A ratiometric fluorescence imprinted sensor based on N-CDs and metal-organic frameworks for visual smart detection of malathion.

Sensitive and rapid detection of pesticide residues in food is essential for human safety. A ratiometric imprinted fluorescence sensor N-CDs@Eu-MOF@MIP (BR@MIP) was constructed to sensitively detect malathion (Mal). Europium-based metal organic frameworks (Eu-MOF) were used as supporters to improve the sensitivity of the BR@MIP. N-doped carbon dots (N-CDs) were used as fluorescent source to produce fluorescent signal. A linear relationship between the concentration of Mal and the fluorescence response of the sensor was found in the Mal concentration range of 1-10 µM with a limit of detection (LOD) of 0.05 µM. Furthermore, the sensor was successfully applied for the detection of Mal in lettuce, tap water, and soil samples, with recoveries in the range of 93.0 % - 99.3 %. Additionally, smartphone-based sensors were used to detect Mal in simulated real samples. Thus, the construction of ratiometric imprinted fluorescence sensor has provided a good strategy for the detection of Mal.

Fluoride derivatization-enabled sensitive and simultaneous detection of biomarkers for nitrogen mustard in human plasma and urine via gas chromatography tandem mass spectrometry.

Methyl-diethanolamine (CAS: 105-59-9), ethyl-diethanolamine (CAS: 139-87-7), and triethanolamine (CAS: 102-71-6) were identified as the degradation products and bio-markers of nitrogen mustard exposure. Sensitive and convenient detection methods for amino alcohol are of great importance to identify nitrogen mustard exposure in forensic analysis. Herein, analytical methods including gas chromatography-tandem mass spectrometry combined with heptafluorobutyryl derivatization and solid phase extraction were established for retrospective detection of the biomarkers in human plasma and urine samples. The efficiency of the method was improved by optimizing the conditions for sample preparation and the GC-MS/MS method. The optimization included the derivatization temperature, reaction time, reagent dosage and solid phase extraction cartridges, eluent and pH of the loading sample. The results indicated that the SCX cartridge resulted in better enrichment and purification effects, and the best recovery could be obtained with pH = 3-4 for the loading samples and an eluent of 2 mL 10% NH4OH/MeOH. The GC-MS/MS parameters were also optimized for better specificity and sensitivity. The established method was fully validated for each analyte both in plasma and urine matrixes. The linear range of analytes in plasma was 1.0-1000 ng mL-1 with a correlation parameter (R2) of ≥0.994, intra-day/inter-day accuracy of 93.7-117%, and relative standard deviation (RSD) of ≤6.5%. Meanwhile the results in urine were 1.0-1000 ng mL-1 with R2 of ≥0.996, intra-day/inter-day accuracy of 94.3-122%, and RSD of ≤6.6%. The detection limit of the analytes was 1.0 ng mL-1. The method was applied for the detection and identification of trace amino alcohols present in urine samples dispatched by the Organization for the Prohibition of Chemical Weapons (OPCW) and the results were confirmed to be correct.

Unveiling glutamic acid-functionalized LDHs: understanding the Cr(VI) removal mechanism from microscopic and macroscopic view points.

Interlayer functionalization modulation is essential for modifying LDHs and improving their selectivity and adsorption capacity for target pollutants. In this work, Glu@NiFe-LDH was synthesized using a simple one-step hydrothermal method and tested for its ability to remove CrO42- from wastewater. The modification significantly increased the composite material's removal ability by 2-3 times, up to 98.36 mg g-1. The behavior of CrO42- adsorption on Glu@NiFe-LDH was further studied by adjusting the affecting factors (i.e., temperature, pH, contact time, initial concentration, and interfering substance), and the adsorption behavior was confirmed as a spontaneous and chemisorption process. And the result was that Glu@NiFe-LDH demonstrated high capacity, efficiency, stability, and selectivity for the adsorption of CrO42- in a single electrolyte and natural water containing competing anions. Furthermore, molecular dynamics simulations (NVT ensemble) were employed to further reveal the mechanism of glutamic acid modification on LDH at the microscopic scale. Additionally, the IRI analysis method revealed the mechanism of weak interaction between glutamic acid molecules and CrO42-. This study provides a detailed understanding of the intercalation mechanism involved in the amino acid modification of LDHs. It explains the adsorption mechanism of metal oxo-acid radicals by amino acid-modified LDHs from a theoretical perspective. The findings offer experiments and a theoretical basis for designing targeted adsorbents in the future.

