Adsorption Of Toxic Gas Research Articles

Theoretical Study and Application of Doped 2D PbSe for Toxic Gases

Herein, 2D doped PbSe is used to design a gas sensor to monitor the presence of SO2 and Cl2. The stability and feasibility of doped materials are studied. Based on first principles, the adsorption of toxic gases by 2D doped PbSe is verified by density of states, Bader charge, electron localization function, and differential charge density calculations. The calculation results show that Ge1Ge3 and Sn1 are suitable for adsorption of Cl2, and the bandgap decreases by roughly 69%. Ge1Ge2 and Sn1 are suitable for adsorption of SO2, and the bandgap decreases by roughly 38%. This provides the possibility of designing gas sensors for SO2 and Cl2 based on 2D doped PbSe.

Flower-like ZnO Nanostructures Local Surface Morphology and Chemistry

This work presents the results of comparative studies using complementary methods, such as scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), and thermal desorption spectroscopy (TDS) to investigate the local surface morphology and chemistry of flower-like ZnO nanostructures synthesized by the thermal oxidation technique on native Si/SiO2 substrates. SEM studies showed that our flower-like ZnO nanostructures contained mostly isolated and irregular morphological low-dimensional forms, seen as rolled-up floss flowers, together with local, elongated, complex stalks similar to Liatris flowers, which contained joined short flosses in the form of nanodendrites. Beyond this, XPS studies showed that these nanostructures exhibited a slight surface nonstoichiometry, mostly related to the existence of oxygen-deficient regions, combined with strong undesired C surface contamination. In addition, the TDS studies showed that these undesired surface contaminations (including mainly C species and hydroxyl groups) are only slightly removed from the surface of our flower-like ZnO nanostructures, causing an expected modification of their nonstoichiometry. All of these effects are of great importance when using our flower-like ZnO nanostructures in gas sensor devices for detecting oxidizing gases because surface contamination leads to an undesired barrier for toxic gas adsorption, and it can additionally be responsible for the uncontrolled sensor aging effect.

Adsorption and gas-sensing properties of Aun (n = 1–3) cluster doped MoTe2 for NH3, NO2, and SO2 gas molecules

In this study, density functional theory calculations were adopted to investigate the adsorption of toxic gases (NH3, NO2, and SO2) on Aun (n = 1–3) doped MoTe2 monolayer. The adsorption structure, band structure, charge transfer, density of states, and molecular orbit were analyzed to better understand the interaction between the gases and the substrates. The results show that the conductivity of MoTe2 monolayer is improved after doping Au atoms. And pristine MoTe2 has poor adsorption capacity for NH3, NO2, and SO2, which belongs to physical adsorption. Compared to pristine MoTe2, the adsorption capacity of these three gases on Aun-MoTe2 is obviously improved. Moreover, Au3-MoTe2 monolayer has strong stability, and its structure hardly deforms after adsorbing gas. In addition, DOS analysis results show that Aun-MoTe2 has the strongest interaction with NO2, while the interaction with NH3 is the weakest. Molecular orbital analysis shows that the conductivity of the systems affected by gas molecules is in order of NO2 > SO2 > NH3 for Au-MoTe2 and Au2-MoTe2, and SO2 > NO2 > NH3 for Au3-MoTe2. These results provide a theoretical basis for the preparation of gas sensors based on Aun-MoTe2 used in industrial toxic gases detection.

Density functional theory investigation of As4 adsorption on Ti, V, Cr, Mn-doped graphene

Coal gasification technology can effectively solve the problem of clean coal utilization, but the problem of volatilization of harmful metals such as arsenic in the coal gasification process cannot be underestimated. In this paper, based on DFT (density functional theory), the adsorption characteristics of As4 on the surface of different carbon-based single-atom Ti/V/Cr/Mn adsorbents (nitrogen atom-doped, single vacancy and double vacancy) were studied. The single-atom adsorbent geometry, adsorption configuration, adsorption energy, electronic structure, electron density and other data were analysed. By comparing and analysing the calculation results of sixteen adsorbents, it is found that the catalyst with the double-deficient nitrogen-doped substrate has higher stability. Through the analysis of charge transfer and density of state, it was found that the adsorption of a single-atom adsorbent catalyst to As4 is related to charge transfer and hybridization. In particular, doped nitrogen atoms can enhance the charge transfer and hybridization of the system. amongst the sixteen adsorbents, the double-vacancy nitrogen-doped Ti catalyst is a promising As4 adsorbent, which provides a reference for further research on the adsorption of toxic gases on the surface of single-atom catalysts and the design of new nonnoble metal adsorbents.

