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1.
Water Res ; 230: 119558, 2023 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-36603309

RESUMO

The global occurrence of per- and polyfluoroalkyl substances (PFAS) in aquatic systems has raised concerns about their adverse effects on ecosystems and human health. Adsorption is a promising technique for the remediation of PFAS, yet effective adsorbents with rapid uptake kinetics and high adsorption capacity are still in high demand, and molecular-level understanding of the interfacial adsorption mechanisms is lacking. In this study, we developed a superior layered rare-earth hydroxide (LRH) adsorbent, ultrathin Y2(OH)4.86Cl1.44·1·07H2O (namely YOHCl) nanosheets, to achieve the effective removal of perfluorooctanoic acid (PFOA). YOHCl nanosheets exhibited ultra-high adsorption capacity toward PFOA (up to 957.1 mg/g), which is 1.9 times and 9.3 times higher than the state-of-the-art layered double hydroxides (MgAl-LDH) and benchmark granular activated carbon (GAC) under the same conditions, respectively. Furthermore, YOHCl nanosheets pose stable performance on the removal of PFOA under various water matrices with robust reusability. We also developed YOHCl-based continuous-flow column, demonstrating its promise in simultaneously removing multiple PFAS with wide range of chain lengths at environmentally relevant concentrations. With the molecular-level investigations, we have revealed that multi-mechanism, including ion exchange, electrostatic attraction and bidentate/bridging coordination, contributed to the strong PFOA-YOHCl affinity, leading to the ultra-high adsorption capacity of PFOA. We have provided emerging LRHs-based adsorbents for the effective remediation of PFAS with molecular-level insights on the interfacial mechanisms.


Assuntos
Fluorcarbonetos , Poluentes Químicos da Água , Humanos , Ecossistema , Poluentes Químicos da Água/análise , Hidróxidos , Fluorcarbonetos/análise , Adsorção
2.
Artigo em Inglês | MEDLINE | ID: mdl-36613194

RESUMO

Layered double hydroxide (LDH)-doped chicken-manure biochar (CMB) with long-term stability was synthesized to immobilize Pb/Cd. MgAl-Cl-LDH-doped CMB (MHs) showed prominent long-term oxidation resistance and the least biodegradation sensitivity. Efficient Pb/Cd adsorption was observed on MHs, and the maximum adsorption capacities of Pb(II)/Cd(II) reached 1.95 mmol/g and 0.65 mmol/g, respectively. Precipitation and isomorphous substitution were identified as the key adsorption mechanisms, which formed highly stable Pb/Cd species (PbAl-CO3-LDH, Pb3(OH)2CO3, CdAl-Cl-LDH and CdCO3). Pb(II) and Cd(II) precipitated with CO32- in MHs; meanwhile, Mg(II) and Ca(II) in LDH layers were substituted by Pb(II) and Cd(II) respectively. Therefore, MHs had the potential for long-term stability of Pb/Cd. Moreover, complexation and electrostatic adsorption also contributed to the Pb/Cd immobilization to a certain extent. When 5% MHs (w/w) was applied to Pb/Cd contaminated smelting site soils, the soil pH increased from 5.9 to 7.3. After applying MHs for 25 d, the content of bioavailable Pb(II) and Cd(II) decreased by 98.8% and 85.2%, respectively, and the content of soluble Pb and Cd dropped by 99.5% and 96.7%. This study paves the way for designing a novel LDH doped CMB as efficient Pb/Cd immobilizers for smelting site soils.


Assuntos
Cádmio , Poluentes do Solo , Animais , Cádmio/química , Esterco , Galinhas , Chumbo , Hidróxidos , Carvão Vegetal/química , Solo/química , Poluentes do Solo/química
3.
Int J Mol Sci ; 24(1)2023 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-36614271

