Role of iron ore in enhancing gasification of iron coke:Structural evolution,influence mechanism and kinetic analysis

The utilization of iron coke provides a green pathway for low-carbon ironmaking.To uncover the influence mechanism of iron ore on the behavior and kinetics of iron coke gasification,the effect of iron ore on the microstructure of iron coke was investigated.Furthermore,a comparative study of the gasification reactions between iron coke and coke was conducted through non-isothermal thermogravimetric method.The findings indicate that compared to coke,iron coke exhibits an augmentation in micropores and specific surface area,and the micropores further extend and interconnect.This provides more adsorption sites for CO_(2) molecules during the gasification process,resulting in a reduction in the initial gasification temperature of iron coke.Accelerating the heating rate in non-isothermal gasification can enhance the reactivity of iron coke.The metallic iron reduced from iron ore is embedded in the carbon matrix,reducing the orderliness of the carbon structure,which is primarily responsible for the heightened reactivity of the carbon atoms.The kinetic study indicates that the random pore model can effectively represent the gasification process of iron coke due to its rich pore structure.Moreover,as the proportion of iron ore increases,the activation energy for the carbon gasification gradually decreases,from 246.2 kJ/mol for coke to 192.5 kJ/mol for iron coke 15wt%.

Approach to estimating non-point pollutant load removal rates based on water environmental capacity: a case study in Shenzhen

An innovative approach based on water environmental capacity for non-point source NPS pollution removal rate estimation was discussed by using both univariate and multivariate data analysis.Taking Shenzhen city as the study case a 67% to 74% NPS pollutant load removal rate can lead to meeting the chemical oxygen demand COD pollution control target for most watersheds.In contrast it is hardly to achieve the ammonia nitrogen NH4-N total phosphorus TP and biological oxygen demand BOD5 pollution control target by simply removing NPS pollutants. This highlights that the pollution control strategies should be taken according to different pollutant species and sources in different watersheds rather than one-size-fits-all .

Kinetics of iron removal from metallurgical grade silicon with pressure leaching

In this paper, the kinetics of pressure leaching for purification of metallurgical grade silicon with hydrochloric acid was investigated. The effects of particle size, temperature, total pressure, and concentration of hydrochloric acid on the kinetics and mechanism of iron removal were studied. It was found that the reaction kinetic model followed the shrinking core model, and the apparent activation energy of the leaching reaction was 46.908 kJ/mol. And the apparent reaction order of iron removal with pressure leaching was 0.899. The kinetic equation was obtained and the mathematical model of iron removal from metallurgical grade silicon （MG-Si） was given as follows：The values calculated from the equation were consistent with the experimental results.

Removal of primary iron rich phase from aluminum-silicon melt by centrifugal separation

Recycling is a major consideration in continued aluminum use due to the enormous demand for high quality products. Some impurity elements gradually accumulate through the repetitive reuse of aluminum alloy scrap. Of them, the iron content should be suppressed under the allowed limit. In the present research, a novel separation method was introduced to remove primary iron-rich intermetallic compounds by centrifugation during solidification of AI-Si-Fe alloys. This method does not use the density difference between two phases as in other centrifugal methods, but uses the order of solidification in AI-Si-Fe alloys, because iron promotes the formation of intermetallic compounds with other alloying elements as a primary phase. Two AI-Si-Fe alloys which have different iron contents were chosen as the starting materials. The iron-rich phase could be efficiently removed by centrifuging under a centrifugal force of 40 g. Coarse intermetallic compounds were found in the sample inside the crucible, while rather fine intermetallic compounds were found in the sample outside the crucible. Primary intermetallic compounds were linked to each other via aluminum-rich matrix, and formed like a network. The highest iron removal fraction is 67% and the lowest one is 7% for AI-12Si-1.7Fe alloy. And they are 82% and 18% for AI-12Si-3.4Fe alloy, respectively.

Removal of iron from ilmenite by KOH leaching-oxalate leaching method

Oxalic acid was used for the removal of iron from the intermediates of ilmenite leached by KOH liquor. Various parameters, such as pH, temperature, initial oxalate concentration, and illumination were investigated. Meanwhile, it was found that orthorhombic crystal Ti2O2（OH）2（C2O4）-H2O formed as the leaching proceeded. Scanning electronic microscope （SEM） images implied that the formation of Ti2O2（OH）2（C2O4）.H2O with good crystallinity proceeded through three stages. Calcining Ti2O2（OH）2（C2O4）·H2O, anatase （350℃） or mtile （550℃） type TiO2 was obtained, respectively. Element analysis found that the calcined product contained 94.9% TiO2 and 2.5% iron oxide, but only about 1600 ppm dissolvable iron oxide was left, which indicates that oxalic acid was comparatively effective on iron oxide removal from the intermediates. Finally, an improved route was proposed for the upgrading of ilmenite into mtile.

