Iron-rich Residue Research Articles

Gold recovery from cyanidation residue by chloride leaching and carbon adsorption – Preliminary results from CICL process

There is a vast amount of globally underutilized low-grade mine tailings and leach residues, including those from primary processing of gold. In this research, the target is to recover the remaining gold (10.9 g/t) from weathered refractory iron-rich residue that had previously been subject to autoclave oxidation, subsequent cyanidation in a conventional carbon-in-leach (CIL) circuit as well as storage at tailings area. Chloride leaching has been considered as one of the most promising cyanide-free gold leaching methods and it has shown positive outcomes in treating primary gold ores, concentrates, and flotation tailings. Therefore, in the current study, the iron-rich residue investigated was subjected to chloride leaching combined with simultaneous carbon adsorption. The investigated parameters included leaching time (2–8 h), chloride concentration ([Cl−] = 0.2–5 M), type and concentration of oxidant ([Cu2+]/[Fe3+] = 0.1–1 M), as well as type and concentration of activated carbon (14–25 g/L), whereas S/L ratio (100 g/L), acidity (pH = 1), and temperature (90 °C) were kept constant. Leaching results indicate that up to 40% of the remaining gold could still be recovered from the investigated residue with optimized chloride leaching. According to the results, the most important parameter for gold recovery was the leaching time. Moreover, of the studied oxidants, cupric ions were shown to contribute more to gold recovery when compared to ferric ions (35% vs. 24% at [Cu2+]/[Fe3+] = 0.1 M). Nevertheless, an increase of cupric concentration from 0.1 M (low-concentrated) to 0.5 M, resulted in only a slight increase in gold recovery (from 36% to 40%), whereas no further improvement in gold recovery was achieved with a 1 M cupric concentration. Two studied activated carbon products showed equal effectiveness in gold adsorption. In-situ carbon adsorption was shown to occur effectively in chloride media, as all dissolved gold could be detected in the activated carbon, and the concentration of remaining gold in the pregnant leach solution was minimal (< 0.02 mg/L). These findings indicate that low-concentrated chloride leaching of leach residues from industrial gold processes can allow an enhanced recovery of gold from previously mined and treated raw materials.

Removal of Lead and Zinc from Blast Furnace Sludge Through High Temperature Carbochlorination

A new dual kiln processing route has been proposed and investigated for removal of heavy metals from the zinc-rich fraction of blast furnace (BF) sludge and recovery of ferrous materials. The zinc in BF sludge exists both as ZnO and ZnS. The thermodynamic analysis indicates that the carbochlorination of the sludge shows a selective heavy metal removal. Lead can be removed at a temperature below 900°C followed by the zinc removal at higher temperatures, producing an iron-rich clean residue free of heavy metals in the end feasible for recycling back to ironmaking. High temperature carbochlorination experiments have been conducted with designed mini-pellets. The experimental results prove that via the proposed dual kiln route, a valuable zinc-rich fraction and a clean iron-bearing residue can be achieved with addition of iron chloride, leaving a small stream of lead-rich residue for further processing. This newly developed recycling flowsheet provides a sequential carbochlorination in two inter-connected rotary kilns, incorporated with efficient dust-capturing systems. In total, over 98% heavy metal removal has been achieved. The Zn-rich dust contains more than 60% of zinc, and the quality of the iron-rich residue is sufficient for re-use in the integrated steel works.

Green approach to ironmaking: Briquetting and hydrogen reduction of mill scale using novel binders

The transition to sustainable and low-carbon ironmaking processes has necessitated innovative solutions. The most prominent solutions are the establishment of a circular economy by recirculating the iron-rich residues from steelworks and the adoption of hydrogen as a clean reducing agent to mitigate fossil CO2 emission. One such residue is mill scale, which is generated during steelmaking, casting, and rolling processes. However, the fine particles and easy reoxidation of the mill scale make it difficult to be used directly in iron and steel production without proper compaction. This paper aims to demonstrate the feasibility of mill scale briquetting using organic binders to meet the requirements of hydrogen-based direct reduction. The study will investigate the influence of binder type, binder dosage, moisture content, and compaction pressure on the briquetting process and the briquettes quality. Moreover, the reducibility of optimized briquettes will be examined by hydrogen at 900 °C using a thermogravimetric analyzer coupled with a quadrupole mass spectroscopy (TGA-QMS). The optimal combination for achieving the best mechanical strength and reducibility was a briquette produced with 1% Alcotac® CB6, 1% KemPel, and 2.5% moisture content, compressed at a pressure of 125 kN.

