Leaching Of Metal Ions Research Articles

MoS2/FeS Nanocomposite Catalyst for Efficient Fenton Reaction.

Nanocomposites containing FeS as catalyst and MoS2 as cocatalyst have been synthesized toward efficient heterogeneous Fenton reaction. The deposition of FeS nanoparticles in situ on the surface of MoS2 nanosheets creates strong contact between the two components and generates a large number of exposed Mo6+ sites and sulfur vacancies, which contribute to the enhanced degradation rate by accelerating Fe3+/Fe2+ cycling and ensuring rapid electron transfer. In addition, the MoS2/FeS nanocomposite catalysts exhibit the best performance at near-neutral conditions (pH 6.5), which solves the challenges in conventional Fenton reactions such as leaching of metal ions, the formation of iron slurry, and the need of adjusting solution pH. Further, the nanocomposite can maintain high efficiency after many recycling experiments. It is believed that the MoS2/FeS nanocomposite represents an efficient heterogeneous Fenton catalyst that can greatly promote the performance of advanced oxidation processes (AOPs) for solving practical environmental issues.

Rational design of copper encapsulated within nitrogen-doped carbon core-shell nanosphere for efficiently photocatalytic peroxymonosulfate activation

Photocatalysis utilizing solar energy is a promising strategy for mitigating energy crisis and environmental pollution. Exploring a cost-effective, stable, eco-friendly, and efficient photocatalytic system is extremely urgent. Herein, copper encapsulated within nitrogen-doped carbon nanosphere (Cu@NC) possessing a unique core-shell structure with high catalytic activity was prepared by ion-exchange and pyrolysis using resin as support. The protective carbon shell can prevent the leaching of metal ions and deactivation of the catalyst. Benefiting from the special structure, Cu@NC exhibited excellent activity and durability toward the degradation of tetracycline by the activation of peroxymonosulfate (PMS). The radical trapping experiments and electron spin resonance analyses were applied to elucidate the main reactive species. This work highlights the great potential of Cu@NC core-shell nanosphere as photocatalyst, which provides a new opportunity for the remediation of environmental pollution.

Epitaxially grown MOF membranes with photocatalytic bactericidal activity for biofouling mitigation in desalination

In this study, we demonstrated the antifouling MOF membrane via the in-situ growth of metal azolate framework-4 (MAF-4) on polyethersulfone (PES) substrates and then epitaxial growth of MAF-7. The basal MAF-4 layer, which was confirmed to bind to the substrate by chelation, was flawless to ensure the desalination performance. The upper MAF-7 shell, which was confirmed to possess crystal characteristics and leave an unbound nitrogen atom, was hydrophilic and smooth to subserve the membrane permeability and antiadhesion. The as-prepared MAF-7@4/PES membrane exhibited exceptional salt rejection (98.7% for NaCl) and preferable permeability (1.24 L m−2 h−1 MPa−1), along with a flux decline ratio of 22.4% by employing bovine serum albumin (BSA) as the model foulant. The synergy of MAF-4 and MAF-7 enhanced the photocatalytic activity of membranes probably imputed to the almost perfect lattice match at the junction interface of epitaxial growth, leading to a bactericidal rate of nearly 100%. The main bactericidal mechanism was proved to be massive detected reactive oxygen species (•OH, H2O2 and •O2−) generated under visible light, rather than the role of leached metal ions and ligand precursor as recognized. Finally, the significant reduction in flux loss and the inhibition of biofilm formation in dynamic filtration indicated MAF-7@4/PES membrane had the potential for the application of desalination with a prominent antifouling property.

