Form Of Fe2O3 Research Articles

Study on the reaction mechanism of multi-source metallurgical dust for zinc extraction and iron enrichment

Multi-source metallurgical dust can realize the purpose of zinc extraction and iron enrichment by high-temperature reduction. In this paper, based on the zinc extraction and iron enrichment from multi-source metallurgical dust in rotary kiln process, thermodynamic calculations and reduction kinetic experiments were carried out to clarify the thermodynamic conditions and kinetic limiting factors of the reduction of Fe-Zn-C-O system of metallurgical dust, and to obtain the suitable parameters of reduction temperature and reaction time, etc. The results showed that Fe mainly existed in the form of Fe2O3 and Fe3O4 in metallurgical dust. Zn mainly existed in the form of ZnO and ZnFe2O4, with a small amount existed in ZnS. The starting temperatures of the reduction of ZnO, ZnFe2O4, ZnS with C were 951.09 °C, 581.55 °C and 1862.44 °C, respectively. Combined with the temperature of the smelting condition of rotary kiln, it was known that the presence of ZnS was the key factor leading to the limitation of zinc removal rate. ZnO and ZnFe2O4 showed higher reduction difficulty compared to iron oxides, so the metallization rate of rotary kiln slag could be improved by controlling the smelting atmosphere. The weight loss rate, metallization rate and dezincification rate of multi-source metallurgical dust showed an increasing trend with the change of temperature and time, and the more desirable effect of weight loss rate, metallization rate and dezincification rate were 46.7%, 87.1%, and 92.5% under laboratory conditions at reduction temperature 1100 °C and reaction time 50 min.

Study on the preparation of ceramic membrane support and its Fe migration rule by high‐aluminum fly ash as raw material

AbstractIn order to reduce the cost of ceramic membrane support, ceramic membrane support was prepared using high‐aluminum fly ash as raw material, and its Fe migration rules during the preparation process are studied. The effects of sintering temperature, pore forming agent content, and binder content on the properties of support, such as porosity, pore size, bending strength and water flux have been investigated. The optimum contents of high‐aluminum fly ash, pore forming agent and binder in the ceramic membrane support are 95%, 4%, and 1% respectively, and its sintering temperature is 1300°C. The porosity, bending strength, pore size, and water flux of the prepared support are 37%, 22 MPa, 665 nm, and 2800 L/h·m2·MPa, respectively. X‐ray powder diffractometer, X‐ray fluorescence spectrometer, X‐ray photoelectron spectrometer, inductively coupled plasma spectrometer, transmission electron microscope, spherical aberration corrected transmission electron microscopy, and laser Raman spectroscopy were used to characterize the support and Fe existing morphology in it. The results show that the main phases of sintered support are mullite, corundum, and silica. Massive mullite is produced when the sintering temperature reaches 1200°C. The content of mullite increases with increasing sintering temperature. About 7.7 % content of total Fe in the support exists in the form of Fe2O3. About 92.3% content of total Fe is dissolved into mullite. Fe is evenly distributed in mullite, and it is enriched at the grain boundary by element segregation. Fe in mullite is difficult to dissolve under strong acid conditions, so its stability is very strong.

Iron Oxide Nanoparticles Produced by a Low-Energy Nd: YAG Laser Ablation Technique and Their Application as Contrast Agent for Magnetic Resonance Imaging