Thermodynamics of Aluminothermic Processes for Ferrotitanium Alloy Production from Bauxite Residue and Ilmenite

Titanium oxide is a major component of bauxite residue (BR) with a high value, but it is often an unwanted element in common BR reuse options such as cement or iron production. Conventional carbothermic reduction smelting of BR produces a slag still containing a large amount of Ti. This study investigates an aluminothermic process for producing an FeTi alloy by combining BR, ilmenite ore, and fluxes. Based on thermodynamic calculations and batch experiments, the amounts of aluminum (reductant) and fluxes were investigated to achieve the optimum alloy production in parallel with a slag that could be further valorized in the cement industry. The mineralogical and chemical analysis of the metallic and slag phase agreed with the thermodynamic calculations. The results obtained by this study can lead to the development of a new process for the complete valorization of BR, paving the way for scaling up aluminothermic processes for producing ferroalloys from all iron-rich residues.

Compounds based on iron mining tailing dams and activated carbon from macauba palm for removal of emerging contaminants and phosphate from aqueous systems.

In this work, an iron-rich residue, which is widely obtained as a by-product in the iron mining industry, and macauba endocarp, waste from the extraction of vegetable oil for the production of biofuels, were used in the preparation of different composites based on iron and carbon. The composites were obtained by manual grinding of the calcined iron residue and activated carbon prepared by the macauba endocarp followed by thermal treatment under nitrogen atmosphere. The effect of the thermal treatment was analyzed by Mössbauer spectroscopy and X-ray diffraction and showed that the increase in the treatment temperature promoted the formation of different reduced iron phases in the final composite, such as Fe3O4, FeO, and Fe0. These composites were used in a combined adsorption/oxidation process through photocatalysis to remove up to 93% of amoxicillin from aqueous phase. The formation of possible reaction intermediates was monitored by electrospray ionization mass spectrometry (ESI-MS) and a mechanism of amoxicillin degradation was proposed. Afterward, the Fe/C composites were conducted to evaluate the impact of several parameters on phosphate adsorption processes and showed a maximum adsorption capacity of 40.3mgg-1. The adsorption capacity obtained for all the materials were greater than those found in the literature.

High-Iron Bauxite Residue (Red Mud) Valorization Using Hydrochemical Conversion of Goethite to Magnetite.

Bauxite residue (BR), also known as red mud, is a byproduct of the alumina production using the Bayer process. This material is not used to make iron or other iron-containing products worldwide, owing to its high content of sodium oxide and other impurities. In this study, we investigated the hydrochemical conversion of goethite (FeOOH) to magnetite (Fe3O4) in high-iron BR from the Friguia alumina refinery (Guinea) by Fe2+ ions in highly concentrated alkaline media. The simultaneous extraction of Al and Na made it possible to obtain a product containing more than 96% Fe3O4. The results show that the magnetization of Al-goethite and Al-hematite accelerates the dissolution of the Al from the iron mineral solid matrix and from the desilication product (DSP). After ferrous sulfate (FeSO4·7H2O) was added directly at an FeO:Fe2O3 molar ratio of 1:1 at 120 °C for 150 min in solution with the 360 g L-1 Na2O concentration, the alumina extraction ratio reached 96.27% for the coarse bauxite residue size fraction (Sands) and 87.06% for fine BR obtained from red mud. The grade of iron (total iron in the form of iron elements) in the residue can be increased to 69.55% for sands and 58.31% for BR. The solid residues obtained after leaching were studied by XRD, XRF, TG-DTA, VSM, Mössbauer spectroscopy, and SEM to evaluate the conversion and leaching mechanisms, as well as the recovery ratio of Al from various minerals. The iron-rich residues can be used in the steel industry or as a pigment.

Cleaning Disposal of High-Iron Bauxite Residue Using Hydrothermal Hydrogen Reduction.