Porous ZrO2 encapsulated perovskite composite oxide for organic pollutants removal: Enhanced catalytic efficiency and suppressed metal leaching

Cobalt-based perovskite material, an effective activator of PMS, is widely employed for wastewater remediation, but still affected by the leakage of the cobalt ions. In this study, a porous core-shell structured perovskite LaFe0.1Co0.9O3-λ/SiO2 core @ZrO2 shell (LFCS@ZrO2) was fabricated and partially etched to enlarge channels to further enhance mass transfer ability. The well-designed core-shell structure can not only restrain metal ion leaching by changing the surface microenvironment but also provide an additional driving force attributed to the enriched concentration gradient, thus enhancing the catalytic oxidation performance. Results showed that the partially etched LFCS@ZrO2 (eLFCS@ZrO2) particles exhibited an increased pore size and showed an attractive catalytic performance as well as a suppressed cobalt ion leaching (3.61 to 0.67 mg/L). Over 99% of tetracycline hydrochloride (20 mg/L) could be degraded in 15 min, and the reaction rate increased 2 folds compared with pristine LaFe0.1Co0.9O3-λ. Besides, quenching test and electron paramagnetic resonance analysis proved that sulfate radicals and singlet oxygen were the two predominant reactive oxygen species during the catalytic oxidation. This work provides a novel perspective for the fabrication of an environmentally friendly perovskite catalyst, which has a great potential application in organic pollutant degradation.

Peroxymonosulfate activation through LED-induced ZnFe2O4 for levofloxacin degradation

• Energy-saving LED photocatalytic by ZnFe 2 O 4 contributes to PMS activation. • Photocatalytic generation of e - (CB) and h + (VB) favors producing SO 4 - ∙ and ∙OH. • Combination of PMS with e - (CB) reduces the recombination of e - (CB) and h + (VB). • Production of ∙O 2 – and 1 O 2 mainly contributes to LEV degradation. • Integrated ZnFe 2 O 4 /LED/PMS strategy leads to defluorination without metal ion leaching. Recently, a lot of attentions were paid on sulfate (SO 4 - ∙) and hydroxyl (∙OH) radicals-based advanced oxidation processes in degradation of fluoroquinolone antibiotic due to their favorable oxidation potential. This work reported an integrated peroxymonosulfate (PMS) activation process by coupling ZnFe 2 O 4 (ZFO) with energy-saving LED for degradation and defluorination of levofloxacin (LEV). The LEV degradation efficiency reached 88.52 % within 180 min in the ZFO-500/LED/PMS system, which was higher than those of other activation systems. Both SO 4 - ∙ and ∙OH were generated in the integrated ZFO-500/LED/PMS system by the photo-generated electrons and holes activation of PMS under the LED irradiation. The recombination of photo-generated electrons and holes was reduced. Plenty of ∙O 2 – and 1 O 2 were produced contributing to LEV degradation. The possible degradation pathways and mechanisms were proposed. This study presented a promising LED-assisted PMS activation process by ZnFe 2 O 4 for antibiotic degradation.

Insights into the mechanism of peroxydisulfate activated by magnetic spinel CuFe2O4/SBC as a heterogeneous catalyst for bisphenol S degradation

• CuFe 2 O 4 /SBC was synthesized via hydrothermal method assisted by PEG-20000. • The CuFe 2 O 4 /SBC/PDS system showed superior stability against metal ions leaching. • CuFe 2 O 4 /SBC could efficiently degrade 84.5% BPS in CuFe 2 O 4 /SBC/PDS system. • The adsorbed BPS on CuFe 2 O 4 /SBC could be further degraded. • The surface-bound radical pathways played a more crucial role. The CuFe 2 O 4 catalyst in advanced oxidation processes had received much attention, while the leaching metal ions and its agglomeration limited its application prospect. The conversion of waste activated sludge (WAS) into sludge-derived biochar (SBC) through pyrolysis could not only be the option of reducing the environmental burden but also converted to be the value-added environmental remediation materials. Hence, the present study prepared as a CuFe 2 O 4 /SBC heterogeneous catalyst to degrade new environmental pollutants (bisphenol S, BPS). To our best knowledge, CuFe 2 O 4 /SBC as a heterogeneous catalyst activating peroxydisulfate to degrade BPS in solution is rarely reported, and the catalytic performances and degradation mechanism of CuFe 2 O 4 /SBC need to be comprehensively investigated. The synergistic effect between CuFe 2 O 4 and SBC enhanced catalytic performances and alleviated agglomeration. The CuFe 2 O 4 /SBC was greatly ameliorated metal ions leaching, but the synthetic strategy could better optimize to further reducing Cu ion leaching. The dominant role of heterogeneous catalysis by CuFe 2 O 4 /SBC also have been elucidated. It was proposed that radical ( OH and SO 4 − ) and non-radical ( 1 O 2 ) oxidation processes worked together for BPS degradation, but surface-bound radical pathways played more crucial roles. Some intermediate products with higher toxicity may be produced due to the non-completely mineralized, thus future attention should be paid to their environmental risks. Hence, the detoxification efficiency of CuFe 2 O 4 /SBC needs to be further strengthened via improving the reaction conditions. Overall, this study provided a new strategy to simultaneously solve the problems of WAS disposal and leaching metal ions of CuFe 2 O 4 .

