Diffusion Coefficient De Research Articles

The Effect of Water to Cement Ratio on Physical and Radiation Shielding Properties of Portland Concrete

Objective: To study the effect of the water to cement ratio (w/c) on 222 Rn diffusion, gamma attenuation, neutron attenuation and Ultra-sonic Pulse Velocity (UPV) for local Portland concrete. Methods: The 222 Rn diffusion coefficient was measured by putting a cubic concrete sample between two sealed compartments. The linear attenuation coefficients for g-rays from 137 Cs and 60 Co sources were measured using broad beam experimental setup. Neutron attenuation ratio was calculated by using Am-Be source with neutron flux 10 7 (n.cm 2 .s -1 ).The Ultrasonic-Pulse Velocities (UPV) (m.s -1 )were measured for all the faces of cubic concrete samples. Findings: Results showed that the effect of increasing w/c on linear attenuation coefficients of g-rays and neutron attenuation ratio were not significant and all results were within the uncertainties range. However, in the case of (UPV),the results showed linear relationship with negative slope. In addition, the effective diffusion coefficients De of 222Rn in concrete samples increased with increasing(w/c)(on the opposite of the behavior of (UPV) and the value of De changed from (3.6±0.39)' 10-10 m 2 .s -1 for w/c = 0.35 to (11.0±0.7)' 10-10 m 2 .s -1 for w/c = 0.6. Application/ Improvements: This study establishes a reliable test and evaluating procedure for determination of D and De by measuring the (UPV) for cubic Portland concrete sample.

Laboratory scale advection-matrix diffusion experiment in Olkiluoto veined gneiss using H-3 and Cl-36 as tracers

ABSTRACTSpent nuclear fuel from Finnish power plants is planned to be deposited deep in the crystalline bedrock. The bedrock needs to be well characterized to properly assess the risks inherent to the long term safety of the site. In the bedrock the possibly released radionuclides are assumed to be mainly transported by water conducting fractures and their transport is retarded by matrix diffusion and sorption. In this work transport properties of an 80 centimeters long veined gneiss drill core sample from Olkiluoto was studied using an advection-matrix diffusion experiment, which was developed to demonstrate the effect of rock matrix for transport of radionuclides in an advective fracture. The experiment was performed using H-3 and Cl-36 as tracers, and effective diffusion coefficients (De) of (1.7 ± 0.7) × 10-13 m2/s and (1.4 ± 1.0) × 10-14 m2/s and porosities of 1.1 ± 0.3 % and 0.23 ± 0.10 % were determined, respectively. A lower porosity and De for Cl-36 than for H-3 indicates an effect of anion exclusion and the results were found to be in agreement with previous laboratory experiments. However, the comparison to results from a similar in-situ experiment showed that the transport of H-3 and Cl-36 is retarded more in laboratory than in in-situ conditions by matrix diffusion.

Restricted diffusion of model sulfides over a NiMo/BK catalyst under hydrodesulfurization reaction conditions

The effective factors (η) of a NiMo/BK catalyst are greater than that of the traditional NiMo/Al2O3; the effective diffusion coefficient (De) decreases with the increasing molecular size of the model sulfides.

Through diffusion study on Olkiluoto veined gneiss and pegmatitic granite from a structural perspective

ABSTRACTSpent nuclear fuel from Finnish power plants is planned to be deposited deep in the crystalline bedrock in Olkiluoto, Finland. The bedrock needs to be well characterized to assess the risks inherent to the long term safety of the site. In the bedrock the possibly released radionuclides are mainly transported by water conducting fractures and their transport is retarded by diffusion and sorption. In porous materials these properties are typically linked to microscopic pore structure (pore size distribution, tortuosity and constrictivity) and chemical nature of the minerals and groundwater.In this work transport properties of veined gneiss (VGN) and pegmatitic granite (PGR) samples from Olkiluoto were studied using various through diffusion experiments and the C-14-PMMA autoradiography. Through diffusion experiments were performed on rock cores using HTO and 36Cl in water phase and He in gas phase as tracers. The effective diffusion coefficients (De) determined for the VGN were found to be dependent on the tracer molecule (De(HTO) < De(He) < De(Cl)) whereas for the PGR such a dependence was not found. The porosity distributions determined by the C-14-PMMA autoradiography revealed the difference in the pore structure between the samples. The porosity of VGN consists mostly of grain boundary pores and pores between biotite lamellae. Due to a high content of nanometer scale pores anion exclusion affected the results of 36Cl and Knudsen diffusion the ones of He for VGN. Furthermore, in the PGR micrometer scale intra- and intergranular fissures form a connected network for diffusive transport and thus all tracers diffuse at the same rate.