3D-Printed river-type thick carbon electrodes for docking possible practical application-level capacitive deionization.

The low carbon mass loading along with serious imbalance between the carbon mass loading and the electrode performance greatly hinders practical applications of capacitive deionization (CDI). Traditional thick bulk-type (BT) carbon electrodes often suffer from extremely limited active sites, thereby being vital to explore a basic strategy to unlock the performance. Herein, 3D-printed thick carbon electrodes were utilized for CDI desalination for the first time. The experimental outcomes revealed that BT electrodes existed a serious salt adsorption capacity (SAC) drop under variable mass loading of 3-30 mg/cm2. In contrary, 3D-printed river-type (RT) electrodes acquired a superior SAC of 10.67 mg/g and achieved 54.1 % SAC rise compared with that of BT electrodes (500 mg/L; 1.0 V; 30 mg/cm2). Meanwhile, RT electrodes took only 12 min to reach the equilibrium SAC of BT electrodes, being 44 min faster. Further, RT electrodes with diverse mass loading of 30-45 mg/cm2 were investigated, and it still kept 7.13 mg/g SAC under ultrahigh mass loading of 45 mg/cm2. This strategy has been successfully extended and carbons with proper micro-meso pore distribution, high specific capacitances and low resistance may be a better selection. Besides, the impact of electrode channel structure on the desalting performance was investigated, and the influence mechanism was revealed via COMSOL simulation. Overall, this work demonstrates the splendid feasibility of utilizing 3D-printed thick carbon electrodes for possible practical application-level CDI desalination.

Tunable zirconium-based metal organic frameworks synthesis for dibutyl phthalate efficient removal: An investigation of adsorption mechanism on macro and micro scale.

The tunable porous structure of metal organic frameworks (MOFs) plays a crucial role in determining their adsorption performance. In this study, we developed and employed a strategy involving monocarboxylic acid assistance to synthesize a series of zirconium-based MOFs (UiO-66-F4) for the removal of aqueous phthalic acid esters (PAEs). The adsorption mechanisms were investigated by combining batch experiments, characterization and theoretical simulation. By adjusting the affecting factors (i.e., initial concentration, pH values, temperature, contact time and interfering substance), the adsorption behavior was confirmed as a spontaneous and exothermic chemisorption process. The Langmuir model provided a good fit, and the maximum expected adsorption capacity of di-n-butyl phthalate (DnBP) on UiO-66-F4(PA) was calculated to be 530.42 mg·g-1. Besides, through carrying out the molecular dynamics (MD) simulation, the multistage adsorption process in the form of DnBP clusters was revealed on a microcosmic scale. The independent gradient model (IGM) method showed the types of weak interactions of inter-fragments or between DnBP and UiO-66-F4. Furthermore, the synthesized UiO-66-F4 displayed excellent removal efficiency (>96 % after 5 cycles), satisfactory chemical stability and reusability in the regeneration process. Hence, the modulated UiO-66-F4 will be regarded as a promising adsorbent for PAEs separation. This work will provide referential significance in tunable MOFs development and actual applications of PAEs removal.

Construction of ACNF/Polypyrrole/MIL-100-Fe composites with exceptional removal performance for ceftriaxone and indomethacin inspired by "Ecological Infiltration System".

Developing advanced adsorbents for removing the alarming level of pharmaceuticals active compounds (PhACs) pollution is an urgent task for environmental treatment. Herein, a novel acid-treated carbon nanofiber/polypyrrole/MIL-100-Fe (ACNF/PPy/MIL-100-Fe) with stable 3D-supporting skeleton and hierarchical porous structure had been fabricated to erasure ceftriaxone (CEF) and indomethacin (IDM) from aqueous solution. ACNF as scaffold achieved the highly uniform growth of MIL-100-Fe and PPy. Viewing the large BET surface area (SBET, 999.7 m2/g), highly exposed accessible active sites and copious functional groups, ACNF/PPy/MIL-100-Fe separately showed an excellent adsorption capacity for CEF (294.7 mg/g) and IDM (751.8 mg/g), outstripping the most previously reported adsorbents. Moreover, ACNF/PPy/MIL-100-Fe reached rapid adsorption kinetics and standout reusability property. Further, the redesigned easy-to-recyclable ACF/PPy/MIL-100-Fe inspired by the electrode formation craft achieved prominent adsorption capacity and good reusability property. The adsorption mechanism was evaluated via Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The outcomes revealed that the splendid adsorption capability mainly depended on the electrostatic interactions, hydrogen bonding and π-π interactions. This work sheds light on one facile practical strategy to exploit advanced materials in water environmental remediation.