Benzohydroxamic acid to improve iron removal from potash feldspar ores

The technological mineralogy of the potash feldspar was investigated and a new collector named Yb105 was adopted to remove iron from potash feldspar ores.The technological mineralogy results indicate that the main components of the ore were feldspar,sericite,quartz and kaolinite,and iron mainly existed in limonite and hematite,most of which can be removed by beneficiation.The results show the benzohydroxamic acid can not only increase the recovery of iron and reduce the consumption of oleic acid collector,but also enhance the collecting performance of oleic acid at low temperature,which can realize the flotation of the ores at a low temperature and play an important role in saving energy to some extent.Compared with oleic oil,the benzohydroxamic acid had a great advantage in removing iron from potash feldspar,a potash feldspar concentrate with Fe grade of 0.23%,K2O grade of 12.59%and Na2O grade of 0.26%was obtained by flotation with Yb105 as collector,and the yield of the concentrate was 82.55%.

Transformation behavior of ferrous sulfate during hematite precipitation for iron removal

The transformation behavior of ferrous sulfate was examined during hematite precipitation for iron removal in hydrometallurgical zinc.Specifically,the effects of the method used for oxygen supply(pre-crystallization or pre-oxidation of ferrous sulfate)and temperature(170–190℃)on the redissolution and oxidation–hydrolysis of ferrous sulfate were studied.The precipitation characteristics and phase characterization of the hematite product were investigated.The results showed that the solubility of ferrous sulfate was considerably lower at elevated temperatures.The dissolution behavior of ferrous sulfate crystals was influenced by both the concentrations of free acid and zinc sulfate and the oxydrolysis of ferrous ions.Rapid oxydrolysis of ferrous ions may serve as the dissolution driving force.Hematite precipitation proceeded via the following sequential steps:crystallization,redissolution,oxidation,and precipitation of ferrous sulfate.The dissolution of ferrous sulfate was slow,which helped to maintain a low supersaturation environment,thereby affording the production of high-grade hematite.

Influence of acid leaching and calcination on iron removal of coal kaolin

Calcination and acid leaching of coal kaolin were studied to determine an effective and economical preparation method of calcined kaolin. Thermogravimetric-differential thermal analysis （TG-DTA） and X-ray diffraction （XRD） demonstrated that 900＆#176;C was the suitable temperature for the calcination. Leaching tests showed that hydrochloric acid was more effective for iron dissolution from raw coal kaolin （RCK）, whereas oxalic acid was more effective on iron dissolution from calcined coal kaolin （CCK）. The iron dissolution from CCK was 28.78wt%, which is far less effective than the 54.86wt% of RCK under their respective optimal conditions. Through analysis by using M？ssbauer spectroscopy, it is detected that nearly all of the structural ferrous ions in RCK were removed by hydrochloric acid. However, iron sites in CCK changed slightly by oxalic acid leaching because nearly all ferrous ions were transformed into ferric species after firing at 900＆#176;C. It can be concluded that it is difficult to remove the structural ferric ions and ferric oxides evolved from the structural ferrous ions. Thus, iron removal by acids should be conducted prior to calcination.

Nitrogen removal efficiency of iron-carbon micro-electrolysis system treating high nitrate nitrogen organic pharmaceutical wastewater

The nitrate nitrogen removal efficiency of iron-carbon micro-electrolysis system was discussed in treating pharmaceutical wastewater with high nitrogen and refractory organic concentration. The results show that the granularity of fillings,pH,volume ratios of iron-carbon and gas-water,and HRT. have significant effects on the nitrogen removal efficiency of iron-carbon micro-electrolysis system. The iron-carbon micro-electrolysis system has a good removal efficiency of pharmaceutical wastewater with high nitrogen and refractory organic concentration when the influent TN,NH4+-N,NO3--N and BOD5/CODCr are 823 mg/L,30 mg/L,793 mg/L and 0.1,respectively,at the granularity of iron and carbon 0.425 mm,pH 3,iron-carbon ratio 3,gas-water ratio 5,HRT 1.5 h,and the removal rates of TN,NH4+-N and NO3--N achieve 51.5%,70% and 50.94%,respectively.