A magnetic resonance imaging contrast agent is proposed using iron oxide nanoparticles (IONPs) synthesized by a pulsed laser ablation technique. Experimentally, an Nd: YAG laser (1064 nm, 7 ns, 30 mJ) was directed and focused on a high-purity iron plate immersed in a liquid solution of deionized water and polyvinylpyrrolidone (PVP). After a few minutes of laser bombardment, iron oxide nanoparticles dispersed in the liquid were homogeneously produced. A reddish yellow color-colloidal IONPs are produced in the water, while its color changes to dark brown for the PVP solution. The characterization results demonstrated that IONPs in the form of Fe2O3 and Fe3O4 made in the PVP have an excellent dispersibility with a spherical shape that is significantly smaller than that of IONPs made in the deionized water at the same laser repetition rate. The produced IONPs are further applied as a contrast agent for the magnetic resonance imaging (MRI) modality by varying concentrations from 0.05 mM to 2.31 mM. The results demonstrated that images of the IONPs sample with a concentration of 2.31 mM showed the highest contrast enhancement (Cenh), with an enhancement factor of 221.875 % for T1-weighted images and 91.227 % for T2-weighted images. IONPs with a concentration of 2.31 mM had the highest signal-to-noise ratio (SNR) for a T1-weighted picture of 52.92, while IONPs with a concentration of 0.05 mM had the highest SNR for a T2-weighted image of 179.117.

An efficient and clean method for the selective extraction and recovery of manganese from pyrolusite using ammonium sulfate roasting-water leaching and carbonate precipitation

Manganese is a fundamental metal raw material that plays a crucial role in sustainable economic and social development. With the battery industry undergoing rapid advancements in the recent years, there has been a consistent rise in the demand for manganese. This study proposes a new scheme for selectively extracting manganese from pyrolusite by the sulfation roasting-water leaching process, while the iron is enriched in the leaching residues in the form of Fe2O3. With a 1.5:1 mass ratio of ammonium sulfate to pyrolusite, a roasting temperature of 650 °C, and a duration of 120 min, the extraction efficiency of manganese was observed to be 96.15%, while iron extraction was only 1.45%. And the leaching residues containing mainly 54.62% SiO2 and 36.10% Fe2O3 were obtained, which could be enriched with iron by flotation. Subsequently, the purified leaching solution was subjected to manganese precipitation using ammonium bicarbonate. Under optimal conditions, the precipitation efficiency of manganese was 99.63%, and the manganese carbonate products were obtained with a particle size of approximately 1–1.5 μm spherical structure, which met the requirements of the industrial manganese carbonate quality standard (HG/T4203-2011). The mechanism studies have proven that MnO2 in pyrolusite was first converted to (NH4)2Mn2(SO4)3 and then to MnSO4, while Fe2O3 was converted to (NH4)3Fe(SO4)3, NH4Fe(SO4)2, Fe2(SO4)3 in turn and finally decomposed to Fe2O3. The ammonia produced during the roasting process can be absorbed to regenerate ammonium sulfate products, and the filtrate from the manganese precipitation can also be crystallized by evaporation to obtain ammonium sulfate products, both of which can be used in the roasting process to reduce production costs. The process of this study proposed is simple and does not require any strong acid or alkali reagents. It offers high efficiency, is environmentally friendly, and is easy to operate, thus providing a new idea and scheme for the multi-component resource utilization of manganese oxide ore.

Thermodynamic and kinetic aspect of solid state reduction of Electric Arc Furnace slag through coke: An experimental study.

Steel slag is one of the major wastes produced during the steelmaking process. In the present scenario, the world’s utilization rate of steel slag is comparatively very low and primarily used for landfills only. The untreated slag used for the dumping will affect the environment adversely and causes loss to the economy as well. In the present study, we are concentrating on steel slag through the latter. The mineralogy of primary slag ensures the presence of various constituent ranges, Fe2O3 /FeO (18–30%), CaO (23–48%), SiO2 (2–6%), MgO (4–17%), and Al2O3 (2–15%), mainly depends on the quality of raw material as well as processing relies on the quality of raw material as well as processing. One of the significant components of steel slag with a large variety of ranges is iron oxides. Iron Oxide is present in the steel slag in the form of FeO, Fe2O3, and FeO.SiO2. This study analyzed the reduction kinetics of steel slag based on the Coats-Redfern method and explained the reduction mechanism of Fayalite for different slag basicity. The investigation involves a temperature range of 960–1478 K with a carbon-to-oxygen ratio of C/O-1.The non-isothermal experiment covers the solid reduction of EAF slag. The TG curve shows the reduction reaction of steel slag and coke from 0.5 to 1.5 is 7.31% to 10.88%. During the investigation, the activation energy of iron reduction process will get decrease with increased slag basicity.