Diffusion behavior of Re(VII) in compacted illite-, hematite- and limonite-montmorillonite mixtures

A through-diffusion method was used to investigate the Re(VII) (as a surrogate to 99Tc(VII)) diffusion in compacted illite-, hematite- and limonite-montmorillonite mixtures. The effective diffusion coefficient De values were in the range of (4.29–6.71) × 10−11 m2/s at pH 3.0 and (3.44–5.72) × 10−11 m2/s at pH 9.0, respectively. Compared to montmorillonite, both De and α values enhanced at least three-folds in montmorillonite mixtures, indicating that the impurities changed the diffusion path. Interestingly, the Kd values of (0.63–3.94) × 10−4 kg/m3 were found in montmorillonite mixtures. However, the change of Da value was less than two-folds, indicating that the illitization and iron corrosion of a back-fill material had no obvious influence on Re(VII) diffusion velocity.

Production of precursors for anti-Alzheimer drugs: Asymmetric bioreduction in a packed-bed bioreactor using immobilized D. carota cells

ABSTRACT(S)-1-Phenylethanol derivatives, which are the precursors of many pharmacological products, have also been used as anti-Alzheimer drugs. Bioreduction experiments were performed in a batch and packed-bed bioreactor. Then, the kinetics constants were determined by examining the reaction kinetics in the batch system with free and immobilized carrot cells. Also, the effective diffusion coefficient (De) of acetophenone in calcium alginate-immobilized carrot cells was investigated. Kinetics constants for free cells, which are intrinsic values, are reaction rate Vmax = 0.052 mmol L−1 min−1, and constants of the Michaelis–Menten KM = 2.31 mmol L−1. Kinetics constants for immobilized cells, which are considered apparent values, are Vmax, app = 0.0407 mmol L−1 min−1, KM, app = 3.0472 mmol L−1 for 2 mm bead diameter, and Vmax, app = 0.0453 mmol L−1 min−1, KM, app = 4.9383 mmol L−1 for 3 mm bead diameter. Average value of effective diffusion coefficient of acetophenone in immobilized beads was determined as 1.97 × 10−6 cm2 s−1. Using immobilized carrot cells in an up-flow packed-bed reactor, continuous production of (S)-1-phenylethanol through asymmetric bioreduction of acetophenone was performed. The effects of the residence time and concentrations of substrate were investigated at pH 7.6 and 33°C. Enantiomerically pure (S)-1-phenylethanol (ee > 99%) was produced with 75% conversion at 4-hr residence time.

Spectro-Electrochemical of Detection Anthracene at Electrodeposited Polyamic Acid Thin Films

Polyamic acid (PAA) thin films were prepared by electrodepositing PAA onto indium tin oxide (ITO) electrode and characterized using electrochemical methods (cyclic voltammetry, square wave voltammetry), Ultraviolet Visible spectroscopy and Ultraviolet Visible/Spectro-electrochemistry (UV/vis Spectro-electrochemistry). The electrodeposited PAA thin films were observed to have two redox couples with a formal of 118 mV and 274 mV. The diffusion coefficient (De) determined from cyclic voltammetry was found to be 7.9x10-6 cm2/s and provide a measure of how fast charge is transported through the thin film. PAA showed a broad absorption peak at 214 nm due to the carbonyl chromophores within the polymer and shoulder peak at 293 nm from a quinoid-type chromophore. The calculated band gap of 4.23 eV suggested the polymer was optically transparent between 300 nm to 800 nm. This indicated that the PAA thin films has emerged as a very promising and cost effective alternative material to ITO with good transparent and conductive properties. PAA thin films were further applied for the detection of anthracene. The analytical response of anthracene was studied at the ITO/PAA using spectro-electrochemistry. The characteristic analytical absorbance signal for anthracene was clearly identified at 375 nm when ITO/PAA electrode was polarised at -800 mV (vs Ag/AgCl). The calibration curve for anthracene showed a linear response from 4.95x10-4 to 1.15x10-2 M. The ITO/PAA showed a low detection limit of (0.0068 g/L) and high sensitivity for anthracene, making it a suitable platform for spectro-electrochemical analysis of polycyclic aromatic hydrocarbons.