Study on the role of copper converter slag in simultaneously removing SO2 and NOx using KMnO4/copper converter slag slurry

To achieve “waste controlled by waste”, a novel wet process using KMnO4/copper converter slag slurry for simultaneously removing SO2 and NOx from acid-making tail gas was proposed. Through the solid-liquid separation for copper slag slurry, the liquid-phase part has a critical influence on removing NOx and SO2. Also, the leached metal ions played a crucial role in the absorption of SO2 and NOx. Subsequently, the effects of single/multi-metal ions on NOx removal was investigated. The results showed that the leached metal from copper converter slag (Al3+, Cu2+, and Mg2+) and KMnO4 had a synergistic effect on NOx removal, thereby improving the NOx removal efficiency. Whereas Fe2+ had an inhibitory effect on the NOx removal owing to the reaction between Fe2+ and KMnO4, thereby consuming the KMnO4. Besides, SO2 was converted to SO42− completely partly due to the liquid catalytic oxidation by metal ions. The XRD and XPS results indicated that the Fe (II) species (Fe2SiO4, Fe3O4) in copper slag can react with H+ ions with the generation of Fe2+, and further consumed the KMnO4, thereby resulting in a decrease in the NOx removal. The characterization of the slags and solutions before and after reaction led us to propose the possible mechanisms. The role of copper slag is as follows: (1) the alkaline substances in copper slag can absorb SO2 and NO2 by KMnO4 oxidation. (2) copper slag may function as a catalyst to accelerate SO2 conversion and improve NOx removal by synergistic effect between leached metal ions and KMnO4.

Manganese ferrite solid nanospheres solvothermally synthesized as catalyst for peroxymonosulfate activation to degrade and mineralize para-nitrophenol: Study of operational variables and catalyst reutilization

MnFe2O4 solid nanospheres (MSN) were synthesized by a solvothermal method. The sample was then used as catalyst to activate potassium peroxymonosulfate (PMS) for the generation of sulfate (SO4.–) and hydroxyl (HO.) radicals to degrade and mineralize para-nitrophenol (PNP) in water. The aim of this work was to study the influence of operational variables on the activity of the MSN catalyst to degrade and mineralize PNP, the PMS consumption kinetics, the leaching of metal ions, and the removal of nitrogen. Results showed that 100% of PNP (0.1 mM) was removed in MSN/PMS system by degradation within 7 h at a dosage of 4 mM of PMS, 0.5 g L−1 of MSN, 40 °C, and pH0 5.8. The reusability of the MSN catalyst was also studied, and a PNP degradation pathway was proposed. The PNP degradation followed a pseudo-first-order kinetic model and the activation energy obtained was 37.1 kJ/mol. Under the above standard reaction conditions, the catalyst showed a good performance after five catalytic runs, with a degradation efficiency that exceeded 98%, and removed around 70% of total organic carbon in each run. The excellent reusability and long-term stability was verified by the characterization of fresh and used catalysts. The sole degradation products were maleic and fumaric acids and nitrate and nitrite ions.

