Iron-rich Waste Research Articles

Recycling of a secondary lead smelting matte by selective citrate leaching of valuable metals and simultaneous recovery of hematite as a secondary resource

A new recycling process, according to the zero-waste concept, was investigated for an iron rich waste stream, more specifically a secondary lead smelting matte. The process consists of a selective citrate leaching of Pb, Cu, Ni and Zn in combination with a roasting step, leading to a simultaneous recovery of hematite as a secondary iron resource. The parameters, such as leaching time, leaching temperature, H2O2 concentration and roasting temperature, were experimentally optimized. The maximum Pb leaching efficiency was 93% and the leachability of Cu (33%) and Zn (11%) increased slightly in the presence of 0.5M H2O2 in 1M citrate at 25°C and pH5.5. Importantly, almost no Fe was leached (<0.6%) from the iron rich matrix material at this condition allowing for a maximal recovery of hematite as a secondary resource after further treatment (i.e. roasting or sulfur removal). The leachability of Pb, Cu, Ni and Zn was strongly affected by the roasting temperature. Maximum leaching efficiency in 1M citrate (25°C, L/S ratio 10, pH6.5) was 93% for Pb, 80% for Cu and 60% for Zn at a roasting temperature of 600°C, while for Ni the maximum leaching efficiency of 53% was reached after roasting at 650°C. Furthermore, when oxidative roasting was applied, the leaching residue consists dominantly of hematite (Fe2O3) with minor quantities of PbSO4, which can be used as pig iron ore (Fe >60wt%).

Efficient reduction of nitrobenzene into aniline using Fe-rich waste from electric furnace dust

Nitroaromatic compounds are widely used in the industry. They are most often resistant to microbial degradation, mutagenic and carcinogenic. As a consequence, reduction of nitroaromatic compounds into less toxic and biodegradable products has been studied using Fe0. Here, we tested iron-rich waste from electric furnace dust to convert nitrobenzene into aniline. Thermal reduction of electric furnace dust under hydrogen at 500 °C gave a material with about 56 % Fe0 and 21 % FeO. This material allowed to decrease 86 % of nitrobenzene during the conversion of nitrobenzene into aniline. In conclusion, electric arc furnace dust can be transformed into an efficient reducing reagent.

Neutralization/purification of the wastewaters from printed circuit boards production using waste by-products

The purpose of this work was development of a new method for the neutralization/purification of printed circuit boards wastewater (PCBW) originating from Zagreb, Croatia, using two industrial by-products. PCBW was characterized with low pH value (2.11) and high concentration of TDS (50190 mg L−1), copper (4190 mg L−1) and iron (2660 mg L−1). Waste base (WB), by-product of the alumina production, and waste sludge, by-product of the electrochemical treatment of groundwater, were employed as neutralization/adsorption agents. Due to its high neutralization capacity WB was used for pH adjustment to pH 8 and heavy metals removal from both effluents, yet the final removal of the contaminants down to the regulated values was assessed by adsorption/coagulation with the iron and aluminum rich waste sludge. Following the combined treatment the removal efficiency of iron and copper was higher than 99.99% with their final concentration in the treated water of 0.151 mg L−1 and 0.129 mg L−1, respectively. Following the ozone base oxidation the removal efficiency of the organic contaminants was more than 83%. The successful application of the industrial waste by-products for neutralization/purification of the PCBW with the removal efficiencies of the contaminants comparable or better than those obtained with conventional treatment represented the main advantage of our presented method.

Treatment of air pollution control residues with iron rich waste sulfuric acid: Does it work for antimony (Sb)?