Effect of confining pressure on diffusion coefficients in clay-rich, low-permeability sedimentary rocks

The effect of confining pressure (CP) on the diffusion of tritiated-water (HTO) and iodide (I−) tracers through Ordovician rocks from the Michigan Basin, southwestern Ontario, Canada, and Opalinus Clay from Schlattingen, Switzerland was investigated in laboratory experiments. Four samples representing different formations and lithologies in the Michigan Basin were studied: Queenston Formation shale, Georgian Bay Formation shale, Cobourg Formation limestone and Cobourg Formation argillaceous limestone. Estimated in situ vertical stresses at the depths from which the samples were retrieved range from 12.0 to 17.4MPa (Michigan Basin) and from 21 to 23MPa (Opalinus Clay). Effective diffusion coefficients (De) were determined in through-diffusion experiments. With HTO tracer, applying CP resulted in decreases in De of 12.5% for the Queenston Formation shale (CPmax=12MPa), 30% for the Georgian Bay Formation shale (15MPa), 34% for the Cobourg Formation limestone (17.4MPa), 31% for the Cobourg Formation argillaceous limestone (17.4MPa) and 43–46% for the Opalinus Clay (15MPa). Decreases in De were larger for the I− tracer: 13.8% for the Queenston shale, 42% for the Georgian Bay shale, 50% for the Cobourg Formation limestone, 55% for the Cobourg Formation argillaceous limestone and 63–68% for the Opalinus Clay. The tracer-specific nature of the response is attributed to an increasing influence of anion exclusion as the pore size decreases at higher CP.Results from the shales (including Opalinus Clay) indicate that the pressure effect on De can be represented by a linear relationship between De and ln(CP), which provides valuable predictive capability. The nonlinearity results in a relatively small change in De at high CP, suggesting that it is not necessary to apply the exact in situ pressure conditions in order to obtain a good estimate of the in situ diffusion coefficient. Most importantly, the CP effect on shale is reversible (±12%) suggesting that, for argillaceous rocks, it is possible to obtain De values that are representative of the in-situ condition by conducting measurements on re-pressurized samples that were obtained with standard drilling practices. This may not be the case for brittle rock samples as the results from limestone suggest that irreversible damage occurred during the pressure cycling.

Investigation of the leaching behavior of lead in stabilized/solidified waste using a two-year semi-dynamic leaching test

Long-term leaching behavior of contaminant from stabilization/solidification (S/S) treated waste stays unclear. For the purpose of studying long-term leaching behavior and leaching mechanism of lead from cement stabilized soil under different pH environment, semi-dynamic leaching test was extended to two years to investigate leaching behaviors of S/S treated lead contaminated soil. Effectiveness of S/S treatment in different scenarios was evaluated by leachability index (LX) and effective diffusion coefficient (De). In addition, the long-term leaching mechanism was investigated at different leaching periods. Results showed that no significant difference was observed among the values of the cumulative release of Pb, De and LX in weakly alkaline and weakly acidic environment (pH value varied from 5.00 to 10.00), and all the controlling leaching mechanisms of the samples immersed in weakly alkaline and weakly acidic environments turned out to be diffusion. Strong acid environment would significantly affect the leaching behavior and leaching mechanism of lead from S/S monolith. The two-year variation of De appeared to be time dependent, and De values increased after the 210th day in weakly alkaline and weakly acidic environment.

Diffusivity in Cement-Silica Fume Based Materials: Experimental and Computer Modeling Results on Mortars

Silica fume cement (SFC) based materials are largely used as a containment barrier for nuclear waste management. The safety of this storage mode depends on the knowledge of the effective diffusion coefficients of such materials. This work proposes a combination of computer models able to estimate the diffusion coefficients of SFC pastes and mortars, from a single investigation of the microstructure by nitrogen adsorption. The approach used consists firstly in manufacturing SFC mortars by varying sand volume fraction from 30 to 65% while silica fume replacement and water to binder ratio were respectively set at 10% and 0.4. Nitrogen adsorption tests were then performed and collected data on C-S-H nature are introduced into a SFC pastes hydration model. The latter provides the mineral composition which is an input parameter in the multilayer transport model that estimates the effective diffusion coefficient (De) of cement pastes. For mortars, a 3D biphasic model (sand and cement matrix) was used to compute the (De) of mortars at different inclusion volume fractions. The numerical results were approved by comparison to experimental data obtained from tritiated water (HTO) diffusion tests performed on manufactured mortars.

