Desorption Method Research Articles

Cost-effective Cu2+ and Pb2+ remediation using peanut shell-derived biosorbents: a physicochemical investigation

ABSTRACT Heavy metals in water bodies are caused chiefly by anthropogenic activities: industrial wastes, agricultural runoff, mining and hazardous waste disposal further the causes. They could enter the water body through varied processes, including those in direct contact with contaminated soils and sediments, along with atmospheric deposition. Recently, nanowaste biomass has been one of the avenues for heavy metal removal from water. The following figures show that these nanoparticles prepared from agricultural and industrial wastes can absorb heavy metal ions. This adsorption involves the complexation of biomass with heavy metal ions, which enhances the binding; thus, these metals can be recovered using different desorption methods. The innovative approach reduces the concentrations of heavy metals to acceptable levels as required by the regulatory guidelines. It also provides a cost-effective and environmentally benign alternative to conventional remediation methods. Various physical techniques then characterised the obtained nano waste materials. The crystal structure of the peanut shell (PS) and its nanoparticles (PSNP) were described by XRD, and the chemical composition was defined according to Raman Spectroscopy and FTIR. Present research identified a biosorbent nanoparticle powder made from peanut shells with 40 to 60 nm particle sizes, as confirmed by FESEM, HRTEM, BET and Zeta analysis. PSNP removal efficiencies achieved for Cu2+ and Pb2+ were 94% and 91%, respectively. Contact time and pH varied to determine the optimum conditions for removing heavy metal ions from contaminated water supplies.

Analysis and Joint Correlation Models on Pore Structures of Graphitized Phenolic Resin Char Under Ni-Zn-B Catalytic Effect

Phenolic resin plastic is mainly composed of phenolic resin and pyrolysis is often used to perform the important task of treating it. While there are large quantities of char generating, the char can be graphitized for upgrading under Ni-Zn-B catalytic effect. Pore structure is an important index for evaluating graphitic carbon. In this study, the phenolic resin char was graphitized with Ni-Zn-B at low temperature based on orthogonal rules (graphitization temperature: 1300 °C, 1400 °C, 1500 °C; retention time: 60 min, 120 min, 180 min; catalyst additive ratio: 5%, 10%, 15%), and their pore structures were determined by N2 adsorption and desorption method. The graphitized phenolic resin chars were porous carbon materials whose specific surface areas were commonly between 110 to 160 m2/g; they also mainly consisted of wholly equivalent micropores and mesopores. The effects of the graphitization conditions on pore structures of GPRCs were analyzed; this revealed that the increase in graphitization temperature destroyed micropores to form mesopores, with a longer retention time leading to the production of small quantities of micropores and mesopores, some micropore spaces were occupied and mesopore skeletons were destroyed to from large pores with more Ni-Zn-B addition. The correlation models of the pore structures and reaction parameters were built; it was found that the multiple linear regression model showed an advantage in predicting micropore structures and the built artificial neural network model was better at predicting the total pore and mesopore.

Efficient Phosphorus capture from treated sanitary wastewater using a waste-derived SiO2@FeOOH composite: Robustness, Ca2+ interactions, and recovery perspectives

Phosphorus uptake and recovery from sanitary wastewater have been considered a promising approach to producing more sustainable fertilizers, in addition to reducing environmental damage caused by the discharge of this nutrient into water streams. In this study, the Phosphorus adsorption/desorption dynamics exhibited by a tailored SiO2@FeOOH adsorbent, produced using quartz sand waste and Fe derived from the acid dissolution of scrap iron, were examined. The adsorbent’s behavior, robustness, and interaction with Ca2+ ions in simulated treated sanitary wastewater were systematically investigated. As a result, the behavior of the adsorbent under controlled conditions was successfully modeled, and relevant interactions between the material and Ca2+ ions were identified under simulated conditions. The performance of the adsorbent was not affected by the presence of nitrate, carbonate, sulfate, ammonium, fluoride, and humic substances in the simulated media. Additionally, the composite can adsorb humic substances and Phosphorus simultaneously, without interfering with its Phosphorus adsorption capacity. In simulated treated wastewater, the adsorption of the nutrient was enhanced in the presence of Ca2+; however, the formation of insoluble Ca/P deposits on the adsorbent surface significantly changed the adsorption dynamics and disturbed the recovery of Phosphorus using the usual alkaline desorption method. The adsorbent exhibited a robust Phosphorus adsorption capacity as high as 40 mg P/g in simulated treated wastewater, showing clear potential for Phosphorus uptake in Wastewater Treatment Plants. Based on the experimental evidence, future perspectives on the final disposal of the spent adsorbent were also discussed within a circular economy framework.

