Multi walled carbon nanotubes (MWCNTs) have attracted more and more attention as adsorbents due to their excellent adsorption properties. By loading metal particles on MWCNTs, the chemical reduction ...ability of adsorbed pollutants could be provided, so as to achieve the purpose of adsorption and degradation of pollutants. Therefore, the removal process of NO3−-N by Fe–Pd–Fe3O4/MWCNTs was studied, including rapid adsorption of initial pollutants, gradual reduction of intermediate products and re-adsorption of final products. The results showed that Fe–Pd–Fe3O4/MWCNTs completely removed NO3−-N within 2 h, 39% and 25% of which were converted into NO2−-N and NH4+-N. The adsorption efficiency, kinetics, capacity and adsorption energy all followed the order of NH4+-N > NO2−-N > NO3−-N. With the recoverability and reusability of Fe–Pd–Fe3O4/MWCNTs having been confirmed in 5 consecutive cycles, the removal rate of NO3−-N still reached 43%. It has been shown that MWCNTs prolonged the reducing power for NO3−-N, due to avoiding the aggregation of metal particles. The rapid adsorption of initial pollutants, effective stepwise reduction and convenient recovery processes were of great value for the rehabilitation of polluted water.
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•50 mg/L Fe–Pd–Fe3O4/MWCNTs completely removed 100 mg/L NO3−-N within 2 h.•36% of adsorbed NO3−-N was converted into N2 or N2O.•The removal efficiency of NO3−-N reached 43% by Fe–Pd–Fe3O4/MWCNTs in 5 cycles.
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•Bimetallic Fe–Pd nanoparticles were immobilized effectively onto resin DOW 3N.•Loading order of Fe and Pd affected the activity and selectivity of DOW 3N-Fe/Pd.•Nitrate removal ...(>95%) using DOW 3N-Fe/Pd was obtained at near-neutral pH.•N2 selectivity of 71.0% was obtained at pH 8.67 without addition of reductant H2.
Nano zero valent iron (nZVI) has emerged as a promising water treatment technology for reduction of contaminants. Unfortunately, for nitrate reduction by nZVI, near 100% of nitrate was converted to undesired ammonia (NH3) and not to nontoxic nitrogen (N2). In this study, supported bimetallic Fe–Pd nanoparticles were prepared by loading Fe and Pd on chelating resin (DOW 3N) by two different methods. The effect of the preparation method, solution pH and Pd loading on the reactivity and selectivity of Fe–Pd composites for nitrate removal was investigated at near-neutral pH in unbuffered solution. The results suggest that DOW 3N-Fe/Pd, which was prepared by loading Pd firstly and then Fe on DOW 3N, showed a remarkable nitrate removal (>95%). The selectivity to N2 was increased with the increase of Pd content and solution pH; the N2 selectivity of 69.2% was obtained at pH 6.75 using DOW 3N-Fe/Pd with 8wt.% Pd–8wt.% Fe. The high selectivity to N2 benefited from the closer contact distance between Pd and Fe on the surface of DOW 3N-Fe/Pd and low intraparticle diffusion resistance.
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•Green synthesize of Fe/Pd and in-situ B-Fe/Pd nanocomposite using pomegranate peel extract.•Above 80 % of TC removal using Fe/Pd bimetal with very less dopant Pd concentration ...(0.015 M) in batch removal studies.•Improved stability and surface functional groups of Fe/Pd bimetal by in-situ coating on bentonite clay.•Enhanced TC removal of 95 % by treating with B-Fe/Pd within 90 min of interaction.•Validation on real water system and residual toxicity analysis to prove biocompatibility of B-Fe/Pd for water treatment.
The residual TC in the aquatic system is a major threat to human and animal lives. In this study, green synthesized bimetallic Fe/Pd and in-situ clay supported Fe/Pd was used for the efficient removal of tetracycline antibiotics from the aqueous system. Green synthesized bimetallic Fe/Pd nanocomposite and in-situ clay supported Fe/Pd (B-Fe/Pd) were characterized by SEM-EDX, FTIR, and XRD to confirm their size and surface functional groups. The batch removal processes were performed to examine the effect of operational parameters such as dopant Pd concentration (5−20 mM), sorbents: Fe/Pd (100−1000 mg/L) and B-Fe/Pd (100−300 mg/L), pollutant TC (20−60 mg/L) and pH (3–9) on the TC removal. At the optimized conditions, Fe/Pd (sorbent dosage 1000 mg/L, pH 7, TC conc. 20 mg/L), and B-Fe/Pd (sorbent dosage 300 mg/L, pH 7, TC conc. 20 mg/L) nanocomposite can remove 81 % and 97 % of TC from aqueous sample. Higher surface area and prolonged shelf-life of B-Fe/Pd with highest removal percentage make it more effective and efficient material for TC removal; further, the statistical optimization of TC removal by B-Fe/Pd was carried out by response surface methodology, and 95 % of TC could be eliminated from the aqueous solution. Reusability studies of B-Fe/Pd showed that the TC removal efficiency up to 3rd cycle with above 60 % TC removal and the validation on real water sample confirmed with above 75 % TC removal. Residual toxicity of B-Fe/Pd interacted TC solution on freshwater chlorella sp. showed less toxicity, which indicates the environmentally friendly and hazardous free nature of B-Fe/Pd.