Diffusion of tocopherols, phospholipids and sugars during oil extraction from sunflower collets using ethanol as solvent

The ethanolic extraction of minor compounds (phospholipids, tocopherols and sugars) present in sunflower collets was studied at 50 and 60 °C in a batch reactor. The extracted material consisted of two phases: a hexane-soluble fraction, comparable to degummed sunflower oils, and a hexane-insoluble fraction high in phospholipids and sugars. Sugars were extracted in large proportion, especially the indigestible raffinose, increasing the nutritional value of the meal. The sugar reduction percentage in the sunflower collets increased over extraction time to up to 60 and 80% at 50 and 60 °C. The effective diffusion coefficient (De) for tocopherols was higher than that for phospholipids (3.950 10−9 and 2.596 10−9 m2/s, respectively), both being temperature-independent in the analyzed range. De of sugars was 6.50 10−10 and 1.51 10−9 m2/s for 50 and 60 °C, respectively. Using ethanol as extraction solvent could improve the oil and meal quality, and help obtain a third phospholipid-rich phase after fractionation.

Consumption and diffusion of dissolved oxygen in sedimentary rocks

Fe(II)-bearing minerals (e.g., biotite, chlorite, and pyrite) are a promising reducing agent for the consumption of atmospheric oxygen in repositories for the geological disposal of high-level radioactive waste. To estimate effective diffusion coefficients (De, in m2s−1) for dissolved oxygen (DO) and the reaction rates for the oxidation of Fe(II)-bearing minerals in a repository environment, we conducted diffusion–chemical reaction experiments using intact rock samples of Mizunami sedimentary rock. In addition, we conducted batch experiments on the oxidation of crushed sedimentary rock by DO in a closed system.From the results of the diffusion–chemical reaction experiments, we estimated the values of De for DO to lie within the range 2.69×10−11<De<6.30×10−11. Values of the second-order rate constant (k, in Lmol−1s−1) were in the range −3.66<log k<−2.83 (from batch experiments) and in the range −3.87<log k<−2.22 (from diffusion–chemical reaction experiments). Many of these values are within the range of previously published rates for reaction between O2(aq) and Fe(II) surface complexes. The average value for the total concentration of reactive sites was about 10−4molm−2 from batch experiments. In contrast, the value of reactive sites estimated from the physical surface area was about 10−8molm−2, indicating that the reaction within intact rock is limited to the sites that originally existed with accessible porosity for O2(aq). This difference arises because the batch experiments used powdered samples, meaning that new sites which formed during milling were added to the original reaction sites. On the basis of these observations and interpretations, diffusion–chemical reaction experiments make it possible to determine the values of the kinetic parameter and diffusivity for an intact rock sample simultaneously.

Chemical treatment of teff straw by sodium hydroxide, phosphoric acid and zinc chloride: adsorptive removal of chromium

In this study, teff (Eragrostis tef) straw has been chemically treated and tested as an adsorbent for Cr(VI) removal. Chemically treatment of teff straw was done by NaOH, H3PO4 and ZnCl2 solutions. Scanning electron micrograph and X-ray diffraction were used for anatomical characterization, whereas Fourier transform infrared spectroscopy was used for surface change characterization of adsorbents. Effects of different experimental parameters like pH (2–12), initial Cr(VI) concentration (100–900 mg/L), adsorbent dose (2.5–20 g/L), contact time (15–360 min) and temperature (288–318 K) were studied. Temperature increment was found to stimulate the adsorption process. Langmuir isotherm was found to give better representation over wide range of temperature for untreated, H3PO4- as well as ZnCl2-treated teff straw, and Freundlich isotherm best represented the isotherm data for NaOH-treated teff straw. Maximum Cr(VI) adsorption capacity of untreated, NaOH-, H3PO4- and ZnCl2-treated teff straw was found to be 86.1, 73.8, 89.3 and 88.9 mg/g, respectively. Respective values of average effective diffusion coefficient (D e) were found to be 2.8 × 10−13, 2.59 × 10−14, 1.32 × 10−13 and 1.14 × 10−13 m2/s, respectively. The negative value of ΔG o for all the adsorbents indicates Cr(VI) spontaneous adsorption. Isosteric heat of adsorption (ΔH st,a) was found to vary with surface coverage (θ). ΔH st,a increased for untreated, H3PO4- and ZnCl2-treated teff straw, and decreased steadily with θ for NaOH-treated teff straw.

