Reduction Of Zinc Oxide Research Articles

The Reduction Reaction Behavior of Steelmaking Dusts with Lignin under Different Atmospheres.

This study investigated lignin as a reducing agent instead of fossil carbon for the reduction of zinc oxide and zinc ferrite contained in steelmaking dusts. Three types of dusts from different steelmaking processes were considered: ferrochrome converter (CRC), electric arc furnace stainless steel (EAFSS) and electric arc furnace carbon steel (EAFCS). Zinc is primarily found in zincite phases within CRC dust, while EAFSS and EAFCS dusts contain franklinite and zincite phases as Zn-bearing minerals. The proximate analysis of lignin showed that the fixed carbon content is 28.9%. Thermogravimetric (TG) analysis coupled with differential scanning calorimetry (DSC) and mass spectrometry (MS) was used to study the reduction behavior of different mixtures of lignin and steel dusts under inert and air atmospheres. Simultaneously, the minimum ratio of lignin out of three different proportions required to achieve a complete reduction of franklinite and zincite phases into metallic zinc was identified. The results indicated that a 1.1 stoichiometric amount of lignin is sufficient for the complete reduction of zinc-bearing minerals into metallic zinc. In conclusion, lignin can be used efficiently for processing steelmaking dusts.

201 The effects of the supplementation of a Zinc-amino acid complex in pig nursery diets with differing pharmacological levels of zinc oxide and complexity

Abstract Diet complexity (DC), which has significance in nursery pig production, generally refers to a greater number of highly digestible ingredients. Increased DC may have even greater significance in scenarios of reduction or withdrawal of zinc oxide (ZnO) in nursery diets. The objectives were to determine 1) the impact of adding Zn-amino acid complex (Zinpro ProPath Zn) to mid- (MC) and low-complexity (LC) diets on nursery pig performance and health compared with a high complexity (HC) diet, and 2) the impact of Zinpro ProPath Zn in diets with and without pharmacologic levels of ZnO. A total of 2,400 mixed-sex weanling pigs [initial body (BW) weight = 5.79 ± 0.15 kg] were assigned to 1 of 5 dietary treatments during nursery (42 d) as follows: 1) HC; MC diet with 2) MC+ZnO) or without 3) MC-ZnO) pharmacologic ZnO; and LC diet with 4) LC+ZnO) or without 5) LC-ZnO) pharmacologic ZnO. All diets except HC were supplemented with Zinpro ProPath Zn (125 mg/kg Zn) and ZnO [3,000, 2,000, and 0 mg/kg Zn during Phases I (14 d), II (14 d) and III (14 d), respectively]. Different DC were achieved by manipulating the inclusion of spray-dried plasma, soy protein concentrate, and whey protein. Growth performance, onset of feed intake, fecal dry matter, number of injectable treatments administered, and serum acute-phase response were assessed. Pigs fed HC (20.0 kg) had greater final BW (FBW) compared with pigs fed MC-ZnO (18.8 kg), which had greater FBW compared with pigs fed LC-ZnO (17.5 kg; SEM = 0.34; P < 0.05). Average daily feed intake (ADFI) was greater in pigs fed HC (0.46 kg/d) compared with MC-ZnO (0.43 kg/d) and LC+ZnO (0.42 kg/d), which had greater ADFI compared with LC-ZnO (0.39 kg/d; SEM = 0.01; P < 0.05). Similarly, average daily gain (ADG) and gain to feed ratio (G:F) were greater in pigs fed HC (0.33 kg/d, 0.72 kg/kg, respectively) compared with pigs fed LC (0.27 kg/d, 0.67 kg/kg, respectively), regardless of ZnO (SEM = 0.01; P < 0.05). There was no effect of dietary treatments on the fecal dry matter or on the onset of feed intake of pigs (P > 0.10). The number of injectable treatments administered was greatest in LC-ZnO (62.7%), followed by LC+ZnO (50.6%), MC regardless of ZnO (44.0%), and HC (36.7%; SEM = 1.04; P < 0.05). Serum alkaline phosphatase was less in LC-ZnO than the other groups (229.8 vs. 280.9 ± 11.9 IU/L; P < 0.05). Taken together, feeding HC diets during the nursery appears to be effective in improving performance and health of pigs, particularly when compared with MC and LC diets without ZnO. Moreover, the addition of Zinpro ProPath Zn may partially attenuate the negative effects of ZnO removal in MC, but not LC, diets.

Exploring Enhanced Hydrolytic Dehydrogenation of Ammonia Borane with Porous Graphene-Supported Platinum Catalysts.