Research on the Adsorption Performance of Zeolites for Dimethyl Ether

The purification and removal of polar impurities in olefin feedstocks is crucial for downstream deep processing, and adsorption is the main method for deep purification of such impurities. This article takes dimethyl ether, a typical oxygen-containing compound impurity in MTOs, as a polar impurity molecule, and LTA and FAU topological zeolites as research objects. The influence of zeolite topology, morphology, skeleton silicon–aluminum (Si/Al) ratio, and ion type on the adsorption and removal of trace dimethyl ether was investigated by XRD, SEM, XRF, and nitrogen adsorption–desorption methods. The FAU topological zeolites show a better adsorption performance for dimethyl ether owing to their larger specific surface area and unobstructed pores compared with LTA zeolites. Among FAU topological zeolites, the NaX zeolite a with lower framework silica–alumina ratio has the highest adsorption capacity for dimethyl ether. Magnesium ion exchange on NaX zeolites (MgNaX) reduce the specific surface area and adsorption capacity of the NaX zeolite. However, after forming with alumina as a binder, the adsorption capacity of the MgNaX–Al2O3 adsorbent is about 13% higher than that of the NaX–Al2O3 adsorbent without Mg ion exchange. This may be due to the decomposition of residual organic Mg salts in the Mg ion exchange samples during high-temperature calcination, resulting in a larger specific surface area for the formed adsorbent. Further characterization of NH3–TPD and CO2–TPD shows that Mg ion exchange weakens the acid–base active sites on the adsorbent surface. The reduction in acid–base sites reduces the occurrence of side reactions such as polymerization and isomerization caused by the exothermic adsorption of olefins on adsorbents. Repeated adsorption data show that the formed adsorbent has excellent regeneration–adsorption performance.

Heteronuclear Fe-Mn Cyclopentadienyl Complexes Supported on Boehmite. Thermochemistry and Thermodynamics of their Decomposition

Boehmite samples with compounds of the composition (C5H5)2FeMnX2(μ-CO)n, where X=Cl, Br and n=1.2, precipitated at room temperature from tetrahydrofuran solutions and then heated in an air flow up to 873 K were obtained and characterized using X-ray diffractometry, infrared Fourier spectroscopy, electron magnetic resonance and temperature-programmed desorption methods. It was shown that the thermal decomposition of these compounds applied to the boehmite samples in the range from room temperature to 873 K occurs stepwise and consists of at least two stages. The first stage of thermal decomposition occurs in the range of 453–753 K, and the second – in the range of 813–843 K. The XRD data show that when calcining at 873 K the boehmite samples with the applied compounds of the above composition and containing these compounds less than 10 wt.%, the diffraction patterns show only reflections characteristic of poorly crystallized aluminum oxide. However, the electron paramagnetic resonance (EPR) spectra of these samples clearly show intense signals characteristic of superpara/ferromagnetic particles of iron and manganese oxides, as well as EPR signals from isolated Fe3+ substituting Al3+ ions in the aluminum oxide structure. EPR spectra most of the iron and manganese is stabilized on the surface of poorly crystallized aluminum oxide in the form of nanostructured iron and manganese oxides.

Methane Desorption-Diffusion Behaviors in Micropores of Coal under Different Water Displacement Pressures.

