Adsorption Amount Research Articles

Insight into multi-ionic adsorption behavior of recycled cement paste exposed to chloride solutions

The multi-ionic adsorption behavior of recycled cement paste (RCP) exposed to NaCl and CaCl2 solutions is investigated in this study by comparing with that of the ordinary cement paste (OCP). The adsorption of Na+, K+, Ca2+, and Cl- in RCP and OCP are quantified by ICP-OES and potentiometric titration. RCP has larger adsorption capacity for Na+, K+, and Cl- compared to OCP, which is attributed to a lager specific surface area of RCP. For the multi-ion adsorption of OCP and RCP in both NaCl and CaCl2 solutions, the adsorption amount of minor cation ions are found to be influenced by the concentration of primary cation ion, reflecting a competitive adsorption among cation ions. Besides, the maximum Na+ adsorption amount is proportional to the product of the specific surface area and the percentage of the silanol groups in CSH measured by 29Si NMR spectroscopy. Additionally, molecular dynamics simulation is conducted to investigate the Na+ and Cl- adsorption behavior of CSH in OCP and RCP at a molecular level. The simulation results confirm the higher adsorption capacity of OCP than RCP.

Flotation separation of chalcopyrite from pyrite and sphalerite using a novel collector: An experimental and mechanism investigation

In this paper, a new collector, named O-isobutyl-N-allyl thionocarbamate (IBATC), was synthesized, and the structure was characterized by Fourier Transform Infrared Spectrometer (FTIR) and 1H NMR, 13C NMR analysis. The collection performance of IBATC was evaluated by flotation tests and interaction mechanism was investigated by means of adsorption amount, zeta potential measurements, FTIR, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation. The flotation tests results proved that IBATC was inclined to collect chalcopyrite compared with pyrite and sphalerite. Especially in the pH range of 9.5–10 and IBATC concentrate of 30–40 mg/L, the recovery of chalcopyrite exhibited more than 80 %. The adsorption amount and zeta potential measurements showed that IBATC had a greater orientation to chalcopyrite. FTIR and XPS analysis demonstrated IBATC chemically adsorbed on chalcopyrite surface, whereas physically adsorbed on pyrite and sphalerite. Further, DFT calculation of the interaction between IBATC and chalcopyrite proved that S atom of IBATC donated electrons to Cu sites on chalcopyrite surface and the adsorption energy was −19.45 kcal/mol, referring to an exothermic reaction. As a result, IBATC showed great capacity for the separation flotation of chalcopyrite, pyrite and sphalerite.

Prediction of Cr(VI) and As(V) adsorption on goethite using hybrid surface complexation-machine learning model

This study aimed to develop surface complexation modeling-machine learning (SCM-ML) hybrid model for chromate and arsenate adsorption on goethite. The feasibility of two SCM-ML hybrid modeling approaches was investigated. Firstly, we attempted to utilize ML algorithms and establish the parameter model, to link factors influencing the adsorption amount of oxyanions with optimized surface complexation constants. However, the results revealed the optimized chromate or arsenate surface complexation constants might fall into local extrema, making it unable to establish a reasonable mapping relationship between adsorption conditions and surface complexation constants by ML algorithms. In contrast, species-informed models were successfully obtained, by incorporating the surface species information calculated from the unoptimized SCM with the adsorption condition as input features. Compared with the optimized SCM, the species-informed model could make more accurate predictions on pH edges, isotherms, and kinetic data for various input conditions (for chromate: root mean square error (RMSE) on test set = 5.90 %; for arsenate: RMSE on test set = 4.84 %). Furthermore, the utilization of the interpretable formula based on Local Interpretable Model-Agnostic Explanations (LIME) enabled the species-informed model to provide surface species information like SCM. The species-informed SCM-ML hybrid modeling method proposed in this study has great practicality and application potential, and is expected to become a new paradigm in surface adsorption model.