Carbon Nanocomposites: The Potential Heterogeneous Catalysts for Organic Transformations

One of the major challenges in chemistry confronted by the chemists is the replacement of conventional homogeneous catalysts by heterogeneous catalysts for the development of green, sustainable and economical chemical processes. Recently, carbón-based nanocomposites have attracted the attention of scientists due to their unique physical and chemical properties such as large surface area and pore volume, chemical inertness, high stability and high electrical conductivity. These NCs have been employed in energy storage, electronic devices, sensors, environmental remediation etc. Owing to the wide availability and low cost, carbón-based materials have been utilized as supports for transition metals and other materials. The carbón-based NCs offer a number of advantages such as high stability, easy recovery, reusability with often minimal leaching of metal ions, and green and sustainable approaches to heterogeneous catalysis for various organic transformations. Hence, they can be used as the substitute for the existing catalyst used for heterogeneous catalysis in industries. In this review, various processing methods for carbón-based nanocomposites and their applications as heterogeneous catalysts for organic transformations like hydrogenation, oxidation, coupling, and multi-component reactions, have been discussed.

Synthesis of an Alginate-Based Fe3O4-MnO2 Xerogel and Its Application for the Concurrent Elimination of Cr(VI) and Cd(II) from Aqueous Solution.

In this study, magnetite–manganese oxide (Fe3O4–MnO2) nanoparticles were synthesized and immobilized on alginate, producing a magnetite–manganese oxide xerogel (mMOX). This eco-friendly xerogel was used as an adsorbent of Cr(VI) and Cd(II). It was mesoporous and thermally stable, as determined by Brunauer–Emmett–Teller and thermogravimetric analysis. A scanning electron microscope coupled with an energy-dispersive X-ray system, Zetasizer, and attenuated total reflectance–Fourier transform infrared were used for characterization of adsorbents. The performance of the mMOX was investigated for the simultaneous adsorption of Cr(VI) and Cd(II) at different temperatures, pH values, contact times, initial concentrations of the adsorbate, and adsorbent doses. The developed xerogel (mMOX) showed high adsorption capacities of 3.86 mg/g for Cr(VI) and 3.95 mg/g for Cd(II) on 120 min of contact time with 5 ppm Cr(VI) and Cd(II) solution. The kinetic data fitted well with the pseudo-second order, while the Freundlich isotherm model was found to be fit for adsorption data. Thermodynamic study revealed the adsorption to be spontaneous and exothermic. The adsorbent showed useful application for real water samples by more than 75% uptake of Cr and Cd with low adsorption of Na, K, and Mg. The regeneration study indicated that the mMOX could be reused up to six cycles with more than 50% removal of Cr(VI) and Cd(II) ions from aqueous solution with minimal leaching of metal ions (Fe, Ca, Na, K, and Mn) into the solution.

Research progress of LDHs as Fenton reaction catalysts

<p indent=0mm>Fenton reaction utilizes the catalytic reaction of H₂O₂ and Fe²⁺ to generate highly active hydroxyl radicals (·OH) quickly to degrade organic compounds without the secondary pollution of by-products, which is widely used in the fields of environmental protection and sewage treatment. However, the difficulty of the regeneration of low-valence metals in the ordinary homogeneous Fenton reaction limits the efficiency of the overall reaction. In addition, the acidic requirements of the reaction system and the introduction of iron ions are not ideal from an environmental perspective. In recent years, layered double hydroxides (LDHs), as a unique layered material, have shown excellent catalytic performance in Fenton reaction and have attracted widespread attention. The active sites of LDHs are usually the metal ions fixed on the solid surface, which can avoid the leaching of metal ions and reduce the pH requirements of the reaction system. Besides, by adjusting the structure of the LDHs layers, a redox cycle of multiple metals can be formed, which promotes the regeneration of the low-valence metals effectively and thus improves the efficiency of the Fenton reaction. This review mainly summarizes the recent progress of LDHs materials as Fenton reaction catalysts. The challenge and prospective trends of LDHs materials as Fenton reaction catalysts are also discussed.

Surface functionalized bioceramics coated on metallic implants for biomedical and anticorrosion performance - a review.