Adsorption of Cefocelis Hydrochloride on Macroporous Resin: Kinetics, Equilibrium, and Thermodynamic Studies

The adsorptions of Cefocelis hydrochloride in aqueous solution on macroporous resin (HP-20) were studied. On the basis of static experiments with HP-20 resin, the adsorption kinetics, isotherms, and thermodynamics of Cefocelis hydrochloride in aqueous solution on macroporous resin (HP-20) were investigated. Adsorption equilibrium data were correlated with the Langmuir and Freundlich equations. Adsorption data of kinetic were modeled using the Crank equation and fitting for the diffusion coefficient (De), and the value of the liquid film mass transfer coefficient (kf) was estimated from Carberry equation. Dynamic adsorption was performed on HP-20 resin packed in a glass column to obtain optimal parameters. The initial concentration, bed height, and residence time were considered to determine the dynamic test for the breakthrough curve. The values of thermodynamic parameters including the isosteric adsorption enthalpy (ΔH), free energy (ΔG), entropy (ΔS), and adsorption activation energy (Ea) demonstrated t...

Re(VII) diffusion in bentonite: Effect of organic compounds, pH and temperature

In order to understand the diffusion properties of anionic radionuclides (RN) in bentonite in the presence of organic compounds with chelating and reducing properties, the effect of humic acid (HA), citrate, oxalate and formate on Re(VII) diffusion was investigated by a through-diffusion method under different pH (pH7.0 and 10.0) and temperature conditions (10–65°C). When the molar ratio of oxalate to Re(VII) was higher than 1:1, the accumulated mass and flux were observed to decrease drastically as a function of time. It can be explained by photocatalytic impact of Fe(III) on the reduction of Re(VII) to insoluble Re(IV) by oxalate. Thus, the diffusion of Re(VII) was also observed to decrease in the presence of minor citrate, oxalate and formate. Effective diffusion coefficient (De) values decreased from 8.7×10−11m2/s to (5.1–5.9)×10−11m2/s. In contrast, HA had no significant impact on Re(VII) diffusion. The De values of 1.54×10−11 and 6.5×10−12m2/s were obtained at pH7.0 and 10.0, respectively. HA thus neither has an effect on the speciation of Re(VII) nor does it change the charge of the surface. The latter is probably due to the fact that HA preferentially interacts with the aluminol sites of the montmorillonite edges without changing the zeta potential of the surface. The dependence of De of Re(VII) on temperature in the absence and presence of citrate or formate was described by the Arrhenius equation. The activation energy, Ea, was in the range of (20.7–25.1) kJ/mol, demonstrating that Re(VII) diffusion followed a pore water diffusion model.

Stabilization characteristics of copper mine tailings through its utilization as a partial substitute for cement in concrete: preliminary investigations

This paper presents the feasibility of incorporating copper mine tailings (MT) as a partial substitute for cement in the development of concrete. The copper mine tailings used for this study have been accumulating for several decades at the tailings dump of Hindustan Copper Ltd. at Khetri, Rajasthan. Hence, alternative uses of MT need to be thought while keeping in mind that the utilization should also take care of the mobility of the elements present in the tailings. Consequently, M25 grade of concrete was designed as per IS: 10262-2009 (Indian standard code of practice for guidelines for concrete mix proportioning, Bureau of Indian Standards, New Delhi), with 0–50 % substitution of cement with MT and water-binder ratio of 0.5. To determine the feasibility of the new design mixes, unconfined compressive strength (UCS) of the concrete mixes was studied. Also, the leaching behaviors of the heavy metals contained in the tailings solidified in the concrete were studied by semi-dynamic leaching test. The effectiveness of solidification/stabilization (S/S) treatment was evaluated by determining diffusion coefficients (D e) and leachability index (L) calculated from the data achieved in semi-dynamic leaching test. It was observed that the UCS values decreased with the increase in MT content. However, at 10–15 % MT substitution, the concrete exhibited acceptable strength. The MT substituted concrete also appeared to be effective in immobilizing the leachable elements in the tailings to a considerable extent thus, stabilizing the waste. Overall, the study suggests that concrete with acceptable properties can be developed using moderate amounts of MT as a partial substitute for cement thus, suggesting an economic and sustainable use of the waste.