Antimony (Sb) in air pollution control (APC) residues from municipal solid waste incineration has gained increased focus due to strict Sb leaching limits set by the EU landfill directive. Here we study the chemical speciation and solubility of Sb at the APC treatment facility NOAH Langøya (Norway), where iron (Fe)-rich sulfuric acid (∼3.6M, 2.3% Fe(II)), a waste product from the industrial extraction of ilmenite, is used for neutralization.Antimony in water extracts of untreated APC residues occurred exclusively as pentavalent antimonate, even at low pH and Eh values. The Sb solubility increased substantially at pH<10, possibly due to the dissolution of ettringite (at alkaline pH) or calcium (Ca)-antimonate. Treated APC residues, stored anoxically in the laboratory, simulating the conditions at the NOAH Langøya landfill, gave rise to decreasing concentrations of Sb in porewater, occurring exclusively as Sb(V). Concentrations of Sb decreased from 87–918μgL−1 (day 3) to 18–69μgL−1 (day 600). We hypothesize that an initial sorption of Sb to Fe(II)–Fe(III) hydroxides (green rust) and eventually precipitation of Ca- and Fe-antimonates (tripuhyite; FeSbO4) occurred. We conclude that Fe-rich, sulfuric acid waste is efficient to immobilize Sb in APC residues from waste incineration.

Chromatic Properties of Industrial Solid Waste Based Ferrites

The hexaferrite and monoferrite powders were prepared by the common solid state reaction method. Similar formulations have been prepared but using chemically-pure commercial reagents or by using a sludge generated by steel wiredraw process as source of iron oxide. This iron-rich industrial waste is mainly composed of Fe2O3 (62 wt%). Zinc and calcium are present in minor quantities and can form complexes such as franklinite (ZnFe2O4) and apatite (Ca5(PO4)3(OH,F,Cl)). Ni/Cr galvanising sludge was also used to enhance the black coloration of monoferrite. After calcination of the mixtures at 1,000 °C and 1,050 °C, typical X-ray diffraction patterns of the expected SrFe12O19 and NiFe2O4 phases were obtained, together with minor peaks of spinel-type (SrFe2O4 and ZnFe2O4) and Fe2O3 phases. Anyway, this resulted in a black pigment with chromatic properties comparable to those of commercial formulations, such as iron cobalt chromite (Fe,Co)(Fe,Cr)2O4 (DCMA 13-40-9), chrome iron nickel (Ni,Fe)(Fe,Cr)2O4 (DCMA 13-50-9), and manganese ferrite (Fe,Mn)(Fe,Mn)2O4 (DCMA 13-41-9).

Production of nanostructured magnetic composites based on Fe0 nuclei coated with carbon nanofibers and nanotubes from red mud waste and ethanol

In this work, a catalytic CVD process using ethanol as carbon source was used to convert an iron rich waste, i.e. red mud (RM), in a magnetic composite. TPCVD (temperature programmed CVD), XRD, Mössbauer, EDS, magnetic measurements, TG/DTA, CHN, BET, Raman, SEM and TEM showed that ethanol gradually reduces the iron phases in the RM to Fe3O4 at 500°C and to Fe1−xO at 600°C. At higher temperatures Fe0 and Fe carbide are the main phases produced with the formation of large amounts of carbon (30–50wt%) especially as nanotubes and nanofibers. These magnetic materials can be separated into two fractions by simple dispersion in water, i.e. a settled material composed of large magnetic particles and the suspended material composed of nanoparticles with average size of 10–100nm. The carbon in the composites can be activated with CO2 increasing the surface area from 79 to 185m2g−1. The magnetic composites were used as adsorbent of model dyes methylene blue and indigo carmine showing excellent results. The composites were also used as support to produce a recyclable Pd catalyst. Tests for the 1,5-cyclooctadiene hydrogenation showed that the catalyst can be easily magnetically separated from the reaction medium and reused for five consecutive times with no deactivation or change in selectivity.

Vitrification of copper flotation waste

The vitrification of an hazardous iron-rich waste (W), arising from slag flotation of copper production, was studied. Two glasses, containing 30 wt% W were melted for 30 min at 1400 °C. The first batch, labeled WSZ, was obtained by mixing W, blast furnace slag (S) and zeolite tuff (Z), whereas the second, labeled WG, was prepared by mixing W, glass cullet (G), sand and limestone. The glass frits showed high chemical durability, measured by the TCLP test. The crystallization of the glasses was evaluated by DTA. The crystal phases formed were identified by XRD resulting to be pyroxene and wollastonite solid solutions, magnetite and hematite. The morphology of the glass–ceramics was observed by optical and scanning electron microscopy. WSZ composition showed a high rate of bulk crystallization and resulted to be suitable for producing glass–ceramics by a short crystallization heat-treatment. WG composition showed a low crystallization rate and good sinterability; glass–ceramics were obtained by sinter-crystallization of the glass frit.

