capability for Co²⁺ and thus oxidizing ability in organic contaminant decomposition.

Hollow cobalt phosphonate spherical hybrid as high-efficiency Fenton catalyst

Organic-inorganic hybrid of cobalt phosphonate hollow nanostructured spheres were prepared in a water-ethanol system through a mild hydrothermal process in the absence of any templates using diethylenetriamine penta(methylene phosphonic acid) as bridging molecule. SEM, TEM and N2 sorption characterization confirmed a hollow spherical micromorphology with well-defined porosity. The structure and chemical states of the hybrid materials were investigated by FT-IR, XPS and thermogravimetric analysis, revealing the homogeneous integrity of inorganic and organic units inside the network. As a heterogeneous catalyst, hollow cobalt phosphonate material exhibited considerable catalytic oxidizing decomposition of methylene blue with sulfate radicals as compared to cobalt phosphonate nanoparticles synthesized in single water system, which could be attributed to enhanced mass transfer and high surface area for the hollow material. Some operational parameters, including pH and reaction temperature, were found to influence the oxidation process. The present results suggest that cobalt phosphonate material can perform as an efficient heterogeneous catalyst for the degradation of organic contaminants, providing insights into the rational design and development of alternative catalysts for wastewater treatment.

Use of tar pitch as a binding and reductant of BFD waste to produce reactive materials for environmental applications

In this work, a new approach is presented for the modification of the hazardous steel industry waste BFD (Blast Furnace Dust) into a versatile material for application in environmental remediation processes. Tar pitch, another waste, was used to agglomerate the very fine (submicrometric) dust particles to produce a compact and robust pelletized material that under simple thermal treatment produces notably reactive reduced Fe phases. SEM, TG/DTA, Mössbauer, XRD, Raman, BET and elemental analyses indicated that the tar/BFD composite (1:1wt ratio) pellets treated at 400, 600 and 800°C lead to tar decomposition to form a carbon binding coat concomitant with the reduction of the Fe oxides to produce primarily Fe3O4 (magnetite), FeO (wüstite) and Fe(0). Preliminary reactivity studies indicated that these treated composites, especially at 800°C, are active for the reduction of Cr(VI)aq and for the elimination of textile dye via reduction and the Fenton reaction.