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•The nanocomposites led the occur of short-cut denitrification.•The generation of NO2−-N and NH4+-N by nanocomposites enriched NO3−-N removal pathway.•The nanocomposites induced ...electrons flow to metabolism and denitrification, respectively.•The nanocomposites had significantly promotion on nitrite reductase activity.•The electron exchange capacity of nanocomposites promoted electron transfer activity.
Aiming at the accumulation of NO2−-N and N2O during denitrification process, this work focused to improve the denitrification performance by Pd-Fe embedded multi-walled carbon nanotubes (MWCNTs). The main conclusions were as follows: 30 mg/L Pd-Fe/MWCNTs have shown an excellent promotion on denitrification (completely TN removal at 36 h). Meanwhile, enzyme activity results indicated that the generation of NO2−-N, NH4+-N by Pd-Fe/MWCNTs led the occur of short-cut denitrification by increasing 203.9% the nitrite reductase activity. Furthermore, electrochemical results and index correlation analysis confirmed that the electron exchange capacity (1.401 mmol eg−1) of Pd-Fe/MWCNTs was positively related to nitrite reductase activity, indicating its crucial role in electron transport activity (0.46 μg O2/(protein·min) at 24 h) during denitrification process by Pd-Fe/MWCNTs played a role of chemical reductant and redox mediator.
•The functions of Fe-Pd@ZIF-8 was identified.•Both adsorption and reductive dichlorination was proposed.•the key factors affecting the removal rate were studied.•The removal of 2,4-DCP from ...wastewater was demonstrated.
Recently, bimetallic Fe-Pd nanoparticles were integrated with metal organic frameworks (MOFs) to produce a new composite catalyst with significant potential for organic contaminant removal due to enhanced adsorption and reduction. Here, 85.9 % of 2,4-dichlorophenol (2,4-DCP) was successfully removed from aqueous solution within 120 min when using a zinc-based zeolitic imidazolate framework (ZIF-8) embedded with Fe-Pd (Fe-Pd@ZIF-8). In comparison only 77.4 and 48.3 % was removed when using ZIF-8 or Fe-Pd alone. Thus, to better understand the function of composite components (ZIF-8 and Fe-Pd) in the removal of 2,4-DCP, and the specific removal mechanism involved, Fe-Pd@ZIF-8 was characterized before and after exposure to 2,4-DCP. This comparison revealed that 2,4-DCP was adsorbed onto the surface of the composite during exposure. Moreover, while ZIF-8 maintained stability following the removal of 2,4-DCP, Fe0 was partially oxidized and Pd functioned as a catalyst in the removal process. Furthermore, kinetic studies demonstrated that the initial adsorption of 2,4-DCP conformed to a pseudo-second-order model and the subsequent reduction conformed to a pseudo-first-order model, whereas isothermal adsorption best fit the Freundlich adsorption model. This observation suggested that removal mechanism of 2,4-DCP involved both adsorption and dechlorination. Finally, Fe-Pd@ZIF-8 was applied to practically remove 2,4-DCP from wastewater, showing a 74.4 % removal efficiency which indicated that the composite was a potential new nanomaterial for practically removing organic contaminants from wastewater.
This paper reports microstructure associated with the L10 and L12 two-phase coexistence region in magnetic Fe-Pd alloys and analyzes the observed complex nanometer scale wetting layer structures. Fe ...- 61.8 at% Pd samples were continuously cooled from the disordered A1 phase through the eutectoid isotherm and aged at 650 °C for various times. X-ray diffraction reveals that the samples first order to L12 then transform to L10-dominant L10 + L12 two-phase mixture. It is shown that L10 forms {110} polytwin microstructure with straight {11¯0} antiphase boundaries (APBs), where L12 exists as nanometer-scale wetting layers along the twin boundaries and APBs. The variant selection for L12/L10 wetting layers is discussed, and evidence of closed/open APB structures is shown with high-resolution transmission electron microscopy.
