This work studies the Pb(II) removal onto bentonite clay modified by hexadecyl trimethyl ammonium bromide (HDTMA). Characterizations of the unmodified and modified materials were performed by using ...XRD, SEM, TG-DSC, FT-IR, and BET surface area analyses. Factors influencing the uptake of Pb(II) from aqueous solution, such as pHsolution, ion strength, uptake time, adsorbent dosage, and initial Pb(II) concentration, were examined. The obtained results showed that bentonite clay was successfully modified by HDTMA, resulting in an increase in its surface area by about 70 %. The Pb(II) adsorption onto modified bentonite clay reached equilibrium at pH = 5.0 after 120 min. Studies within the isotherm and kinetic models demonstrated that the adsorption followed the Sips isotherm and pseudo-second-order kinetic models. The maximum monolayer adsorption capacity calculated from the Langmuir model at 30 °C was 25.8 mg/g, which is much higher than that obtained for the unmodified sample (18.9 mg/g). The FT-IR and TG-DSC analyses indicated that the formation of inner-sphere complexes plays a fundamental role in the mechanism of Pb(II) uptake onto HDTMA-bentonite clay. This mechanism of Pb(II) adsorption was further investigated, for the first time, by using the positron annihilation lifetime (PAL) and electron momentum (EMD) measurements. The PAL and EMD analyses indicated that the existence of Al and Si mono-vacancies in the HDTMA-bentonite should have essential contributions to the adsorption mechanism. In particular, we found a very interesting mechanism that the Pb(II) adsorption should occur inside the interlayer spaces of the HDTMA-bentonite.
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•Bentonite clay was modified by HDTMA to enhance the Pb(II) removal.•The Langmuir monolayer adsorption capacity of HDTMA-modified bentonite was 25.8 mg/g.•The mechanisms of Pb(II) adsorption were studied via different analytical methods.•The formation of inner-sphere complexes played a major mechanism in the Pb(II) uptake.
In this study, we have utilized a simple and sensitive colorimetric assay using unmodified gold nanoparticles to detect sulfanilamide in the presence of dopamine. The remarkable point of our ...analytical assay is based on the color change of the gold nanoparticles solution according to their dispersion or agglomeration state. Furthermore, the presence of sulfanilamide in the dopamine-coated nanogold solutions retarded the aggregation of the nanoparticles, leading to a delay in the color change. The impacts of pH, the initial concentrations of dopamine and sulfanilamide, and different interferents on the colorimetric response were investigated. The limit of detection (LOD) is 0.3 μM, which is lower than those of previously reported methods for sulfanilamide determination under the optimal conditions (0.1 mM dopamine concentrations, pH 7.0, incubation time of 15 minutes). For quantitative measurement using UV-Vis spectra, a good linear relationship (
R
2
= 0.9920 and
R
2
= 0.9951) between the sulfanilamide concentration and absorption intensity was obtained in the ranges of 0.5-20 and 20-80 μM, respectively. The proposed method also showed low interference with the co-existence of some amino acids and organic chemicals in the mixture. Moreover, it was also applied to determine sulfanilamide in milk and pork samples, with good quantitative recoveries varying in the range of 97.2-101.9% and 98.3-107.7%, respectively. Increasing the sulfanilamide concentration changed the color of the dopamine-coated gold nanoparticles gradually from blue to red, which indicates that our proposed assay unlocks great potential in sulfanilamide analysis with naked-eye readout.
In this study, we have utilized a simple and sensitive colorimetric assay using unmodified gold nanoparticles to detect sulfanilamide in the presence of dopamine.
Manganese dioxide nanomaterials have wide applications in many areas from catalysis and Li–ion batteries to gas sensing. Understanding the crystallization pathways, morphologies, and formation of ...defects in their structure is particularly important but still a challenging issue. Herein, we employed an arsenal of X-ray diffraction (XRD), scanning electron microscopy (SEM), neutron diffraction, positron annihilation spectroscopies, and ab initio calculations to investigate the evolution of the morphology and structure of α-MnO2 nanomaterials prepared via reduction of KMnO4 solution with C2H5OH prior to being annealed in air at 200–600 °C. We explored a novel evolution that α-MnO2 nucleation can be formed even at room temperature and gradually developed to α-MnO2 nanorods at above 500 °C. We also found the existence of H+ or K+ ions in the 1 × 1 tunnels of α-MnO2 and observed the simultaneous presence of Mn and O vacancies in α-MnO2 crystals at low temperatures. Increasing the temperature removed these O vacancies, leaving only the Mn vacancies in the samples.