Flow Channel with Wrinkles and Calcium Sites in a Ca-MOF for Direct One-Step Ethylene Purification from C2 Gases and MTO Products Separation.

The strategy of flow channel with wrinkles and calcium sites for single-step C2H4 purification from C2 gases and methanol-to-olefins (MTO) products separation was realized in FJI-Y9. The adsorption amounts showed a total reversal order of C3H6 > C2H6 > C2H2 > C2H4 at 298 K. Modeling indicated that the wrinkles and Ca2+ facilitated the full contact of C3H6 and C2H6. Breakthrough experiments illustrated that FJI-Y9 could yield pure C2H4 in a single step with a productivity of 0.78 mmol g-1. In a lone adsorption/desorption cycle for MTO product separation, the productivities of C3H6 and C2H4 were 1.96 and 1.29 mol g-1, standing as the highest recorded values.

Removal of methyl blue from aqueous solutions with nano-magnetic Pinus brutia biochar

In the study, the removal of dye (methyl blue) from aqueous solutions by batch/agitation adsorption method was investigated using Pinus brutia (PB). For this purpose, first, PB wood was collected and made into wood chips (PB), and then Pinus brutia biochar (PBB) was made. The PBB was modified to gain nano-magnetic properties. The biochar structure was characterized by FT-IR. PBB and nM-PBB were used for the removal of MB dye. The adsorbent amount, temperature, pH, time and dye concentration were investigated in the adsorption process with adsorption isotherms, kinetics and thermodynamics to estimate their MB removal efficiency. Sorption equilibrium for MB dye was reached by nM-PBB within 60 min and adsorption efficiency up to 99.007% was reached. While the adsorption kinetics followed a pseudo-second-order kinetic model, the Langmuir isotherm model, with a maximum adsorption capacity of 107.527 mg/g (nM-PBB), showed homogeneous physiochemical adsorption. The efficiency was found to be a spontaneous endothermic reaction. It can be suggested that nM-PBB can be used to remove MB.

Studies into confined methane adsorption in shale nanopores using a simplified local density model

The large number of nanopores in shale reservoirs provide an effective storage space for gases, which can assist in accurately characterizing the confined adsorption characteristics, including the adsorption amount of fluid in nanopores that is important for a detailed understanding of shale gas storage mechanisms and production prediction. Although the simplified local density (SLD) model has been widely used to describe the behavior of confined adsorption in slit-like pores, its application in relation to cylindrical pores has not been studied in detail. In this study, the importance of fluid–fluid interaction and fluid–solid interaction has been analyzed, with the expressions for the distribution of confined attractive parameter in cylindrical pores are derived by combining with the (3/8)σff assumption to establish a new SLD model. The reliability of the new model was verified by the publicly available experimental methane excess adsorption data for shale at different temperatures and the simulation results from the Grand Canonical Monte Carlo (GCMC). Moreover, by comparing with the SLD model with the slit pore structure, it was found that the adsorption isotherms and the confined fluid density distribution pattern characterized by the SLD model with the cylindrical pores were closer to the actual reservoir conditions of shale. In addition, the densities characterized by SLD models with a (3/8)σff assumption and with a (1/2)σff assumption at different Λb have been discussed and analyzed, and it is found that the selection of a suitable Λb would help to improve the accuracy of SLD model. The results might provide new theoretical insights into confined methane adsorption, with the new SLD model providing better engineering applications in shale gas development, gas storage, and pore structure characterization.

