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A three-component nano-electrocatalyst, magnetite coated molybdenum disulfide hybridized with reduced graphene oxide (Fe3O4@MoS2/RGO), is synthesized by a two-step hydrothermal ...method. This catalyst is applied as an effective substitution for the platinum catalyst in methanol oxidation and hydrogen evolution reactions. Cyclic voltammetry, chronoamperometry, and linear sweep voltammetry are used to evaluate the performance of the electrocatalyst in acidic and basic media. The results of methanol oxidation reaction on the hybridized nano-electrocatalyst showed good electrocatalytic properties with considerable diffusion currents. This fact is confirmed by the Tafel plots and the calculated kinetic parameters of electron transfer. Fe3O4@MoS2/RGO showed an anodic transfer coefficient and exchange current of 0.464 and 4.80 × 10−8, respectively that are higher than Fe3O4/RGO. The presence of the porous MoS2 in catalyst has a key effect on supplying electroactive sites for electron transfer. Also, the high actual surface area obtained for the hybridized nano-electrocatalyst (A = 0.0295 cm2). The maximum power density of 35.03 mW cm−2 obtained for a single cell containing the prepared hybridized catalyst as the anode which shows a competitive feature of the synthetic catalyst compared to other reports. Furthermore, the synthetic catalyst shows the low-value overpotential of 108 mV and Tafel slope of 48 mV dec−1 during the hydrogen evolution process in acidic media. This is attributed to the synergistic effect between Fe3O4 and MoS2 and also increase the electron transfer rate due to adding conductive RGO to the catalyst. The results show that the synthetic nanocatalyst can have promising applications for hydrogen evolution and methanol oxidation reactions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Palladium-supported o-phenylenediamine-functionalized Fe3O4 magnetic nanoparticles are presented. A convenient synthetic route for the nanocatalyst and also its application in Suzuki–Miyaura coupling ...of various aryl halides with phenylboronic acids are described. A high reaction yield (98%) was been obtained in a short reaction time (10 min) through use of this highly efficient nanocatalyst. From a mechanistic aspect, firstly, effective electronic interactions between heteroatoms such as oxygen and Pd(II) provide a suitable condition for covalent bonding by the ingredients in the Suzuki–Miyaura coupling reaction. Secondly, Pd(II) is converted to Pd(0) by use of sodium borohydride in the presence of triphenylphosphine in basic conditions, and then it plays a main role in the catalytic process. However, the most distinguished properties of this catalytic system are the ease of catalyst separation and great reusability. The palladium-supported o-phenylenediamine-functionalized Fe3O4 nanoparticles can be easily recovered by use of an external magnet and can reused at least ten times with no significant decline in catalytic activity. This novel system was structurally characterized by various analytical methods, and the results obtained are well interpreted in the context.
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•A novel Pd-supported nanoscale catalytic system was designed and characterized.•A highly efficient nanocatalyst with excellent reusability and superparamagnetic behavior was synthesized.•It successfully catalyzed Suzuki–Miyaura coupling reactions for synthesis of biphenyls.•High reaction yields in short reaction times were obtained under mild conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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Manganese catalyst was immobilized on Fe3O4/graphene hybrids to facilitate magnetic separation.Magnetic manganese catalyst exhibited high efficacy and long-term stability for ...catalytic PMS activation.The minerlization efficiency and the biotoxicity of BPA byproducts were evaluated.The degradation pathways of BPA and the possible activation mechanism of PMS were proposed.
A heterogeneous manganese/magnetite/graphene oxide (Mn-MGO) hybrid catalyst was fabricated through the reduction of KMnO4 by ethylene glycol in the presence of magnetite/GO (MGO) particles. The Mn-MGO catalyst exhibited high efficacy and long-term stability in activating peroxymonosulfate (PMS) to generate sulfate radicals for the removal of bisphenol A (BPA) from water. The results of the batch experiments indicated that an increase in the catalyst dose and solution pH could enhance BPA degradation in the coupled Mn-MGO/PMS system. Regardless of the initial pH, the solution pH significantly dropped after the reaction, which was caused by catalytic PMS activation. The production of sulfate radicals and hydroxyl radicals was validated through radical quenching and electron paramagnetic resonances (EPR) tests. BPA degradation pathways were proposed on the basis of LC⿿MS and GC⿿MS analyses. Finally, a possible mechanism of catalytic PMS activation was proposed that involved electron transfer from MnO or Mn2O3 to PMS with the generation of sulfate radicals, protons and MnO2, as well as the simultaneous reduction of MnO2 by PMS.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•Biwettable Janus nanoparticles are facily synthesized via sequential adsorption of cellulosic materials.•Biodegradable and environmentally friendly cellulosic materials used for the ...synthesis.•The M−Janus nanoparticles enhance phase separation of oily wastewaters and water-in-crude oil emulsions.•The M−Janus nanoparticles exhibit excellent interfacial activities.
