Increasing Calcination Temperature Research Articles

Production, characterization, and photocatalytic properties of Eu:Y2O3 nanopowders

AbstractEu:Y2O3 nanophosphors (NPs) with different Eu concentrations (3, 5, and 7 at%) were successfully synthesized via the sol–gel method. All synthesized powders had a cubic bixbyite‐type crystal structure with space group Ia‐3. It was observed they had agglomerated sphere‐like morphologies. In addition, a neck formation between the particles, which was the result of the sintering effect at the increasing calcination temperature, was also observed by scanning electron microscopy analysis. Raman and X‐ray photoelectron spectroscopy (XPS) analyses confirmed that the Eu dopant entered into the Y2O3 host. The XPS peak positions shifted to relatively higher binding energy values with increasing dopant concentration and calcination temperature. Increasing Eu dopant concentration in the host structure also increased the 3+ valence ions. The band gap values of the NPs varied between 4.30 and 4.54 eV. The powders doped with 5 at% Eu was active as photocatalysts and the powders that were synthesized at 800°C exhibited highly photocatalytic activity.

Effect of calcination temperature on structural, antibacterial, radiation shielding and magnetic properties of cubic spinel cobalt nanoferrite

For the first time, Cobalt ferrite (CoFO) nanoparticles (NPs) were synthesized by solution combustion method using BigThyme leaf extract as a reducing agent followed by varying the calcination temperature as-formed — 800 °C. At all the calcination temperatures, Bragg reflections matches well with FCC cubic spinel structure. Crystallite size increases from 12–79 nm with increase in calcination temperature. The SAED pattern and d-spacing from Transmission electron microscopy matches well with the PXRD pattern and the calculated crystallite size matches well with the Scherrer’s formula. The direct energy band gap was found to be 1.55 eV. The effect of calcination temperature on different magnetic properties such as retentivity, coercivity, saturation of magnetization, squareness ratio and Bohr magneton was discussed in detail. Large coercivity (2.26 kOe) is observed at low calcination temperature. Further, X-ray/gamma radiation absorption parameters such as mass attenuation coefficient, half value layer and Zeff are established which is an essential in the field of radiation dosimetry. CoFO NPs exhibited sensitivity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The cytotoxic properties were examined on cervical cancer HeLa cells and compared with the cisplatin drug. CoFO NPs shows higher % cell viability and less % cell death. Thus, CoFO NPs can be used as a drug carrier in cancer therapy.

Enhancement in photocurrent conversion efficiency via recrystallization of zinc tin hydroxide nanostructures

Herein, the synthesis of cubic phase zinc tin hydroxide is reported by the hydrolysis assisted co-precipitation method followed by calcination in 150–850 °C. The recrystallization of zinc tin hydroxide (ZnSn(OH)6) to zinc tin oxide (Zn2SnO4) phase is observed with the intermediate amorphous phase (ZnSnO3) by increasing the calcination temperature. Increase in calcination temperature also causes the partial alteration in the cubic morphology and diminution in average particle size. The M-O-M and M-O vibration modes have distinct peaks in the FT-IR spectra below 1500 cm−1. Four Raman active vibration modes in ZnSn(OH)6 and two Raman active vibration modes in Zn2SnO4 phase are observed, while no Raman active mode is present in intermediate amorphous ZnSnO3. Chemical states of various elements and compositions are examined by X-ray photoelectron spectroscopy. The ZnSnO3 electrodes has the lowest charge transfer resistance and higher lifetime of the photogenerated charge carriers. Photoelectrochemical measurements rendered enhanced photocurrent density for ZnSnO3 and Zn2SnO4 phases, which is approximate 85 and 50 times higher as compared to ZnSn(OH)6 based photoelectrode, respectively. Due to crystalline nature, the Zn2SnO4 phase has better photo-stability.

Impact of calcination temperature on structural and optical properties of erbium-doped zinc ferrite nanoparticles

ABSTRACT Erbium-doped zinc ferrite nanoparticles (ZnFe1.9Er0.1O4) were prepared by the sol–gel auto-combustion method. In order to study the impact of calcination temperature, the prepared powder was divided into four parts and calcinated at 700, 900, 1100 and 1300°C. XRD confirmed the formation of a spinel structure with a single phase and Fd3m space group. Crystallite size increased from 19.45 to 30.22 nm with the increase in calcination temperature. SEM images showed agglomerated flakes having voids and pores on the surface. The average grain size increased from 157.76 to 237 nm with the increase in calcination temperature. FTIR showed two fundamental absorption bands related to octahedral and tetrahedral sites along with other three absorption bands in the frequency range 400–4000 cm−1. The optical energy bandgap was increased from 3.8166 to 4.2779 eV with the increase of calcination temperature. Hence, it is concluded that the optical energy bandgap can be tuned with the calcination temperature.