Effect of amine type on acidic toxic gas adsorption at ambient conditions on modified CuBTC

Two amine-modified copper-based Metal Organic Frameworks (MOF (CuBTC)) of different surface chemical and textural features were synthesized and used as adsorbents of acidic toxic gases (NO2 and H2S) in both moist (71% relative humidity (R.H.)) and dry conditions. The initial and exhausted samples were characterized by nitrogen adsorption, powder X-ray diffraction, scanning electron microscopy, thermal gravimetric analysis and Fourier transform infrared spectroscopy. The addition of melamine prevented full growth of CuBTC crystals and resulted in amorphous-like particles with sizes less than 200 nm. The material was non-porous with a small surface area. When urea was used as an amine source, the resulting particles maintained the overall octahedral shape of the parent CuBTC MOF and the material was more porous than the parent MOF. While the urea-modified CuBTC sample performed well as an NO2 adsorbent in the presence of moisture, the reactivity of the melamine-modified sample and its physical properties provided a favorable environment for the removal of H2S. The incorporation of amines into the MOF structure also resulted in surface defects /open copper sites that favored the removal of toxic gases in dry conditions. The reactivity of the adsorbents with toxic gases was demonstrated by the changes in the adsorbent colors, in texture, and in surface chemistry (organic salts, complexes, sulfides and nitrates were formed).

Removal of sulfur dioxide by carbon impregnated with triethylenediamine, using indigenously developed pilot scale setup.

In order to provide protection against extremely toxic gases, activated carbon (AC) adsorption has long been regarded to be a useful technology in terms of gas removal. AC without chemical impregnation has been considerably less effective than impregnated ACs. AC in present use was modified with an organic amine, i.e., triethylenediamine (TEDA) to enhance the physical and chemical properties of AC in order to remove specific poisonous gases. With the rising concern on environmental pollution, there has been an increased curiosity in ACs as the means for eliminating pollutants from environment. Purpose of this study was to assess the TEDA impregnated AC in terms of adsorption capability for simulant gas like SO2. Analysis was done in a properly designed setup. By using the scheme reported here, significant adsorption of toxic gas was obtained. Maximum removal capability observed by AC-4 for SO2 gas was 374 mg/g-C and its breakthrough time was 264 min. Breakthrough time and adsorption capacity of AC-4 was found to be 25 times and 10 times greater as compared to raw AC. Different characterization techniques were also used to study impregnated AC. It was found that chemical adsorption was the crucial means by which TEDA-impregnated AC removed the simulant gas. Langmuir model was best to represent equilibrium, and adsorption kinetics follow second-order model. The process was endothermic, favorable, and spontaneous.

Investigating the Influence of Hexanuclear Clusters in Isostructural Metal-Organic Frameworks on Toxic Gas Adsorption.

The efficient capture of toxic gases, such as ammonia (NH3) and sulfur dioxide (SO2), can protect the general population and mitigate widespread air pollution. Metal-organic frameworks (MOFs) comprise a tunable class of adsorbents with high surface areas that can meet this challenge by selectively capturing these gases at low concentrations. In this work, we explored how modifying the metal ions in the node of an isostructural MOF series from a transition metal to a lanthanide or actinide influences the electronic environment of the node-based active site. Next, we investigated the adsorption properties of each MOF toward the relatively basic NH3 and relatively acidic SO2 gases. Within the NU-907 family of MOFs, we found that Zr6-NU-907 exhibits the best uptake toward NH3 at low pressures, while Th6-NU-907 demonstrates the best low-pressure performance for SO2 adsorption. Tracking the infrared (IR) stretching frequency of the node-based μ3-OH groups provides insights into the electronegativity of the metal ion and suggests that the most electronegative metal ion (Zr) affords the node with the best NH3 uptake at low pressures. In contrast, the Th6 node contains additional coordinated water groups relative to the other M6 nodes, which appears to yield the MOF with the greatest affinity for SO2 uptake that occurs predominately through reversible physisorption interactions. Finally, in situ NH3 IR spectroscopic studies indicate that both NH4+ and Lewis-bound NH3 species form during adsorption. Combined, these results suggest that tuning the electronic properties and structure of the node-based active site in an MOF presents a viable strategy to change the affinity of an MOF toward toxic gases.