Graphene is a good support for immobilizing catalysts, due to its large theoretical specific surface area and high electric conductivity. Solid chemical converted graphene, in a form with multiple layers, decreases the practical specific surface area. Building pores in graphene can increase specific surface area and provide anchor sites for catalysts. In this study, we have prepared porous graphene (PG) via the process of equilibrium precipitation followed by carbothermal reduction of ZnO. During the equilibrium precipitation process, hydrolyzed N,N-dimethylformamide sluggishly generates hydroxyl groups which transform Zn2+ into amorphous ZnO nanodots anchored on reduced graphene oxide. After carbothermal reduction of zinc oxide, micropores are formed in PG. When the Zn2+ feeding amount is 0.12 mmol, the average size of the Pt nanoparticles on PG in the catalyst is 7.25 nm. The resulting Pt/PG exhibited the highest turnover frequency of 511.6 min-1 for ammonia borane hydrolysis, which is 2.43 times that for Pt on graphene without the addition of Zn2+. Therefore, PG treated via equilibrium precipitation and subsequent carbothermal reduction can serve as an effective support for the catalytic hydrolysis of ammonia borane.

Hydrogen reduction process for zinc-bearing dust treatment: Reduction kinetic mechanism and microstructure transformations in a novel and environmentally friendly metallurgical technique

The iron and steel sector generates 80 million tons of zinc-containing dust annually, traditionally treated using carbon-based pyrometallurgical processes, which have significant drawbacks, including large carbon emissions, high energy consumption, and low production value. To address the above issues, a green hydrogen reduction method was developed for zinc-bearing dust treatment. This study examined the thermodynamics, reduction kinetics, and phase transformation during the process, revealing that at 800 °C, the hydrogen partial pressure for zinc oxide reduction is only 45.56 %. The direct reduction of zinc-containing dust pellets with hydrogen reveals that the limiting step of iron oxide and zinc reductions both are interfacial chemical reaction control at the reduction temperature of 800–950 °C, with an apparent activation energy of 16.42 kJ/mol and 71.39 kJ/mol. The kinetic mechanism indicates that reducing iron and zinc oxides is more accessible in a hydrogen reduction system, with lower apparent activation energies than carbothermal reduction. Consequently, hydrogen reduction offers a more efficient and environmentally friendly solution for treating zinc-bearing dust.

The catalytic effect of the metal bath on the zinc oxide reduction

The iron and steel industry generates about 8 million tons of electric arc furnace dust (EAFD) per year. The current standard process for treating this material stream is the Waelz process, which is not optimal in terms of the recovery rate for zinc. Therefore, alternative process concepts have been developed in recent years in which carbothermal reduction does not run over solid carbon but with carbon dissolved in a liquid metal bath. In the literature, a catalytic effect is attributed to this approach. However, quantification in terms of a kinetic evaluation has not been carried out to date. In the present study, the catalytic effect of the metal bath on the reduction of zinc oxide is investigated based on different experimental studies. It was found that carbon-saturated nickel (Ni) increases the kinetics by a factor of up to 10, and carbon-saturated iron (Fe) increases the kinetics by up to 30, with the catalytic effect increasing with a higher ZnO concentration. In the case of iron, the carbothermic reduction is additionally overlapped by a metallothermic reaction and thus further accelerated.

Synthesis and Characterization of Silver Doped Zinc Oxide Nanoparticle from Beetle Leaf Extract- Evaluation of Antimicrobial Activity Against Human Pathogenic Bacteria and Fungi

Abstract: Plants or natural resources have been found to be a good alternative method for nanoparticles synthesis. In this study, silver doped zinc oxide nanoparticles (AgZno4NPs) synthesized from Piper betle leaves extract were investigated for their antibacterial and antifungal activity. ZnO nanoparticles were prepared from the reduction of Zinc oxide and NaBH4 was used as reducing agent, later doped with silver nitrate. Silver doped zinc nanoparticles were mixed thoroughly and subjected for characterization studies. Prepared nanoparticles were characterized by Visual inspection, Ultraviolet-visible spectroscopy (UV), Fourier transform infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) techniques. Antimicrobial activities of the synthesized silver nanoparticles were tested against Staphylococcus aureus ATCC 25923, Salmonella typhi ATCC 14028, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. UV–Vis spectrum of reaction mixture showed strong absorption peak with centering at 400 nm. The FT-IR results imply that Ag-Zn NPs were successfully synthesized and capped with bio-compounds present in P. betle and particle size ranging from <100nm. The result revealed that AgZn-Extract NPs showed 12.78±0.64 mm zone of inhibition against S. typhi, whereas streptomycin (positive control) showed maximum 15.15±0.40 mm zone of inhibition for S.mutans. Again, maximum zone of inhibition found for S. mutans. The results obtained by this study can’t be directly extrapolated to human; so further studies should be undertaken to established the strong antimicrobial activity of Ag-Extract NPs for drug development program