Hydraulic fracturing not only enhances the flow conductivity of coal seams but also transforms the CH4 adsorbed in coal seams into free CH4 and then outputs it via the desorption-diffusion process, thus improving the output quantity and efficiency of CH4. In this paper, taking the coal from Changping mine in Shanxi as the research object, the 3D macromolecule model of coal was established by using analytical test experiments, and the molecular dynamics simulation method of desorption and diffusion was applied to study the characteristics of methane desorption rate and diffusion behaviors under different driving water pressures through the parameters of gas-water concentration distribution, desorption and diffusion rates, and the interaction energies between the coal and the gas-liquid. The results show that the water drive can increase the desorption rate of methane. With the increase of methane adsorption pressure, the desorption effect of water drive becomes stronger and then weaker. The desorption effect of water drive was best when the methane adsorption pressure was 5 MPa and the pressure difference was 2 MPa. Generally, the water drive promoted the methane diffusion, but if the water drive time was too long, it formed a water plug, and the water drive methane inhibited the diffusion. In shallow reservoirs, water drive can obviously promote the desorption-diffusion of methane. The binding energy between CH4 molecules is mainly composed of the repulsive force, while that between water molecules is mainly the adsorption force. In the binding energy between CH4 molecules and coal structures, the van der Waals (VDW) force accounts for 99% of the effect; in the binding energy between water molecules and coal structures, the electrostatic force contributes 84% to ∼88% thereto. The VDW force is significantly influenced by the pressure, while the electrostatic force is slightly affected. As the water displacement differential pressure is increased, the binding energy between CH4 molecules and coal structures decreases.

Laser-Induced Ablation and Desorption of Deuterium-Containing Tungsten Films

The laser-induced desorption (LID) and laser-induced ablation (LIA) methods are compared with each other regarding the possibility of measurements an absolute quantitative analysis of hydrogen isotopes content in first wall materials of fusion reactors. Deuterium containing tungsten films with a thickness of 300–400 nm on a silicon substrate were used as model samples. To implement the LID, the samples were irradiated with laser pulses with a duration of 200 microseconds and an energy density of 50–150 J/cm2, for LIA – 12 ns and 5–15 J/cm2. The registration of residual gases was carried out by quadrupole mass spectrometry. Computer simulation of laser pulse heating was performed for the LID process. The simulation results and experimental data showed that heating at an energy density of 100–150 J/cm2 is sufficient to degas tungsten films of the studied thickness. A comparison of the amount of desorbed deuterium in the LID (150 J/cm2) and LIA (15 J/cm2) modes shows that it is identical within the measurement error and is equal to 4.15±0.15·1014 cm-2.

In Situ Conductive Heating for Thermal Desorption of Volatile Organic-Contaminated Soil Based on Solar Energy

A novel conductive heating method using solar energy for soil remediation was introduced in this work. Contaminated industrial heritage sites will affect the sustainable development of the local ecological environment and the surrounding air environment, and frequent exposure will have a negative impact on human health. Soil thermal desorption is an effective means to repair contaminated soil, but thermal desorption is accompanied by a large amount of energy consumption and secondary pollution. Therefore, a trough solar heat collection desorption system (TSHCDS) is proposed, which is applied to soil thermal desorption technology. The effects of different water inlet temperature, water inlet velocity and soil porosity on the evolution of soil temperature field were discussed. The temperature field of contaminated soil can be numerically simulated, and a small experimental platform is built to verify the accuracy of the numerical model for simulation research. It is concluded that the heating effect is the best when the water entry temperature is the highest, at 70 °C, and the temperature of test point 4 is increased by 50.71% and 1.42%, respectively. When the inlet water flow rate is increased from 0.1 m/s to 0.2 m/s, the heating effect is significantly improved; when the inlet water flow rate is increased from 0.5 m/s to 1.5 m/s, the heating effect is not significantly improved. Therefore, when the flow rate is greater than a certain value, the heating effect is not significantly improved. The simulation analysis of soil with different porosity shows that larger porosity will affect the thermal diffusivity, which will make the heat transfer effect worse and reduce the heating effect. The effects of soil temperature distribution on the removal of petroleum hydrocarbon C6–C9 and trichloroethylene (TCE) were studied. The results showed that in the thermal desorption process of petroleum hydrocarbon C6–C9-contaminated soil, the removal rate of pollutants increased significantly when the average soil temperature reached 80 °C. In the thermal desorption of trichloroethylene-contaminated soil, when the thermal desorption begins, the soil temperature rises rapidly and reaches the target temperature, and a large number of pollutants are removed. At the end of thermal desorption, the removal of both types of pollutants reached the target repair value. This study provides a new feasible method for soil thermal desorption.