In modern days, the usage of trauma fixation devices has significantly increased due to sports injury, age-related issues, accidents, and revision surgery purposes. Numerous materials such as stainless steel, titanium, Co-Cr alloy, polymers, and ceramics have been used to replace the missing or defective parts of the human body. After implantation, body fluids (Na+, K+, and Cl-), protein, and blood cells interact with the surface of metallic implants, which favours the release of ions from the metallic surface to surrounding body tissues, leading to a hypersensitive reaction. Body pH, temperature, and interaction of immune cells also cause metal ion leaching and lose host cell interaction and effective mineralization for better durability. Moreover, microbial invasion is another important crisis, which produces extracellular compounds onto the biomaterial surface through which it escapes from the antimicrobial agents. To enhance the performance of materials by improving mechanical, corrosion resistance, antimicrobial, and biocompatibility properties, surface modification is a prerequisite method in which chemical vapour deposition (CVD), physical vapour deposition (PVD), sol-gel method, and electrochemical deposition are generally involved. The properties of bioceramics such as chemical inertness, bioactivity, biocompatibility, and corrosion protection make them most suitable for the surface functionalization of metallic implants. To the best of our knowledge, very limited literature is available to discuss the interaction of body proteins, pH, and temperature onto bioceramic coatings. Hence, the present review focuses on the corrosion behaviour of different ceramic composite coating materials with different conditions. This review initially briefs the properties and surface chemistry of metal implants and the need for surface modifications by different deposition techniques. Further, mechanical, cytotoxicity, antimicrobial property, and electrochemical behaviour of ceramics and metal nitride coatings are discussed. Finally, future perspectives of coatings are outlined for biomedical applications.

Efficient degradation of sulfamethoxazole by CoCu LDH composite membrane activating peroxymonosulfate with decreased metal ion leaching

• Two types of membranes decorated with CoCu-LDH nanoparticles was fabricated. • LDH-based membranes exhibited excellent activity in PMS activation process. • The practical applicability of LDH@PVDF membrane was investigated. • The reactive mechanism of LDH@PVDF/PMS system was proposed. In this study, we prepared two types of composite membranes decorated with CoCu layered double hydroxide (LDH) nanoparticles, i.e. LDH@Calotropis gigantean fiber (LDH@CGF) and LDH@polyvinylidene fluoride (LDH@PVDF) for the first time. Besides, the application potential of different types of composite functional membranes based on LDH in PMS activation system was compared. Both of the LDH-based composite membranes exhibited excellent activity in peroxymonosulfate (PMS) activation process. More importantly, the composite membrane could be separated from the treated water to meet the need of practical application. The superior composite membrane was identified as LDH@PVDF, which was with excellent PMS activation capability and pretty lower metal ions leaching concentration (cobalt 0.044 mg L −1 , copper 0.026 mg L −1 ). And then, LDH@PVDF was employed to investigate the PMS activation performance in various pharmaceutical pollutants removal processes. Besides, the activity of LDH@PVDF for SMX degradation in real aquatic environment (tap water and wastewater) was detected, proving the wide practical applicability of LDH@PVDF membrane. Finally, the possible SMX degradation pathway and PMS activation mechanism occurring in LDH-based composite membrane/PMS system were proposed. Hence, this study for LDH-based membranes construction may provide new insights into the environmentally-friendly catalytic membranes preparation and practical application in wastewater treatment.

Enhanced the visible light photocatalytic decomposition of antibiotic pollutant in wastewater by using Cu doped WO3

Due to the rapid increase in the use of tetracycline (TC), a broad-spectrum antibiotic, the environmental residues of TC in water have aroused critical health issues. This work investigates the effectiveness and capability of Cu ions loaded WO3 (Cu-WO3) for the enhancement of photocatalytic decomposition of TC in wastewater. Different techniques were employed to characterize the catalyst such as XRD, XPS, FESEM, TEM and UV–vis. The optical properties analysis showed that Cu doped WO3 was successfully narrowed the bandgap energy, resulting in improved the removal efficiency of TC. Experimental results illustrate that Cu doping effectively improved the photocatalytic activity of WO3 and 2.5 %. wt. Cu doped exhibited the highest TC degradation efficiency (96.8 %). The photocatalytic decomposition of TC by Cu-WO3 was significantly increased under strongly alkaline conditions (pH 8–10). The reusability of catalysts and the leaching of transition metal ions was also investigated. After the fifth cycle, the photocatalytic degradation of TC by Cu-WO3 only reduced by 18.2 %, indicated that the Cu-WO3 can use as an excellent photocatalyst response for the TC degradation. The radical screening, the intermediates products and the proposed mechanism were discussed in detail. Finally, the Cu-WO3 was applied to remove TC from wastewater and it could efficiently remove 93.7 % TC within 60 min. Based on these findings, Cu-WO3 can use as a good candidate with long-time stability for photodegradation of TC in wastewater.