Synthesis of functionalized α -Fe2O3 nanoparticles: Characterization and applications

In this study, EDTA functionalized α -Fe2O3 (Ferric Oxide) NPs were synthesized via chemical and green synthetic methods. FTIR spectra confirmed the functionalization of NPs with EDTA. X-ray diffraction confirmed the formation ‘α’ form of Fe2O3. UV–Vis diffuse reflectance spectra were applied to study the band gap of the NPs and was determined as 2.75 eV. MB and MG dyes were used as model dyes to study the adsorption and photocatalytic properties of NPs under visible and ultraviolet light radiation respectively. FESEM and HRTEM methods are used to study the morphology of the synthesized nanoparticles. Surface functionalization played a significant role in understanding the adsorption of dyes onto the surface of the photocatalyst. The crystallite size of chemical synthesized and green synthesized α- Fe2O3 was found to be 12 nm and 9 nm respectively. Maximum degradation efficiency of 58% and 86% was obtained for the degradation of MB and MG respectively and 85.9% of corrosion inhibition efficiency was also achieved. The results proved that functionalization of nanoparticles will lead enhancement of the following mediated synthesized EDTA functionalized α -Fe2O3 is a promising material to use for different application. Hence, green synthesized NPs are expected to offer significant insight into their multifunctional applications.

Simultaneous adsorption of Cd and As by a novel coal gasification slag based composite: Characterization and application in soil remediation

Cadmium (Cd) and arsenic (As) co-contamination has become increasingly serious in China agricultural soil due to rapid industrialization and urbanization. The opposite geochemical behaviors of Cd and As pose huge challenges for developing a material for their simultaneous immobilization in soils. Coal gasification slag (CGS) as a by-product of coal gasification process, is always dumped into a local landfill, which has a negative impact on environment. Few reports have been available on applying CGS as a material to immobilize simultaneously multiple soil heavy metals. A series of iron-modified coal gasification slag (IGS) composites IGS3/5/7/9/11 (with different pH values) were synthesized by alkali fusion and iron impregnation. After modification, carboxyl groups were activated, and Fe was successfully loaded onto the surface of IGS in the form of FeO and Fe2O3. The IGS7 exhibited the best adsorption capacity with the maximum Cd and As adsorption capacity of 42.72 mg/g and 35.29 mg/g, respectively. The Cd was mainly adsorbed through electrostatic attraction and precipitation, while the As through complexation with iron (hydr)oxides. IGS7 significantly reduced the bioavailability of Cd and As in soil with Cd bioavailability reduced from 1.17 mg/kg to 0.69 mg/kg and As bioavailability reduced from 10.59 mg/kg to 6.86 mg/kg at 1 % IGS7 addition. The Cd and As were all transformed to more stable fractions after IGS7 addition. The acid soluble and reducible Cd fractions were transformed into oxidizable and residual Cd fractions, and the non-specifically and specifically adsorbed As fractions were transformed to amorphous iron oxide-bound As fraction. This study provides valuable references for the application of CGS to the remediation of Cd and As co-contaminated soil.

