High Adsorption Energy Research Articles

Adsorption of pentabromodiphenylether pollutant by metals (Si, Ge, Sn) encapsulated Zn12O12 nanoclusters: a computational study

Abstract In recent times, the use of nano-materials as detectors and sensors for various environmental systems is constantly being explored; however, the detection limit of most analytical instruments remains below the mark of 100 % efficiency. As a result, the efficacy of Zn 12 O 12 , Si dop Zn 12 O 12 , Ge dop Zn 12 O 12 , Sn dop Zn 12 O 12 and Pb dop Zn 12 O 12 nanostructured materials is examined in this work to detect 2,2,4,4,5-pentabromodiphenylether (dbph). Density functional theory (DFT) utilizing the ωB97XD/def2svp method was employed to investigate the sensor properties and adsorption potency of the nano-materials under consideration. Interestingly, dbph@Zn 12 O 12 emerged the best candidate for the efficient sensing of dbph with highest adsorption energy and minimal adsorption distance of −0.0554 kJ/mol and 2.8324 Å respectively. In the same vein, dbph@Zn 12 O 12 was shown to have the greatest stability, conductivity and least reactivity with energy gap value of 8.3299 eV for the adsorption of dbph. More so, the predominance of strong electrostatic bonds in the chemical interactions of the electrons in the QTAIM analysis follows the order; dbph@Zn 12 O 12 > dbph@Sn dop Zn 12 O 12 > dbph@Pb dop Zn 12 O 12 > dbph@Ge dop Zn 12 O 12 > dbph@Si dop Zn 12 O 12 . It follows from the data obtained herein that dbph@Zn 12 O 12 complex is the most stable and energetically favorable for the adsorption of dbph. This showed that Zn12O12 is a potential nanomaterial for detecting the presence of dbph compared to the studied nanomaterials.

Experimental and quantum chemical investigation into the nature of jet fuel deposition on surfaces

Chemical analysis of undissolved deposits formed on a simulated jet fuel burner feed arm suggest a higher concentration of oxidized polar fuel species at the wall-deposit interface. To investigate the nature of their adsorption, the adsorption energies of various jet fuel species classes were calculated using plane-wave DFT methods on two oxide surfaces Fe2O3-(0001) and Cr2O3-(0001), which were chosen to represent a stainless steel surface. A mixed termination approach was chosen to encapsulate the heterogeneous nature of stainless steel surfaces. On metal-terminated Fe2O3 and Cr2O3 surfaces, the order of the absolute adsorption energies was RSO3H > RSO2H > RCOOH > RSH > ROH > RCOH > RH. Dissociative chemisorption was observed for all the acid species, with sulfur acids having a higher absolute adsorption energy on Cr2O3 but carboxylic acids having a higher adsorption energy on Fe2O3. On oxygen-terminated Fe2O3, the order of the absolute adsorption energies was RSO2H > RSR > RSO3H > RSH > ROH > RCOH > RCOOH > RH. On the other hand, for oxygen-terminated Cr2O3, the order of the absolute adsorption energies were RSO2H > RSR > RSH > RSO3H > RCOH > ROH > RCOOH > RH. In contrast to the metal terminated surface, acids do not chemisorb on the oxygen terminated surfaces. Instead, the sulfur acids are found to form surface hydroxyl species from the dissociation of the acidic -OH group. The reactivity of the surfaces followed the general pattern: metal terminated-Fe2O3> metal-terminated Cr2O3, oxygen-terminated Fe2O3≈ Cr2O3. Overall, a combination of experimental and quantum chemical techniques confirmed the theory that sulfur acids are the initial species to deposit on stainless steel.

The potential of 2D carbon nitride monolayer as an efficient adsorbent for capturing mercury: A DFT study

Owing to its large surface area and the close similarity between nitrogen and mercury (Hg) in C3N, two-dimensional C3N monolayer has the potential of controlling the release of gaseous Hg0. Using density functional theory (DFT), we investigated the adsorption and conversion mechanism of Hg species on this monolayer surface. The findings demonstrated that C4N2 site on the surface of the C3N monolayer is more capable of adsorbing Hg0 than C6 site. Also, the recovery time of the C3N monolayer for Hg0 was approximately 17.63 s and 3.49 μs at 298 and 400 K, respectively. The analyses of electronic structure, charge transport, geometric structure, and adsorption stability demonstrated that the C3N monolayer is an encouraging material for Hg0 adsorption. The C3N monolayer could adsorb the oxidizing species of mercury (namely HgBr, HgCl, HgS, and HgO,) more easily than Hg0, with higher adsorption energy. Overall, the C3N monolayer is a promising sorbent material, which is capable of controlling gaseous mercury in an efficient way.