This letter considers a multi-pair decode-and-forward relay network where a power-splitting (PS) protocol is adopted at the energy-constrained relay to provide simultaneous wireless information and ...energy harvesting (EH). To achieve higher efficiency of EH, we propose a new PS-based EH architecture at the relay by incorporating an alternating current (AC) computing logic, which is employed to directly use the wirelessly harvested AC energy for computational blocks. Under a nonlinear EH circuit, our goal is to maximize the fairness of end-to-end rate among user pairs subject to power constraints, resulting in a non-convex problem. We propose an iterative algorithm to achieve a suboptimal and efficient solution to this challenging problem by leveraging the inner approximation framework. Numerical results demonstrate that the proposed algorithm outperforms the traditional direct current computing and other baseline schemes.
Summary
This paper presents a charge‐based integrate‐and‐fire (IF) circuit for in‐memory binary spiking neural networks (BSNNs). The proposed IF circuit can mimic both addition and subtraction ...operations that permit better incorporation with in‐memory XNOR‐based synapses to implement the BSNN processing core. To evaluate the proposed design, we have developed a framework that incorporates the circuit's imperfections effects into the system‐level simulation. The array circuits use 2T‐2J Spin‐Transfer‐Torque Magnetoresistive RAM (STT‐MRAM) based on a 65‐nm commercial CMOS and a fitted magnetic tunnel junction (MTJ). The system model has been described in Pytorch to best fit the extracted parameters from circuit levels, including the cover of device nonidealities and process variations. The simulation results show that the proposed design can achieve a performance of 5.10 fJ/synapse and reaches 82.01% classification accuracy for CIFAR‐10 under process variation.
A novel compact charge‐based integrate‐and‐fire neuron circuit design has been targeted for energy‐efficient in‐memory neuromorphic computing that serves well as a computation macro for typical BSNNs. Based on the 2T‐2J STT‐MRAM structure and a 65‐nm commercial CMOS technology process, the design can achieve 5.10 fJ/synapse and 82.01% classification accuracy for CIFAR‐10, exhibiting clear advantages in performance compared to the state‐of‐the‐art.
In the present study, Lam Dong bentonite clay was utilized as a novel resource to effectively synthesize microporous ZSM-5 zeolite (Si/Al ∼ 40). The effects of aging and hydrothermal treatment on the ...crystallization of ZSM-5 were carefully investigated. Herein, the aging temperatures of RT, 60, and 80 °C at time intervals of 12, 36, and 60 h, followed by high temperature hydrothermal treatment (170 °C) for 3-18 h were studied. Techniques such as XRD, SEM-EDX, FTIR, TGA-DSC, and BET-BJH were applied to characterize the synthesized ZSM-5. Bentonite clay showed great benefits as a natural resource for ZSM-5 synthesis and is cost efficient, environment friendly, and has a large reserves. The form, size, and crystallinity of ZSM-5 were greatly influenced by aging and hydrothermal treatment conditions. The optimal ZSM-5 product had high purity, crystallinity (∼90%), and porosity (BET ∼380 m
2
g
−1
) as well as thermal stability, which are beneficial for adsorptive and catalytic applications.
In the present study, Lam Dong bentonite clay was utilized as a novel resource to effectively synthesize microporous ZSM-5 zeolite (Si/Al ∼ 40).
The present study focused on the synthesis of novel NH2-PC700 adsorbent through the pyrolysis of NH2-MIL-88B (Fe) material under different pyrolysis temperatures (500, 700, and 900 °C) and ...investigated its application for ciprofloxacin adsorption. The obtained adsorbents were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption/desorption isotherm measurements. The parameters of the adsorption experiments that affect the removal efficiency, including solution pH (3–10), contact time (0–240 min), and initial concentration (10–40 mg/L), were also studied in detail. For the adsorption kinetic and isotherm studies, nonlinear models combined with error functions such as adjusted coefficient of determination (Radj2), mean relative error (MRE), and squares of the errors (SSE) were used to evaluate the compatibility between kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and Bangham) and isotherm (Langmuir, Freundlich, Temkin, and Dubinin–Radushkevitch) adsorption equations. Besides, the role of amino functionalization for the ciprofloxacin (CFX) adsorption of NH2-PC700 adsorbent was also explained. Through the Langmuir model, the maximum CFX adsorption capacity of NH2-PC700 was calculated to be 102.5 mg/g, considerably higher than that of NH2-MIL-88B (Fe). This outcome suggested that NH2-PC700 could be a promising adsorbent for the CFX remediation.