Highly sustainable water mist-responsive superwetting sponge (DTMO/FS-50/Hollow-CuCo-ZIF@Sponge) for speedy pollutants removal and solvent-free regeneration

Smart solvent-responsive superwetting materials are particularly favored due to their ability to handle different types of pollutants. However, most of them rely on organic solvent vapors, and neglect the desorption efficiency of pollutants, especially using the solvent-free desorption method. A responsive sponge was fabricated by coating hollow MOFs particles with different sizes, greatly enhancing roughness and porosity, and followed by modification with short-chain fluorinated surfactants, long-chain siloxanes, tannic acid, and polydopamine. There are several advantages in this paper: (I) a hollow MOFs structure was achieved, greatly enhancing specific surface area, porosity, and active sites, which acted as a superior container for responsive modifiers network. (II) the reactions among biomass dopamine hydrochloride (PDA), tannic acid (TA), long-chain siloxanes, short-chain fluorinated surfactants and PU substrate, formed smart responsive biomass macromolecular networks, not only greatly improved adhesion between hollow MOFs and sponge substrate, but also showed enhanced synergistic effects for smart wettability transition. (III) the coated sponge showed smart responsive superwetting behaviors under environmentally friendly water mist rather than organic vapors or unfriendly vapors. (IV) the coated sponge could handle various kinds of pollutants based on polarity selection, and also quickly desorb the pollutants after change the polarity under water mist activation. The intelligent sponge can quickly and selectively adsorbed various microplastics and efficiently deal with oil-in-water and oil-in-water emulsions. It has good mechanical durability, maintaining a separation capacity of more than 88 % after repeated adsorption and desorption of MPs180 times.

Engineering of the ferrite-based support for enhanced performance of supported Pt, Pd, Ru, and Rh catalysts in hydrogen generation from NaBH4 hydrolysis

A series of M/NiCo-Ferrite (M: Pt, Pd, Ru, and Rh) nanoparticles were successfully synthesized, through a facile sol–gel auto-combustion followed by impregnation-reduction approach, as a catalyst for hydrogen generation from hydrolysis of NaBH4. All synthesized samples were characterized by XRD, N2 adsorption–desorption method, ICP-OES, FE-SEM, and EDX analysis. Compared to the other samples, it was observed that the Rh/NiCo-Ferrite sample exhibited higher particle distribution and surface area. To evaluate the hydrogen generation rate, the hydrolysis was carried out at a temperature of 35 °C, with an aqueous solution containing 5 wt.% NaBH4 and 3 wt.% NaOH. The experimental findings indicate that the Rh/NiCo-Ferrite sample exhibited a superior rate of hydrogen generation, with an average value of 11,667 mL/min.gcat, compared to the other samples studied. Enhanced catalytic properties may be responsible for its high activity. In addition, the activation energy of hydrolysis of sodium borohydride over the Rh/NiCo-Ferrite sample was 54.5 kJ/mol which is lower than the activation energy of many Ferrite-based catalysts. Moreover, the re-usability test of the Rh/NiCo-Ferrite sample denoted a decline in the catalytic activity after 4 recycling experiments due to the alterations in morphology and the reduction in the quantity of active phase.

Catalytic hydrogenation of CO2 to aromatics over indium-zirconium solid solution and sheet HZSM-5 tandem catalysts

The presence of acids and bases, coupled with its exceptional CO2 adsorption capacity and thermal stability, has established zirconia as a highly esteemed promoter and carrier. Researchers have found that the In2O3 supported ZrO2 exhibits high activity and remarkable stability. Therefore, xIn-yZr(T) solid solutions were prepared with different calcination temperatures and In/Zr molar ratios. The solid solutions were then combined with sheet HZSM-5 zeolite from tandem catalysts, which were investigated for their catalytic performance in converting CO2 to aromatics. The X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption, NH3 temperature-programmed desorption, pyridine infrared radiation, X-ray photoelectron spectroscopy, electron paramagnetic resonance, CO2 temperature-programmed desorption and H2 temperature-programmed reduction characterization methods were used to investigate the physicochemical properties of catalysts. Density Functional Theory calculations were used to investigate the energy of thermal desorption and H2 reduction to generate oxygen vacancies on the surface of In2O3(111) and Zr/In2O3(111). Additionally, the influence of oxygen vacancies on CO2 adsorption energies was simulated. It was found that the incorporation of a moderate amount of zirconium carriers promoted the generation of oxygen vacancies and provided better metal-carrier interactions. The 4In-1Zr(500 °C)/HZSM-5 tandem catalyst exhibits excellent catalytic stability, achieving a CO2 conversion of 24.3 % and aromatics selectivity of 37.3 %.