A mathematical model for electrochemical chloride removal from marine cast iron artifacts

The aim of this article was to theoretically study diffusion and migration of chloride ions during electrochemical chloride removal. The proposed model would enable optimization of its application by predicting the optimal treatment time and current combination. A mathematical model for simulating the transport behavior of chloride ions was developed by consideration of diffusion and migration of chloride ions when a constant DC current density was applied through the marine cast iron artifacts. The corresponding tests were conducted to validate the mathematical model. This model predicted the data of the extraction ratio of the chloride ion that correlated satisfactorily with the experimental values. An important issue in electrochemical chloride removal was to understand how chloride ions moved, taking account of diffusion and migration of chloride ions and the release of binding chloride ions. The effects of the treatment time, externally applied current density, chloride diffusion coefficient, and rate constant of release of binding chloride ion on chloride removal are studied. The specific quantitative details applied to one-dimensional model were discussed here. This article has proposed a mathematical model for the first time, which was showed to be a useful tool that can reveal the ionic transport mechanism and optimize the application during electrochemical chloride removal.

Effect of calcium compounds on direct reduction and phosphorus removal of high-phosphorus iron ore

The increasing demand for iron ore in the world causes the continuous exhaustion of magnetite resources.The utilization of high-phosphorus iron ore becomes the focus.With calcium carbonate(CaCO_(3)),calcium chloride(CaCl_(2)),or calcium sulfate(CaSO_(4))as additive,the process of direct reduction and phosphorus removal of high-phosphorus iron ore(phosphorus mainly occurred in the form of Fe_(3)PO_(7) and apatite)was studied by using the technique of direct reductiongrinding-magnetic separation.The mechanism of calcium compounds to reduce phosphorus was investigated from thermodynamics,iron metallization degree,mineral composition and microstructure.Results showed that Fe_(3)PO_(7) was reduced to elemental phosphorus without calcium compounds.The iron-phosphorus alloy was generated by react of metallic iron and phosphorus,resulting in high phosphorus in reduced iron products.CaCO_(3) promoted the reduction of hematite and magnetite,and improved iron metallization degree,but inhibited the growth of metallic iron particles.CaCl_(2) strengthened the growth of iron particles.However,the recovery of iron was reduced due to the formation of volatile FeCl_(2).CaSO_(4) promoted the growth of iron particles,but the recovery of iron was drastically reduced due to the formation of non-magnetic FeS.CaCO_(3),CaCl_(2) or CaSO_(4) could react with Fe_(3)PO_(7) to form calcium phosphate(Ca_(3)(PO_(4))_(2)).With the addition of CaCO_(3),Ca_(3)(PO_(4))_(2) was closely combined with fine iron particles.It is difficult to separate iron and phosphorus by grinding and magnetic separation,resulting in the reduced iron product phosphorus content of 0.18%.In the presence of CaCl_(2) or CaSO_(4),the boundary between the generated Ca_(3)(PO_(4))_(2) and the metallic iron particles was obvious.Phosphorus was removed by grinding and magnetic separation,and the phosphorus content in the reduced iron product was less than 0.10%.

Simultaneous removal of Cr(Ⅵ), Cd, and Pb from aqueous solution by iron sulfide nanoparticles: Influencing factors and interactions of metals

Cadmium(Cd),lead(Pb),and hexavalent chromium(Cr(Ⅵ)) are often found in soils and water affected by metal smelting,chemical manufacturing,and electroplating.In this study,synthetic iron sulfide nanoparticles(FeS NPs) were stabilized with carboxymethyl cellulose(CMC) and utilized to remove Cr(Ⅵ),Cd,and Pb from an aqueous solution.Batch experiments,a Visual MINTEQ model,scanning electron microscopy(SEM),X-ray diffraction(XRD),and X-ray photoelectron spectrometer(XPS) analysis were used to determine the removal efficiencies,influencing factors,and mechanisms.The FeS NP suspension simultaneously removed Cr(Ⅵ),Cd,and Pb from an aqueous solution.The concentrations of Cr(Ⅵ),Cd,and Pb decreased from 50,10,and 50 mg·L^(-1) to 2.5,0.1,and 0.1 mg·L^(-1),respectively.The removal capacities were up to 418,96,and 585 mg per gram of stabilized FeS NPs,respectively.The acidic conditions significantly favored the removal of aqueous Cr(Ⅵ) while the alkaline conditions favored the removal of Cd and Pb.Oxygen slightly inhibited the removal of Cr(Ⅵ),but it had no significant influence on the removal of Cd and Pb.A potential mechanism was proposed for the simultaneous removal of Cr(Ⅵ),Cd,and Pb using FeS NPs.The interactions of the three heavy metals involved a cationic bridging effect on Cr(Ⅵ) by Cd,an enhanced adsorption effect on Cd by [Cr,Fe](OH)_3,precipitation of PbCrO_4,and transformation of PbCrO_4 to PbS.Therefore,FeS NPs have a high potential for use in the simultaneous removal of Cr(Ⅵ),Cd,and Pb from contaminated aqueous solutions.