•The novel NH2-PC700 was synthesized from amino-functionalized metal-organic frameworks.•Nonlinear kinetic and isotherm models were fitted well.•Adsorption behavior obeyed pseudo-second-order and Freundlich models.•The maximum ciprofloxacin adsorption capacity was calculated to be 102.5 mg/g.
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Pomelo fruit peel, an organic waste, was utilised as a biosorbent to remove Ni(II) from aqueous solutions. Some major factors influencing Ni(II) uptake such as pH, adsorption time, and initial Ni(II) ...concentration were examined. Several isotherm and kinetic models including the Langmuir, Freundlich, Sips, pseudo-first-order, pseudo-second-order, and intra-diffusion models were fit to the experimental data. Results showed that the Ni(II) uptake obtained an equilibrium at pH=6 after 80 min at 303 K. The Sips isotherm model described the Ni(II) adsorption better than other models and the monoadsorption capacity calculated from the Langmuir model was 9.67 mg/g. The adsorption of Ni(II) followed pseudo-second-order kinetic models with three stages.
Removing hazardous metals from aqueous solution using biomaterials synthesized from waste resources with low cost is a novel strategy in environmental science and application. Among those hazardous ...metals, lead is one of the most dangerous elements because it significantly affects human-body organs. In the present study, biochar prepared from pomelo fruit peel using a green synthesized method was utilized to remove Pb(II) from aqueous solution. The effects of pH, adsorption time, ion strength, and Pb(II) initial concentration on the Pb(II) adsorption of this material were investigated. The Langmuir, Freundlich, Sip, pseudo-first-order, pseudo-second-order, and intra-diffusion models were used to study the isotherm and kinetic properties of the material. Results showed that the uptake followed the intra-diffusion kinetic model and the maximum Pb(II) mono-adsorption capacity determined from the Langmuir equation was 92.13 mg/g at 303 K. Furthermore, by combining conventional characterization methods as SEM-EDX, BET-BJH and FT-IR with advanced nuclear analytical techniques as positron annihilation lifetime (PAL) and electron momentum distribution (EMD), we found that the Pb(II) adsorption should be occurred via three stages, namely (i) electrostatic attractions that affect the external diffusion; (ii) ion-exchanges that control the internal diffusion; and (iii) chemical interactions. In particular, the PAL and EMD analyses provided, for the first time, an in-depth study on the adsorption mechanism that the ion-exchanges and/or electrostatic interactions occurred due to the diffusion of Pb(II) ions into the defects, vacancies, and/or vacancy clusters and/or the filling of Pb(II) ions into the micropores of biochar.
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•Biochar prepared from pomelo fruit peel was used to remove Pb(II) effectively.•Characteristics of biochar were investigated by XRD, SEM-EDX, BET, FT-IR, and PALS.•The adsorption capacity is 92.13 mg/g at 303 K higher than some other materials.•In-depth study of Pb(II) adsorption mechanisms was proposed using modern analytical methods.
•Bimetallic Al/Fe Metal-Organic Framework (Al/Fe-MOF) was synthesized by the microwave-assistant method.•Al/Fe-MOF showed excellent photocatalytic activity with the rate constant of 2.8 × 10−2 ...min−1.•Al/Fe-MOF showed high stability after three cycles.•The reaction mechanism of rhodamine B photodegradation process over Al/Fe-MOF also investigated.
MIL–88B(Fe) (MIL: Materials Institute Lavoisier) and bimetallic Al/Fe Metal-Organic Framework (Al/Fe-MOF) were synthesized by the microwave-assistant method. The as-synthesized samples were used as an effective catalyst for photo-Fenton degradation of rhodamine B (RhB) under visible light irradiation. The Al/Fe-MOF catalyst caused to degrade more than 96% of RhB in up to 120 min with the rate of reaction reached 2.8 × 10−2 min−1, while the rate achieved using MIL–88B(Fe) reached 1.2 × 10−2 min−1. Besides, the reaction mechanism of RhB photo-Fenton degradation process over Al/Fe-MOF also investigated. These results indicate that Al/Fe-MOF has been considered as a potential catalyst for wastewater treatment.
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