Study on the recovery of phosphorus and iron from molten modified high-phosphorus industrial slag by carbothermal reduction

To effectively recycle phosphorus and iron resources in high-phosphorus industrial slag during molten modification process, the thermodynamic conditions and influence laws of recovery of valuable elements from converter slag with different P2O5 content by carbothermal reduction after melting and modification are systematically analyzed. The results show that the reduction rates of P2O5 and FeO decrease with the increase of P2O5 content at 1450 °C and the basicity of 1.0. Meanwhile, the experimental results prove that the reduction of FeO precedes the reduction of P2O5.The phosphorus element in initial industrial slag mainly exists in the form of Ca5(PO4)2SiO4 and increases with the increase of P2O5 content. With the progress of the carbothermal reduction reaction, the Ca5(PO4)2SiO4 content in experimental slags after reduction decrease significantly. The iron element in initial industrial slag mainly exists in the form of FeO, (MgO)0.239 (FeO)0.761 and Ca2Fe2O5 and disappear after carbothermic reduction reaction. In the range of P2O5 content of 4–8 wt.%, P2O5 content has little effect on the thermodynamic trend of the formation of phosphorus-containing phase Ca5(PO4)2SiO4, but it is not good for the thermodynamic trend of gasification dephosphorization reaction in the carbothermic reduction process. Therefore, the increase of P2O5 content is not conducive to the occurrence of carbothermic reduction gasification dephosphorization reaction.

Genetic Mechanism of Uranium Concentration in Ferruginous Sandstone of the Wajid Group in Southern Saudi Arabia

Uranium anomalies were discovered in ferruginous sandstone in the Khusayyayn Formation of the Wajid Group in southern Saudi Arabia. Based on field surveys, ground radiometric surveys, and chemical analysis, this paper summarizes the characteristics of the lithology and lithofacies of the ferruginous sandstone and analyzes the genetic mechanism of uranium concentration in ferruginous sandstone. Ferric iron basically exists in the form of Fe2O3 in ferruginous sandstone, with an average content of 28.95 wt.%. The formation period of the ferruginous sandstone occurred during the early synsedimentary and later diagenesis stages from the Carboniferous to the Devonian. The uranium anomaly is hosted in thin-bedded and lenticular ferruginous sandstone, with a uranium content ranging from 50 to 766 ppm. The average U-Ra equilibrium coefficient of ferruginous sandstone was 1.00, indicating that the uranium was weakly reformed after the uranium concentration. Ferric ions are closely related to uranium mineralization. The initial concentration of the uranium occurred during the deposition of the ferruginous sandstone. Most of the uranium was adsorbed by a ferric colloidal solution, and part of it was reduced by Fe2+, organic carbon, and sulfur in the uranium preconcentrated stage during the deposition of ferruginous sandstone. The uranium ore was superimposed, transformed, and concentrated due to the change in the pH environment in the early Neogene.

Catalytic ozonation of high-salinity wastewater using salt-resistant catalyst Fe-Bi@γ-Al2O3

In this study, a salt-tolerant Fe-Bi@γ-Al2O3 catalyst with stable structure and excellent catalytic performance was prepared with an impregnation method by using γ-Al2O3 as the carrier. The effects of calcination temperature and calcination time on the catalytic activity of the Fe-Bi@γ-Al2O3 catalyst were evaluated. The catalyst was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, BET, X-ray diffraction, and X-ray fluorescence spectrometry to analyze the relationship between the catalyst's apparent morphology, structural characteristics, and catalytic activity. The optimal working conditions and organic degradation mechanism of Fe-Bi@γ-Al2O3 catalytic ozonation of a high-salinity organic wastewater system were studied. The active components Fe and Bi were successfully loaded on the surface of γ-Al2O3 in the form of Fe2O3 and Bi2O3 crystals. Under the working conditions of ozone aeration rate of 0.2 L/min, catalyst filling rate of 10 %, and pH = 11, the removal rate of COD in high-salinity organic wastewater was 83.9 %. The degradation mechanism of organic matter in wastewater was analyzed using ultraviolet absorption peak and three-dimensional fluorescence spectrum. Kinetic analysis of the COD removal rate of high-salinity organic wastewater under optimal working conditions was carried out. A 3E evaluation model of Fe-Bi@γ-Al2O3 catalyst for ozonation treatment of high-salinity organic wastewater was established to realize overall evaluation of the process performance.