The rapid and sensitive detection of trace copper ions by L-cysteine capped ZnS nanoparticle fluorescent probe and the insight into micro-mechanism: Experiments and DFT study.

L-cysteine (L-Cys) capped ZnS fluorescent probe (L-ZnS) were synthesized by binding ZnS nanoparticles in situ with L-Cys, the fluorescence intensity of L-ZnS increased more than 3.5 times than that of ZnS due to the cleavage of S-H bonds and the formation of Zn-S bonds between the thiol group of L-Cys and ZnS. The addition of copper ions (Cu2+) can effectively quench the fluorescence of L-ZnS to realize the rapid detection of trace Cu2+. The L-ZnS showed high sensitivity and selectivity to Cu2+. The LOD (limit of detection) of Cu2+ was as low as 7.28 nM and linearity in the concentration range of 3.5-25.5 µM. Meanwhile, for the first time, electron localization function (ELF), bond order density (BOD), and natural adaptive orbital (NAdO) analysis in the Multiwfn wavefunction program based on density functional theory were carried out to probe the binding sites and binding mode of L-Cys with Cu2+, it indicated that the deprotonated carboxyl oxygen atoms of L-Cys had the lowest electrostatic potential (ESP) and provided lone pair electrons to coordinate with Cu2+ to form non-luminescent ground state complexes, which led to fluorescence quenching of L-ZnS. From the microscopic point of view of atoms, the mechanism of fluorescence enhancement of L-Cys capped ZnS and the mechanism of fluorescence quenching after adding Cu2+ were revealed in depth, the theoretical analysis results were accordance with the experiments.

Investigation of the adsorption performance and mechanism of 2-mercaptoethane sulfonic acid intercalated modified layered double hydroxide on heavy metal ions.

In the adsorption process of functionalized layered double hydroxide (LDH) to target pollutants it, is essential to investigate the role of functional groups. In this work, 2­mercaptoethane sulfonic acid (MS) was used as an intercalation modifier to prepare functionalized NiFe-LDH by solvothermal method. The interfacial interaction between the functional groups and the NiFe-LDH surface was studied via molecular dynamics simulation. During the intercalation process, the more negatively charged sulfonic acid group tends to self-assemble electrostatically with the LDH laminate, while the sulfhydryl group is involved in complexing heavy metal ions. The adsorption experiments showed that the adsorption performance of the adsorbent for the three ions of Cd2+, Mn2+, and Co2+ at 298.15 K was 266.16 mg/g, 175.60 mg/g, and 106.56 mg/g, respectively, which were 10 times, 8.7 times, and 4.9 times higher than that of unmodified NiFe-LDH. Meanwhile, Multiwfn wavefunction analysis combined Visual Molecular Dynamics (VMD) was applied to analyze and visualize the reaction active sites & the interactions between MS and NiFe-LDH, and the complexation of the functional group of MS with metal ions, to insight the role of the functional groups in MS molecule, and to reveal the cause that the adsorption capacity of modified NiFe-LDH for heavy metals greatly improves from the view of atoms.

A photoelectrochemical immunosensor based on magnetic all-solid-state Z-scheme heterojunction for SARS-CoV-2 nucleocapsid protein detection.