Competitive adsorption of heavy metals onto xanthate-modified sludge hydrochar and its solidification as secondary minerals

In this study, a sulfur-modified magnetic hydrochar was synthesized by grafting thiol-containing groups onto the sludge-derived hydrochar. The modified hydrochar exhibited effective adsorption of Cu2+, Pb2+, Zn2+, and Cd2+ over a wide pH range and in the presence of coexisting ions, and showed almost no secondary leaching in three acidic solutions. In the mult-metal ion system, the modified hydrochar exhibited maximum adsorption capacities were 39.38, 105.74, 26.53, and 38.11 mg g−1 for Cu2+, Pb2+, Zn2+, and Cd2+, respectively. However, the binding capacity and adsorption amount of modified hydrochar for metal ions were lower in the mult-metal ion system compared to the unit-metal ion system. Notably, Pb2+ showed a strong inhibitory effect on the adsorption of other heavy metal ions by modified hydrochar due to strong competition for xanthate functional groups. The Pb2+ occupied the xanthate and native functional groups (–OH, –NH2, and Fe–O etc.), leaving only a small amount of adsorption sites for Cu2+, Zn2+ and Cd2+. Simulation results further supported these findings, indicating that Pb2+ had the highest density profiles near the four functional groups, and the density profiles of the four heavy metals near the xanthate functional groups were greater compared to the other three functional groups. Furthermore, the SEM-EDS, TOF-SIMI, and XPS results indicated that modified hydrochar achieved excellent mineral binding mainly through electrostatic interaction, ion exchange, and chelation. Overall, these results highlight the sulfur-modified magnetic hydrochar as a highly efficient adsorbent for heavy metals in environmental applications.

Dye adsorption onto iron oxide prepared by green method mediated by leaf extract of Falcaria vulgaris

ABSTRACT Iron oxide nanoparticles were green synthesised by Falcaria vulgaris extract. Characterisation of samples was carried out by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Investigating factors, such as pH, adsorbent dosage, temperature, contact time and the dose effect of the initial concentration of methylene blue dye, was done on adsorption of methylene blue. The synthesised nanoparticles exhibited a relatively spherical and irregular surface, with a size of about 35 nm, a haematite crystal phase and a saturation magnetisation of 8.3 emu/g. The highest adsorption of methylene blue (76%) was achieved at a pH value of 6, with an optimal adsorbent quantity of 0.004 g/L and a starting concentration of 80 mg/L. The adsorption behaviour of synthesised iron oxide nanoparticles follows from Langmuir isotherm and has a maximum adsorption capacity of 49.169 mg/g. The kinetics of methylene blue dye removal using iron oxide nanoparticles followed a second-order kinetic equation. The adsorption activity of iron oxide nanoparticles showed very little change even after two regeneration cycles. Therefore, the obtained adsorbent regained its adsorption capacity with the help of the photo-Fenton process and is reusable again.

Synergy of Post-Crosslinked imprinting strategy and silanol chemistry for the anisotropic construction of molecularly imprinted polymers onto Halloysite nanotubes

Searching for alternative porous substrates which can realize anisotropic preparation of “tailor-made” complementary binding sites is an important way to improve the identification efficiency and interfacial stability of the surface molecularly imprinted polymers (SMIPs). In this work, a functional polymer (FP) with multi-functional properties was firstly synthesized using 3-(isobutenyloxy) propyltrimethoxysilane, 1-(vinylbenzyl) thymidine and cinnamoyloxyethyl methacrylate (CEMA) as monomers, and then FP with post-crosslinking property was covalently deposited onto theoutersurfaceof halloysite nanotubes (HNTs) using silanol chemistry to prepare 2′-deoxyadenosine (dA) imprinted sorbents (HNTs-SMIPs). More than 65 % of dA molecules was captured within the first 2.0 h. The number of high affinity site from the total binding sites of HNTs-SMIPs is estimated to be as high as 73.25 %, and the maximum adsorption amount of HNTs-SMIPs is 48.78 μmol g -1 at 25 °C. The imprinting factor (IF) of HNTs-SMIPs towards dA is 1.89, and 79.49 % the adsorption capacity is remained after five adsorption–desorption cycles. In addition, 70.2 % of the dA from spiked human urine samples can be selectively extracted by HNTs-SMIPs. HNTs-SMIPs have excellent interfacial stability and strong affinity for the template molecule dA, and this work provides a new strategy for the specific separation and enrichment of dA.