Influence of varying thermal treatment on bioactive material with equal Ca/P ratio: A local drug delivery system for bone regeneration.

Designing a biomaterial with excellent bioactivity, biocompatibility, mechanical strength, porosity, and osteogenic properties is essential to incorporate therapeutic agents in order to promote efficient bone regeneration. The work intended to prepare bioactive glass with tailor-made equal Ca/P (CP) ratio to obtain clinophosinaite (Cpt) as dominant phase. Clinophosinaite (Na3 CaPSiO7 ) is one of the rarest phases of bioactive glass (BG), which is supposed to play key role in bioactivity. The novelty of this work is to track the required sintering temperature to attain equimolar calcium phosphate-containing clinophosinaite phase and its behavior. Further, its consequent physicochemical and biological properties were analyzed. Phase transition from Rhenanite to Cpt, and later the Cpt emerged as dominant phase with increase of calcination temperature from 700 to 1000°C was studied. The quantifying evolution of Cpt with Rhenanite over increasing annealing temperature also results with the major morphological modifications. BET analysis confirmed the surface area and porosity (Type-IV mesoporous) were gradually elevated upto 900°C, which had contrary effect on mechanical strength. Formation of hydroxyl carbonate apatite (HCA) layer confirmed the bioactivity of the prepared samples at varying time intervals. The CP samples demonstrated better hemocompatibility in post-immersion (i.e., less than 1% of lysis) when compared with pre-immersion. Enhanced protein adsorption and cumulative release (85%) of Simvastatin (SIM) drug was attained at 900°C treatment.

Hierarchical Fe2O3 hexagonal nanoplatelets anchored on SnO2 nanofibers for high-performance asymmetric supercapacitor device

Metal oxide heterostructures have gained huge attention in the energy storage applications due to their outstanding properties compared to pristine metal oxides. Herein, magnetic Fe2O3@SnO2 heterostructures were synthesized by the sol–gel electrospinning method at calcination temperatures of 450 and 600 °C. XRD line profile analysis indicated that fraction of tetragonal tin oxide phase compared to rhombohedral hematite was enhanced by increasing calcination temperature. FESEM images revealed that hexagonal nanoplatelets of Fe2O3 were hierarchically anchored on SnO2 hollow nanofibers. Optical band gap of heterogeneous structures was increased from 2.06 to 2.40 eV by calcination process. Vibrating sample magnetometer analysis demonstrated that increasing calcination temperature of the samples reduces saturation magnetization from 2.32 to 0.92 emu g-1. The Fe2O3@SnO2-450 and Fe2O3@SnO2-600 nanofibers as active materials coated onto Ni foams (NF) and their electrochemical performance were evaluated in three and two-electrode configurations in 3 M KOH electrolyte solution. Fe2O3@SnO2-600/NF electrode exhibits a high specific capacitance of 562.3 F g-1 at a current density of 1 A g-1 and good cycling stability with 92.8% capacitance retention at a high current density of 10 A g-1 after 3000 cycles in three-electrode system. The assembled Fe2O3@SnO2-600//activated carbon asymmetric supercapacitor device delivers a maximum energy density of 50.2 Wh kg-1 at a power density of 650 W kg-1. The results display that the Fe2O3@SnO2-600 can be a promising electrode material in supercapacitor applications.

In situ low-temperature pyrolysis fabrication type II BiOIO3/Bi4O5I2 heterostructures with enhanced visible-light-driven photooxidation activity.