Roasting-induced phase change and its influence on phosphorus removal through acid leaching for high-phosphorus iron ore

In the present study, roasting-induced phase change and its influence on phosphorus removal via leaching has been investigated for high-phosphorus iron ore. The findings indicate that phosphorus in the ore is associated with goethite and exists mainly in amorphous Fe3PO7 phase. The phosphorus remains in the amorphous phase after being roasted below 300℃. Grattarolaite （Fe3PO7） is found in samples roasted at 600-700℃, revealing that phosphorus phase is transformed from the amorphous form to crystalline grattarolaite during roasting. Leaching tests on synthesized pure grattarolaite reveal a low rate of phosphorus removal by sulfiaric acid leaching. When the roasting tem- perature is higher than 800℃, grattarolaite is found to react with alumina to form aluminum phosphate, and the reactivity of grattarolaite with alumina increases with increasing roasting temperature. Consequently, the rate of phosphorus removal also increases with increasing roasting temperature due to the formation of acid-soluble aluminum phosphate.

Efficiency and Mechanism of Phosphorus Removal by Coagulation of Iron-manganese Composited Oxide

Iron-manganese composited oxide（FeMnO） was prepared with potassium permanganate and ferrous salt. Interface performance, charge property and structure topography of the FeMnO were investigated. Coagulation efficiency and pollution removal mechanism of the FeMnO were approached. Results show that the main compositions of the FeMnO are δ-manganese dioxide and ferric hydroxide. The specific surface area is about 146.22 m^2/g. The FeMnO contains rich hydroxyl with extremely strong adsorption action and chemical adsorption activity. The zero charge point of the oxide in pure water is about 8.0 of pH value. Under neutral pH value conditions, the FeMnO particle surface carried positive charges. The FeMnO particles are quasi-spherical micro-particles with irregular sizes adjoined each other to form net construction. Phosphorus removal efficiency of the FeMnO is remarkable, the total dissoluble phosphorus of settled water can be reduced below detecting level（0.3 μtg/L） at a FeMnO dosage of 6 mg/L, and total phosphorus below detecting level at a FeMnO dosage of 10 mg/L, for water samples containing total phos- phorus of 1281.70 μg/L and total dissoluble phosphorus of 1187.91 μtg/L. The mechanism of effective coagulation for phosphorus removal is combined results of multiple actions of adsorption, charge neutralization, adsorption/bridging and so on.

Removal of phosphorus from iron ores by chemical leaching

Alkali-leaching and acid-leaching were proposed for the dephosphorization of Changde iron ore, which contains an average of 1.12% for phosphorus content. Sodium hydroxide, sulfuriced, hydrochloric and nitric acids were used for the preparation of leach solutions. The results show that phosphorus occurring as apatite phase could be removed by alkali-leaching, but those occurring in the iron phase could not. Sulfuric acid is the most effective among the three kinds of acid. 91.61% phosphorus removal was attained with 1% sulfuric acid after leaching for 20 rain at room temperature. Iron loss during acid-leaching can be negligible, which was less than 0.25%.The pH value of solution after leaching with1% sulfuric acid was about 0.86, which means acid would not be exhausted during the process and it could be recycled, and the recycle of sulfuric acid solution would make the dephosphorization process more economical.

Separation of Kaolinite from Ion-Adsorption Rare Earth Tailings in Southern China and Iron Removal Treatment

Several hundred million tons of ion-adsorption rare earth tailings exist in Ganzhou, Southern China, which is a severe environmental hazard. To reduce and reutilize the tailing, kaolinite has been separated from the tailings by mechanical separation in laboratory scale and pilot scale. The results show that the tailing is mainly composed of fine kaolinite and coarse quart. Quartz and kaolinite can be separated by sieves, shaker, spiral chute or hydrocyclone, which has the similar results in laboratory scale and pilot scale. 30.2% of the tailings can be re-sourced and applied in ceramic industries. 41.7% of kaolinite can be obtained after sorting and iron removal by magnetic separator in pilot scale, which can be applied in ceramic industries according to the Chinese national standard (TC-3). The results give a progressive solution to re-source the tailings economically.

Science Letters:Simultaneous removal of nitrate and heavy metals by iron metal

Great attention should be paid now to simultaneously removing common pollutants, especially inorganic pollutants such as nitrate and heavy metals, as individual removal has been investigated extensively. Removing common pollutants simul- taneously by iron metal is a very effective alternative method. Near neutral pH, heavy metals, such as copper and nickel, can be removed rapidly by iron metal, while nitrate removal very much slower than that of copper and nickel, and copper can accelerate nitrate removal when both are removed simultaneously. Even a little amount of copper can enhance nitrate removal efficiently. Different mechanisms of these contaminants removal by iron metal were also discussed.