Power ultrasound as a pretreatment to convective drying of mulberry (Morus alba L.) leaves: Impact on drying kinetics and selected quality properties

The effect of ultrasound pretreatment prior to convective drying on drying kinetics and selected quality properties of mulberry leaves was investigated in this study. Ultrasound pretreatment was carried out at 25.2–117.6W/L for 5–15min in a continuous mode. After sonication, mulberry leaves were dried in a hot-air convective dryer at 60°C. The results revealed that ultrasound pretreatment not only affected the weight of mulberry leaves, it also enhanced the convective drying kinetics and reduced total energy consumption. The drying kinetics was modeled using a diffusion model considering external resistance and effective diffusion coefficient De and mass transfer coefficient hm were identified. Both De and hm during convective drying increased with the increase of acoustic energy density (AED) and ultrasound duration. However, De and hm increased slowly at high AED levels. Furthermore, ultrasound pretreatment had a more profound influence on internal mass transfer resistance than on external mass transfer resistance during drying according to Sherwood numbers. Regarding the quality properties, the color, antioxidant activity and contents of several bioactive compounds of dried mulberry leaves pretreated by ultrasound at 63.0W/L for 10min were similar to that of mulberry leaves without any pretreatments. Overall, ultrasound pretreatment is effective to shorten the subsequent drying time of mulberry leaves without damaging the quality of final product.

Impact of fracturing fluid on multi-scale mass transport in coalbed methane reservoirs

The effect of fracturing fluid on multi-scale mass transport, including methane desorption, diffusion and percolation, was investigated on an anthracite coal from the Qinshui Basin. Methane sorption and diffusion characteristics were measured using the volumetric method. The Langmuir equation was used to fit the sorption isotherm data and unipore model to estimate the effective diffusion coefficient (De). The impairment of gas permeability, characterized by the residual resistance factor (Frr,g), was determined using the pulse-decay method. In addition, changes in pore structure and surface properties were also analyzed by SEM/EDX, low-temperature N2 adsorption and XPS. The results show that the methane adsorption capacity was reduced by 10.5% after fracturing fluid treatment. The Langmuir volume (VL) decreased while the Langmuir pressure (PL) increased, which is beneficial for gas desorption. The effective diffusion coefficient (De) exhibited a negative correlation with pressure and decreased by 23.0% to 37.6%. The gas permeability was significantly diminished and Frr,g for a macro-fractured sample was much greater than that for a micro-fractured sample. Furthermore, due to the adsorption of fracturing fluid on pore/fracture walls, the mass transport channels were narrowed and hydrophilia was enhanced. This possibly explains the reduction of gas adsorption capacity and mass transport rate in coal.

Microstructure, short-term and long-term leaching behaviour of zinc encapsulated by calcium carbide residue-fly ash

This study evaluates the use of a calcium carbide residue-fly ash mixture as a new material to encapsulate zinc. Zinc was added into both calcium carbide residue-fly ash pastes (ZnCF) and ordinary Portland cement (ZnOPC) for comparison purposes. The fracture surfaces, crystalline phases, and zinc leaching behaviours of pastes were determined. A new crystalline phase of calcium zincate (Ca(Zn2(OH)6).2H2O) was detected. The compressive strengths of ZnCF pastes were dramatically decreased, whereas the strengths of the ZnOPC pastes were slightly decreased. However, the compressive strengths of the ZnCF pastes after curing for 28 days were comparable to those of solidification cements used for hazardous waste disposal in secured landfills. Evaluation of the short-term leaching behaviour showed that the zinc concentrations that leached out were much lower than the allowable limit (500 mg/L). The diffusion coefficient (De) and leachability index (LX) for long-term leaching of samples were not significantly different.

H&lt;sub&gt;2&lt;/sub&gt;-CO混合ガスによる酸化鉄の還元反応の速度解析

A lot of steel engineers researched various means to decrease reducing agents at a blast furnace in order to reduce CO2 emissions. For example, injection of H2, waste plastics and carbon neutral materials such as biomass into a blast furnace is better alternative. When iron oxide is reduced by H2 gas, CO2 don' t form. We have studied optimal reduction conditions of iron oxide. In this work, we focused on H2-CO gas mixtures reduction of iron oxide. In order to prepare samples, reagent Fe2O3 was mixed with SiO2 and CaO in the mass ratio of Fe2O3：SiO2：CaO = 80：7.14：12.86. Then the mixture was pelletized by handrolling and sintered at 1220℃ (Sinter-A, a porous sample) or 1250℃ (Sinter-B, a relatively porous sample). The formed pellets were reduced from Fe2O3 to FeO at 800℃ and from FeO to Fe 1100℃. From weight loss curves of samples, chemical reaction rate content (kc) and effective diffusion coefficient (De) in a product layer were calculated by using an unreacted core model. The values of kc and De in H2 reduction were much higher than those values in CO reduction. The particle size of the reduced Fe in H2 reduction was smaller than that one in CO reduction.