Effect of Mg modification on the catalytic performance of zinc malachite for methanol synthesis

The complex conditions of methanol production from coke-oven gas have brought challenges to the copper-based methanol synthesis catalyst. In this work, a series of zinc-malachite samples with different Mg contents were prepared. The zinc-malachite and calcined samples were characterized by in-situ X-ray diffraction (XRD), thermogravimetry-mass spectrometry (TG-MS), N2 physical adsorption, H2 programmed temperature reduction (H2-TPR), CO2 programmed temperature desorption (CO2-TPD) and other methods. The effects of Mg addition on the structure of zinc-malachite and its catalytic performance of methanol synthesis were investigated. The results showed that the addition of Mg increased the degree of Cu substitution inside the zinc-malachite structure and promoted the formation of high temperature carbonates in the catalyst after roasting. With the increase of Mg content, the specific surface area of the calcined catalyst increased gradually, and the Cu grain size decreased simultaneously. In-situ XRD results showed that a small amount of Mg could effectively inhibit the growth of copper grain size during the heat treatment. The evaluation showed that the initial activity of the catalyst increased first and then decreased with Mg addition, and the activity of the Mg-doped catalyst remained at a relatively high level after heat treatment. The appropriate Mg addition is beneficial to the initial activity and thermal stability of Cu-based methanol synthesis catalyst.

The preparation and investigation of ionic functional resins for deep dehydration of toluene

Toluene is a solvent and raw material widely used in industrial production. Reducing the water content of toluene to less than 10 mg/kg is of significant importance in fine chemicals. In this study, different ionic functional resins containing strong hydrophilic sulfonate groups were synthesized. These ionic functional resins exhibit an exceptional depth of toluene dehydration and an extremely high water absorption capacity. The most effective hydrogen functional resin has a water adsorption capacity of 679.7 mg/g, which is more than 2.5 times of 3A molecular sieve, and can dehydrate toluene from 180 mg/kg to less than 3 mg/kg. The specific surface area and pore size distribution of the resins were analyzed by nitrogen adsorption and desorption methods, and results show that these resins are mesoporous materials. The multilayer adsorption mechanism of the ionic functional resins was determined by fitting the adsorption isotherms using a Modified Dent model. The effects of contact time, oil-agent ratio, regeneration temperature, and number of regenerations were also investigated, and fixed-bed penetration curves were obtained to provide data for practical industrial applications. The results show that low-temperature drying at 80 °C is sufficient to regenerate the ionic functional resin. Finally, competitive adsorption studies with toluene and water reveal that the resin exhibit a higher affinity for water than for toluene.

Oxygen‐Rich Porous Organic Polymer for Thermal Energy Storage

Oxygen atoms have been widely used in porous organic polymers, which has attracted much attention from researchers. Herein, porous organic polymer with high oxygen content is synthesized with oxygen‐rich monomer as construction unit and anhydrous aluminum chloride as catalyst; then phase‐change materials (PCMs) composites are prepared by self‐adsorption method. The pore properties of the oxygen‐rich porous organic polymer are characterized by nitrogen absorption and desorption method. The properties of the PCM composites are characterized by scanning electron microscopy, X‐ray diffraction, Fourier‐transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The results show that the oxygen‐rich porous organic polymer has high Brunauer–Emmett–Teller surface area (465 m2 g−1) and excellent thermal stability. The PCM composites possess high encapsulation rate (50.6 wt%) and latent heat (124.7 kJ g−1). After several thermal cycles, the thermal properties of all PCM composites are almost unchanged, and no leakage phenomenon is found. It can be seen that oxygen‐rich porous polymers have potential applications in PCM adsorption and thermal energy storage.