Adsorption of toxic gases on metal doped C3N monolayer: A theoretical study

In this work, the adsorption properties of toxic gases (NOx and SO2) on metal (Ag, Cu, Al) doped C3N monolayer are studied by using the first principle calculation. To explore the possible application of doped C3N monolayer as NO2 and SO2 gases detection and capture materialsmetal, the structure and the adsorption behavior of gases in different doped C3N are studied along different directions. At the same time, we also consider the behavior of adsorption of gas molecules (H2O, N2, NO). The results show that metal doped C3N is a promising ideal material, which can be used as an ideal adsorbent and good sensing material for NOx and SO2.

Reconfigurable Modular Platform for Prolonged Sensing of Toxic Gases in Particle Polluted Environments

The prolonged sensing of toxic gases in polluted particles and harsh environments is a challenging task that is also in high demand. In this work, the proof of principle of a sensitive, low-cost, and low-maintenance reconfigurable platform for filter-free and continuous ammonia (NH3) sensing in polluted environments is simulated. The platform can be modified for the detection of various toxic gases and includes three main modules: a microfluidic system for in-line continuous dust filtering; a toxic gas adsorption module; and a low-frequency microwave split-ring resonator (SRR). An inertia-based spiral microfluidic system has been designed and optimized through simulation for the in-line filtration of small particles from the intake air. Zeolite Y is selected as the adsorbent in the adsorption module. The adsorption module is a non-metallic thin tube that is filled with zeolite Y powder and precisely fixed at the drilled through-hole into the 3D microwave system. For the sensing module, a low-frequency three-dimensional (3D) split-ring resonator is proposed and optimally designed. A microwave resonator continuously monitors the permittivity of zeolite Y and can detect small permittivity alterations upon the presence of ammonia in the intake air. The microwave resonator is optimized at a frequency range of 2.5–3 GHz toward the detection of ammonia under different ammonia concentrations from 400 to 2800 ppm. The microwave simulation results show a clear contrast of around 4 MHz that shifts at 2.7 GHz for 400 ppm ammonia concentration. The results show the proof of principle of the proposed microfluidic-microwave platform for toxic gas detection.

Room Temperature Gas Sensor Application of Carbon Nanowalls using Electrical Resistance Change by Surface Adsorption of Toxic Gases

Carbon is not only a readily available material, but also has appropriate properties through various structural modifications. Carbon nanowalls (CNWs), based on carbon with vertical porous nanostructure, offer broad sensing surface area. Using carbon nanowalls, we demonstrated it function as gas sensing layer in our work. Carbon nanowalls synthesized via plasma enhanced chemical vapor deposition (PECVD) was in form numerous nanoflakes. In addition, various defect on its surface with high D band and low G band in Raman spectra was observed. When ammonia (NH3) and nitrogen dioxide (NO2) that may cause environmental pollution as an analyte gas were adsorbed on carbon nanowalls during exposing to them, difference in electrical resistance over 300 percentage between ammonia and nitrogen dioxide appeared. In various characteristics such as response time, sensitivity, saturation-recovery and selectivity, carbon nanowalls-based gas sensor exhibited better performance in nitrogen dioxide than ammonia. The reason for these performance is that the charge transfer of nitrogen dioxide greater than that of ammonia. In addition, the electron affinities of ammonia and nitrogen dioxide are 0.55 ± 0.10 and 2.11 ± 0.18 eV, respectively, which may sufficiently affect the each reaction between two analyte gases. Through this work, we offer several results of the proof-of-concept study for the gas sensor application of carbon nanowalls.