Sulfur vacancies-induced electron delocalization effect of cobalt sulfide for enhanced catalytic activation of peracetic acid and norfloxacin degradation

Antibiotics have attracted widespread attention due to their potential risks to human health and environment. In this study, a heterogeneous advanced oxidation process (AOP) of peracetic acid (PAA) activation by cobalt material was developed to degrade a typical antibiotic, norfloxacin (NOR). Cobalt sulfide materials with sulfur vacancies (CoSx) were synthesized through a two-step hydrothermal process. The optimized material (CoSx-2) could efficiently activate PAA system, achieving 91.8% NOR degradation in 5 min. The Co(II)/Co(III) species in CoSx was key to activating PAA, as Co(II) initiated the reaction and Co(III) activation caused the production of CH3C(=O)OO• species. Moreover, the presence of sulfur vacancies (VS) led to the generation of hydroxyl radicals (•OH) and singlet oxygen (1O2) via chain reactions with CH3C(=O)OO•. Density functional theory (DFT) calculations reveal the contribution of VS to enhanced catalytic PAA activation, as the lower work function (5.76 eV), higher adsorption energy (-3.43 eV), bridge effect of delocalized electrons and shifted d-band center are achieved to reduce the energy barrier for electron transfer during catalytic reaction. In addition, DFT calculation on Fukui index further explains that 18 N and 21 N are reactive sites of NOR for electrophilic attack, leading to primary degradation pathways of C–N cleavage, defluorination, dealkylation and hydroxylation. This study gives a new perspective on the regulation of material structure for efficient activation of PAA and promotes the practical application of heterogenous PAA-based AOPs for emerging contaminants removal in water treatment process.

Two-dimensional GeSe monolayer doped with single main-group element atom for hazardous gas detection: A first-principles study

Currently, the identification of sensing materials that can selectively and rapidly respond to hazardous gases is urgent for safeguarding the environment and human life. The adsorption of hazardous gas molecules (NO, NO2, SO2, CO, and H2S) on the GeSe monolayer doped with single main-group element atom is investigated and compared based on first-principles density functional theory (DFT). NO2 has the highest adsorption energy and charge transfer adsorbed on both pristine GeSe and doped GeSe monolayer. At ambient temperature, for any doped GeSe monolayers adsorbing gas molecules (including H2O, O2, and N2), the occupation function value of NO2 is the highest. The analysis of density of states (DOS) and band structure indicates that NO2 interacts with different modified GeSe monolayers in terms of atomic orbitals. Moreover, Al-GeSe has the largest change of work function before and after the adsorption of NO2, meaning that Al-GeSe has the greatest response to NO2. current-voltage (I-V) characteristics demonstrate that Al-GeSe exhibits a remarkable current change after the adsorption of NO2. These results illustrate that Al-GeSe has a strong physical and chemical interaction with NO2, yielding a high response and selectivity, which is anticipated to be the optimal gas sensing material for NO2.

Adsorption studies of dye molecule on two-dimensional assembly of porphyrin using density functional theory

<p>Highly toxic dye molecules can be found in trace amounts in the treated effluent from several industrial wastes. A challenging research area of this decade is the dye treatment and adsorption from the effluents of these industries using low-cost alternative adsorbents. Recent studies have demonstrated the effectiveness of metal oxides and porous materials in the adsorption of dye, so we have taken into consideration an organic porous material made with metal free porphyrin. The adsorption of dye molecules on the surface of the porphyrin sheet is investigated. Porphyrin is an organic substance with several special properties. Density functional theory (DFT) is used to investigate the adsorption of charged and neutral dye, as well as complex heavy metal dye, on the surface of porphyrin sheets. Positive dye has a higher affinity for the adsorbent than negative dye, according to the data on adsorption; however, complex dye has a higher adsorption energy than the other dyes, which is consistent with the cohesive energy of the PS-dye complex. In the present work the adsorbing capacity of PS for different dye molecules is demonstrated by the topological analysis and DFT calculations on the electronic structure.</p>