Novel visible-light-driven heterostructure semiconductors are considered as promising photocatalysts for the elimination of environmental organic pollutants. Herein, a solvent-assisted low-temperature in situ calcination strategy was developed to fabricate type II BiOIO3/Bi4O5I2 heterojunction by using BiOIO3 as self-sacrificed template. The phase transition temperature of BiOIO3 was reduced under solvent-assisted operating conditions. By controlling the elevated temperature from 200 to 300 °C, an in situ stepwise pyrolysis reaction occurred during the calcination process, which was described as BiOIO3 → BiOIO3/Bi4O5I2 → Bi4O5I2. The light absorption edge of different samples significantly red shifted from 385 to 632 nm with the increase of calcination temperature. Meanwhile, two interlocked interface lattice fringes were identified in high resolution transmission electron microscope (HRTEM) of BiOIO3/Bi4O5I2-250 composites, confirming the formation of BiOIO3/Bi4O5I2 heterojunction. The as-obtained BiOIO3/Bi4O5I2 heterojunction demonstrated the optimal photodegradation performance, which brought about 99.4% of bisphenol A (BPA) degraded within 30 min visible light (λ > 420 nm) illumination. Besides, after 5 repeated cycles, the photoactivity of BiOIO3/Bi4O5I2 heterojunction still maintained 91.5%, unfolding its high photostability. The superior photoreactivity of BiOIO3/Bi4O5I2 nanosheets was assigned to the formation of well-matched type II heterojunction, which significantly enhanced the separation and migration of photoinduced charge carriers. Superoxide radical (O2-) and hole (h+) are dominant reactive species in this photodegradation system. Based on active species quenching experiments and electron paramagnetic resonance (ESR) measurements, a possible type II heterojunction mechanism for enhanced photodegradation performance of BiOIO3/Bi4O5I2 heterostructure was proposed. This work affords an innovative method for design and construction of type II composites toward sustainable water purification.

Effects of key factors on the densification and grain growth behaviour of sintered magnesia from magnesite

Giving magnesia a denser microstructure is a goal relentlessly pursued by refractory scientists and related entrepreneurs. In this study, the effects of the key factors of ball milling, calcination temperature, and starting raw material (high-purity magnesite) size on the densification and grain growth behaviour of sintered magnesia were systematically investigated using a typical two-step sintering method. The results revealed that ball milling reduces the size of light-burned magnesia (pre-calcination product) to a certain extent, which is reflected in a higher tap density; moreover, both the density and grain size of the magnesia samples rise with increasing calcination temperature, implying that the activity of light-burned magnesia is not the only controlling factor for densification; in addition, the smaller magnesite particle size improves the density and grain size of the magnesia samples by weakening the negative effect of the pseudomorphic aggregates. More adequate ball milling, more moderate calcination temperature, and smaller size of magnesite (also for other magnesium salts), therefore, can be the preferred process for the two-step sintering preparation of sintered magnesia.

Impact of calcination temperature on the spin–spin relaxation time (T2) of MgFe2O4 nanoparticles (in vitro)

MgFe2O4 nanoparticles were prepared by the sol–gel method at calcination temperatures of 300 and 500 °C. Then, the effect of calcination temperature on their structural, magnetic, and cytotoxic properties was investigated. In this regard, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR) techniques were used to study structural features, vibrating sample magnetometry (VSM) and electron paramagnetic resonance spectroscopy (EPR) methods were used to evaluate the magnetic properties, and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test was used to evaluate the cytotoxicity. XRD and FESEM results showed that the particle size should increase with increasing calcination temperature. FTIR spectra indicated the presence of absorption bands in the range 390–560 cm−1 at both calcination temperatures, which is a common feature of spinel ferrite. Also, the VSM analysis showed that the superparamagnetic property decreases with increasing calcination temperature. Spin–spin relaxation time ( T2) was evaluated as one of the important parameters in increasing the quality of magnetic resonance imaging scans by EPR. EPR results showed that the T2 increases with increasing calcination temperature. The cytotoxic effects (MTT test) of MgFe2O4 nanoparticles at different concentrations on normal human fibroblast cells (HU-02) showed dose-dependent cell death. This study showed that lowering the calcination temperature can improve the spin–spin contrast ( T2).