Adsorption of Scandium Ions by Amberlite XAD7HP Polymeric Adsorbent Loaded with Tri-n-Octylphosphine Oxide.

In an actual economic context, the demand for scandium has grown due to its applications in top technologies. However, further development of new technologies will lead to an increase in the market for Sc related to such technologies. The present study aims to improve and upgrade existing technology in terms of efficient scandium recovery, proposing a new material with selective adsorptive properties for scandium recovery. To highlight the impregnation of Amberlite XAD7HP resin with tri-n-octylphosphine oxide extractant by the solvent-impregnated resin method, the obtained adsorbent material was characterized by physico-chemical techniques. Further, the specific surface of the adsorbent and the zero-point charge of the adsorbent surface have been determined. Different parameters, such as initial concentration, adsorbent amount, contact time, or temperature, have been studied. The initial pH effect was investigated when a maximum adsorption capacity of 31.84 mg g-1 was obtained at pH > 3, using 0.1 g of adsorbent and a contact time of 90 min and 298 K. An attempt was made to discuss and provide a clear representation of the studied adsorption process, proposing a specific mechanism for Sc(III) recovery from aqueous solutions through kinetic, thermodynamic, and equilibrium studies. Adsorption/desorption studies reveal that the prepared adsorbent material can be reused five times.

Scaling considerations and optimal control for an offshore wind powered direct air capture system

The optimal design and operation of an offshore wind powered direct air capture (DAC) system is complex owing to the intermittent energy supply and the modularity of the units. A solid amine DAC process involves multiple individual units which undergo periodic loading to capture carbon dioxide (CO2) from ambient air, followed by regeneration to produce pure CO2 for utilisation or sequestration. The modular nature of a solid DAC process is exploited in this study to investigate the optimal design and coordinated operation of multiple DAC units mounted on a single 15 MW offshore wind turbine platform, with battery energy storage for additional short term power buffering. Important design parameters considered include the number of independently controllable units, the cyclic capacity of each unit (proportional to the amount of adsorbent) and the battery capacity and maximum power ratings. The design study results highlighted the diminishing returns to the CO2 capture rate with scaling, with a full design optimisation based upon cost estimations left for future work as the technology matures. It was found the optimal configuration was 14 DAC units, each with a cyclic capacity of 2000 kg CO2 , giving a total annual capture rate of 45 600 ton yr−1 and a wind utilisation factor of 96.6%. Furthermore, it was found that a rules-based control strategy based on high and low loading limits was competitive with a machine learning based controller and outperformed a model predictive control scheme.

Synthesis, performance and mechanism of shrinkage-reducing agents with water-reducing function for cement-based materials

Three shrinkage-reducing agents (SRAs) possessing a water-reducing capacity with different structures were synthesized by aqueous free radical copolymerization. Their structures were characterized by Gel Permeation Chromatography (GPC), specific anion charge density, and Fourier Transform Infrared Spectrometer (FTIR) measurements. Their abilities to reduce surface tension and their adsorption and dispersing effectiveness in cement paste as well as their impacts on cement hydration and compressive strength, autogenous shrinkage, drying shrinkage, and pore structure of cement mortar were investigated. Results clearly showed that the three synthesized SRAs with a water-reducing function reduced the surface tension of pore solution, with the water-reducing SRA with butyl exerting the most significant effect due to its lower molecular mass. They enhanced the flowability of cement paste because of their adsorption on cement grains. The water-reducing SRA with dimethyl amino exhibited higher adsorption amounts on cement grains due to higher charge density, resulting in higher initial flowability of cement paste and more significant hydration retardation. Their presence decreased the autogenous shrinkage of cement mortar by reducing the surface tension of pore solution, delaying the cement hydration, and decreasing the capillary pore volume. Their addition also mitigated the drying shrinkage due to the synergistic effect of surface tension reduction, pore structure coarsening, and porosity (2.5–50 nm) reduction. Among the three, the water-reducing SRA with butyl demonstrated a higher capability of reducing the drying shrinkage and had a favorable effect on the compressive strength of mortar at later ages.