Rapid, convenient and accurate detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is urgently needed to timely diagnosis of coronavirus pandemic (COVID-19) and control of the epidemic. In this study, a signal-off photoelectrochemical (PEC) immunosensor was constructed for SARS-CoV-2 nucleocapsid (N) protein detection based on a magnetic all-solid-state Z-scheme heterojunction (Fe3O4@SiO2@TiO2@CdS/Au, FSTCA). Integrating the advantages of magnetic materials and all-solid-state Z-scheme heterostructures, FSTCA was implemented to ligate the capture antibody to form magnetic capture probe (FSTCA/Ab1). It can simplify the separation and washing process to improve reproducibility and stability, while allowing immune recognition to be performed in the liquid phase instead of the traditional solid-liquid interface to improve anti-interference. Besides, the heterojunction inhibited the recombination of photogenerated electron/hole (e-/h+) and promoted the light absorption to provide superior photoelectric substrate signal. The mechanism of photogenerated e-/h+ transfer of FSTCA were investigated by the electron spin resonance (ESR) spectroscopy. SiO2 spheres loaded with Au NPs utilized as an efficient signal quencher. The steric hindrance effect of SiO2@Au labeled detection antibodies (SiO2@Au-Ab2) conjugates significantly diminished light absorption and hindered the transfer of photogenerated electrons, further amplifying the signal change value. Based on the above merits, the elaborated immunosensor had a wide linear range of 10 pg mL-1-100 ng mL-1 and a low detection limit down to 2.9 pg mL-1 (S/N = 3). The fabricated PEC immunosensor demonstrated strong anti-interference, easy operation, and high sensitivity, showing enormous potential in clinical diagnosis of SARS-CoV-2.

CdTe QDs-sensitized TiO2 nanocomposite for magnetic-assisted photoelectrochemical immunoassay of SARS-CoV-2 nucleocapsid protein.

A sensitive, reliable, and cost-effective detection for SARS-CoV-2 was urgently needed due to the rapid spread of COVID-19. Here, a "signal-on" magnetic-assisted PEC immunosensor was constructed for the quantitative detection of SARS-CoV-2 nucleocapsid (N) protein based on Z-scheme heterojunction. Fe3O4@SiO2@Au was used to connect the capture antibody to act as a capture probe (Fe3O4@SiO2@Au/Ab1). It can extract target analytes selectively in complex samples and multiple electrode rinsing and assembly steps were avoided effectively. CdTe QDs sensitized TiO2 coated on the surface of SiO2 spheres to form Z-scheme heterojunction (SiO2@TiO2@CdTe QDs), which broadened the optical absorption range and inhibited the quick recombination of photogenerated electron/hole of the composite. With fascinating photoelectric conversion performance, SiO2@TiO2@CdTe QDs were utilized as a signal label, thus further realizing signal amplification. The migration mechanism of photogenerated electrons was further deduced by active material quenching experiment and electron spin resonance (ESR) measurement. The elaborated immunosensor can detect SARS-CoV-2 N protein in the linear range of 0.005-50 ng mL-1 with a low detection limit of 1.8 pg mL-1 (S/N = 3). The immunosensor displays extraordinary sensitivity, strong anti-interference, and high reproducibility in detecting SARS-CoV-2 N protein, which envisages its potential application in the clinical diagnosis of COVID-19.

Sensitive fluorescent detection and micromechanism of Mn-doped CuS probe for oxytetracycline hydrochloride.

The novel CuMnS nanoflower fluorescent probe based on Mn-doped CuS was developed to achieve the fluorescence detection of oxytetracycline hydrochloride (OTC), the fluorescent sensor has good selectivity and stability. The doping of Mn significantly increased the fluorescence intensity of CuS, which was above 10 times that of CuS. When the predominant species of OTC molecule was zwitterionic OTC+/-at the solution pH of about 5.00, the fluorescence quenching efficiency of CuMnS by OTC reached the highest. Through fluorescence lifetime and UV absorption, the sensing mechanism between CuMnS and OTC was found to be static quenching. Moreover, Multiwfn wavefunction analysis program based on density function theory (DFT) calculation was applied to compare the interactions between different OTC species and CuMnS at different pH, to reveal the micromechanism of fluorescence quenching of CuMnS by OTC from the views of atoms. The molecular surface quantitative analysis and basin analysis of different OTC species demonstrated that the N atom and O atoms of tricarbonylamide moiety of zwitterionic OTC+/- can provide lone pair electrons to form a non-fluorescent ground state complex with CuMnS. Meanwhile, the electrostatic attraction of OTC+/- with negatively charged CuMnS was also beneficial to the interaction, resulting in the effective fluorescence quenching of CuMnS. This work offers a convenient method for sensitively detecting OTC and broadens the application of CuMnS in the field of fluorescence detection.