Facile wet mechanochemistry coupled K2FeO4 activation to prepare functional coal-derived hierarchical porous carbon for supercapacitors

The high power characteristics of supercapacitors (SC) are attractive for grid scale energy storage. The core to achieve the large scale application of SC lies in the preparation of high performance electrode materials. Herein, a facile wet mechanochemistry (WMC) coupled K2FeO4 activation is used to fabricate O/N/S doped coal-derived hierarchical porous carbon (CHPC). K2FeO4 generates high-energy sputtering O2 under mechanical force to impact precursor, leading to an increase in lattice defects, and full exposure of active sites, which facilitates activation of precursor and coupling of heteroatoms. Furthermore, K2FeO4 has the pore forming ability of K-based component and the catalytic graphitization effect of Fe-based component, which could synergistically regulate pore structure and graphitization of CHPC. Experimental exploration combined with density functional theory calculation showed that the unique micro-mesopores structure of CHPC provides a fast ion transport channel and a large ion accessible specific surface area (SSSA). Meanwhile, the high heteroatom doping and graphitization synergistic promote ion storage (high adsorption energy, Eads) and electron transport. The specific capacitance (C) of optimized CHPC900 can obtain 335 F g−1 under 0.5 A g−1. The C retention is 96.2% after 10,000 cycles at 1 A g−1. CHPC900//CHPC900 delivers remarkable energy/power characteristics (9.9 Wh kg−1 of 125 W kg−1).

The solution of wetting issues in GaN epitaxy on (111) SCD with magnetron sputtered AlN

Single crystal diamond (SCD) is an ideal heatsink for GaN-based devices. However, wetting issue of buffer on SCD hinders the GaN quality, limiting the full utilization of SCD's heat-dissipation ability. In this paper, the first-principles calculation revealed the high adsorption energy of Al and N adatoms on the surface of (111) SCD. The high energy of adatoms lead to a poor nucleation of AlN on (111) SCD, which caused inferior buffer layer. We propose a solution by pre-depositing AlN on (111) SCD via the ex-magnetron sputtering, which greatly enhances the quality of buffer layer and GaN film. Three different thicknesses of sputtered AlN (25 nm, 50 nm, and 100 nm were studied, and all showed improvement in GaN quality. The enhanced quality had been confirmed by the detailed characterization. GaN on (111) SCD with sputtered AlN presents narrower rocking curves of X-ray Diffraction (XRD). Additionally, GaN on 50 nm sputtered AlN/(111) SCD demonstrated superior quality, achieving a full width at half maximum of XRD for 1878/1945″ at 002/102.

Physicochemical and adsorptive properties of biochar derived from municipal sludge: sulfamethoxazole adsorption and underlying mechanism

Municipal sludge waste could be transformed into useful biochar through pyrolysis process. In this study, municipal sludge-derived biochar (SBC) was successfully synthesized via the one-pot pyrolysis method, and the yield of sludge biochar gradually decreased with the pyrolysis temperature increased from 300°C to 800°C. The sludge biochar exhibited an alkaline surface due to the gradual accumulation of ash and the formation of carbonate and organic anion during high-temperature pyrolysis process. Moreover, the prepared samples were analyzed by different characterization techniques including BET, SEM, and XPS. Adsorption experiments using the optimized biochar sample of SBC800 resulted in a 95% sulfamethoxazole (SMX) removal efficiency and the maximum adsorption capacity of 7033.4 mg/kg, which was 47.5 times higher than that of SBC300. The adsorption process of SBC800 for SMX was more in line with the Freundlich and D-A isotherm model, the whole process was an exothermic reaction. SBC800 could effectively remove SMX through pore filling effect, electrostatic attraction, hydrogen bonding, hydrophobic effect, and π-π EDA interaction. Site energy distribution analysis showed that SMX preferentially occupied the high-energy adsorption site of SBC800, and then gradually diffused to the low-energy adsorption site. This study proposed a sustainable method for recycling municipal sludge for organic pollutant removal.