Separation effect of Li+, Na+, and Mg2+ with alumina–lithium LDH doped with amorphous titanium dioxide

Alumina–lithium layered double hydroxide doped with amorphous titanium dioxide (TiO2@AlLi–LDH) was synthesized through the coprecipitation of Li+ and Al3+. The structural characteristics of TiO2@AlLi–LDH were analyzed via XRD, XPS, BET and DSC–TG. Titanium oxide anions could be inserted between layers in TiO2@AlLi–LDH, and TiO2@AlLi–LDH consists of nanoflake-sized particles. The average diameter of the particles is 231.0 nm, and the particle size distribution curve is close to the normal distribution curve. The BET surface area is 174.02 m2·g−1 after recrystallization. The Li+ adsorption process of TiO2@AlLi–LDH can be described by the pseudo–second–order model, and the adsorption capacity is 11.54 mg·g−1. The structure of TiO2@AlLi–LDH was destroyed because of the reaction between Mg2+ and CO32−. The presence of Na+ significantly reduces the Li+ adsorption ability of TiO2@AlLi–LDH without destroying the structure. The separation coefficient of Mg2+/Li+ is 4269.76 when the initial mass ratio of Mg2+/Li+ is 350.20, and the separation coefficient of Na+/Li+ is 226.20 when the initial mass ratio of Na+/Li+ is 329.40. The Li+ adsorption amount of TiO2@AlLi–LDH in Qarhan salt lake brine is 5.66 mg·g−1, suggesting potential for industrial application.

Mechanism of lithium adsorption by AlLi-LDH with Al–O octahedral ring

Aluminum–lithium layered double hydroxide (AlLi-LDH) was synthesized using a co-precipitation method for Li+ adsorption. AlLi-LDH crystallized in space group of P32 or C2/m, where the microstructure had regular spherical shapes with diameters of 5–10 μm. The space group of AlLi-LDH only belonged to P32 after Li+ adsorption. The Li+ adsorption from a solution with a Li+ concentration of 95.4 mg/L reached 8.98 mg/g after 1 h. The adsorption amount increased to 16.50 mg/g after 48 h, where the Li+ adsorption capacity determined by applying the second-order adsorption model was 17.57 mg/g. The Mg2+/Li+ separation coefficient was 29536 when the mass ratio of Mg2+ to Li+ was 1067. The interaction strength of Li–O was weaker for AlLi-LDH in the P32, where the interaction occurs via the electrostatic effect. The Li+ adsorption and desorption occurred more readily in AlLi-LDH belonging to P32 space group.

Integration of adsorption, reduction, and filtration in PANI/PVDF nanofiber composite membrane for removal of Cr(VI).

Here, polyaniline/polyvinylidene fluoride (PANI/PVDF) nanofiber composite membrane was fabricated using electrostatic spinning technology to remove hexavalent chromium Cr(VI). The employment of PANI not only extremely enhanced the hydrophilic property of the nanofiber membrane, but also facilitated the transfer of Cr2O72- from water to the membrane. The PANI/PVDF membrane had an extremely excellent performance in getting rid of Cr(VI) and a quite large flux (250 L/m2 h). The maximum adsorption quantity of the membrane could reach 334.5mg/g in which adsorption played 52.12% part and reduction played 47.87% part. The removal rate could reach nearly 100% immediately in the permeate solution under filtration while it needed 240min to reach 100% only by static adsorption. Therefore, the interception of the membrane and the adsorption reduction of PANI had synergistic effect on removal of Cr(VI). Furthermore, the removal rate of Cr(VI) could still reach 95.97% after reused 8 times. The membrane showed a very good reusability and application prospect.