Magnetic/fluorescent dual-modal lateral flow immunoassay based on multifunctional nanobeads for rapid and accurate SARS-CoV-2 nucleocapsid protein detection.

The SARS-CoV-2 pandemic has posed a huge challenge to rapid and accurate diagnosis of SARS-CoV-2 in the early stage of infection. In this work, we developed a novel magnetic/fluorescent dual-modal lateral flow immunoassay (LFIA) based on multifunctional nanobeads for rapid and accurate determination of SARS-CoV-2 nucleocapsid protein (NP). The multifunctional nanobeads were fabricated by using polyethyleneimine (PEI) as a mediate shell to combine superparamagnetic Fe3O4 core with dual quantum dot shells (MagDQD). The core-shell structure of MagDQD label with high loading density of quantum dots (QDs) and superior magnetic content realized LFIA with dual quantitative analysis modal from the assemblies of individual single nanoparticles. The LFIA integrated the advantages of magnetic signal and fluorescent signal, resulting excellent accuracy for quantitative analysis and high elasticity of the overall detection. In addition, magnetic signal and fluorescent signal both had high sensitivity with the limit of detection (LOD) as 0.235 ng mL-1 and 0.012 ng mL-1, respectively. The recovery rates of the methods in simulated saliva samples were 91.36%-103.60% (magnetic signal) and 94.39%-104.38% (fluorescent signal). The results indicate the method has a considerable potential to be an effective tool for diagnose SARS-CoV-2 in the early stage of infection.

The sensitive detection and mechanism of Fe-3,5-dimethyl pyrazole fluorescent sensor to diethylenetriamine pentamethylene phosphonic acid: Experimental study and quantum chemical calculation.

Diethylenetriamine pentamethylene phosphonic acid (DTPMP) is one of the most commonly used amino organic phosphonates. The existing methods for DTPMP detection are complicated, time-consuming, and cannot detect trace DTPMP in the natural environment. In the present work, the Fe-based 3,5-dimethyl pyrazole fluorescent sensor (Fe-DP) was constructed. The addition of Fe3+ to DP solution can greatly decrease the fluorescent intensity of DP, while the addition of different concentrations of DTPMP will restore the fluorescence intensity of DP to different degrees, to achieve quantitative detection of DTPMP, and the detection limit (LOD) of DTPMP was lower as 0.105 µΜ. The Fe-DP fluorescent sensor exhibited excellent anti-interference ability and good stability. Moreover, the fluorescence quenching mechanism of DP by Fe3+ was revealed by UV absorption spectrum and Multiwfn wavefunction analysis based on density function theory (DFT). The results revealed that the excitation of DP belonged to local excitation, in which the electrons were donated primarily by the N atom with double bond and redistributed within the pyrazole ring.The fluorescence quenching of adding Fe3+ was not caused by resonance energy transfer or charge transfer, which did not belong to dynamic quenching, but due to the ground state complex formed by the coordination of Fe3+ and the double bond N atom on the DP pyrazole ring.

Efficient removal of heavy metal ions by diethylenetriaminepenta (methylene phosphonic) acid-doped hydroxyapatite.

Diethylenetriaminepenta (methylene phosphonic) acid (DTPMP) was first used as a dopant to modify hydroxyapatite and applied to remove Pb2+. The adsorption capacity of modified hydroxyapatite for Pb2+ can reach 2185.92 mg/g, which was 10.4 times that of commercial nanohydroxyapatite. The characterizations after adsorption of Pb2+ indicated the existence of chelation and the formation of the low bioavailability Pb10(PO4)6(OH)2. Moreover, the interaction of different components containing DTPMP, HAP, and pollutant Pb2+ was investigated by molecular dynamics (MD) simulation, which indicated that the organic-phosphonic group of DTPMP (PO3H-) had a stronger complex effect with calcium ions or lead ions than that of the inorganic-phosphate group of HAP (PO43-) with the two metal ions, which affected the crystallinity of HAP, and greatly improved the removal effect of DTPMP doped HAP composites for Pb2+ contaminants, the existence of amino groups can further enhance the affinity between DTPMP and HAP or lead ions. The chelation mechanism of DTPMP and Pb2+ was probed in depth by combining basin analysis, topology analysis of atoms in molecules (AIM), electron localization function (ELF) analysis, bond order density (BOD) & natural adaptive orbital (NAdO)analysis and orbital component analysis.