Insights into different toxic molecular gases on the Fe-dimer anchored at C2N monolayer as potential sorbents and gas sensors: A theoretical approach

The fundamental aspects, including geometric structure, adsorption energy, thermodynamic properties, charge transfer, and magnetic properties of carbon nitride C2N and double-atom catalyst (Fe2@C2N) monolayers with the adsorption of CO, NO, HCN, CS2, and SO2 molecules, were investigated using DFT and DFT-D3 correction dispersion methods. Compared to pristine C2N, the Fe2@C2N monolayer is more energetically efficient with high adsorption energies and has apparent charge transfer with these toxic gases. Our results revealed that NO preferred to be adsorbed on the Fe2@C2N with a superior Eads of −7.006 eV. The electric conductivity, sensitivity, and selectivity of C2N are significantly influenced by CO, NO, HCN, CS2, and SO2 molecules. Moreover, the opening of band gaps induced by the adsorption of NO gas molecules at Fe2@C2N can be used as an electronic signal to detect NO gas. Intriguingly, the partial density of states (PDOS) indicated that the NO adsorption of pristine C2N and Fe2@C2N monolayers exhibited half-metallicity behavior and magnetic properties. Non-covalent interactions (NCI) and the quantum theory of atoms in molecules (QTAIM) descriptors were examined to analyze the interaction process. This study can provide a new avenue for synthesizing and developing highly sensitive candidates and inexpensive green double-atom catalysts to capture and detect CO, NO, HCN, CS2, and SO2 molecules from the atmosphere at ambient temperature.

Insights into simultaneous adsorption of orthophosphate (PO43−) and 1-hydroxyethane 1,1-diphosphonic acid (HEDP) by kaolin/lanthanum carbonate composites: Experimental analysis and DFT calculations

Orthophosphate and phosphonate often co-exist in industrial wastewater, and it is a challenge to remove the above inorganic and organic phosphorus simultaneously to meet the stringent total phosphorus (TP) discharge standard. The kaolin-based lanthanum carbonate (LC) composites have been demonstrated to decontaminate TP (PO43− and HEDP) from reverse osmosis (RO) concentrate effectively, while the individual and simultaneous adsorption behavior and mechanisms are still not clear. In this study, the individual and simultaneous PO43− and HEDP adsorption were compared. The adsorption kinetics, isotherms, initial pH and matrix effects were performed. The results showed that PO43− exhibited a nice adsorption performance, and was severely suppressed in the presence of HEDP. The maximum adsorption capacities were obtained at initial pH of 4.0, and the co-existing Ca2+ significantly enhanced both PO43− and HEDP removal, while HCO3−/CO32− markedly interfered with their adsorption process. LaCO3OH was the main composition in the composites for PO43− and HEDP adsorption, and no La-P compounds formed after adsorption. A variety of characterization methods were adopted to explore the adsorption mechanisms, and electrostatic attraction, inner-sphere complexation and hydrogen bond were responsible for PO43− and HEDP adsorption. The density functional theory (DFT) calculations were applied to distinguish the PO43− and HEDP adsorption from the molecular level, and the binuclear bidentate complexation configuration of H2HEDP2− species (H2HEDP-BB) with higher adsorption energy (-165.42 KJ/mol) resulted in the predominant species of HEDP in the competitive adsorption. In the fixed-bed column experiments, both PO43− and HEDP adsorption performance also matched the results of batch experiments and DFT calculations. This study provides insights into the competitive adsorption of orthophosphate and phosphonate by LC-based adsorbent.

Inquest for the interaction of canonical and non-canonical DNA/RNA bases with ternary based 2D Si2BN and doped Si2BN for biosensing applications

