•MXene doped composite CMAC was prepared by ultrasound–assisted electrostatic self–assembly.•CMAC exhibited high adsorption performance for the tested three anionic dyes.•Classical models and ASPM ...were both applied to elucidate the adsorption mechanism.•The adsorption mechanism was the synergistic effect of physicochemical interactions.
In this paper, a porous adsorbent synthesized from biomass activated carbon and MXene, named as CMAC composite, was utilized for the removal of three anionic azo dyes, allure red (AR), congo red (CR) and sunset yellow (SY). The formation of this heterostructure adsorbent was achieved by electrostatic self–assembly of negatively charged 2D MXene nanosheets and activated carbon with the assistance of a cationic surfactant (CTAB) solution. This method impeded the re–stacking of MXene nanosheets, effectively reduced the multilayer plate structure of MXene and enlarged the layer spacing, thus promoting the exposure of available active sites to further enhance the adsorption performance. The CMAC was physicochemically characterized via different analytical techniques and the dye adsorption isotherms at three temperatures were quantified. The experimental results showed that CMAC displayed excellent adsorption efficiency for CR with adsorption capacities above 1400 mg/g. The adsorption of the dyes coincided with the Langmuir model, pseudo–second order kinetic model and intraparticle diffusion model. A multilayer statistical physical model was employed to explain the adsorption mechanism between the tested dyes and CMAC. The simulation results provided the possible adsorption directions of the dye molecules on the adsorbent surface under different operating conditions, and the decrease of the active sites density DM indicated that the aggregation of dye molecules existed only when CMAC adsorbed SY. The adsorption energy calculations showed that the adsorption of AR and CR by CMAC was heat–absorbing and the adsorption of SY was exothermic. The adsorption mechanism can be attributed to the synergistic effect of physical adsorption, hydrogen bonding and electrostatic interactions.
The usage of various herbicides in the agricultural field leads to water pollution which is a big threat to the environment. Herein, the pods of the Peltophorum pterocarpum tree were used as a cheap ...resource to synthesize activated carbon (AC) by low-temperature carbonization to remove 2,4-dichlorophenoxyacetic acid (2,4-D) – an abundantly used herbicide. The exceptional surface area (1078.34 m2/g), mesoporous structure, and the various functional groups of the prepared AC adsorbed 2,4-D effectively. The maximum adsorption capacity was 255.12 mg/g, significantly higher than the existing AC adsorbents. The adsorption data satisfactorily modelled using Langmuir and pseudo-second-order models. Also, the adsorption mechanism was studied using a statistical physics model which substantiated the multi-molecular interaction of 2,4-D with the AC. The adsorption energy (<20 kJ/mol) and thermodynamic studies (ΔH°: −19.50 kJ/mol) revealed the physisorption and exothermicity. The practical application of the AC was successfully tested in various waterbodies by spiking experiments. Hence, this work confirms that the AC prepared from the pods of P. pterocarpum can be applied as a potential adsorbent to remove herbicides from polluted waterbodies.
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•Mesoporous activated carbon derived from Peltophorum pterocarpum resulted in exceptional surface area of 1078.34 m2/g.•Removal efficiency reached 94% at pH 2 with sorption capacity of 255.12 mg/g.•Monolayer with single energy model was fitted with the experimental isotherm data.•Significant results (>90%) were obtained on removing 2,4-D from spiked waterbodies.
We leverage recent breakthroughs in neural density estimation to propose a new unsupervised ANOmaly detection with Density Estimation (ANODE) technique. By estimating the conditional probability ...density of the data in a signal region and in sidebands, and interpolating the latter into the signal region, a fully data-driven likelihood ratio of data versus background can be constructed. This likelihood ratio is broadly sensitive to overdensities in the data that could be due to localized anomalies. In addition, a unique potential benefit of the ANODE method is that the background can be directly estimated using the learned densities. Finally, ANODE is robust against systematic differences between signal region and sidebands, giving it broader applicability than other methods. We demonstrate the power of this new approach using the LHC Olympics 2020 R&D dataset. We show how ANODE can enhance the significance of a dijet bump hunt by up to a factor of 7 with a 10% accuracy on the background prediction. While the LHC is used as the recurring example, the methods developed here have a much broader applicability to anomaly detection in physics and beyond.