RESUMO

The use of degrading enzymes in polymer formulation is a very attractive strategy to manage the end-of-life of plastics. However, high temperatures cause the denaturation of enzymes and the loss of their catalytic activity; therefore, protection strategies are necessary. Once protected, the enzyme needs to be released in appropriate media to exert its catalytic activity. A successful protection strategy involves the use of layered double hydroxides: cutinase, selected as a highly degrading polyester hydrolytic enzyme, is thermally protected by immobilization in Mg/Al layered double hydroxide structures. Different triggering media are here evaluated in order to find the best releasing conditions of cutinase from LDH. In detail, phosphate and citrate-phosphate buffers, potassium carbonate, sodium chloride, and sodium sulfate solutions are studied. After the comparison of all media in terms of protein release and activity retained, phosphate buffer is selected as the best candidate for the release of cutinase from LDH, and the effect of pH and concentration is also evaluated. The amount of the enzyme released is determined with the Lowry method. Activity tests are performed via spectrophotometry.


Assuntos
Hidróxidos , Polímeros , Hidróxidos/química , Fosfatos
4.
Molecules ; 28(1)2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36615541

RESUMO

Immobilizing natural antioxidant and biologically active molecules in layered double hydroxides (LDHs) is an excellent method to retain and release these substances in a controlled manner, as well as protect them from thermal and photochemical degradation. Herein, we describe the preparation of host-guest systems based on LDHs and rosmarinic and glycyrrhetinic acids, two molecules obtained from the extraction of herbs and licorice root, respectively, with antioxidant, antimicrobial, and anti-inflammatory properties. Intercalation between the lamellae of the mono-deprotonated anions of rosmarinic and glycyrrhetinic acid (RA and GA), alone or in the presence of an alkyl surfactant, allows for readily dispersible systems in biobased polymer matrices such as poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and a 60/40 wt./wt. PLA/PBS blend. The composites based on the PLA/PBS blend showed better interphase compatibility than the neat blend, correlated with increased adhesion at the interface and a decreased dispersed phase size. In addition, we proved that the active species migrate slowly from thin films of the composite materials in a hydroalcoholic solvent, confirming the optimization of the release process. Finally, both host-guest systems and polymeric composites showed antioxidant capacity and, in the case of the PLA composite containing LDH-RA, excellent inhibitory capacity against E. coli and S. aureus.


Assuntos
Ácido Glicirretínico , Ácido Láctico , Ácido Láctico/química , Staphylococcus aureus , Antioxidantes/farmacologia , Escherichia coli , Polímeros/química , Poliésteres/química , Hidróxidos/química
5.
Chemosphere ; 316: 137737, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36608877

RESUMO

Dissolved organic matter (DOM) is distributed ubiquitously in water bodies. Ferric ions can flocculate DOM to form stable coprecipitates; however, Al(III) may alter the structures and stability of Fe-DOM coprecipitates. This study aimed to examine the coprecipitation of Fe, Al, and DOM as well as structural developments of Fe-DOM coprecipitates in relation to changes in Fe/Al ratios and pHs. The results showed that the derived Fe/Al/DOM-coprecipitates could be classified into three categories: (1) at pH 3.0 and 4.5, the corner-sharing FeO6 octahedra associated with Fe-C bonds with Fe/(Fe + Al) ratios ≥0.5; (2) the Fe-C bonds along with single Fe octahedra having Fe/(Fe + Al) ratios of 0.25; (3) at pH 6.0, the ferrihydrite-like Fe domains associated with Fe-C bonds with Fe/(Fe + Al) ratios ≥0.5. At pH 3.0, the Fe and C stability of the coprecipitates increased with increasing Al proportions; nonetheless, pure Al-DOM coprecipitates were unstable even if they exhibited the maximum ability for DOM removal. The associations of Al-DOM complexes and/or DOM-adsorbed Al domains with external surfaces of Fe domain or Fe-DOM coprecipitates may stabilize DOM, leading to lower C solubilization at pH 4.5. Although the preferential formation of Fe/Al hydroxides decreased Fe/Al solubilization at pH 6.0, adsorption instead of coprecipitation of DOM with Fe/Al hydroxides may decrease C stabilization in the coprecipitates. Aluminum cations inhibit DOM releases from Fe/Al/DOM-coprecipitates, promoting the treatment and reuse efficiencies of wastewater and resolving water shortages. This study demonstrates that Al and solution pH greatly affect the structural changes of Fe-DOM coprecipitates and indirectly control the dynamics of Fe, Al, and C concentrations in water.