Study of toxic gas adsorption on silicon substrate integrated with piezoelectric material for sensing application using COMSOL Multiphysics

This paper aims to study the analytical response of micro cantilever based gas sensor for the quantification of NOx gas molecules, simultaneously discussing the possibility of a different measurement technique. Numerous packed and digital gas sensors are available in the market, but each with its own limits. MEMS sensors provide smart working, portable, save space, and reusable. Hence the micro cantilever beam deposited with an active material such as palladium, reduced graphene oxide to monitor and obtain the concentration of NOx was identified in terms of deflection for deposited mass. The physics and study provided by COMSOL Multiphysics will be exploited for the current usage. Various materials such as silicon and diamond as a substrate were simulated and compared. This paper discussed about the different micro cantilever beam structures for the gas sensing mechanism and selects the better structure based on their deformation in structure due to applied mass. The excellent trapping substrate material for NOx is chosen. A new measurement technique using piezoelectric material will be discussed. The proposed method will be discussed based on their pros and cons by compared with other sensors. The drawbacks of the proposed technique are also highlighted. Overcoming the drawback of conventional measurement methodology and devising a novel sensor to make it compatible for gas sensing.

Adsorption of toxic gases on borophene: surface deformation links to chemisorptions.

β12 borophene has received great attention because of its intriguing mechanical and electronic properties. One of the possible applications of borophene is gas sensing. However, the interaction between common gases and β12 borophene remains to be clarified. In this work, we study the interactions of β12 borophene towards five hazardous gases, namely, CO, NO, NH3, NO2, and CO2 using various non-empirical van der Waals density functionals and provide an insight into the adsorption behavior of borophene. The adsorption mechanism and molecular vibrations are discussed in great detail. Among the gases considered, CO2 is physisorbed while other gases are chemically bonded to β12 borophene. We also demonstrate that the deformation at the ridge of borophene enables its active pz orbital to strongly hybridize with frontier orbitals of the studied polar gases. Consequently, borophene is predicted to interact strongly with CO, NO, NH3, and especially NO2, making it a sensitive sensing material for toxic gases.

Fractal approach to concentration distribution of atmospheric fine particle sizes

With the increase of particulate pollution in the atmosphere, it becomes extremely significant to understand the overall distribution characteristics of particulates and their adsorption of toxic gases for the source analysis and precise controlling of atmospheric particulate matters. The fractal theory was adopted to analyze particle sizes distribution characteristics in Xi?an city, China. Results showed the fractal dimension of particulate matters distribution ranged from 4.32-4.83, with an average fractal dimension of 4.54. A higher fractal dimension predicts a higher concentration of fine particles. Additionally the effects of outdoor temperature, humidity, and wind speed on the fractal dimension were also studied experimentally

Environmental applications of carbon-based materials: a review

Environmental pollution is a major issue, yet actual remediation techniques are limited. Carbon-based materials are increasingly used to treat air and water. Here we review the applications of carbon nanomaterials made of biochar, activated carbon, carbon nanotubes and graphene for the adsorption of toxic gases, the removal of pollutants from ecosystems, and the improvement of anaerobic digestion. Carbon materials have been found efficient in removing nitric oxide, hydrogen sulfide, heavy metals, dyes, pharmaceutical compounds and other pollutants from the environment, with adsorption efficiencies reaching 80% and degradation efficiencies up to 99%. Biochar addition induces a 60% improvement in biogas production. Similarly, in composting, up to 60% less ammonia emissions were observed when biochar was added. Biomass-based carbon materials appear economical, sustainable and eco-friendly.

Screening of Porous Materials for Toxic Gas Adsorption: Classical Density Functional Approach

A computer-aided method was developed to screen promising toxic gas adsorbents. The method was based on classical density functional theory (CDFT) with molecular models constructed using quantum de...

Adsorption of organic and inorganic pollutants on activated bio-carbons prepared by chemical activation of residues of supercritical extraction of raw plants

Abstract Activated bio-carbons were developed from residues of supercritical extraction of raw plans such as: raspberries, blackcurrant, nettle and green tea. The physicochemical properties of the activated bio-carbons were characterized by low-temperature nitrogen sorption and Boehm titration. All materials were used for the adsorption of methylene blue and methyl red from liquid phase. The influence of different parameters such as initial concentration, contact time and pH of dyes solution on the effectiveness of organic dyes adsorption was evaluated. The possibility of using the Langmuir and Freundlich isotherm models for description of the character of the sorption processes was checked. The experimental data were found to be well described by the pseudo-second order model. All materials were also used for nitrogen dioxide adsorption form gas phase. The presence of steam in the stream of gases has a positive effect on adsorption of toxic gas by bio-sorbents obtained. The maximum sorption capacity of the activated bio-carbons towards methylene blue was 146 mg/gads, methyl red −103 mg/gads while that towards nitrogen dioxide was 81 mg/gads. The most effective adsorbent of organic and inorganic pollutants proved to be the activated bio-carbon obtained from the residues of supercritical extraction of raspberries.