•Adsorption mechanism of Pb2+, Hg2+ and Zn2+ from aqueous solution on a biomass char was studied.•Calculations with statistical physics models and DFT were used to explain heavy metal ...adsorption.•Electronegativity and thermodynamic stability of metal-adsorbent complexes explained the antagonistic adsorption.
This study reports the combination of new statistical physics models and density functional theory (DFT) for the analysis and understanding of the adsorption of heavy metals on a flamboyant biomass-based adsorbent. Single and ternary isotherms of the adsorption of Pb2+, Hg2+ and Zn2+ ions on an adsorbent obtained from the pyrolysis of flamboyant biomass were determined experimentally at pH 5 and 298–313 K. Experimental studies showed that the adsorption of Hg2+ on flamboyant char was higher than those of Zn2+ and Pb2+ in both single and ternary solutions. A strong antagonistic effect for the multicomponent adsorption of Zn2+ was identified due to the presence of other competitive metal ions in the ternary solution. The endothermic adsorption mechanism involved in both mono- and multi-metallic solutions was explained via the integration of the results from the adsorbent physicochemical characterization and calculations using statistical physics models and density functional theory. Theoretical studies showed that the single-compound adsorption of heavy metals correlated with the calculated DFT binding energies of oxygen-containing functionalities of flamboyant surface. On the other hand, the electronegativity and the thermodynamic stability of the metal – active site complexes determined the adsorbent selectivity and adsorption capacities in the simultaneous removal of these heavy metals. In particular, the carboxylic functional groups of flamboyant char were the main active sites involved in the adsorption of these heavy metals in both mono- and multi-component aqueous solutions. These new findings contribute to a deeper understanding of the mechanisms involved in the multicomponent adsorption of relevant water pollutants such as heavy metals using carbon-based adsorbents.
This paper reports on the search for heavy neutrinos with masses in the range 140<MN<493 MeV/c2 using the off-axis near detector ND280 of the T2K experiment. These particles can be produced from kaon ...decays in the standard neutrino beam and then subsequently decay in ND280. The decay modes under consideration are N→ℓα±π∓ and N→ℓα+ℓβ−ν(−)(α,β=e,μ). A search for such events has been made using the Time Projection Chambers of ND280, where the background has been reduced to less than two events in the current dataset in all channels. No excess has been observed in the signal region. A combined Bayesian statistical approach has been applied to extract upper limits on the mixing elements of heavy neutrinos to electron-, muon- and tau- flavored currents (Ue2, Uμ2, Uτ2) as a function of the heavy neutrino mass, e.g., Ue2<10−9 at 90% C.L. for a mass of 390 MeV/c2. These constraints are competitive with previous experiments.
Given the lack of evidence for new particle discoveries at the Large Hadron Collider (LHC), it is critical to broaden the search program. A variety of model-independent searches have been proposed, ...adding sensitivity to unexpected signals. There are generally two types of such searches: those that rely heavily on simulations and those that are entirely based on (unlabeled) data. This paper introduces a hybrid method that makes the best of both approaches. For potential signals that are resonant in one known feature, this new method first learns a parametrized reweighting function to morph a given simulation to match the data in sidebands. This function is then interpolated into the signal region, and then the reweighted background-only simulation can be used for supervised learning as well as for background estimation. The background estimation from the reweighted simulation allows for nontrivial correlations between features used for classification and the resonant feature. A dijet search with jet substructure is used to illustrate the new method. Future applications of Simulation Assisted Likelihood-free Anomaly Detection (salad) include a variety of final states and potential combinations with other model-independent approaches.