Assuntos
Matéria Orgânica Dissolvida , Sais , Ferro/química , Compostos Férricos/química , Hidróxidos/química , Água
6.
Inorg Chem ; 62(3): 1178-1191, 2023 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-36607645

RESUMO

Increasing demands for pollution-free energy resources have stimulated intense research on the design and fabrication of highly efficient, inexpensive, and stable non-noble earth-abundant metal catalysts with remarkable catalytic activity for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Morphology control of the catalysts is widely implemented as an effective strategy to change the surface atomic coordination and increase the catalytic behavior of the catalysts. In this study, we have designed a series of Mn-Co catalyts with different morphologies on the graphite paper substrate to enhance OER and HER activities in alkaline media. The prepared catalysts with different morphologies were successfully obtained by adjusting the amount of ammonium fluoride (NH4F) in the hydrothermal process. The electrochemical tests display that the cubic-like Mn-Co catalyst with pyramids on the faces at a concentration of 0.21 M NH4F exhibits the best activity toward both OER and HER. The cubic-like Mn-Co catalyst with pyramids on the faces showed overpotentials of 240 and 82 mV at a current density of 10 mA cm-2 for OER and HER, respectively. Also, the cubic-like Mn-Co catalyst with pyramids on the faces required overpotentials of 319 and 216 mV to reach the current density of 100 mA cm-2 for OER and HER, respectively. The current density of this catalyst at η = 0.32 V was 701.05 mA cm-2 for OER, and for HER, the current density of the catalyst was 422.89 mA cm-2 at η = 0.23 V. The Tafel slopes of the Mn-Co catalyst with cubic-like structures with pyramids on the faces were 78 and 121 mV dec-1 for OER and HER, respectively. A two-electrode overall water electrolysis system using this bifunctional Mn-Co catalyst exhibited low cell voltages of 1.60 in the alkaline electrolyte at the standard current density of 10 mA cm-2 with appropriate stability. These electrochemical merits exhibit the considerable potential of the cubic-like Mn-Co catalyst with pyramids on the faces for bifunctional OER and HER applications.


Assuntos
Fluoretos , Água , Manganês , Hidróxidos , Cobalto , Carbonatos , Eletrólise , Hidrogênio , Oxigênio
7.
Chemosphere ; 315: 137716, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36592839

RESUMO

The unabated usage of priority anthropogenic stressors is a serious concern in the global environmental context. Pharmaceutical drugs such as furazolidone (FL) and nilutamide (NL) have far-reaching repercussions due to the presence of the reactive nitroaromatic moiety. Despite the widespread awareness regarding the dangers posed by nitroaromatic drugs, the promises to alleviate the environmental consequences of drug pollution are often unmet. Accordingly, implementing practices to monitor their presence in various media is a highly desirable, but challenging undertaking. With the advent of deep eutectic solvent-assisted synthesis, it has become possible to fabricate LDH-based sensor materials with minimal energy inputs in a sustainable and scalable manner. In this work, we have framed a series of CoFe-LDH electrocatalysts utilizing deep eutectic solvent-assisted hydrothermal strategies for the simultaneous detection of FL and NL. The CoFe-LDHs intercalated with three distinct anions, namely, (i) Cl-, (ii) SO42-, and (iii) CO32- are compared so as to establish a relationship between anion intercalation and electrochemical activity. Amongst the prepared electrodes, the CF-LDH-ii/SPCE displays highly appreciable selectivity, linear response range (0.09-237.9 µM), low detetion limits (FL = 1.2 nM and NL = 3.8 nM), high sensitivity (FL = 29.71 µA µM⁻1 cm⁻2 and NL = 19.29 µA µM⁻1 cm⁻2), good reproducibility and repeatability towards FL and NL in water and urine samples. Thus, with tailored gallery anions, the proposed electrocatalyst establishes enhanced electrocatalytic performance for the real-time analysis of pharmaceutical contaminants.