Degradation of terbuthylazine by Fe/TiO2 with visible-light-driven photo-Fenton catalytic activity

In order to improve the catalytic activity of Fenton catalyst, a composite catalyst, Fe/TiO2, with both visible-light photocatalytic and Fenton-like catalytic activities was synthesized via a brief solvothermal process. The XRD and SEM results indicated that Fe was dispersed homogeneously on the surface of TiO2 in the form of Fe2O3, and the loading of Fe did not have significant effects on the particle size and morphology of TiO2. The EDS results showed that the loading content of Fe was about 1.4 wt%. The photocatalytic results showed that the prepared Fe/TiO2 composite catalyst had excellent catalytic behaviors for terbuthylazine degradation under visible-irradiation with H2O2 assistance, the degradation ratio reached up to 90% after 120 min. The reinforced degradation performance were primarily attributable to the introduction of carrier TiO2, which expanded visible response range by H2O2 adsorption, and accelerated the cycle of Fe (Ⅱ)/Fe (Ⅲ). The fluorescent spectroscopy results revealed that the degradation process of terbuthylazine involved the generation and participation of active species such as hydroxyl radicals and superoxide radicals. This study is expected to provide a visual approach for designing a novel photo-Fenton catalyst to jointly utilize both photocatalytic and Fenton activities, which can be better applied to the actual use of organics purification in wastewater.

Influence of phase formation conditions on the dielectric properties of Bi0.5La0.5MnO3 ceramics modified with magnetoactive elements

Modified solid solutions based on the multiferroic Bi0.5La0.5MnO3 were synthesized by conventional ceramic technology. The modifiers were introduced stoichiometrically in the form of Fe2O3, Co2O3 by the formula Bi0.5La0.5Mn1-xZxO3. The processes of phase formation, structural characteristics, dielectric properties, and microstructure were studied. Anomalies in the dielectric permittivity spectra were found, probably associated with the Maxwell-Wagner polarization. Correlations were established between the macro-properties of the samples and the phase transition phenomena characteristic of them.

Adsorption properties and mechanism of Cr(VI) by Fe2(SO4)3 modified biochar derived from Egeria najas

The aquatic plant Egeria najas based biochar was innovatively constructed by modifying it with Fe2(SO4)3 (Fe2(SO4)3 @EN-BC) for Cr(VI) removal. The characterizations of Fe2(SO4)3 @EN-BC confirmed that Fe2(SO4)3 was attached to biochar in form of Fe2O3 after hydrolysis and calcination under high temperature. The results showed that Fe2(SO4)3 @EN-BC had a high removal efficiency of Cr(VI) with approaching 99.88%, which was about 7 times higher compared to unmodified biochar (EN-BC). Batch experiments of Cr(VI) removal included initial concentration, reaction temperature, solution pH and kinetics were conducted. The adsorption kinetics could be more accurately explained using pseudo-second order kinetics model, indicating the chemical adsorption controlled the reaction process. According to the Langmuir model, the maximum adsorption capacities for Cr(VI) were 138.79, 159.36 and 190.91 mg/g at 298, 313 and 333 K, respectively. Moreover, based on FTIR and XPS results, the Fe2(SO4)3 @EN-BC surface was loaded with many functional groups conducive to Cr(VI) adsorption. The main removal mechanisms of Cr(VI) by Fe2(SO4)3 @EN-BC included adsorption and reduction, and the percentage of Cr(VI) removed by adsorption and reduction were 19.1% and 80.9%, respectively.