Pretreatment of Raw Biochar and Phosphate Removal Performance of Modified Granular Iron/Biochar

Biochar is a potential carrier for nutrients due to its porous nature and abundant functional groups. However, raw biochar has a limited or even negative capacity to adsorb phosphate. To enhance phosphate removal and reduce phosphate releases, acidic, alkaline, and surfactant pretreatments, followed by granulation and ferric oxide loading, were applied to raw biochar powder (Bp). The alkaline pretreatment proved to be the most effective method and exhibited significant pore expansion and surface oxidation. Bg-OH-FO showed the highest phosphate removal efficiency at 99.2% (initial phosphate concentration of 20 mg/L) after granulation and ferric oxide loading. Static adsorption results indicated that a pH value of 4 was the most suitable for phosphate adsorption because of the surface properties of Bg-OH-FO and the distribution of P (V) in water. Higher temperatures and a larger initial phosphate concentration led to better adsorption; the adsorption capacity of Bg-OH-FO was 1.91 mg/g at 313 K with an initial phosphate concentration of 50 mg/L. The Bg-OH-FO adsorption process was endothermic in nature. The Freundlich model seemed to be the optimum isotherm model for Bg-OH-FO. Under continuous adsorption, the flow rate and bed depth were changed to optimize the operation conditions. The results indicate that a slow flow rate and high bed depth helped increase the removal efficiency (η) of the fixed bed. The breakthrough curves fitted well with the Yoon–Nelson model. © 2017, Tianjin University and Springer-Verlag GmbH Germany.

Application of Iron Nanoparticles Synthesized by Green Tea for the Removal of Hexavalent Chromium in Column Tests

Nano zero valent iron particles (nZVI) are popular the last few years because of the numerous applications in remediation of a wide range of pollutants in contaminated soils and aquifers. The nZVI particles can be 10 - 1000 times more reactive than granular or micro-scale ZVI particles due to the small particle size, large specific surface area and high reactivity. An alternative green synthesis procedure was used for the production of nano zero valent iron particles (nZVI) using green tea (GT) extract, which is characterized by its high antioxidant content. Polyphenols in green tea extract possess double role in the synthesis of nZVI, because they not only reduce ferric cations, but also protect nZVI from oxidation and agglomeration as capping agents. The objective of current study was to simulate ata laboratory scale the attachment of GT-nZVI particles on soil material and study the effectiveness of attached nanoparticles for removing hexavalent chromium (Cr(VI)) from contaminated groundwater flowing through the porous soil bed. Column tests were carried out with various flowrates in order to examine the effect of contact time between the attached on porous medium nZVI and the flow-through solution on Cr(VI) reduction. After the completion of column tests the soil material in each column was split in 5 vertical sections, which were further subjected to chemical analyses and leaching tests. According to the results of the study increasing the contact time favors the reduction and removal of Cr(VI) from the aqueous phase. The reductive precipitation of Cr can be described as a reaction that follows a pseudo-first order kinetic law, with rate constant equal to k = 0.0243 ± 0.0011 min-1. Leaching tests indicated that precipitated chromium is not soluble. In the examined soil material, the total amount of precipitated Cr was found to range between 280 and 890 mg/(kg soil), while soluble Cr was less than 1.4 mg/kg and most probably it was due to the presence of residual Cr(VI) solution in the porosity of soil.

Removal of hexavalent chromium from aqueous solution by iron nanoparticles

Groundwater remediation by nanoparticles has received increasing interest in recent years. This report presents a thorough evaluation of hexavalent chromium removal in aqueous solutions using iron (Fe0) nanoparticles. Cr(VI) is a major pollutant of groundwater. Zero-valent iron, an important natural reductant of Cr(VI), is an option in the remediation of contami- nated sites, transforming Cr(VI) to essentially nontoxic Cr(III). At a dose of 0.4 g/L, 100% of Cr(VI) (20 mg/L) was degraded. The Cr(VI) removal efficiency decreased significantly with increasing initial pH. Different Fe0 type was compared in the same con- ditions. The reactivity was in the order starch-stabilized Fe0 nanoparticles>Fe0 nanoparticles>Fe0 powder>Fe0 filings. Electro- chemical analysis of the reaction process led to the conclusion that Cr(OH)3 should be the final product of Cr(VI). Iron nanopar- ticles are good choice for the remediation of heavy metals in groundwater.