The hydrothermal hydrogen reduction process for treating high-iron bauxite residue (red mud) was investigated, and the optimum conditions of alumina extraction as well as the enrichment of iron minerals were verified by experiments. Results show that the surface magnetization of Al-goethite under the function of hydrogen reduction accelerates its conversion to hematite and/or magnetite. This conversion releases the substituted Al in goethite as well as the undigested gibbsite/boehmite and further enriches the iron content in residue. After hydrothermal hydrogen reduction with H2/Red mud ratio of 0.085mol/20g at 270°C for 60min, the alumina relative recovery ratio reaches 95.40% and the grade of iron (total iron in the form of iron element) in the residue can be enriched to 55.85%. Further, co-processing of the obtained iron-rich residue in the steel industry can achieve a significant reduction of red mud discharge.

Recovery of iron rich residues from integrated steel making process by hydrated lime/molasses pressurised cold agglomeration

This study aimed at verifying the technical feasibility of recovering and reusing several iron-rich residues from the steel production process through the production of briquettes that could potentially be reintroduced as a ferrous source into the converters during the transformation of hot metal into liquid steel. An experimental investigation was carried out on a pilot-scale briquetting plant that implements a pressurised cold agglomeration; 8 mixtures, with contents varying between 60 and 66% Basic Oxygen Furnace (BOF) slag and a maximum of 27% of stock-house dusts and process sludges were tested. In the context of the circular economy, beet molasses was added in varying amounts as a binder, along with cheaper hydrated lime. Experimental results showed how each mixture of recycled materials was able to make briquettes with a high average crushing resistance (73.3 daN for the best mixture, indicated as 2b mix). The X-ray powder patterns, chemical and scanning electron microscopy (SEM) characterization of 2b mix briquettes revealed clean raw residues as well as the presence of limited amount of unwanted compounds such as phosphorus and sulphur, due to the molasses used. By adopting a replacement ratio of 1 between commercial and 2b mix briquettes, a possible safe use of 2b mix briquettes in BOF converters has been estimated. As a lesson, although other investigations need to be carried out (i.e., the reduction disintegration index assessment), briquetting has proven to be effective. It must be intended as an integration rather than a replacement of the input materials generally used in the BOF converter.

Closed-loop solvometallurgical process for recovery of lead from iron-rich secondary lead smelter residues

A solvometallurgical process based on acetic acid was developed for the recovery of lead from iron-rich residues (matte and slag).

Utilização do pó de aciaria elétrica modificado termicamente em reações para redução do nitrobenzeno à anilina

Nitroaromatic compounds appear as important agents in environmental contamination, with the highlight, its high resistance to microbial degradation. The reductive processes using metallic iron have been studied by several researchers with the purpose of formation of substrates that are less recalcitrant compounds. In this study the flue dust electric iron rich residue was thermally reduced under flowing hydrogen gas to obtain a composite phase reduced iron. This composite was used as reducing agent in transformation reaction of nitrobenzene to aniline. The results show that heat treatment of the residue promoted the formation of phases of reduced iron as FeO and Fe This material has high efficiency in reduction reaction of nitrobenzene to aniline, where the concentration of this contaminant was reduced ca. 86%.

Study on simultaneous recycling of EAF dust and plastic waste containing TBBPA

In the present work we investigated the fates of zinc, lead, and iron present in electric arc furnace dust during thermal treatment of the dust with tetrabromobisphenol A (TBBPA) and tetrabromobisphenol A diglycidyl ether (TBBPADGE). Mixtures of these materials were compressed into pellets and heated in a laboratory-scale furnace at 550°C for 80min, under oxidizing and inert conditions.The solid, condensed, and gaseous-phase products were characterized using an array of analytical methods: scanning electron microscopy, X-ray diffraction, electron probe microscopy, inductively coupled plasma, ion chromatography, and gas chromatography.The results indicated that heating the mixtures under specific conditions enabled high separation of zinc and lead from iron-rich residues, by a bromination–evaporation process. In the case of TBBPADGE, a maximum of 85% of zinc and 81% of lead were effectively separated under the above conditions.The process is based on the reaction between the highly reactive HBr gas evolved during thermal degradation of the flame-retarded materials with zinc (ZnO and ZnFe2O4) and lead in the dust, followed by complete evaporation of the formed metallic bromides from the solid residue.