Density functional theory (DFT) is invoked to investigate the interaction between the canonical (CN) and non-canonical (NC) bases with pristine Si2BN (Si2BN) and Phosphorous-doped Si2BN (P-dop-Si2BN) sheets. Inquest for the better sensing substrate is decided through the adsorption energy calculation which reveals that doping of phosphorous atom enhances the adsorption strength of AT (-83.74 kcal/mol) AU (-82.77 kcal/mol) and GC (-96.36 kcal/mol) base pairs. The CN and NC bases have higher adsorption energy than the previous reported values which concludes that the P-dop-Si2BN sheet will be optimal substrate to sense the bases. Meanwhile, the selected CN and NC (except hypoxanthine) bases interact with sheet in parallel manner which infers the π-π interaction with Si2BN and P-dop-Si2BN sheets. The energy gap variation (ΔEg%) of the P-dop-Si2BN complexes has a noticeable change, ranging from −24.75 to −197.28% which thrust the sensitivity of the P-dop-Si2BN sheet over the detection of CN and NC bases. The natural population analysis (NPA) and electron density difference map (EDDM) confirms that charges are transferred from CN and NC bases to Si2BN and P-dop-Si2BN sheet. The optical property of the P-dop-Si2BN complexes reveals that the noticeable red and blue shift in the visible and near-infrared regions (778 nm to 1143 nm) has been observed. Therefore, the above results conclude that the P-dop-Si2BN sheet plays a potential candidate to detect the CN and NC bases which contribute to the development of biosensors and DNA/RNA sequencing devices. Communicated by Ramaswamy H. Sarma

Novel α-amino acid-like structure decorated biochar for heavy metal remediation in acid soil

Neither chemical nor physical adsorption play well in heavy metals remediation in acid soil due to the competing behavior of abundant protons, where stable chelators that can be reused are of significant demand. Herein, biochar with abundant nitro and carboxyl groups is prepared, which can be assembled into self-supporting electrode. Under the catalyzation of electricity, the surface decorated -NO2 on the biochar can be in situ transformed into -NH2. Combined with the carboxyl group that attached on the same carbon atom, a special α-amino acid-like structure modified biochar (α-AC@BC) can be successfully constructed. Due to the strong affinity between the α-amino acid-like ligand and heavy metals, this α-AC@BC exhibits high removal efficiencies of 83.41%, 80.94%, 92.54% and 77.05% for available copper, cadmium, lead and zinc respectively, even in a strong acid soil with low pH of 4. After four adsorption-desorption cycles, the α-AC@BC could still eliminate 83.88% of copper. The high adsorption energy among -NH2, -COOH and heavy metals (−2.99 eV for copper, −1.90 eV for lead, −1.30 eV for zinc and −0.91 eV for cadmium) could form steady coordination structure to guarantee a highly practical application potential of α-AC@BC in strong acid soil. This study provides a novel concept for the decontamination of multiple heavy metal polluted acid soil.

Trimetallic Oxide Electrocatalyst for Enhanced Redox Activity in Zinc-Air Batteries Evaluated by In Situ Analysis.

Researchers are investigating innovative composite materials for renewable energy and energy storage systems. The major goals of this studies are i) to develop a low-cost and stable trimetallic oxide catalyst and ii) to change the electrical environment of the active sites through site-selective Mo substitution. The effect of Mo on NiCoMoO4 is elucidated using both in situ X-ray absorption spectroscopy and X-ray diffraction analysis. Also, density functional theory strategies show that NiCoMoO4 has extraordinary catalytic redox activity because of the high adsorption energy of the Mo atom on the active crystal plane. Further, it is demonstrated that hierarchical nanoflower structures of NiCoMoO4 on reduced graphene oxide can be employed as a powerful bifunctional electrocatalyst for oxygen reduction/evolution reactions in alkaline solutions, providing a small overpotential difference of 0.75V. Also, Zn-air batteries based on the developed bifunctional electrocatalyst exhibit outstanding cycling stability and a high-power density of 125.1mW cm-2 . This work encourages the use of Zn-air batteries in practical applications and provides an interesting concept for designing a bifunctional electrocatalyst.

Highly selective gas sensors for formaldehyde detection based on ZnO@ZIF‑8 core-shell heterostructures

Formaldehyde is a hazardous volatile organic pollutant commonly found indoors, making selective and accurate detection of formaldehyde crucial. To achieve this, ZnO@ZIF-8 core-shell heterostructures were fabricated using the sacrificial template method, where the 3D ZnO flower-like structures served as the core material. This innovative approach utilizing the ZIF-8 shell as a “selective gas filter” offers a novel pathway for enhancing the selectivity of formaldehyde sensors. Subsequent investigations revealed that the thickness of the ZIF-8 shell significantly influences the material’s performance. Among various configurations tested, the 2-ZnO@ZIF-8 sensor demonstrates the best formaldehyde detection properties, including high response (5 ppm, 5.03), excellent selectivity, short response and recovery times (29/40 s), excellent long-term stability, and a low theoretical detection limit (12.86 ppb) at 175 °C. The enhanced sensing properties can be attributed to the ZIF-8 surface’s high adsorption energy for formaldehyde molecules and the selective screening of gas molecules by ZIF-8. Overall, our study presents a promising strategy for developing highly selective gas sensors for formaldehyde detection, with the potential to contribute to improved indoor air quality monitoring and safety measures.