Facile synthesis of Co-Rh bimetallic catalysts for methane decomposition: Effect of support morphology

In this study, the performance of 10 wt.% Co -1 wt. % Rh/TiO2 catalysts with varying textural properties have been investigated to produce the hydrogen and carbon nanotubes via the methane decomposition process. An improved evaporation-induced self-assembly approach synthesized the mesoporous TiO2 supports, and Co-Rh nanoparticles over the as-synthesized TiO2 supports were created by the co-impregnation method. XRD, BET, TGA, SEM, and TEM studies characterized the fresh and used catalysts. The findings revealed that the texture of TiO2 support has an important influence on catalytic performance. With the increase in calcination temperature, the specific surface area of the catalysts decreases while the anatase content of TiO2 species increases. The catalyst prepared with TiO2 calcined at 600 °C displayed superior catalytic activity and stability due to the better metal dispersion and higher anatase phase content in support. The initial activity depended on the specific surface area, whereas the stability or the hydrogen productivity for the equal deactivation level was related to the anatase composition of the catalyst. The nature of deposited carbon varies due to the phase composition of TiO2. The SEM and TEM images revealed that anatase TiO2 generated smaller multi-walled carbon nanotubes (MWCNTs) with a more consistent diameter distribution than the other catalysts. Catalysts with an amorphous composition increase the formation of CHx carbon species. The apparent activation energies for various Co-Rh catalysts varied between 65 and 85 kJ mol−1. The Co-Rh bimetallic combination had more significant activity than the Ni metal.

Selective production of guaiacol from lignin via catalytic transfer hydrogenolysis using Ru-Cu/Zirconia

In this study, the effect of calcination temperature of zirconia support (400, 600, and 800 °C) and the role of bimetallic Ru-Cu over monometallic (Cu, Ru) catalysts are evaluated for catalytic transfer hydrogenolysis of alkali lignin. The prepared catalysts were characterized extensively for crystallinity, pore size distribution, acidity, thermal stability and chemical oxidation state. The transformation of zirconia from non-crystalline to crystalline phase was observed with increasing calcination temperature. The pores transformed from wide ink bottle shape into cylindrical shape with increased calcination temperature. The XPS analysis revealed the existence of Cu0 (60%) in presence of Ru with a concomitant reduction in Ru4+ on the surface of the catalyst, which is attributed to increased crystallinity of zirconia in the presence of copper. High yields of total monomers (32.4 wt.%) and guaiacol (12.7 wt.%) were obtained under the optimized condition (270 °C, 3 h) with Ru-Cu/ZrO2 when ZrO2 was calcined at 800 °C. The mesoporous nature of zirconia and the strong metal-support interaction exhibited by Ru-Cu are shown to influence the formation of monomers. Increase in temperature from 225 to 270 °C enhanced the yield of guaiacol, 4-methyl guaiacol and 4-ethyl guaiacol with a concomitant reduction in the yield of trans-isoeugenol, demonstrating the cleavage of C–C bonds. The recyclability tests of the catalyst showed that the yield of guaiacol remained stable even after two cycles of catalyst reuse without calcination.

Highly sensitive detection of H2S gas at low temperature based on ZnCo2O4 microtube sensors

It is extremely necessary to detect Hydrogen sulfide (H2S) due to the hazardous nature. Thus, it is required to design a material which can detect H2S gas at low temperature. In this work, ZnCo2O4 microtubes are prepared by using absorbent cotton as template, combining immersion method in metal salt solution (Zn:Co=1:2) with calcination treatment in air. The influence of calcination temperature on the particle size and sensing property was also discussed. The diameter of particles on the ZnCo2O4 microtubes increases with increasing calcination temperature. The hollow microtubes of ZnCo2O4 materials calcined at 600 °C (ZCO-600) exhibit superb sensing performance to H2S at 90 °C with the lowest detection limit of 50 ppb. The optimum operating temperature (90 °C) was lower than the other reported ZnCo2O4 sensors. ZCO-600 sensor also shows excellent selectivity, repeatability, stability, humidity resistance and the good linear relationship in ppb and ppm level H2S. In addition, the feasible sensing mechanism of ZCO-600 to H2S is explored on the basis of XPS analysis. Thus, ZnCo2O4 as a sensing material possesses widespread application prospects for the detection of trace H2S gas.

A study of structural, morphological, optical and humidity sensing properties of CaCu3Ti4O12 powders synthesized by combustion method

Calcium Copper Titanate (CCTO) powder was synthesized via a low-cost facile combustion method at various calcination temperatures and times. The structural properties of the prepared CCTO powder were investigated from an X-ray diffraction (XRD) study, which confirmed the formation of the cubic phase with space group Im3. Further, Rietveld refinement of the XRD data was performed for the detailed structural analysis of the samples. The surface morphology of the CCTO powder was studied by Field Emission Scanning Electron Microscopy (FESEM), which showed an increase in particle size with an increase in the calcination temperature. The optical properties of the powders were examined by UV–vis Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence Spectroscopy. The optical bandgap values, estimated from Tauc’s plot, increase with the increase in calcination temperature due to the elimination of structural defects or localized states inside the bandgap. The porous single-phase CCTO ceramic was subjected to a homemade experimental set-up combined with an LCR meter to investigate its room temperature humidity sensing characteristics in capacitive mode at various operating frequencies. At 100 Hz, the obtained humidity response curve for the CCTO-based sensor showed a 560 % increment in capacitance as the Relative Humidity (RH) changed from 40 % to 90 %.