Corrosion Behavior of Low Carbon Steel Pipe in Condensate Environment

Low carbon steel pipe is widely used in various pipeline applications because it has good mechanical properties. The application of low carbon steel developed generally does not involve corrosion resistance. To find out the behavior of low carbon steel pipe in condensate fluids, the immersion test was carried out. The method for the immersion test is the planned-interval test. The corrosion rate of this steel was determined by weight loss, whereas the corrosivity of the condensate fluids was measured by a multimeter Hach HQ40d. The morphology of corrosion products is characterized by using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and x-ray diffraction (XRD). The result of immersion of low carbon steel pipe in the condensate fluids shows that the liquid corrosivity and corrodibility of low carbon steel pipe tend to decreases with the length of exposure time. The decrease of metal corrodibility is identical to the lower corrosion rate at a longer exposure time due to the layer a corrosion product formed. The corrosion products during immersion tests are uniform with iron oxide in the form of FeO(OH) and Fe2O3.H2O.
 GRAPHICAL ABSTRACT

Effect of FeO content on melting characteristics and structure of nickel slag

Nickel smelting produces a large amount of nickel slag which contains a lot of Fe in the form of FeO. The effect of FeO content on the melting properties and structure of nickel slag is investigated by thermodynamic calculations and experiments, using the nickel slag of water quenching furnace as raw material, which is simplified to CaO-SiO2-FeO-MgO slag system. The results are as follows: with increasing FeO content, the precipitated primary phase changes from melilite to olivine. The liquidus temperature, softening temperature, hemispherical temperature, flow temperature, viscosity, and critical viscosity temperature of the slag system tend to decrease gradually, but the solid phase temperature tends to decrease first and then increase. The centre of the symmetric stretching vibration band of the [SiO4]4 tetrahedron -in the slag system shifts to the low wavenumber region. The mole fraction of O0 in the slag continuously decreases, and the mole fraction of O- and O2- increases. The complex silicon-oxygen tetrahedron structure gradually disintegrates and the structural unit tends to be simple.

Catalytic graphitization in anthracite by reduced iron particles and investigating the mechanism of catalytic transformation via molecular dynamics

Anthracite graphitization was catalyzed by reduced iron particles, where iron was introduced in the form of Fe2O3, reduced during the carbothermal reaction. This graphite as an alternative solution for the lithium-ion battery anode material, and the precursor of the anode material was obtained. The degree of graphitization of synthetic graphite regulated via changing the amount of Fe2O3 and catalytic temperature. Graphite with the graphitization degree of 96.51% was obtained under the conditions of the catalytic temperature of 2400 °C, Fe2O3 content of 20%. HRTEM of graphite after Fe-catalyzed graphitization revealed that the graphite layer spacing gradually approached the ideal graphite. Molecular dynamics (MD) provides significant insight into the mechanism of Fe-catalyzed graphitization at the molecular level. The mechanism of Fe-catalyzed graphitization was inevitably related to the formation and breakage of Fe–C bonds. With the formation and breakage of Fe–C and C–C bonds, a regular aromatic 6-membered ring was finally formed due to the strong bonding between Fe and C. Fe promoted the integration of irregular 5- and 7-membered rings into two regular aromatic 6-membered rings. These two processes were continued in the process of catalytic graphitization. This result provided MD support to explore the mechanism of Fe-catalyzed graphitization.

Study on performance and mechanism of enhanced low-concentration ammonia nitrogen removal from low-temperature wastewater by iron-loaded biological activated carbon filter

In order to strengthen the treatment of low-concentration ammonia nitrogen wastewater at low temperature, iron-loaded activated carbon (Fe-AC) with ultrasonic impregnation method was used as the filter material of biofilter process. The performance and mechanism of ammonia nitrogen removal from simulated secondary wastewater by iron-loaded biological activated carbon filter (Fe-BACF) were studied at 10 °C. The characterization results showed that iron was loaded on the surface of AC in the form of Fe2O3, and the specific surface area, total pore volume, pore size and alkaline functional group content of Fe-AC were obviously increased. After the formation of biofilm on the surface of filter media, the average removal rate of ammonia nitrogen by Fe-BACF (97.9%) was significantly higher than that of conventional BACF (87.8%). The improved surface properties increased the number and metabolic activity of microorganisms, and promoted the secretion of EPS on the surface of Fe-BAC. The results of high-throughput sequencing showed that the existence of Fe optimized the bacterial community structure on the surface of Fe-BAC, with the increase of the abundances of psychrophilic bacteria and ammonia nitrogen removal bacteria. The mechanism of enhanced ammonia nitrogen removal by Fe-BACF was the joint action of many factors, among which the main causal relationship was that modification of iron could optimize the number and category of microorganisms on Fe-BAC surface by improving the surface properties, thus improving the biological nitrogen removal ability. Results of this study provided a practical way for the treatment of low ammonia nitrogen wastewater in cold regions.