Development of a methodology for optimizing the component composition of the charge for the processing of gts of steelmaking, providing the efficiency of useful components extraction

The article deals with the recycling issues of electric steelmaking dusts by thermodynamic extraction of iron, zinc and lead in order to reduce the impact on the environment and increase the industry resource base. The purpose of the research was to determine the influence of the quantitative content of low-calorie and high-calorie carbon on the processes of zinc oxide reduction in gas purification dust and its further sublimation using a vacuum in a closed system of a resistance heating furnace. Determined the dependence of the zinc extraction degree and the increase of iron oxides in the samples studied.

Kinetic Analysis of Recovering Zinc from Electric Arc Furnace Dust by Vacuum Carbothermic Reduction at 20 Pa

Electric arc furnace dust (EAFD) presents a contamination hazard due to its heavy metal leachability. The traditional disposal methods of landfill or stacking not only pose a threat to the environment but also waste metal resources. This paper adopted vacuum carbothermic reduction to dispose of EAFD and the zinc metal could be obtained as a product. The reduction ratios of the EAFD were carried out under various reaction temperatures and times at 20 Pa. Furthermore, the kinetics of the reduction process was also studied. The reduction ratio of the reaction process can be facilitated through increasing the temperature or lengthening the time and can reach up to 99.6% under the condition of 1373 K with 60 min. The zinc ferrite and zinc oxide were reduced first and then iron oxide reduction occurred. The reduction process could be divided into three stages: Stage 1 involved the direct reduction of zinc ferrite and zinc oxide, and the control step was the phase boundary reaction with the apparent activation energy of 48.54 kJ/mol; Stage 2 involved the reduction of zinc oxide and iron oxide, and the control step was also the phase boundary reaction with the apparent activation energy of 56.27 kJ/mol; Stage 3 involved the escape of gas phase products and the control step was diffusion with the apparent activation energy of 105.3 kJ/mol.

Influence of Different Carbon Content on Reduction of Zinc Oxide via Metal Bath

Electric arc furnace dust (EAFD) is an important secondary resource for the zinc industry. The most common process for its recycling is the pyro-metallurgical treatment in the Waelz process. However, this process focuses on the recycling of the zinc, whereas the recovery of other metals from the EAFD—such as iron and other alloying elements—is neglected. An up-to-date version of reprocessing can involve multi-metal recycling by means of a metal bath containing carbon. The use of a liquid iron alloy requires a higher processing temperature, which enables the reduction and melting of iron oxides as well as other compounds occurring in the dust. Furthermore, the Zn yield is higher and the reduction kinetics are faster than in the Waelz process. This paper is only focused on the zinc reduction in such a metal bath. In order to determine the influence of the carbon content in the molten metal on the reduction rate, experiments were carried out on the reduction behavior of zinc oxide using a synthetic slag. This slag, with a basicity B2 = 1, was applied to an iron bath with varying carbon contents. (0.85%, 2.16%, 2.89%, and 4.15%) The decrease in the zinc oxide concentration was monitored, along with the reaction rates calculated from these data. It was found that the reaction rate increases with rising carbon content in the melt.

Cathodic Reduction of Zinc Oxide in Alkaline Electrolyte

Cathodic Reduction of Zinc Oxide in Alkaline Electrolyte

Energy and exergy analysis of the zinc/zinc oxide thermochemical cycle for hydrogen production and fuel cell power generation

Water-splitting thermochemical cycles have emerged as a possible solution for the decentralized production of hydrogen using solar energy. A useful tool to select the most promising thermochemical cycles among those proposed in the literature is represented by the exergy analysis. In this context, the exergy and energy analyses of the zinc/zinc oxide thermochemical water-splitting cycle, coupled with the production of electrical energy in a fuel cell, are here carried out and discussed. The aim has been to identify the steps in the process characterized by the highest inefficiencies and to propose possible solutions to increase the overall thermodynamic efficiency. Calculations were carried out using the commercial process simulator PRO/II. The cycle consists of two steps: (i) the endothermic thermal reduction of solid zinc oxide to liquid zinc and oxygen, carried out in a solar thermo-reactor at 2025 °C, and (ii) the non-solar, exothermic hydrolysis of zinc to form hydrogen and solid zinc oxide. This work reports three possible process schemes based on the zinc/zinc oxide redox reactions, each differing from the others in terms of envisaged modes of heat recovery. In addition, the effect of carrying out the hydrolysis step under adiabatic, rather than isothermal conditions, has been analysed. Four values of conversion were considered (1, 0.9. 0.8, and 0.7) and the effect on fuel cell power generation, utility consumption, and energy and exergy efficiency was evaluated. It was found that the exergy efficiency increased from about 14% for the classical zinc/zinc oxide cycle to almost 40% in the most efficient scenario considered here. The variation of hydrogen conversion in the fuel cell led to a decrease in generated power, from 16.41 MW at hydrogen conversion of 1 down to 11.48 MW at hydrogen conversion of 0.7.