Large‐scale synthesis of nano‐ZIF‐90 from zinc chloride application orientation heat storage materials

AbstractThe paper presents the results of the first research on the synthesis of nano‐ZIF‐90 from zinc chloride. More specifically, the paper also introduces the results of large‐scale pure nano‐ZIF‐90 synthesis with a high specific surface, uniform cubic crystals, and good thermal strength. ZIF‐90 is synthesized from zinc chloride‐containing medium capillaries, which have both a weak acid center and a strong base center. The post‐synthetic ZIF‐90 was also evaluated for heat storage based on its ability to adsorb water, methanol, and ethanol. XRD, FTIR, SEM, TEM, N2 adsorption and desorption methods, TG mass thermal analysis, and NH3‐TPD/CO2‐TPD were used to study the ZIF‐90 crystallization process with modifications of precursors, solvents, additives, and reaction conditions. From this, a large‐scale synthesis of nano‐ZIF‐90 from high‐efficiency zinc chloride has been derived. DSC measurements are used to evaluate the enthalpy adsorption of water, methanol, and ethanol on ZIF‐90.

Study on the regeneration of activated carbon adsorbed with radon by using a deep depressurization method

ObjectiveTo develop a heating-free, rapid, and efficient method for the regeneration of activated carbon by introducing deep depressurization. MethodsA validation experimental setup was designed to systematically investigate the impacts of various desorption methods, durations, and conditions on the desorption effectiveness of activated carbon with adsorbed radon and water. Consecutive repetitive and expanded experiments were carried out. ResultsThe combination of continuous ventilation and deep depressurization was proved the most effective in the desorption of activated carbon. Considering factors such as overall energy consumption and time, the optimal desorption duration for activated carbon was determined at 2 ​h. Reducing the relative humidity of radon-laden air and increasing the desorption environmental temperature significantly enhanced the desorption rate. Under a temperature range of 24–25°C, a relative humidity range of 5%–15%, and a flow rate of 0.3 ​L/min, a desorption rate of 85% was achieved for 122.5 ​g of activated carbon after 2 ​h of desorption. Moreover, the desorption results remained stable throughout 10 repetitions. Further experiments on a kilogram-scale activated carbon bed demonstrate that under a vacuum level meeting the requirement for moisture evaporation and an appropriate flow rate, the desorption rate of the activated carbon reached that of a smaller activated carbon bed, independent of the shape of the activated carbon bed. ConclusionThe deep depressurization method shows great promise as a rapid and efficient online method for the regeneration of activated carbon with adsorbed radon and water.

Efficient adsorption performance and mechanism of fluoroquinolone antibiotic onto the acid wash-assisted Co NPs/N-C adsorbent

In this study, ZIF-67 was employed as a template, and applied a novel combined treatment method of thermal and acid treatment to provide rapid mass transfer channels and additional adsorption sites for pollutant molecules, thus achieving high adsorption capacity and shorter adsorption time. The adsorption of Co NPs/N-C on ciprofloxacin reached equilibrium within 70 min with a maximum adsorption capacity of 486.20 mg·g−1. Furthermore, the adsorption capacity was enhanced by 1.9 times after acid-wash. The fitted data indicated that the pseudo-second-order kinetics model could more accurately describe the adsorption process, with intraparticle diffusion and liquid film diffusion jointly determining the adsorption rate, primarily involving chemical adsorption. The Langmuir model best described the antibiotic adsorption isotherm, indicating monolayer adsorption on Co NPs/N-C. Based on various characterizations before and after adsorption, it was confirmed that antibiotics were adsorbed onto Co NPs/N-C through hydrogen bonding and π-π interactions. Additionally, this adsorbent exhibited strong continuous treatment capability, a simple and efficient desorption method, as well as efficient treatment efficiency for actual water bodies. This study suggests that Co NPs/N-C can be considered an efficient and promising adsorbent, and the proposed strategy can potentially serve as an antibiotic adsorbent for continuous wastewater treatment.