The influence of calcination temperature on the optical, magnetic and capacitive properties of NiO nanocrystals prepared with gas–liquid diffusion method

• The morphology of NiO samples evolve with increasing calcination temperature. • The hydrophilicity of nickel oxide decreases with the increase of calcination temperature. • The magnetic susceptibility of NiO samples decreases with decreasing defects and oxygen vacancies. Three NiO nanocrystals have been obtained by calcinating nickel-based precursor synthesized with a gas–liquid diffusion method. The characterization methods such as XRD, SEM, TEM and BET were used to analyze the structure and morphology of NiO samples. XRD data analysis indicated the crystallites size of three NiO samples increased with increasing calcination temperatures. SEM and TEM characterization can also demonstrate an increase in the size of the nano-microspheres. The optical properties were investigated by Ultraviolet–visible (UV–vis) analysis. Surface wettability test was realized by measuring the contact angle. The magnetic measurement was conducted with vibrating sample magnetometer. The electrochemical testing technologies such as CV and GCD were used to evaluate electrochemical behavior of three NiO samples in 2 mol L −1 KOH. The test results showed that surface area, hydrophilicity, magnetic susceptibility and specific capacitance all decreased with the increase in calcination temperatures. The optical properties study indicated that there were both red shift and decreasing intensity for absorption peaks of the NiO samples with the increase in calcination temperature.

Critical role of Cs doping in the structure and NH3 decomposition performance of Ru/MgO catalysts

The NH3 decomposition activity of Ru/MgO catalysts for the production of H2 decreases with increasing calcination temperature. Here, we found that this decrease in activity was the result of the interaction between the Ru and MgO support becoming stronger, causing formation of cationic Ru species. To mitigate this decrease in activity, we investigated the use of doping Ru/MgO catalysts with rare earth, alkali, or alkaline earth metals and found that Cs was particularly effective at enhancing catalytic activity, even at high calcination temperatures. Further examination revealed that doping with Cs weakened the interaction between the Ru and MgO support, resulting in the production of metallic Ru species. The metallic Ru produced by the doping of Cs enhanced the associative desorption of N atoms, which is the rate-limiting step of the NH3 decomposition reaction.

Investigation of the Structural and Optical Properties of Zinc Ferrite Nanoparticles Synthesized via a Green Route.

We report herein the synthesis of ZnFe2O4 (ZF) nanoparticles via a simple and eco-friendly green route using lemon juice as a reducing agent and fuel. The effect of different calcination temperatures on the particle size and bandgap of grown ZF nanoparticles was investigated. The structural, morphological and optical properties of the synthesized nanoparticles were evaluated using synchrotron x-ray diffraction (S-XRD), field emission scanning electron microscopy (FE-SEM) and UV-visible diffuse reflectance spectroscopy (UV-Vis-DRS), respectively. S-XRD confirmed a spinel F-d3m phase in all four samples calcined at 350°C, 550°C, 750°C and 1000°C. The crystallite size calculated from the Debye–Scherrer equation showed an increase from 14 nm to 20 nm with the increase in calcination temperature. Williamson–Hall (W-H) analysis revealed an increase in the particle size from 16 nm to 21 nm and a decrease in the lattice microstrain from 0.913 × 10−3 to 0.154 × 10−4 with the increase in calcination temperature. The optical bandgap of the ZF nanoparticles obtained from UV-Vis-DRS decreased from 2.265 eV to 2.225 eV with the increase in calcination temperature. The ZF nanoparticles with tunable particle size, lattice microstrain and optical bandgap have potential application in ferrofluid, electromagnetic shielding, photocatalysis, hyperthermia, dye degradation and other areas.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11664-022-09813-2.

The Effect of sp2 Content in Carbon on Its Catalytic Activity for Acetylene Hydrochlorination.