Construction of g-C3N4/Au/NH2-UiO-66 Z-scheme heterojunction for label-free photoelectrochemical recognition of D-penicillamine.

The wide clinical application of d-penicillamine (D-PA) makes it inevitably accumulates in the environment, seriously threatening human health and the ecological environment. To better supervisory control D-PA, a highly sensitive and reliable photoelectrochemical (PEC) sensor based on gold nanoparticles (Au NPs) loaded on graphitic carbon nitride sheet and hexagonal NH2-UiO-66 composite (g-C3N4/Au/NH2-UiO-66) was synthesized. Tactfully using the strong bonding between D-PA and Au NPs and the effective carrier separation of Z-scheme heterojunction, the designed g-C3N4/Au/NH2-UiO-66 PEC sensor without an extra recognition unit exhibited a selective and sensitive photocurrent to D-PA. With the aid of UV diffuse reflectance spectra (UV-DRs), electron paramagnetic resonance (EPR) characterization, and free radical capture experiments, the electron transfer path of the PEC sensing system was deduced. The proposed g-C3N4/Au/NH2-UiO-66 PEC-based sensor achieved a low detection limit of 0.0046 µM (S/N = 3) with a wide linear response ranging from 10 nM to 400 µM. In addition, its good stability and selectivity also laid a good foundation for practical applications.

Investigation of the efficient adsorption performance and adsorption mechanism of 3D composite structure La nanosphere-coated Mn/Fe layered double hydrotalcite on phosphate.

Severe water eutrophication due to large releases of phosphorus has become a worldwide environmental problem. Adsorption active sites is less of traditional adsorbents in the phosphorus removal process resulting in low removal efficiency, so the new high-efficiency phosphorus removal adsorbents become an effective way to solve the problem. In this work, quercetin modified MnFe layered double hydrotalcite three-dimensional composites structures encapsulated by lanthanum (La(III)) nanoparticles (QLa@MnFe-LDH) were successfully prepared by a classical hydrothermal method. The results of the adsorption experiments show that La(III) nanosphere-encapsulated MnFe-LDH provides a more adequate binding site for phosphate adsorption. The adsorption performance of QLa@MnFe-LDH for phosphate was outstanding, the maximum adsorption capacity was 346.5 mg/g at 298.15 K, which was 300 % higher than that of MnFe-LDH. Moreover, QLa@MnFe-LDH retained its high adsorption capacity (>315.5 mg/g) over a wide range of pH (4.0 âˆ¼ 7.0). The active sites of the reactions were predicted by Multiwfn and Visual Molecular Dynamics (VMD), and novel visualization studies of weak interactions were applied to theoretical studies. The modified MnFe-LDH encapsulated by La nanospheres has a strong adsorption capacity for phosphate adsorption. Therefore, the modified QLa@MnFe-LDH was expected to become an effective adsorption material for phosphorus removal.

Efficient detection for Nitrofurazone based on novel Ag2S QDs/g-C3N4 fluorescent probe.

In the paper, a novel fluorescent probe based on Ag2S QDs/g-C3N4 composite was synthesized by loading Ag2S quantum dots (Ag2S QDs) on the surface of g-C3N4 through in-situ synthesis method and developed to detect Nitrofurazone (NFZ) sensitively. The results showed that the linear detection range of Ag2S QDs/g-C3N4 to NFZ was 0-30 µM, with a low detection limit of 0.054 µM. The results of time-fluorescence-resolved spectroscopy and UV-vis absorption spectroscopy exhibited that the possible detection mechanism of Ag2S QDs/g-C3N4 to NFZ was proposed to be Internal Filtration Effect (IFE). Moreover, Multiwfn wavefunction analysis was employed to uncover the possible interaction between the Ag2S QDs/g-C3N4 and NFZ, thereby further revealing the fluorescence detection mechanism from the scale of atoms. Combining experiments and theoretical calculations, we proposed the sensing mechanism of the formation of non-fluorescent ground state complex linked by hydrogen bonds. This work indicated that the Ag2S QDs/g-C3N4 composite processed the ability to detect NFZ efficiently and sensitively.