In this paper, a new type of adsorbent MXene/carbon foam hybrid aerogel (MCF) was synthesized from Ti3C2TX-MXene and melamine foam (MF), and its removal properties of both cationic and anionic dyes ...were studied. The physicochemical properties of MCF were analyzed by a variety of characterization techniques, while its dye adsorption mechanism was further elucidated by the statistical physics models. The results show that MCF exhibited excellent adsorptive efficiency towards the two hazardous dyes methylene blue (MB) and Congo red (CR), and their adsorption capacity were 356.97 mg/g and 647.75 mg/g, respectively, which were fitted better for the Langmuir equation and quasi-second-order kinetic model. Moreover, the mechanism of MCF-MB and MCF-CR adsorption systems was discussed through the saturated multilayer model at the molecular level. The numerical simulation results show that the MB molecules were adsorbed by MCF in the form of dimer, which was a process of multi-anchoring (303 K and 318 K), single connection (333 K) and mixed adsorption orientation. On the contrary, CR molecules were adsorbed as monomers, which was a process of multi-anchored and pure non-parallel adsorption directions (303 K and 318 K) and mixed adsorption orientation (333 K). From the statistical physical and thermodynamic analysis, the adsorption mechanism of MB and CR onto MCF was mainly determined by the receptor density (Dm), which was a reversible endothermic adsorption process driven by the physical interaction, and high temperature was beneficial to the occurrence of high adsorption capacity.
•MCF aerogel was fabricated by bridging and cross-linking of MXene and MFCS.•MCF exhibited excellent adsorption capacity for both cationic and anionic dyes.•MCF also showed favorable properties of mechanical strength.•Statistical physics models were applied to elucidate the adsorption mechanism.
We explore the sensitivity of photon-beam experiments to axionlike particles (ALPs) with QCD-scale masses whose dominant coupling to the standard model is either to photons or gluons. We introduce a ...novel data-driven method that eliminates the need for knowledge of nuclear form factors or the photon-beam flux when considering coherent Primakoff production off a nuclear target, and show that data collected by the PrimEx experiment in 2004 could improve the sensitivity to ALPs with 0.03≲m_{a}≲0.3 GeV by an order of magnitude. Furthermore, we explore the potential sensitivity of running the GlueX experiment with a nuclear target and its planned PrimEx -like calorimeter. For the case where the dominant coupling is to gluons, we study photoproduction for the first time, and predict the future sensitivity of the GlueX experiment using its nominal proton target. Finally, we set world-leading limits for both the ALP-gluon coupling and the ALP-photon coupling based on public mass plots.
Dijet events are studied in the proton-proton collision data set recorded at s=13 TeV with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to integrated luminosities ...of 3.5 fb−1 and 33.5 fb−1 respectively. Invariant mass and angular distributions are compared to background predictions and no significant deviation is observed. For resonance searches, a new method for fitting the background component of the invariant mass distribution is employed. The data set is then used to set upper limits at a 95% confidence level on a range of new physics scenarios. Excited quarks with masses below 6.0 TeV are excluded, and limits are set on quantum black holes, heavy W′ bosons, W* bosons, and a range of masses and couplings in a Z′ dark matter mediator model. Model-independent limits on signals with a Gaussian shape are also set, using a new approach allowing factorization of physics and detector effects. From the angular distributions, a scale of new physics in contact interaction models is excluded for scenarios with either constructive or destructive interference. These results represent a substantial improvement over those obtained previously with lower integrated luminosity.
We present a recast in different benchmark models of the recent CMS search that uses the end cap muon detector system to identify displaced showers produced by decays of long-lived particles (LLPs). ...The exceptional shielding provided by the steel between the stations of the muon system drastically reduces the Standard Model background that limits other existing ATLAS and CMS searches. At the same time, by using the muon system as a sampling calorimeter, the search is sensitive to LLPs energies rather than masses. We show that, thanks to these characteristics, this new search approach is sensitive to LLPs masses even lighter than a GeV, and can be complementary to proposed and existing dedicated LLP experiments.
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