Identification of metal residues associated with bit-use on prehistoric horse teeth by scanning electron microscopy with energy dispersive X-ray microanalysis

Our ability to identify evidence of the use of horses for transportation from archaeozoological remains is important for improving our understanding of the role of horses in socioeconomic changes throughout prehistory. When a horse is used with a bit, the bit can come into contact with the anterior (‘front’) surface of the lower second premolar (P 2). Here, results of X-ray microanalysis, undertaken in a variable pressure scanning electron microscope, of chemical elements on the anterior surface of four archaeological horse P 2 are presented. Analysis of dental materials (enamel and cementum) returned expected results, with calcium, phosphorous and oxygen dominating. Iron-rich residues are also identified on the front of two of the teeth, which are interpreted here as deriving from contact with iron bits. It is proposed that such analyses may provide a useful additional method for identifying bitting damage in archaeological horses or corroborating interpretations made from macroscopic examinations.

Effect of Industrial Byproducts Containing High Aluminum or Iron Levels on Plant Residue Decomposition

Excess phosphorus (P) in soils is a result of manure and fertilizer additions that exceeded crop P requirements. Reducing or eliminating future P fertilizer additions or manures is one method of remediation. Another would be to treat manures or soils with byproducts that contain iron (Fe), aluminum (Al), or calcium (Ca) that adsorb P readily. A study was conducted in which two industrial byproducts and 14C-labeled soybean leaves and stems were added to two soils and soil organic matter and residue decomposition were monitored. Water treatment residue (WTR) containing high Al content and iron-rich residue (IRR) were added to Sassafras and Matapeake soils at rates from 0.5 to 10.0 g kg−1 soil. Lime (CaO) was added as a treatment to determine the effect of increased pH. Additions of WTR to either soil did not affect decomposition of 14C-labeled soybean leaves and stems, soil organic matter decomposition recorded by total CO2 evolution or residual soil 14C. Addition of IRR affected decomposition of 14C-labeled soybean leaves and stems, soil organic matter decomposition recorded by total CO2 and residual soil 14C. Although no one factor explained the effects on decomposition, salinity may be a factor as well as pH. Lime addition corrected the low soil organic matter decomposition as a result of the 10 g kg−1 IRR amendment. Lime also reduced salinity about 20%. Remediation of high P soils or treatment of manure is beneficial, but additional tests on biological effects on industrial byproduct addition may be necessary.

Biomass yield and phosphorus availability to wheat grown on high phosphorus soils amended with phosphate inactivating residues. II. Iron rich residue

Reducing the environmental risk from soluble phosphorus (P) in long-term poultry manured fields can involve increased use of chemical soil amendments such as aluminum (Al), calcium (Ca), and iron (Fe). Iron salts have been proven effective in removing soluble P from wastewater and have been used to inactivate P in poultry litter and litter-amended soils. The potential for P deficiency in crops grown on Fe treated soils is of concern. A growth chamber experiment was conducted using Matapeake, Evesboro, and Woodstown soils with Mehlich 3 extractable P (M3-P) levels above 800 mg kg−1 in order to 1) determine the effects of a Fe-rich residue (IRR) on crop biomass yield and on plant P, Mn, and Fe contents, and 2) examine pH, electrical conductivity (EC), P, Mn, and Fe concentrations in soils after three cropping cycles with wheat. IRR was mixed with the soils at rates of 0, 10, 25, and 50 g kg−1 and incubated for seven weeks. Three crops of wheat (Triticum aestivum) were grown in succession. Biomass yield (BM) and tissue P concentrations were significantly reduced with the additions of IRR for all three soils, but the differences were much less at the 10 g kg−1 application rate than at the 25 and 50 g kg−1 rates. Biomass yield was 29% lower than the control at the 10 g kg−1 IRR rate compared to 74% lower at the 50 g kg−1 rate. Even though tissue P concentrations were reduced, levels were within the range considered sufficient for wheat growth for all treatments. The high Mn and DTPA-Fe in the IRR treatments increased tissue Mn and Fe concentrations, but the levels were below the concentration considered to be toxic to most crops. Water soluble P and M3-P concentrations were lowered with increased IRR application rate for each soil and correlated positively with tissue P for the three soils. DTPA extractable Mn concentrations in soil increased, but Fe concentrations decreased with increased IRR application, for the three soils. IRR treatments initially increased both pH and EC in the three soils, however, reductions in pH and EC values were found with subsequent cropping cycles. Further studies to identify and limit the negative impact of IRR on plant growth are needed before the materials should be considered for field application to sequester soluble P in high P soils.

Availability of arsenic, copper, lead, thallium, and zinc to various vegetables grown in slag-contaminated soils.