Recycling of zinc-hydrometallurgy wastes in glass and glass ceramic materials

The aim of Brite-Euram project CT94 -1018 has been to recycle jarosite (JW), an iron rich hazardous waste resulting from the hydrometallurgy of zinc ores, to obtain glass and glass-ceramic materials. Granite scraps and mud (GW), generated by the caving, cutting and sawing of the blocks, and glass cullet have been utilized as additives to define the batch composition. The average compositional ranges are 40–70% for JW, 20–40% for GW and 10–40% for glass-cullet. Several compositions were prepared and tailored for the final product destination; melted at the 1400–1450°C temperature range. Glass-ceramic materials have been obtained from the glassy-phase by means of a controlled nucleation and crystallization thermal treatment, yielding a 40–55% crystalline volume fraction. The properties of the glass and glass-ceramics have been tailored to favor the commercial exploitation of the products in the building industry, in the form of paving tiles wall covering panels, glass fibers for insulation and coloring pigments for ceramics. A 1 ton/day vitrification pilot plant, able to work in a continuous or discontinuous way, has been realized and tested using different waste streams.

The Use of Ferric Salts for Controlling Sulfide Odors in High-Strength Pulp and Paper Manufacturing Wastes

Iron salts are effective in controlling sulfide odors produced by sludge blanket samples of a facultative waste treatment lagoon receiving concentrated sulfite waste from a pulp and paper manufacturing facility. Complex interactions between dissolved iron species and reduced sulfides interfere with predictions of effective chemical dosing, requiring site/season-specific dose determinations. For example, samples collected during periods of warmer weather, when metabolic rates are higher in the sludge blanket, require higher dosages of ferric chloride for odor control. A technique is presented that uses jar tests to determine effective dosage rates of iron salts to produce a desired odor-free period in a particular waste. Potentially, large volumes of sludge may be generated through the possible precipitation of metal–sulfide complexes. Iron-rich waste products may provide a cost effective source of ferric iron for these applications. Key words: Wastewater; pulp and paper wastes; reduced sulfides; odor control; iron salts; chemical requirements

Ingestion of host blood by the monogenean Pseudodiplorchis americanus: a quantitative analysis

SUMMARYPseudodiplorchis americanus infects the urinary bladder of a desert toad and feeds exclusively on blood, producing the iron-rich waste product haematin. The host, Scaphiopus couchii, retains dilute urine within the urinary bladder as a water store throughout hibernation and parasite waste will therefore not be eliminated. This study utilized atomic absorption spectrophotometry to quantify the iron within the urinary bladders of infected and uninfected toads after different periods of hibernation. During the first 4 months hibernation, no detectable iron, above that of the controls, was found in the urine and bladder tissue of infected animals, but after 5–6 months hibernation there was a small but not significant increase. The iron contained within most individual parasites was greater than that detected in the urine and bladder tissue of the host, and the total iron in each parasite infrapopulation was 3–83 times greater than the urinary bladder iron. This suggests that the parasites do not regurgitate their gut contents during host hibernation. The amount of iron in individual parasites increased with time after migration to the bladder and this was used to estimate the amount of blood ingested by P. americanus. At a controlled temperature of 25 °C, the estimated rate of ingestion increased from 0·33 μl blood/parasite/week by worms 2 weeks post-migration to a maximum of around 1·6 μl by worms 5 months post-migration. The rate of blood ingestion by older worms was also calculated as a function of the hibernation period (since this did not correspond to worm age) assuming complete gut evacuation at the start of hibernation. This provided maximum estimates of ingestion rate of 1·9–5·3 μl blood/parasite/week.