Assuntos
Hidróxidos , Nanotubos , Solventes , Reprodutibilidade dos Testes , Solventes Eutéticos Profundos , Carbonatos , Preparações Farmacêuticas
8.
J Colloid Interface Sci ; 634: 14-21, 2023 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-36528967

RESUMO

The construction of low-cost oxygen evolution reaction (OER) electrocatalysts with high activity and good durability is a considerable challenge for facilitating the efficient utilization of green energy. Herein, the prism-like materials of institute lavoisier frameworks-88 (MIL-88) was first synthesized by a hydrothermal method. Then, Co-Ni layered double hydroxides (CoNi-LDHs) nanosheets were directly wrapped on the MIL-88 surface by electrodeposition to form core-shell MIL-88@CoNi-LDHs composites. Due to the distinct structure and synergistic effect between the MIL-88 core and CoNi-LDHs shell, it was found that MIL-88@CoNi-LDHs had outstanding OER activity with a small Tafel slope (45.55 mV dec-1), low overpotential (314 mV) at 10 mA cm-2, and superior durability. This study provides a prospective pathway to exploit highly efficient low-cost electrocatalysts for OER.


Assuntos
Estruturas Metalorgânicas , Estudos Prospectivos , Galvanoplastia , Hidróxidos , Oxigênio
9.
J Colloid Interface Sci ; 634: 121-137, 2023 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-36535152

RESUMO

In the present work, we report the preparatory strategy of MgCr-layered double hydroxide (LDH) nanosheets with 90% degree of delamination by employing a formamide-assisted co-precipitation and mild hydrothermal route for the degradation of methylene blue (MB) under solar light exposure. The as-synthesized MgCr-LDH nanosheets were characterized by assorted characterization techniques such as powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Raman, thermogravimetric analysis (TGA), N2 adsorption-desorption measurement, X-ray photoelectron spectroscopy (XPS) and UV-Visible diffused reflectance spectroscopy (UV-DRS). The XRD pattern of MgCr-LDH nanosheets quantified the strain (ε) and dislocation density (δ) of 1.371 lines-2 m-4 and 0.5723 lines m-2 related to the (110) plane with d-spacing value of 1.6169 Ȧ. With a minimum band gap of ∼2.63 eV, the as-synthesized MgCr-LDH nanosheets displayed 90.6% MB photodegradation under the experimental protocols such as catalyst dosage of 30 mg/L, initial MB concentrations of 20 ppm, pH of 7 and time duration of 2 h under solar light exposure. Further, the recyclability test of the photocatalyst signifies material stability up to four successive cycles with 90% retention of MB degradation under sunlight exposure. The superior catalytic performances of the MgCr-LDH nanosheets could be ascertained to the suppression of excitonic recombination and effective light harvestation properties, synergistically contributed by the porous structural aspects via association of uni/multi-lamellar nanosheets, surface defect sites and photoactive Cr3+ cations. Additionally, the surface -OH groups of LDH contributed towards the generation of •OH radicals for triggering the catalytic performances. This type of work advances the novel ideas for establishing highly potent photocatalysts via synergizing structural and surface properties, paving towards effective wastewater treatment.


Assuntos
Hidróxidos , Azul de Metileno , Fotólise , Azul de Metileno/química , Hidróxidos/química , Difração de Raios X
10.
Chemosphere ; 313: 137467, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36481172