DFT study on adsorption of small gas molecules on Pt-capped armchair and zigzag single-walled carbon nanotubes

The adsorption of small gas molecules (CO, O2 and N2) on Pt-capped armchair and zigzag single-walled carbon nanotubes (SWCNT) has been investigated by density functional theory (DFT) method to determine the potential for gas sensor detection. Results indicated that O2 and N2 molecules with lower adsorption energies (1.66 eV and 1.00 eV) exhibited weak chemical adsorption on SWCNT(4,4)-Pt. However, CO demonstrates strong chemical adsorption with a high adsorption energy of 2.23 eV on SWCNT(4,4)-Pt. The adsorption energy of CO on SWCNT(7,0)-Pt shows the chemical adsorption between CO and SWCNT(7,0)-Pt. In addition, these findings also implied Pt-capped SWCNT could act as small gas molecule sensors to detect CO toxic gas at room temperature. In this system, CO is the electron donor and SWCNT-Pt is the electron receptor. The interaction of Pt and carbon nanotube backbone delocalized π electrons could not only increases the conductivity of SWCNT-Pt, but also enhances the conductivity of SWCNT-Pt-CO. The HOMO-LUMO gap (Δε) of Pt-capped SWCNT(7,0) reduced from 0.43 eV to 0.39 eV after CO adsorption, and the Δε value of Pt-capped SWCNT(4,4) decreased by 0.08 eV. The electrical conductivity of Pt-capped armchair and zigzag SWCNT has increased after the adsorption of CO molecule. The results may be helpful for designing a promising Pt-capped SWCNT-based CO sensors.

Scalable synthesis of K+/Na+ pre-intercalated α-MnO2 via Taylor fluid flow-assisted hydrothermal reaction for high-performance asymmetric supercapacitors

In this work, a two-step synthetic method: Couette-Taylor flow mixing, and hydrothermal method have been used to synthesize α-manganese oxide pre-intercalated with sodium and potassium ions (Na+/K+@α-MnO2) for supercapacitor application. In addition, the effects of different aqueous electrolytes on the energy storage properties of the Na+/K+@α-MnO2 nanowires are investigated. The results show that KOH is a better electrolyte than NaOH and Na2SO4, with Na+/K+@α-MnO2 nanowires exhibiting a higher specific capacitance of 124 Fg−1 in KOH electrolyte. This is attributed to the high ionic conductivity and smaller hydrate ion of K+ ions. DFT calculations reveal that K+ ions have a higher adsorption energy and a higher partial density of states than Na+ ions, indicating more favourable pseudocapacitive behaviour for K+ ions compared to Na+ ions. Furthermore, the asymmetric capacitor device based on N-CNTs@CF//Na+/K+@α-MnO2 delivers a specific energy density of 21 Wh kg−1 and a specific power density of 450 W kg−1, with excellent cycling performance (∼94 % capacity retention after 5,000 cycles). Our findings demonstrate that the pre-intercalation of α-MnO2 nanowires account for enhanced cycling stability, as well as higher capacitance.