Self-templated poly schiff base-Fe derived Fe-N co-doped porous carbon nanosheets for efficient electrocatalysis

Rational design and fabrication of two-dimensional (2D) functional materials is of important significance in tackling fundamental issues for electrocatalysis. Here, a novel synthesis strategy is developed using basic zinc carbonate (BZC) nanosheets as 2D self-template to construct Fe-Nx active sites in porous carbon nanosheets (Fe-N-PCNS). Poly schiff base (PSB) is synthesized by in-situ polymerization reaction on the surface of BZC nanosheets, then coordinates with iron ion to obtain PSB-Fe@BZC complex. During pyrolysis, PSB-Fe@BZC complex undergoes a series process of decomposition of BZC nanosheets, reduction of zinc oxide and zinc evaporation, in which BZC nanosheets plays a decisive role in fabricating hierarchically porous carbon nanosheets with uniformly dispersed Fe-Nx active sites. As a result, Fe-N-PCNS displays an excellent electrocatalytic performance for oxygen reduction reaction with positive half-wave potential (0.91 V), large kinetic limiting current density (54.3 mA cm−2), high stability and superior methanol resistance in alkaline media, which surpasses those of Pt/C catalyst. Moreover, Fe-N-PCNS demonstrates remarkable electrocatalytic performance in primary Zn-air batteries with the outstanding discharge durability (with 18 cycles over 100 h). This self-templated strategy provides a new way for the fabrication of unique 2D carbon-based electrocatalysts.

Carbothermic Reduction of Zinc Containing Industrial Wastes: A Kinetic Model

Effective recycling of zinc-containing industrial wastes, most importantly electric arc furnace dust, is of tremendous importance for the circular economy of the steel and zinc industry. Herein, we propose a comprehensive kinetic model of the combined carbothermic and metallothermic reduction of zinc oxide in a metal bath process. Pyro-metallurgical, large-scale lab experiments of a carbon-saturated iron melt as reduction agent for a molten zinc oxide slag were performed to determine reaction constants and accurately predict mass transfer coefficients of the proposed kinetic model. An experimentally determined kinetic model demonstrates that various reactions run simultaneously during the reduction of zinc oxide and iron oxide. For the investigated slag composition, the temperature-dependent contribution of the metallothermic zinc oxide reduction was between 25 and 50 pct of the overall reaction mechanism. The mass transfer coefficient of the zinc oxide reduction quadrupled from 1400 °C to 1500 °C. The zinc recovery rate was > 99.9 pct in all experiments.

Exploring Efficiencies: Examining the Possibility of Decreasing the Size of the Briquettes Used as the Batch in the Electric Arc Furnace Dust Processing Line

Sintering of well-prepared briquetted mixtures in a shaft furnace is one of the possible methods of electric arc furnace dust (EAFD) utilization. Simultaneously, some metal oxides from exhaust gases can be separated. In this way, various metals are recovered, particularly zinc. As a result, zinc-free briquettes are produced with a high iron content, which can be used in the steelmaking process. This method is still being developed. In Ostrowiec Świetokrzyski, Poland, a prototype line of a new method for the reduction of zinc oxide in a shaft furnace with simultaneous sintering of briquettes was installed. The batch for the shaft furnace was actually briquetted in the roller press, which produces briquettes with a volume of 13 cm3. It may prove beneficial to reduce the size of the resulting briquettes, as a smaller size could prove more efficient in reducing zinc in the furnace. Decreasing the volume of the briquettes causes an increase in the power consumption in the drive system and brings an increase in the briquetting force, which occurred in the compaction zone. It could be harmful to the roller press construction. The aim of this article was to prove that decreasing the volume of briquettes of the EAFD mixtures had no negative effects on the roller press which was installed in the prototype line.

Optimization of the zinc oxide reduction in the charging process of zinc‐air flow batteries

Optimization of the zinc oxide reduction in the charging process of zinc‐air flow batteries

Microwave catalyzed carbothermic reduction of zinc oxide and zinc ferrite: effect of microwave energy on the reaction activation energy.