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•Effect of surface structure and Pd doping of Fe catalysts on the hydrodeoxygenation of phenol is studied by DFT.•The adsorption strength of phenol follows the sequence of Fe(111) > ...Fe(110) > Fe(211).•Fe(211) favors the formation of benzene while the ring hydrogenation is more selective on Fe(110) and Fe(111).•Doping Pd does not significantly impact phenol adsorption and reaction path on Fe(110) and Fe(111).•Doping Pd on Fe(211) enhances the reaction rates and the selectivity to benzene.
Density functional theory (DFT) calculations were performed to investigate the effects of surface structure and Pd doping of Fe catalysts on the activity and selectivity of phenol hydrodeoxygenation (HDO). Phenol adsorption via binding with the aromatic ring was found to be energetically more stable than adsorbing through solely the hydroxyl group on Fe(110), Fe(111) and Fe(211) surfaces. The adsorption strength on monometallic Fe surfaces increased in the sequence of Fe(211) < Fe(110) < Fe(111). Pd doping did not have a significant influence on the adsorption stability of phenol. The (211) facet of Fe featured particular steps showed good activity toward aromatics production, as evidenced by the lower barriers associated with the dehydroxylation followed by H addition to form benzene than the direct hydrogenation on the aromatic ring. In contrast, the ring saturation products would be dominant on Fe(110) and Fe(111) surfaces due to lower hydrogenation barriers on the aromatic ring of phenol as compared to the CAr-O bond cleavage. The kinetically preferred pathway for phenol conversion on Pd doped Fe(110) and Fe(111) surfaces was the direct hydrogenation on the aromatic ring, same to that identified on monometallic (110) and (111) surfaces. In comparison, on Fe(211), the difference in kinetic barrier between dehydroxylation and ring hydrogenation pathways became larger in the presence of Pd, promoting the selectivity to benzene formation. In the presence of Pd dopant, the H2 molecule was readily dissociated and the surface H* coverage was increased, leading to a lowering of the adsorption enthalpy of key surface species and ultimately enhancing the rates of HDO.
The effect of Mn addition on the structural and magnetic properties of Fe–Pd ferromagnetic shape memory alloys is investigated. In particular, a complete characterization of the influence of the ...partial substitution of Fe by Mn has been performed on Fe
69.4−
x
Pd
30.6Mn
x
(
x
=
0, 1, 2.5 and 5) alloys. The substitution of 1% Fe by Mn fully inhibits the undesirable irreversible face-centered tetragonal to body-centered tetragonal transformation without decreasing the face-centered cubic to face-centered tetragonal temperature. In addition, the substitution of 2.5% Fe by Mn gives rise to the highest thermoelastic transformation temperature observed to date in the Fe–Pd system, probably due to an increase in the valence electron concentration. The magnetocaloric effect has been evaluated in this alloy system for the first time. Nevertheless, the low values obtained suggest that the Fe–Pd alloys are not good candidates for magnetic refrigeration applications.
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•A novel composite membrane with nanosize surface pores was prepared.•Microgels decorated by Fe–Pd nanoparticles were immobilized in membrane pores.•A cross-flow model of membrane was ...applied to dechlorination for the first time.•Dechlorination and separation were simultaneously realized by one-step operation.
A novel composite membrane with membrane pores loading acrylic acid microgels coated by Fe–Pd bimetallic nanoparticles (NPs) was prepared for the dechlorination of trichloroethene (TCE) in water. This membrane was prepared by firstly immobilizing acrylic acid microgels in poly (vinylidene fluoride) (PVDF) membrane pores and then in-situ synthesis of Fe–Pd bimetallic nanoparticles (NPs). The Fe–Pd NPs coupled with the porous membranes enabled dechlorination to be conducted in a cross-flow model including a penetrative flow and a tangential flow. In such a model, a large number of dechlorination occurred in penetrative flow fluid while no dechlorination occurred in tangential flow fluid. Thus, products and reactants are always timely isolated in the cross-flow dechlorination process. The composite membrane prevents Fe–Pd NPs from contamination because its nanosize surface pores stop colloids and bovine serum albumin (BSA) from entering into the membrane interior. However, these small surfaces pores cannot slow the diffusion of reactants into membrane pores, and thus make the as-formed composite membrane also show a fast dechlorination rate in a batch reaction. All in all, TCE dechlorination by the composite membrane shows many advantages including the fast dechlorination rate, the convenient operation, the timely isolation of products from reactants, and the ignorable extra steps for separation of metal NPs.