CO2 desorption and mass transfer characteristic study in micropacked bed reactors

The chemical desorption method with amine-based solvent have been widely applied in CO2 capture and storage (CCS) industrial. However, there is still exist mass transfer limitation and difficult to achieve packing/catalyst immobilization in conventional reactors for CO2 desorption process. In this work, micropacked bed reactors (μPBRs) with glass beads are adopted to investigate CO2 desorption performance. Effects of absorbent type, temperature, initial concentration of absorbent, liquid superficial velocity, initial loading of absorbent, particle size, and N2 superficial velocity on the desorption efficiency and desorption rate are discussed. The desorption efficiency of μPBR is 36 ∼ 81 % based on the MDEA absorbent. The value of desorption rate in μPBR is from 0.38 to 3.37 mmol/min, which is bigger than microchannel reactor. Liquid phase mass transfer coefficient of μPBR is 0.06 ∼ 1.38 s−1 for CO2 desorption process, which is 1–3 orders higher than that of packed column. Then, an empirical correlation of mass transfer coefficient is developed in μPBR. μPBR has a high mass transfer rate with an advantage of fixed packing/catalyst compared with other CO2 desorption equipment.

Systematic analysis of dual-functional catalysts for simultaneous CO-NOx reduction: Toward an effective catalyst design strategy

The development of a multifunctional catalyst suitable for application in existing facilities with limited space, with specific emphasis on its capability to concurrently remove CO and NOx is vital for meeting stringent environmental regulations. This is particularly pertinent to industries such as liquefied natural gas-based power plants and multipollutant-emitting industrial facilities. Another important consideration is that the catalyst should operate over a wide temperature range to facilitate its application across various industrial sites. In this study, we synthesized vanadium-based catalysts with a series of noble metals (Pt, Pd, and Au). The V–W–Pd/TiO2 catalyst achieved a simultaneous CO–NOx reduction efficiency greater than 90% in the widest temperature range, 228–321 °C. The excellent catalytic activities resulted from the Pd active sites, which oxidated CO and adsorbed NOx. This enables the catalyst to easily participate in the NH3-SCR reaction and facilitates NOx reduction. Moreover, we systematically analyzed the reaction properties of each catalyst using diffuse reflectance infrared Fourier transform and temperature programmed desorption methods. This enabled the elucidation of the reaction characteristics and competitive adsorption properties of the catalysts.

Establishment of a headspace-thermal desorption and gas chromatography-mass spectrometry method (HS-TD-GC-MS) for simultaneous detection of 51 volatile organic compounds in human urine: Application in occupational exposure assessment

Volatile organic compounds (VOCs) are a group of ubiquitous environment pollutants especially released into the workplace. Assessment of VOCs exposure in occupational populations is therefore a crucial issue for occupational health. However, simultaneous biomonitoring of a variety of VOCs is less studied. In this study, a simple and sensitive method was developed for the simultaneous determination of 51 prototype VOCs in urine by headspace-thermal desorption coupled to gas chromatography-mass spectrometry (HS-TD-GC-MS). The urinary sample was pretreated with only adding 0.50 g of sodium chloride to 2 mL of urine and 51 VOCs should be determined with limits of detection (LODs) between 13.6 ng/L and 24.5 ng/L. The method linearity ranged from 0.005 to 10 μg/L with correlation coefficients (r) of 0.991 to 0.999. The precision for intraday and inter-day, measured by the variation coefficient (CV) at three levels of concentration, was below 15 %, except for 4-isopropyl toluene, dichloromethane, and trichloromethane at low concentration. For medium and high levels, recoveries of all target VOCs were within the standard range, but 1,1-dichloropropene and styrene, which were slightly under 80 % at low levels. In addition, the proposed method has been used to determine urine samples collected in three times (before, during and after working) from 152 workers at four different factories. 41 types of prototype VOCs were detected in workers urine. Significant differences (Kruskal-Wallis chi-squared = 117.18, df = 1, P < 0.05) in the concentration levels of VOCs between the exposed and unexposed groups were observed, but not between the three sampling times (Kruskal-Wallis chi-squared = 3.39, df = 2, P = 0.183). The present study provides an alternative method for biomonitoring and assessing mixed exposures to VOCs in occupational populations.