Development of technology of utilization of products of ferritization processing of galvanic waste in the composition of alkaline cements

A study of the products of ferritization processing of galvanic waste: sludge and spent process solutions is carried out. As a result of experiments on dynamic leaching of heavy metal ions, the immobilization properties of the sludge, obtained at different process parameters of ferritization are determined. It is shown that the level of immobilization of heavy metals in ferrite sludge after leaching is 99.96 wt % and in the sludge of traditional wastewater neutralization &lt;97.83 wt %. The studies determine the possibility of reliable utilization of ferritized galvanic waste – introduction into the charge to produce alkaline cements. It is found that the main crystalline phases in the structure of alkaline cements with ferrite sludge are calcite, quartz and heavy metal ferrites. In addition, jelly-like formations are found, which are further capable of crystallization. Such formations reliably bind heavy metals in the chemical structure of cement. It is found that when using up to 10 wt % of ferrite sludge in the total weight of cement, the compressive strength of artificial stone reaches 40 MPa, which meets the requirements of the current standard. The chemical stability of the alkali cement matrix using ferrite sludge is confirmed by the study of leaching of heavy metals for one day in neutral, alkaline and acidic media. It is shown that the degree of immobilization of heavy metal ions in cement with a ferrite sludge content of 30 wt % is &gt;99.98 %. In addition, the concentrations of heavy metal ions during leaching meet the national and international standards for their MPC in drinking water and soil. This approach will allow solving the problem of utilization of hazardous galvanic waste and production of general construction materials

Heterogeneous Catalytic Ozonation of Phenol by a Novel Binary Catalyst of Fe-Ni/MAC

Iron-nickel supported on modified active carbon (Fe-Ni/MAC) was prepared and characterized by XRD, SEM, XPS and EDS, followed by evaluating the practicability of Fe-Ni/MAC in treating real wastewater with a high concentration of phenol. Results showed that the optimal conditions for catalytic ozonation obtained by response surface methodology (RSM) were catalyst 10 g/L, ozone 68 mg/L, pH 9 and reaction time 90 min. Fe-Ni alloy and NiFe2O4 were demonstrated to be the dominant active species involved in catalytic reaction. The Fe-Ni/MAC catalyst can be reused six times with a satisfactory performance and little leaching of metal ions. Although some radicals like ·OH and ·O2− functioned well, singlet oxygen (1O2) was regarded as the most important radical in the Fe-Ni/MAC process. Most noticeably, the fluorescence excitation emission matrices (EEMs) certified that as much as 1243 mg/L phenol in the real wastewater was completely degraded, which made Fe-Ni/MAC a fairly practical catalyst.

Comparison of Methods for Surface Modification of Barium Titanate Nanoparticles for Aqueous Dispersibility: Toward Biomedical Utilization of Perovskite Oxides.

Colloidal perovskite barium titanate (BaTiO3, or BT) nanoparticles (NPs), conventionally used for applications in electronics, can also be considered for their potential as biocompatible computed tomography (CT) contrast agents. NPs of BT produced by traditional solid-state methods tend to have broad size distributions and poor dispersibility in aqueous media. Furthermore, uncoated BT NPs can be cytotoxic because of leaching of the heavy metal ion, Ba2+. Here, we present and compare three approaches for surface modification of BT NPs (8 nm) synthesized by the gel collection method to improve their aqueous stability and dispersibility. The first approach produced citrate-capped BT NPs that exhibited extremely high aqueous dispersibility (up to 50 mg/mL) and a small hydrodynamic size (11 nm). Although the high dispersibility was found to be pH-dependent, such aqueous stability sufficiently enabled a feasibility analysis of BT NPs as CT contrast agents. The second approach, a core/shell design, aimed to encapsulate BT nanoaggregates with a silica layer using a modified Stöber method. A cluster of 7-20 NPs coated with a thick layer (20-100 nm) of SiO2 was routinely observed, producing larger NPs in the 100-200 nm range. A third approach was developed using a reverse-microemulsion method to encapsulate a single BT core within a thin (10 nm) silica layer, with an overall particle size of 29 nm. The -OH groups on the silica layer readily enabled surface PEGylation, allowing the NPs to remain highly stable in saline solutions. We report that the silica-coated BT NPs in both methods exhibited a low level of Ba2+ leaching (≤3% of total barium in NPs) in phosphate-buffered saline for 48 h compared to the unmodified BT NPs (14.4%).