In-Depth Study of Heavy Metal Removal by an Etidronic Acid-Functionalized Layered Double Hydroxide.

Sorption methodologies play a pivotal role in heavy metal removal to meet the global requirements for uninterrupted access to drinkable water. Standard sorption technologies lack efficiency due to weak adsorbent-metal interaction. To this end, a layered cationic framework material loaded with phosphonate was first fabricated by a facile intercalation method to capture hazardous metals from an aqueous solution. To inquire the removal mechanisms, batch experiments, detection technologies, and simulation calculations were employed to study the interactions at the interface of clay/water. Specifically, the functionalized layered double hydroxide possessed excellent chelation adsorption properties with Zn2+ (281.36 mg/g) and Fe3+ (206.03 mg/g), in which model fitting results revealed that the adsorption process was chemisorption and monolayer interaction. Further, the interfacial interaction between the phosphonate and clay surface was evaluated by molecular dynamics simulation, and a new concept named the interaction region indicator was used to characterize weak interaction and coordinate bonds. The deep insight into the chelation mechanism was visually presented via the orbital interaction diagram. In addition, the regeneration of the spent adsorbent, adsorption column test, and acute toxicity analysis demonstrated that the synthesized material has immense potential in terms of practical usage for the treatment of toxic pollutants. These results provide a novel path for researchers to properly understand the adsorption behavior.

Porous P, Fe-doped g-C3N4 nanostructure with enhanced photo-Fenton activity for removal of tetracycline hydrochloride: Mechanism insight, DFT calculation and degradation pathways.

This study fabricated an efficient P and Fe co-doping graphitic carbon nitride catalyst (Fe- CN/P) by thermal polymerization of melamine, FeCl3, and 2-hydroxyphosphonoacetic acid (HPAA) mixture. The Fe-CN/P catalyst exhibited much better tetracycline hydrochloride (TCH) degradation performance than that of single doping and neat CN. Various characterizations indicated that the introduction of HPAA significantly increased the specific surface area of CN and improved charge separation as well as transfer efficiency. Based on Fe 2p XPS analysis and indirect determination of hydroxyl radical (·OH) content, the separated photogenerated electrons accelerated the reduction of Fe(III) and activated photo-Fenton reaction, resulting in more ·OH species generation. The effect of pH value, catalyst dosages, H2O2 concentration, the type of cations and anions as well as water matrices on the degradation of TCH by Fe-CN/P was systematically investigated. The main degradation pathways of TCH were proposed according to the LC-MS intermediates detection and DFT calculation. The results indicated that reactive oxide species (ROS) were more likely to attack the atoms with high Fukui index (f0). This work provides new ideas for adjusting the morphology and electronic structure of CN to enhance its photo-Fenton catalytic activity.

New insights into the capture performance and mechanism of hazardous metals Cr3+ and Cd2+ onto an effective layered double hydroxide based material.

The phosphonate functionalized layered double hydroxide constructed through intercalation reaction, and efficiently applied to capture toxicant metal ions. The characterization results indicated that the functionalized composite with many functional groups has adsorption potential to heavy metals. The strong chelation of the phosphonate groups with heavy metal ions proved it an excellent adsorbent leading to a maximum adsorption capacity of 156.95 mg/g (Cr3+) and 198.34 mg/g (Cd2+) separately. The data of kinetics and isotherm revealed that the chelating adsorption was dominated by chemisorption and monolayer interaction. Notably, the spent adsorbent presented satisfactory reusability after six cycles. Furthermore, the Forcite simulation with the CLAYFF-CVFF force field implied that the critical mechanism for modifiers and the surface sites of the interlayer is electrostatic interaction. Our in-depth exploration in terms of the weak interactions not only demonstrated the strength and nature but also provided a novel way to intuitively capture the type of interactions that occurred around interesting regions. In the end, we made detailed investigations on the chelation mechanism, and the covalent nature played a leading role in the binding interaction. This work provides a valuable strategy for researchers to design novel materials in practice.