RESUMO

Biochar is an emerging eco-friendly and high-efficiency heavy metal (HM) adsorbent that exhibits satisfactory HM remediation effects in both water and soil environments. However, few studies have investigated the mechanisms and application of biochar in the remediation of combined HM-contaminated environments. Therefore, in the present study, a novel corn straw biochar-loaded calcium-iron layered double hydroxide composite (CaFe-LDH@CSB) was synthesized via the coprecipitation method and applied as a remediation adsorbent to remove HMs in both water and soil environments. The results indicated that the HM adsorption mechanism of CaFe-LDH@CSB in the aquatic phase involved a chemical endothermic adsorption process of functional group-complexed monolayers, dominated by precipitation, ion exchange, complexation and π bond interactions. The maximum adsorption capacity for Cd(II), Pb(II), Zn(II) and Cu(II) in the aqueous phase reached 24.58, 240.96, 57.57 and 39.35 mg g-1, respectively. In addition, application of CaFe-LDH@CSB in the combined HM-contaminated soil treatment helped to increase the soil pH, which increased by 5.1-17.9% in low-contamination (LC) soil and by 7.0-13.9% in high-contamination (HC) soil. Moreover, application of CaFe-LDH@CSB effectively decreased the acid-soluble fraction of HMs and increased the HM residual fraction. The immobilization mechanism of CaFe-LDH@CSB in the soil was concluded to involve pore filling, functional group action and electrostatic interactions. Overall, this study provided a novel LDH biochar composite that can be effectively applied in the remediation of combined HM-contaminated water and soil environments.


Assuntos
Metais Pesados , Poluentes do Solo , Zea mays , Adsorção , Metais Pesados/química , Carvão Vegetal/química , Hidróxidos , Solo/química , Água , Poluentes do Solo/análise , Cádmio
11.
Phys Chem Chem Phys ; 25(2): 983-993, 2023 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-36519362

RESUMO

The solvation structures of calcium (Ca2+) and magnesium (Mg2+) ions with the presence of hydroxide (OH-) ion in water are essential for understanding their roles in biological and chemical processes but have not been fully explored. Ab initio molecular dynamics (AIMD) is an important tool to address this issue, but two challenges exist. First, an accurate description of OH- from AIMD needs an appropriate exchange-correlation functional. Second, a long trajectory is needed to reach an equilibrium state for the Ca2+-OH- and Mg2+-OH- ion pairs in aqueous solutions. Herein, we adopt a deep potential molecular dynamics (DPMD) method to simulate 1 ns trajectories for the Ca2+-OH- and Mg2+-OH- ion pairs in water; the DPMD method provides efficient machine-learning-based models that have the accuracy of the SCAN exchange-correlation functional within the framework of density functional theory. The solvation structures of the cations and the OH- in terms of three different species have been systematically investigated. On the one hand, we find that OH- have more significant effects on the solvation structure of Ca2+ than that of Mg2+. We observe that the OH- substantially affects the orientation angles of water molecules surrounding the cation. Through the time correlation functions, we conclude that the water molecules in the first solvation shell of Ca2+ change their preferred orientation faster than those of Mg2+. On the other hand, with the presence of the cation in the first solvation shell of OH-, we find that the hydrogen bonds of OH- are severely altered, and the adjacent water molecules of OH- are squeezed. The two cations have substantially different effects on the solvation structure of OH-. Our work provides new insight into the solvation structures of Ca2+ and Mg2+ in water with the presence of OH-.


Assuntos
Simulação de Dinâmica Molecular , Água , Água/química , Cálcio/química , Magnésio/química , Hidróxidos/química , Cátions
12.
J Colloid Interface Sci ; 634: 793-803, 2023 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-36565621

RESUMO

To decontaminate wastewater affected by high concentrations of aqueous hexavalent chromium (Cr(VI)) and improve the capability of layered double hydroxide (LDH) as an electrode in the capacitive deionization (CDI) process, nickel-ferric-LDH (NiFe-LDH) and NiFe-LDH/molybdenum disulfide (NiFe/MoS2) were synthesized using a hydrothermal method. Characterization results indicated that the flower-like cluster framework of MoS2 was decorated with the NiFe-LDH. Addition of MoS2 improved the conductivity, capacitance reversibility, charge efficiency, coulombic efficiency, and stability of NiFe/MoS2. The CDI performance of aqueous Cr(VI) was evaluated using NiFe/MoS2 and activated carbon as the anode and cathode, respectively. The process reached equilibrium within 240 min. The deionization capacity and removal ratio for Cr(VI) (100 mg/L, 100 mL) were 49.71 mg/g and 99.42 %, respectively, at 1.2 V and 20 mL/min. The isothermal data were accurately described using the Langmuir model, and the theoretical maximum deionization capacity of NiFe/MoS2 for Cr(VI) was 106.2 mg/g. The interaction mechanisms included electrostatic attraction, surface complexation, and reduction. These findings indicate that NiFe/MoS2 has feasible applications in practical wastewater treatment for Cr(VI) removal.