Adsorptive Desulfurization of Iraqi Light Naphtha Using Calcite and Modified Calcite

This study used the adsorption method to remove sulfur compounds from light naphtha fuel by using calcite and modified calcite as adsorbents. The calcite was prepared from chicken eggshells by heating and activation methods. It was modified by mixing it with commercial activated carbon as a new adsorbent. XRD and FTIR were used to characterize the adsorbents. Light naphtha fuel from the Al-Diwaniyah refinery, with a sulfur concentration of 776 ppm, was used in batch adsorption studies. Various operation conditions that affect the adsorption process were studied such as temperature (20–40 °C), weight of the adsorbent (1-3 g), and contact time (15–45 min) at constant mixing speed (300 rpm). In this study, the Minitab Program-Box-Behnken design was used to design experiments in batch adsorption studies of light naphtha, which is considered more straightforward and accurate because it shows the effect of each dependent factor on the adsorption efficiency and removal ratio. Results and analysis showed that the increase in temperature, the amount of adsorbent, and contact time would increase the removal efficiency. The analysis of adsorption equilibrium isotherms shows that the experimental data follows the Freundlich isotherm model for adsorbents. According to the results of the study, the highest removal percentages of sulfur content of light naphtha using calcite and modified calcite were 61% and 79%, respectively.

CO2 adsorption by coal fly ash zeolite and modified zeolite-templated carbon

Coal fly ash (CFA), as the main by-product of coal-fired power plants, has a high content of silica-aluminium elements that can be used to prepare zeolite by the alkali fusion method with sound CO2 adsorption capacity. Among the four effect factors of Si/Al, NaOH/CFA, H2O/AFP(alkali fusion product), and crystallisation time, NaOH/CFA had the greatest effect on the CO2 adsorption performance of coal fly ash zeolite (CFAZ), followed by Si/Al and H2O/AFP, and crystallisation time had the least effect. The CO2 adsorption performance of the samples was tested and analysed using the thermal analysis method, the CO2 adsorption amount of CFAZ reached 4.23 mmol g–1 (30 °C, 101 kPa). In addition, the CFAZ and the zeolite-templated carbon (ZTC) adsorption performance is poor at high temperatures. The co-precipitation method modification of CFAZ and ZTC can produce layered double hydroxide derived material, which can adsorb CO2 at high temperatures reached at 3.35 mmol/g (650 °C, 101 kPa). Moreover, ZTC modified with polydivinylbenzene as the hydrophobic material has a sound CO2 adsorption effect in high-humidity environments. Thus, different adsorbents also could be produced using CFA to capture CO2 with a wide temperature range between 25 and 650 °C.

Synthesis of MgO nanomaterials using ultrasonic electrodeposition and their adsorption performance for Pb(II)

This study reports the successful synthesis of MgO nanomaterials while employing ultrasonic electrodeposition and heat treatment procedures. The capability and mechanism of these materials for removing Pb (II) from industrial soil were then investigated under ultrasonic powers of 100 W, 150 W, and 200 W. The surface morphology and phase composition of the nanomaterials were analyzed through SEM and XRD. The MgO nanomaterials prepared at 150 W displayed a high adsorption capacity for Pb (II), reaching up to 68.9 mg g−1, under conditions of pH 4.5, temperature 30 °C, Pb (II) concentration of 50 mg/L, and an optimal reaction time of 20 min. The maximum adsorption capacity of MgO nanomaterials prepared at 150 W ultrasonic power was observed to be 43.7 mg g−1 under the condition of 30 °C, Pb (Ⅱ) concentration of 50 mg/L, the optimal deposition time of 20 min, and pH 7. Analysis of the Pb (II) adsorption process on the surface of MgO nanomaterials was carried out using the pseudo-second-order kinetic and Langmuir models. The results revealed that Pb (II) adsorption on MgO nanomaterials exhibited distinct monolayer and chemical adsorption properties. Moreover, the Pb (II) adsorption capacity on MgO nanomaterials was found to be significantly influenced by temperature. The highest adsorption amount of Pb (II) by MgO nanomaterials was observed at a temperature of 30 °C. Further, the Langmuir model revealed the adsorption properties of MgO for Pb (II), with a correlation coefficient higher than 0.99. Therefore, the results confirm that ultrasonic power affects the adsorption performance of MgO nanomaterials prepared by ultrasonic electrodeposition, with the adsorption performance of MgO nanomaterials prepared at 150 W being the best.