Clean removal of silicon (IV) and vanadium (V) from high concentration chromium (VI) solutions in the chromate production processes

How to effectively and environmentally purify chromate solutions containing impurities such as silicon and vanadium, and avoid the generation of Cr(VI)-containing residues are important issues to be solved urgently. Herein, a novel Cr2O3∙2.7H2O adsorbent with stable three-dimensional nanoflower structure was fabricated using the hydrothermal method, which was successfully implemented in the removal of Si(IV) and V(V) from dichromate system. Batch adsorption experiments revealed that the saturated adsorption capacity of Si(IV) was 140.06 mg/g at pH 9 and 132.98 mg/g V(V) at pH 2. Furthermore, density functional theory (DFT) calculations revealed that V(V) anionic species exhibited high adsorption energies (−990.70 kJ/mol, −697.10 kJ/mol) and small adsorption distances from the β-CrOOH(012) (≈1.89 Å, 1.98 Å), verifying the selective adsorption of Cr2O3∙2.7H2O on V(V) in Cr(VI)–Si(IV)–V(V) ternary systems. The integrated mechanisms of electrostatic interaction, coordination, polymerization and precipitation for the removal behaviors were proposed via FT-IR, XPS and DFT calculations. In the real Na2Cr2O7 complex solutions, the simultaneous removal rates of 88.48% Si(IV) and 80% V(V) were achieved, with optimal adsorption conditions at a pH of 8 and a temperature of 333 K. Furthermore, the desorbed Cr2O3∙2.7H2O can be effectively converted into high-value nano Cr2O3, indicating the potential of this new green adsorbent. Therefore, this study not only imparts theoretical and practical insights into the purification of chromate solutions but also contributes to the advancement of cleaner chromium compound production by facilitating the high-value conversion of the adsorbent.

Stable and efficient As2O3 removal from simulated flue gas using Al2O3/CaSiO3 prepared by anhydrous grinding and calcination method

CaSiO3 exhibits good arsenic capture performance, but it falls short of meeting the actual needs of power plants due to its susceptibility to acidic gases that inhibit its arsenic capture ability. In this study, an Al2O3/CaSiO3 adsorbent was prepared by combining the anhydrous grinding and calcining methods. Arsenic vapor capture was conducted in flue gas containing or free of SO2 and HCl within the temperature range of 800–1000 ℃. The research indicated that the preparation method used in this study resulted in uniform Al2O3 doping that was less prone to agglomeration, thereby creating a good pore structure. The Al2O3/CaSiO3 adsorbent exhibited the strongest arsenic capture capacity when the atomic molar ratio of Al/Si was 1:5, with an arsenic capture amount of 871.2 mg/kg, which was significantly higher than the capture capacity of the control group calcium silicate. The doping of Al atoms altered the structure and charge distribution of CaSiO3 silica-oxygen chains, resulting in the formation of Al active sites with higher adsorption energy, which is more favorable for the adsorption of arsenic. Although the Al2O3/CaSiO3 adsorbent reacts with acidic gases to form CaSO4 and CaCl2, which can inhibit arsenic capture, it still maintains a high arsenic capture rate. Al2O3/CaSiO3 has excellent arsenic removal, sintering resistance, and acid resistance, making it a promising composite adsorption material for arsenic removal.

Pt-and Pd-doped carbon nanotubes with different diameters as CO sensors: A comparative DFT study

The density functional theory (DFT) is employed to assess the electronic characteristics and vibrational frequencies of CO adsorbed by several Zigzag carbon nanotubes with different diameters that are substitutionally doped using Pt and Pd. Computations were based on the Quantum Espresso (PBE) and Gaussian 16/6-31G(d,p) or LanL2DZ basis sets. The formation energy, adsorption energy, and interaction distances between CO and carbon nanotube as a function of the tube diameter were evaluated for Pt- and Pd- doped carbon nanotubes. Such doped nanotubes have relatively higher adsorption energy at smaller diameters, amounting to −2.784 eV and −2.635 eV for Pd-doped and Pt-doped carbon nanotubes, respectively. The adsorption energies of CO gas on Larger tubes Pt and Pd doped carbon nanotube are −2.207 eV, and −2.583 eV eV, respectively. Following CO adsorption, the smaller diameter Pt-doped carbon nanotube has a relatively greater change in electrical conductivity and chemical reactivity than other Pd- or Pt-doped nanotubes with relatively higher diameters. These changes are attributed to energy gaps concerning the alpha and beta HOMO and LUMO molecular orbitals. The computed Raman active mode frequencies extensively depend on diameter pre- and post-adsorption on the Pd- and Pt -nanotubes. This work offers several scientific suggestions concerning the use of Pt and Pd doped carbon nanotubes with different diameters for CO molecule sensor use cases. Such sensor materials having charge movement-based sensing might be employed as acceptors or donors.