Assuntos
Molibdênio , Níquel , Hidróxidos , Cromo , Ferro , Água , Eletrodos
13.
J Environ Manage ; 329: 117009, 2023 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-36535146

RESUMO

In this work, the magnetic layered double hydroxide composite as a new adsorbent was synthesized and applied for efficient copper (II) and nickel (II) ions removal from aqueous samples. After fabrication, the adsorbent was identified and characterized via Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy and vibrating sample magnetometer (VSM), while FE-SEM reveals and denote layered structure of present adsorbent. The magnetic strength of 20.34 emu g-1 supplies sufficient magnetic property which leads to a solution fast separation of the adsorbent from the sample solution by an external magnet. Then, central composite design (CCD) based on response surface methodology (RSM) was used to optimize the effects of various parameters on the removal process and accordingly best operational conditions was fixed at: 0.039 g of adsorbent, 6.31 min sonication, pH (8) and 17 mgl-1 of both copper (II) and nickel (II) ions concentrations, respectively. Moreover, the "Lack of Fit p-values" of analysis of variance were obtained to be 0.3758 and 0.8750 for nickel (II) and copper (II) ions, respectively which is not significant value denoting suitability of the current model. Amongst different isotherm and kinetic models, the current adsorption process followed the Freundlich and pseudo-second-order models, while the criterion for judgment is based on their higher correlation coefficients (more than 0.9) compared to other models. Kinetic judgment is based on the closeness of experimental and theoretical adsorption capacity and higher R2 values. The Freundlich model based on the multilayer process occurs owing to the adsorption of ions onto the heterogeneous surface of the adsorbent. The adsorbent showed the maximum adsorption capacities of 200.00 mg g-1 and 109.92 mg g-1 for Cu2+ and Ni2+ ions, respectively. Experimental results explore that the chemical and electrostatic interactions were responsible for the under-study model ions. The relative standard deviations assign to both metal ions adsorption was 1.63-3.78% representing the applicability of the composite for practical purposes.


Assuntos
Cobre , Poluentes Químicos da Água , Cobre/análise , Adsorção , Níquel/análise , Espectroscopia de Infravermelho com Transformada de Fourier , Hidróxidos/química , Fenômenos Magnéticos , Poluentes Químicos da Água/química , Cinética , Concentração de Íons de Hidrogênio , Íons
14.
Sci Total Environ ; 806(Pt 1): 150379, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34571222

RESUMO

Organoarsenic contaminants existing in water body threat human health and ecological environment due to insufficient bifunctional treatment technologies for organoarsenic degradation and inorganic arsenic immobilization. In order to safely and efficiently treat organoarsenic contaminants discharged into the aquatic environment, Co-Mn-Fe layered double hydroxide (CoMnFe-LDH) and Co-Mn-Fe layered double oxide (CoMnFe-LDO) were fabricated and employed as peroxymonosulfate (PMS) activator for organoarsenic degradation and inorganic arsenic immobilization, and p-arsanilic acid (p-ASA) was selected as target pollutant. Results demonstrated that the satisfactory removal of p-ASA (100.0%) in both CoMnFe-LDH/PMS and CoMnFe-LDO/PMS systems was obtained within 30 min, and substantial inorganic arsenic adsorption could be achieved (below 0.5 mg/L) in two systems with converting major inorganic arsenic species to arsenate. As XPS, ESR and quenching experiment revealed, the existence and generation of surface-bound radicals in two systems were identified. Based on density functional theory calculation and XPS analysis, the catalytic mechanism of CoMnFe-LDO/PMS system that PMS could be activated via direct electron transfer from adsorbed p-ASA was clarified, which differed from PMS activation via coupling with surface hydroxyl groups in CoMnFe-LDH/PMS system. Catalytic performance assessment under various critical operation parameters indicated that CoMnFe-LDH presented more stable ability of p-ASA removal in a wide pH range and complex aquatic environment. The recycle experiment demonstrated the excellent stability and reusability of CoMnFe-LDH(LDO). Besides, seven degradation products of p-ASA in CoMnFe-LDH/PMS system including phenolic compounds, azophenylarsonic acid, nitrobenzene and benzoquinne were identified by UV-Vis spectra and LC-TOF-MS analysis, and the corresponding degradation pathway was proposed. In summary, compared to CoMnFe-LDO/PMS, CoMnFe-LDH/PMS holds great promise for the development of an oxidation-adsorption process for efficient control of organoarsenic pollutant.