Adsorption of toxic gases on molecularly imprinted polymer coated QCM: measurements and modeling for partial pressure in gas mixture

An adsorption-based array sensor coated with different molecularly imprinted polymers (MIPs) was fabricated to effectively and simultaneously detect specific volatile organic compounds (VOCs) such as benzene and isopropyl methyl ketone (IMK). The synthesized MIPs showed remarkable recognition properties such as sensitivity and selectivity for their target molecule. Furthermore a detection method for array sensors was formulated based on several adsorption equilibrium isotherm models to determine individual partial pressures in the VOCs mixture from the overall adsorption capacities on array sensor elements. The results indicated that the detection method provided relatively good predictions for binary target species within the experimental error.

Multistimuli-Responsive Self-Healable and Moldable Nickel(II)-Based Gels for Reversible Gas Adsorption and Palladium Sequestration via Gel-to-Gel Transformation.

We report the in situ formation of Ni-based supramolecular organogel and organic-aqueous gels using amine appended triazole ligand, having varying morphology and rheological properties. These gels are self-healable and moldable or injectable respectively depending on the absence or presence of water in the gelation medium. Our studies reveal that the formation and rupture of hydrogen bonds assisted by the solvent movement is responsible for the self-healing nature of the gels. The porous structure of the gel has been observed from the migration of dye molecules on the self-healed gel. In addition, the gels show dual function of reversible adsorption of toxic gases and sequestration of heavy metal ions, especially palladium via gel-to-gel transformation. It is imperative to stress that such transformation is extremely rare for small molecule based metallogels. The dynamic nature of Ni-Ntriazole interactions has been utilized in achieving the reversible gas/vapor responsive behavior of the metallogels, which could be suitable in developing colorimetric probes for the detection of toxic gases and heavy metal ions. Such multifunctional gels are exceptional in contemporary literature and are expected to find utility in fabricating smart multistimuli-responsive gel-based materials in the future.

Design of double-component metal–organic framework air filters with PM2.5 capture, gas adsorption and antibacterial capacities

A biodegradable cellulose-based air filter (Ag-MOFs@CNF@ZIF-8) with multi-layer structure was fabricated by in situ generation of double-component metal-organic frameworks (MOFs) and reinforcement of cellulose nanofiber (CNF). It exhibits good filtration performance, gas adsorption, antibacterial activity and mechanical property. The presence of MOFs could enhance the interaction between the filter and particulate matter (PM) and significantly improve the specific surface area of the composite filter. Thus, the filtration efficiency of the composite filter could reach 94.3% for PM2.5 and the nitrogen adsorption capacity increased to 109 cm3 g−1. Furthermore, the Ag-MOFs@CNF@ZIF-8 filter exhibited excellent antibacterial activity against Escherichia coli with an inhibition zone diameter of 18.1 mm. The compressive strength of the composite filter could be up to 501 kPa, approximately 3.8 times higher than that of pure cellulose filter. Herein, this composite filter has a great application potential in PM2.5 removal, toxic gas adsorption and healthcare fields.

Chemical activation of biochar for energy and environmental applications: a comprehensive review

Abstract Biochar (BC) generated from thermal and hydrothermal cracking of biomass is a carbon-rich product with the microporous structure. The graphene-like structure of BC contains different chemical functional groups (e.g. phenolic, carboxylic, carbonylic, etc.), making it a very attractive tool for wastewater treatment, CO2 capture, toxic gas adsorption, soil amendment, supercapacitors, catalytic applications, etc. However, the carbonaceous and mineral structure of BC has a potential to accept more favorable functional groups and discard undesirable groups through different chemical processes. The current review aims at providing a comprehensive overview on different chemical modification mechanisms and exploring their effects on BC physicochemical properties, functionalities, and applications. To reach these objectives, the processes of oxidation (using either acidic or alkaline oxidizing agents), amination, sulfonation, metal oxide impregnation, and magnetization are investigated and compared. The nature of precursor materials, modification preparatory/conditions, and post-modification processes as the key factors which influence the final product properties are considered in detail; however, the focus is dedicated to the most common methods and those with technological importance.