Multicomponent nanoparticles as means to improve anaerobic digestion performance

Sufficient quantity of trace metals is essential for a well performing anaerobic digestion (AD) process. Among the essential trace elements in active sites of multiple important enzymes for AD are iron and nickel ions. In the present study, iron and nickel in the form of Fe2O3 and NiO were coated on TiO2 nanoparticles to be used in batch and continuous operation mode. The effect of TiO2, Fe2O3–TiO2, and NiO–TiO2 nanoparticles on each step of AD process was assessed utilizing simple substrates (i.e. cellulose, glucose, acetic acid, and mixture of H2–CO2) as well as complex ones (i.e. municipal biopulp). The hydrolysis rate of cellulose substrate increased with higher dosages of the coated TiO2 with both metals. For instance, the hydrolysis rate was increased up to 54% at Fe2O3–TiO2 and at a concentration of 23.5 mg/L for NiO–TiO2 it was increased up to 58%, while higher dosage suppressed the hydrolytic activity. Experimental results revealed that low dosages of NiO–TiO2 increased the accumulated methane production up to 24% probably by increasing the enzymatic activity of acetoclastic methanogenesis. NiO–TiO2 showed positive effect on batch and continuous AD of biopulp and improved methane yield up to 8%.

Corrosion rate and corrosion behaviour analysis of carbon steel pipe at constant condensed fluid

This study investigates the corrosion rate and corrosion behavior of carbon steel pipe at constant condensed fluid from a geothermal power plant. The corrosion rate of the steel was determined by weight loss analysis, whereas the corrosivity of the condensate fluids was measured by a multimeter Hach HQ40d. The morphology of the corrosion products formed was characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and x-ray diffraction (XRD) analysis. Results showed that the corrosion rate in the liquid part of the condensate fluids is constant during the immersion period when water quality parameters are constant. Meanwhile, the corrosion rate of low carbon steel pipe decreases though with the longer exposure period in the condensate fluid. The decrease of metal corrodibility identical to the lower corrosion rate at a longer exposure time due to the protective corrosion layer formed. The corrosion products during immersion tests identified in the corrosion test were uniform with iron oxide in the form of FeO(OH) and Fe2O3*H2O.

Selective recovery of manganese from electrolytic manganese residue by using water as extractant under mechanochemical ball grinding: Mechanism and kinetics

This research aimed to address the issue of residual manganese in electrolytic manganese residue (EMR), which is difficult to recycle and can easily become an environmental hazard and resource waste. This research developed a method for the efficient and selective recovery of manganese from EMR and the removal of ammonia nitrogen (ammonium sulfate) under the combined action of ball milling and oxalic acid. The optimum process parameters of this method were obtained through single-factor experiment and response-surface model. Results showed that the recovery rate of manganese can exceed 98%, the leaching rate of iron was much lower than 2%, and the leaching rates of manganese and ammonia nitrogen after EMR ball grinding were 1.01 and 13.65 mg/L, respectively. Kinetics and mechanism studies revealed that ammonium salts were primarily removed in the form of ammonia, and that insoluble manganese (MnO2) was recovered by the reduction of FeS and FeS2 in EMR under the action of oxalic acid. Iron was solidified in the form of Fe2O3 and Fe2(SiO3)3. The technology proposed in this research has great industrial application value for the recycling and harmless treatment of EMR.