Assuntos
Ácido Arsanílico , Arsênio , Humanos , Hidróxidos , Peróxidos
16.
Sci Bull (Beijing) ; 67(17): 1763-1775, 2022 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-36546062

RESUMO

Anodic urea oxidation reaction (UOR) is an intriguing half reaction that can replace oxygen evolution reaction (OER) and work together with hydrogen evolution reaction (HER) toward simultaneous hydrogen fuel generation and urea-rich wastewater purification; however, it remains a challenge to achieve overall urea electrolysis with high efficiency. Herein, we report a multifunctional electrocatalyst termed as Rh/NiV-LDH, through integration of nickel-vanadium layered double hydroxide (LDH) with rhodium single-atom catalyst (SAC), to achieve this goal. The electrocatalyst delivers high HER mass activity of 0.262 A mg-1 and exceptionally high turnover frequency (TOF) of 2.125 s-1 at an overpotential of 100 mV. Moreover, exceptional activity toward urea oxidation is addressed, which requires a potential of 1.33 V to yield 10 mA cm-2, endorsing the potential to surmount the sluggish OER. The splendid catalytic activity is enabled by the synergy of the NiV-LDH support and the atomically dispersed Rh sites (located on the Ni-V hollow sites) as evidenced both experimentally and theoretically. The self-supported Rh/NiV-LDH catalyst serving as the anode and cathode for overall urea electrolysis (1 mol L-1 KOH with 0.33 mol L-1 urea as electrolyte) only requires a small voltage of 1.47 V to deliver 100 mA cm-2 with excellent stability. This work provides important insights into multifunctional SAC design from the perspective of support sites toward overall electrolysis applications.


Assuntos
Eletrólise , Ureia , Nitrogênio da Ureia Sanguínea , Hidrogênio , Hidróxidos , Oxigênio
17.
Molecules ; 27(24)2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-36558084

RESUMO

Phosphorus is one of the main causes of water eutrophication. Hard biochar is considered a promising phosphate adsorbent, but its application is limited by its textural properties and low adsorption capacity. Here, an adhesion approach in a mixed suspension containing egg white is proposed for preparing the hybrid material of Mg/Al-layered double hydroxide (LDH) and almond shell biochar (ASB), named L-AE or L-A (with or without egg white). Several techniques, including XRD, SEM/EDS, FTIR and N2 adsorption/desorption, were used to characterize the structure and adsorption behavior of the modified adsorbents. The filament-like material contained nitrogen elements at a noticed level, indicating that egg white was the crosslinker that mediated the formation of the L-AE hybrid material. The L-AE had a higher phosphate adsorption rate with a higher equilibrium adsorption capacity than the L-A. The saturation phosphate adsorption capacity of L-AE was nearly three times higher than that of L-A. Furthermore, the number of surface groups and the density of the positively charged surface sites follow the ASB < L-A < L-AE order, which is consistent with their phosphate adsorption performance. The study may offer an efficient approach to improving hard biochar's adsorption performance in wastewater treatment.