We report the influence of sp2 content in carbon catalyst on the catalytic activity for acetylene hydrochlorination. Nanodiamonds (NDs) were used as the precursor and calcinated under different temperatures. The resulting ND500, ND700, ND900, and ND1100 catalysts were characterized, and the sp2 content increased with increasing calcination temperature. The specific activities of the catalysts first increased and then decreased with increasing sp2 content. The highest catalytic activity could be obtained in the ND-900 catalyst with a sp2 value of 43.9%. The density functional theory results showed that the adsorption sites for acetylene and hydrogen chloride were located at the interface between sp2 and sp3 configuration.

Fabrication and characterization of Y2Si2O7 fibers prepared by electrospinning

Ceramic fibers have played an important role in the thermal protection field of aerospace vehicles at high-temperature over the past decades. In this work, Y2Si2O7 precursor fibers were prepared by electrospinning and characterized. The spinning solution consisted of yttrium nitrate, tetraethyl orthosilicate, and polyvinyl alcohol. The microstructure and elements distribution of fibers was investigated by scanning electron microscopy. The decomposition of organic components and crystallization process of yttrium silicate were explored by thermogravimetry-differential scanning calorimetry. The phase composition of fibers was analyzed by X-ray diffraction. The results showed the fibers were composed of uniform tiny grains after calcined at 1000 °C and the phase of the fibers was α-Y2Si2O7. The size of grains increased with increasing calcination temperature and the intact fibrous structure was maintained. The average diameter of the precursor fibers was 1383 ± 345 nm and decreased to 786 ± 171 nm after calcined at 1300 ℃. Elements distribution was uniform in the fibers, confirming a good homogeneity of the fibers.

Investigation of photocatalytic activity of TiO2 nanotubes synthesized by hydrothermal method

TiO2 nanotubes were synthesized by hydrothermal reaction using commercially available TiO2 powder at 150 °C for 24 h. The transmission electron microscopy, X-ray diffraction, nitrogen adsorption-desorption isotherms and Fourier Transform-Infrared spectroscopy were used to characterize the nanotubes. Anatase phase was not transformed into rutile phase in the range of calcination temperature studied. Increase in calcination temperature result in enhancement of crystallinity and reduction in BET surface area. Photocatalytic removal of Reactive Red 239 (RR239) was investigated using prepared TiO2 nanotubes. Effects of pH, TiO2 nanotube dosage, initial RR239 concentration and calcination temperature were studied. 99%, 97% and 55% of removal efficiency values were attained at pH = 3, 5 and 7, respectively within 60 min or reaction time. With an increase in dosage of TiO2 nanotube in the range of 0.25–0.75 g dm−3, removal rate increased by a steeper slope. Complete removal of RR239 was observed at 20 mg dm−3 RR239 concentrations within 30 min but longer time was required for complete removal at higher concentrations. Langmuir-Hinshelwood kinetic expression was proposed based on nonlinear regression analysis. The removal efficiency of nanotubes calcined at 300 − 450 °C significantly increased but further increase in calcination temperature caused to decrease the efficiency.100% and 85% removal efficiency values were observed using actual solar light within 120 min of reaction time in July and January, respectively. Experiments conducted with scavengers showed that holes and adsorbed hydroxyl radicals were the major species involved in removal of RR239. A pathway for degradation of RR239 was suggested according to detected intermediate compounds.

The mineral phase reconstruction of copper slag as Fenton-like catalysts for catalytic oxidation of NOx and SO2: Variation in active site and radical formation pathway

Herein, the copper slag through CaO-thermal treatment was used as a heterogeneous catalyst to activate H2O2 into free radicals to remove NOx and SO2. The NOx removal capacity of modified copper slag exhibited a volcano-type tendency with increased calcination temperatures. Because of the iron phase transformation and decrease in surface exposure Cu species by adjusting surface properties, the copper slag delivers a higher NOx capacity and H2O2 utilization rate than raw copper slag and bare H2O2. In addition, the interaction of multi-phases of modified copper slag was illustrated by simulation experiments. Moreover, the possible formation pathway of free radicals in the alkaline medium was proposed based on the electron paramagnetic resonance (EPR) as well as chemical quenching experiments. The surface-bound hydroxyl radical through ≡Fe3+ sites is decisive for free radical formation in alkaline conditions. Our findings shed new light on the feasibility of SO2 and NOx removal by metallurgical slag via mineral phase reconstruction as a novel heterogeneous catalyst.