To anticipate a possible hazard resulting from the plant uptake of metals from slag-contaminated soils, it is useful to study whether vegetables exist that are able to mobilize a given metal in the slag to a larger proportion than in an uncontaminated control soil. For this purpose, we studied the soil to plant transfer of arsenic, copper, lead, thallium, and zinc by the vegetables bean (Phaseolus vulgaris L. 'dwarf bean Modus'), kohlrabi (Brassica oleracea var. gongylodes L.), mangold (Beta vulgaris var. macrorhiza ), lettuce (Lactuca sativa L. 'American gathering brown'), carrot (Daucus carota L. 'Rotin', 'Sperlings's'), and celery [Apium graveiolus var. dulce (Mill.) Pers.] from a control soil (Ap horizon of a Entisol) and from a contaminated soil (1:1 soil-slag mixtures). Two types of slags were used: an iron-rich residue from pyrite (FeS2) roasting and a residue from coal firing. The metal concentrations in the slags, soils, and plants were used to calculate for each metal and soil-slag mixture the plant-soil fractional concentration ratio (CRfractional,slag), that is, the concentration ratio of the metal that results only from the slag in the soil. With the exception of TI, the resulting values obtained for this quantity for As, Cu, Pb, and Zn and for all vegetables were significantly smaller than the corresponding plant-soil concentration ratios (CRcontrol soil) for the uncontaminated soil. The results demonstrate quantitatively that the ability of a plant to accumulate a given metal as observed for a control soil might not exist for a soil-slag mixture, and vice versa.

Use of Aluminum‐ and Iron‐Rich Residues to Immobilize Phosphorus in Poultry Litter and Litter‐Amended Soils

AbstractPoultry production is concentrated on Maryland's eastern shore on areas with sandy soils low in sesquioxides. Water quality has been affected by runoff and leaching of phosphorus from poultry litter‐amended fields. Phosphorus movement is of major concern because P is a limiting nutrient for eutrophication in surface water. The objectives of this study were to (i) evaluate the ability of Al‐rich drinking water treatment residue (DWTR) and iron‐rich residue (IRR) to reduce water‐soluble P and Bray and Kurtz no. 1‐extractable phosphorus (BK‐1 P) in poultry litter and three long‐term litter‐amended soils and (ii) determine the effects of these residues on pH and electrical conductivity (EC) in the amended litter and soils. Poultry litter and soils were treated with four rates of DWTR and IRR and incubated for 7 wk at 25°C. Litter and soils were sampled at 2, 4, and 7 wk. Both residue materials increased the pH of the litter and the soils. The DWTR was more effective in reducing both water‐soluble P and BK‐1 P in litter at all rates. At the 25 and 50 g kg−1 rates, reductions in water‐soluble P with IRR were comparable with that of DWTR, but DWTR was twice as effective as IRR in reducing BK‐1 P concentration. The results showed that water‐soluble P and BK‐1 P in poultry litter and long‐term litter‐amended soils can be substantially reduced by incorporating residues rich in Al and Fe; these residues may be useful for reducing P runoff and leaching from poultry litter and litter‐amended fields.

Acidified mining residue for correction of iron chlorosis on calcareous soils

Abstract A leaching process for extraction of copper from copper bearing ore results in an iron rich residue. Acidification of this residue with sulfuric acid yields a fertilizer product containing 16 ‐ 20% Fe. This product has been shown to be effective in correcting iron chlorosis. With respect to row crops, placement close to the germinating seed is more effective than broadcast treatments. Broadcast treatments have been shown to be highly effective for correcting iron chlorosis of turf. Some residual effects have been observed. The highly acidic nature of the product is believed to contribute strongly to its effectiveness.

藤岡製錬所の電解鉄および電解鉄粉の製造

Fujioka Smelter, which was brought into production in 1966, is producing electrolytic iron, using, as raw material, iron-rich residues produced in the zinc fuming process at Annaka Smelter and Onahama Plant of Ryoho Recycle Co.The process is composed of reducing and smelting the material in the electric furnace, and refining pig iron in the converter, and then casting anodes which will be electrolyzed to the purest iron “Mairon” in cathodic plates. These electrorefined plates are crushed into coarse fragments called “Flakes”, a part of which are shipped to the user with the rest being pulvelized into fine electrolytic iron powder for various uses.