Assuntos
Fosfatos , Poluentes Químicos da Água , Fosfatos/química , Adsorção , Clara de Ovo , Hidróxidos , Carvão Vegetal/química , Poluentes Químicos da Água/análise , Cinética
18.
Molecules ; 27(24)2022 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-36558096

RESUMO

In this study, the calcium gangue material calcite (-10 µm) was used to investigate the effects of different kinds of metal ions and dosages on the dispersion behavior of calcite. The test results showed that the dispersion behavior of calcite was poor under strongly alkaline conditions without the addition of metal ions, and the reason for that was calcite dissolved ions. The degree of influence of different metal ions on calcite dispersion behavior was Fe3+ > Mg2+ > Na+. The three metal ion dosage tests showed that the dispersion behavior of calcite became poorer with the increase of metal ion dosage. This mainly showed that with the increase of Na+ dosage, the trend of the dispersion behavior of calcite was not obvious, but with the increase of Fe3+ and Mg2+ dosage, the trend of calcite dispersion behavior changed more. The dispersion behavior of calcite was devastated by 5 × 10-4 mol/L Fe3+ at pH = 4-12. The different mechanisms of the three metal ions were identified by zeta potential, solution chemistry, and XPS analysis. Na+ only changed the zeta potential value of the calcite surface, which acted as a compressed electric double layer. However, the formation of metal hydroxide species or metal hydroxide surface precipitation due to the adsorption of Fe3+ and Mg2+ on the mineral surface resulted in the change of the dispersion behavior of calcite.


Assuntos
Cálcio , Minerais , Carbonato de Cálcio , Hidróxidos
19.
Water Sci Technol ; 86(11): 3014-3027, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36515203

RESUMO

The removal of phosphate ions by capacitive deionization has become one of the most frontier research topics in the water treatment field in recent years. In this work, hybrid electrodes composed of nickel-iron layered double hydroxide (NiFe-LDH) - anchored on activated carbon fiber (ACF)-were synthesized by a hydrothermal method and subsequently applied in capacitive deionization to remove phosphate ions. The adsorption performance of the two hybrid electrodes on phosphate ions was compared by capacitive deionization experiments. The experiment was carried out for 3 hours to reach equilibrium, and the optimum adsorption of 33.48 mg/g was obtained using NiFe-LDH/ACF-2 hybrid electrode at room temperature (25 °C) and pH = 6.0. The results showed that increasing the loading capacity of NiFe-LDH on ACF might enhance the adsorption capacity of phosphate ions. Furthermore, the calculation of adsorption kinetics and adsorption isotherms elucidated that the adsorption capacity increased with the increasing of applied voltage. Meanwhile, the experimental data were fitted well with pseudo-first-order kinetics and Langmuir isotherms. Notably, it was observed that the pH first increased, then decreased during the adsorption due to the electrolysis of water, while the form of phosphate ions was transformed, with low pH favoring the adsorption of phosphate ions.


Assuntos
Purificação da Água , Eletrodos , Purificação da Água/métodos , Adsorção , Hidróxidos , Fosfatos , Carvão Vegetal , Fibra de Carbono , Íons
20.
Int J Mol Sci ; 23(23)2022 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-36498884

RESUMO

The efficient removal of lead (II) from aqueous solution remains a big problem and the development of novel nanomaterials as adsorbents by various technologies to solve this problem is promising. This study contributed a novel nanostructure of MIL-88A-layered double hydroxides (LDHs) as the adsorbent for Pb2+, which was synthesized by a two-step solvothermal method with MIL-88A(Fe) as the precursor. The as-prepared material featured a chestnut-like core-shell structure, and exhibited excellent removal performance towards Pb2+ from water in comparison to MIL-88A(Fe) and LDHs (directly synthesized). The adsorption of Pb2+ by the MIL-88A-LDHs conformed to the pseudo-second-order kinetic model and the Langmuir and Freundlich isotherm models. The maximal adsorption capacity was 526.32, 625.00, and 909.09 mg g-1 at 278, 298, and 318 K, respectively. The thermodynamic parameters suggested that the adsorption was an endothermic, entropy-increasing, and spontaneous reaction. X-ray photoelectron spectroscopy (XPS) analysis indicated that the surface complexation was mostly responsible for Pb2+ elimination. The MIL-88A-LDHs can be readily regenerated and showed good cyclic performance towards Pb2+. Thus, the as-prepared MIL-88A-LDHs may hold promise for the elimination of aqueous heavy metals.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Purificação da Água/métodos , Água , Poluentes Químicos da Água/química , Hidróxidos/química , Adsorção , Cinética
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