Recently, more attention has been paid to the use of microwave (MW) energy in accelerating chemical reactions. The effect of microwave energy on the reduction of zinc oxide and zinc ferrite was investigated. The results indicated that the temperatures required to initiate zinc oxide and zinc ferrite reduction under MW heating were 550 and 450 °C, respectively, while under conventional thermal (CT) heating, were 950 and 850 °C, respectively. Apparently, the MW reaction had a negative standard Gibbs free energy (ΔG) at a lower temperature (∼400 °C) when compared to the CT reaction. Additionally, the activation energy (Ea) substantially decreased from 223.7 and 221.1 kJ mol−1 under CT heating to 64.8 and 32.9 kJ mol−1 under MW heating for Zn oxide and zinc ferrite, respectively. The enhancement in zinc reduction under MW energy was due to the rapid and bulk heating phenomena of MWs as well as the interactions occurring between the electromagnetic MW pattern and the molecules of heated materials.

Tuning the structures of boron nitride nanosheets by template synthesis and their application as lubrication additives in water

Using boric acid (H3BO3) as a boron source and zinc acetate [Zn(Ac)2] as a release chemical, various boron nitride nanosheets (BNNSs) are synthesized in the presence of ammonia (NH3). The structures of the BNNSs are tuned by changing the preparation procedures and the mole ratios of H3BO3 and Zn(Ac)2. The results indicate that Zn(Ac)2 is an excellent template and release agent for the formation of BNNSs owing to the suitable decomposition temperature, the easy reduction of zinc oxide (ZnO) in NH3, and the relatively low boiling point of zinc (Zn). As two-dimensional layered materials, all of the prepared BNNSs can reduce the friction coefficient (FC) of pure water, and the large-area and thick nanosheets show better tribological performances than the small-area and thin nanosheets, possibly as a result of the weakened mechanical strength at the reduced sizes.

Study on Reduction of Zinc Oxide by High Frequency Dielectric Heating

Study on Reduction of Zinc Oxide by High Frequency Dielectric Heating

Dielectric properties and carbothermic reduction of zinc oxide and zinc ferrite by microwave heating.

This paper aims to study the dielectric properties and carbothermic reduction of zinc oxide (zincite, ZnO) and zinc ferrite (franklinite, ZnFe2O4) by microwave heating. To achieve this aim, the dielectric properties were measured with an open-ended coaxial method to understand the behaviour of the samples under microwave irradiation. The effects of microwave power, duration time and sample mass on the heating rate, and the effects of the stoichiometric amount of graphite on the reduction of ZnO and decomposition of ZnFe2O4 were investigated. The results show that ZnFe2O4 has significantly higher dielectric properties compared to ZnO. Generally, for both samples, the dielectric values at room temperature were quite low, indicating that both ZnO and ZnFe2O4 are poor microwave absorbers. It was found that the temperatures have a more significant effect on the imaginary permittivities than on the real permittivities. The heating rate showed that the sample temperature increased with increase in microwave power and sample mass. Using 700 W of microwave power and two times the stoichiometric amount of graphite, almost complete reduction of ZnO was achieved in 12 min, while ZnFe2O4 completely decomposed to zincite and wustite in 3 min.

Solar carbothermal reduction of aerosolized ZnO particles under vacuum: Modeling, experimentation, and characterization of a drop-tube reactor

A vacuum aerosol particle reactor was tested for the carbothermal reduction of zinc oxide using concentrated solar power as a heat source. A steady state reactor model was developed to investigate the effect of pressure dependent particle residence time and radiative input power on the zinc production rate. Radiative heat transfer to the particle cloud is solved by Monte Carlo ray tracing, accounting for spectral and directional optical properties and temperature dependent chemical kinetics. Experiments with the solar drop-tube reactor were conducted to ascertain the reaction capacity of the system at pressures between 1 and 960mbar by varying the reactant feed rate between 4 and 56g·min−1. Experiments show that the zinc production rate is maximal at around 100mbar and significantly diminishes under high vacuum. Model and experimental results indicate that the reaction at 1mbar is inhibited due to insufficient residence time and heat up of the particles in the reaction zone. Maximum experimental zinc production rate was 51.4mmol·min−1, while feeding 56g·min−1 of solid reactants and operating the reactor at 100mbar with 9.8kW of radiative input power. Extrapolation to higher feed rates with the reactor model predicts a peak zinc production capacity of 52.1mmol·min−1 at a feed rate of 68g·min−1, achieving a net thermal efficiency of 3.2%.