Analysis of Eco-Toxicity Studies of Leaching of Metal Ions from Flyash-Sewage Sludge Mixture in Poecilia Reticulata (Guppy Fish)

Analysis of Eco-Toxicity Studies of Leaching of Metal Ions from Flyash-Sewage Sludge Mixture in Poecilia Reticulata (Guppy Fish)

Facile synthesis and synergistic mechanism of CoFe2O4@three-dimensional graphene aerogels towards peroxymonosulfate activation for highly efficient degradation of recalcitrant organic pollutants

Magnetic CoFe2O4 is a promising heterogeneous catalyst with great separation and catalytic performance on peroxymonosulfate (PMS) activation. However, for extremely recalcitrant organic pollutants (e.g. Benzotriazole (BTA)), CoFe2O4/PMS system exhibits much low catalytic performance and high metal ion leaching. As such, CoFe2O4 supported on three-dimensional graphene aerogels (CoFe2O4@3DG) was synthesized via facile hydrothermal method. It turns out that 3DG as supporter significantly enhances specific surface area, redox activity and electron transfer of composite. The degradation rate constant in the CoFe2O4@3DG/PMS system (0.0203 min−1) is 15 times higher than that in the CoFe2O4/PMS system (0.0013 min−1). It results from synergistic activation of PMS by CoFe2O4 and 3DG to generate multiple reactive oxygen species (•OH, SO4−•, O2−• and 1O2). Particularly, high graphitization structure and low oxygen groups content of 3DG facilitate PMS adsorption on its surface and electron transfer from BTA to PMS. Ultimately, BTA is degraded into CO2, NH3 and intermediates through benzene and triazole ring-opening reactions. Moreover, CoFe2O4@3DG/PMS system displays good stability and recyclability. Therefore, this study provides a new way to improve CoFe2O4 activity for extremely recalcitrant organic pollutants degradation and new insights into synergistic activation of PMS by CoFe2O4 and 3DG, which further advances cobalt-based catalysts in heterogeneous catalysis.

Effect of fluoride agents on surface characteristics of NiTi wires. An ex vivo investigation

AimTo analyze the degree of corrosion of nickel titanium arch wires in patients with and without exposure to fluorides. Material and methodsThis was an ex vivo study comprising of 60 subjects undergoing fixed orthodontic treatment. Group 1(controls) comprised of 30 sets of new unused NiTi wires and unused 11, 15 brackets, Group 2(patients) comprised of 30 sets of non fluoridated NiTi wires and 11, 15 brackets and Group 3(patients) had 30 sets of fluoridated NiTi wires and 11, 15 brackets. NiTi wires were used over 6 months of treatment(0.014″,0.016″, 16 × 22”, each wire was used for 2 months and replaced with the next size). All wires were retrieved, stored and analyzed. At 6 months, brackets from 11 to 15 were debonded in both treatment groups. Archwires and brackets in 3 groups were subjected to SEM analysis at 500 and 1000X to observe differences. Additionally, EDX Spectroscopy was undertaken to evaluate surface elemental compositional differences in groups. ResultsSignificant differences among groups were evident in brackets and archwires tested. Maximum degradation, cracks and dark spots were seen in wires and brackets exposed to fluoride agents. EDX spectroscopy revealed least Ni% in fluoridated wires and brackets. ConclusionsIncreased leaching of metal ions was evident when wires and brackets are exposed to fluoride agents during treatment. Use of non fluoridated mouthwash and toothpastes may be considered in orthodontic patients without risk of caries to mitigate such effects