Preparation of antimicrobial composite from Arabic gum-grafted-poly(p-phenylene diamine)/MOF(Fe) decorated with Cu nanoparticles as a unique nanobiosorbent for removal of cloxacillin antibiotic

The growth of the world population has led to an increase in the demand for fresh water. Water pollution is often caused by hasty urbanization without proper management of hazardous waste. Therefore, it is vital to implement new methods to remove pollutants from water. In the current study, an antimicrobial nanocomposite adsorbent composed of Arabic gum-grafted-poly(para phenylene diamine) (AG-g-PpPA) decorated with metal-organic framework and copper nanoparticles (AG-g-PpPA@MOF(Fe)/Cu) was synthesized via in-situ copolymerization. The nanocomposite was utilized for eliminating the antibiotic cloxacillin from water solutions. The effects of different factors were analyzed, including pH, the quantity of adsorbent, contact time, and preliminary cloxacillin concentrations. Ideal parameters were pH 7, 5 mg adsorbent dosage, 10 min contact time, and an initial 500 mg/L cloxacillin concentration. The adsorption process followed the Freundlich isotherm equation, with a maximum adsorption ability of 400 mg/g. The kinetics information appropriately fits a pseudo-second-order model. Thermodynamic calculation showed the adsorption occurred spontaneously. The nanocomposite also displayed antibacterial action in contradiction to Escherichia coli and Staphylococcus aureus. Additionally, the adsorbent could be recovered and reused effectively. The excellent adsorption ability highlights the potential of AG-g-PpPA@MOF(Fe)/Cu adsorbent for eliminating pharmaceutical pollutants from wastewater.

Heterogeneous reaction of NO2 with hematite: The effects of UV irradiation, O2 and relative humidity

Heterogeneous reactions on mineral dust surfaces are increasingly considered important in the removal of gaseous pollutants and the formation of secondary aerosols. Although the heterogeneous reaction of NO2 on the hematite surface has been investigated in many previous studies, little is known about the reaction of NO2 with hematite under ambient conditions. In this work, heterogeneous reactions of NO2 with hematite at 298 K were investigated via a coated-wall flow tube reactor and in situ diffuse reflectance Fourier transformed infrared spectroscopy (DRIFTS). The influence of UV illumination, relative humidity (RH) and O2 on the uptake coefficients and adsorption amount of NO2, as well as the nitrate formation on the hematite surface, has been analyzed comprehensively. UV irradiation shows a significant effect on the true uptake coefficient (γBET), which increases from 2.00 × 10−6 to 4.76 × 10−6 in the N2 stream and 1.32 × 10−6 to 4.07 × 10−6 in the air stream under dry conditions (∼0.3 % RH). RH (in the range of 0–67 %) exhibits an inhibitory effect on the adsorption of NO2 on the hematite surface because of the competition between NO2 and water molecules, that is, γBET and adsorption amount of NO2 decrease with an increase in RH under both the dark and light reaction conditions. Meanwhile, both the γBET and adsorption amount of NO2 on hematite decrease in the air stream compared to those in N2 conditions. In addition, the results from the DRIFTS experiments indicate that the presence of UV irradiation promotes the conversion of NO2 to nitrate and both the RH and O2 suppress the nitrate formation. From this research, the heterogeneous reactions between NO2 with mineral dust under ambient conditions will be better understood.