A new class of magnetically responsive and interfacially active Janus (M−Janus) nanoparticles was designed and synthesized by sequential adsorption of cellulosic materials: hydrophobic ethyl cellulose (EC) and hydrophilic carboxymethyl cellulose (CMC) on the opposite sides of magnetite (Fe3O4) nanoparticles. The adsorption study using quartz crystal microbalance with dissipation (QCM-D) proved the concept of proposed synthesis of M−Janus nanoparticles. The adsorption of EC and CMC on magnetite nanoparticles was confirmed by zeta-potential measurements, thermogravimetric analysis (TGA), characterization using Fourier transform infrared spectroscopy (FTIR) and TEM. The surface wettabilities of the opposite sides on the M−Janus nanoparticles were investigated by measuring contact angles of nanoparticle surfaces deposited from the oil-water interfaces using the Langmuir-Blodgett method. SEM images revealed an excellent dispersion of M−Janus nanoparticles in both aqueous and organic phases. The results from the coalescence time and crumpling ratio measurement of particles-stabilized oil droplets along with the interfacial pressure-area isotherms demonstrated stronger interfacial activities of M−Janus nanoparticles and a stiffer interface with adsorbed M−Janus nanoparticles as compared with the interfaces stabilized by conventional interfacially-active nanoparticles. The microscopy images confirmed the deposition of M−Janus nanoparticles at the emulsion droplet surface during the phase separation process. The M−Janus nanoparticles not only exhibited excellent capability and high efficiency in separating emulsified water from water-in-crude oil emulsions and the oil from oily wastewaters under an external magnetic field, but also retained high interfacial activity and hence desirable separation efficiency after five-cycle applications. Because of the environmentally friendly and biodegradable cellulosic materials used in the synthesis, the M−Janus nanoparticle can achieve effective oil/water phase separation without causing further pollution to the continuous phase.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•La/Fe3O4-BC and Ce/Fe3O4-BC were synthesized through co-precipitation method.•Doped magnetic biochars especially La/Fe3O4-BC exhibited superior adsorption performance.•Inner-sphere ...complexion was the main mechanism under neutral conditions.
To improve the biochar’s adsorption performance towards phosphate as well as to endow the biochar with magnetic property, novel rare earth element doped magnetic biochars, Ce/Fe3O4-BC and La/Fe3O4-BC, were prepared by separately co-precipitating cerium (Ce) and lanthanum (La) with FeCl3, FeCl2 and biochar. For comparison, Fe3O4-BC without doping Ce or La was also synthesized. The characterization results indicated that Ce and La ions were successfully doped into the magnetite. The La/Fe3O4-BC had higher magnetic saturation and point of zero charge than Ce/Fe3O4-BC. A series of batch experiment results demonstrated that the phosphate adsorption capacity of biochar has been greatly improved after Ce or La doping, especially La. The phosphate adsorption capacity of La/Fe3O4-BC was 20.5 mg/g at pH 6.5, which was 1.6 and 2.9 times than that of Ce/Fe3O4-BC and Fe3O4-BC, respectively. The adsorption kinetics and isotherms of phosphate onto La/Fe3O4-BC and Ce/Fe3O4-BC were best fitted by the pseudo-second order and Freundich model, respectively, indicating that the adsorption process was a multilayer process and controlled by chemical reaction. The combined results of batch experiments and physiochemical analyses revealed that the possible mechanisms were the formation of inner-sphere complex at neutral conditions and electrostatic attraction between positively charged adsorption sites and phosphate under acid conditions. The enhanced phosphate adsorption performance and endowed magnetic property indicated La/Fe3O4-BC could be used as a promising adsorbent in phosphate removal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Non-oxidative graphene was economically fabricated on a mass production basis.•Non-oxidative graphene was used to synthesize with magnetite for arsenic removal.•The ...magnetite/non-oxidative graphene composites effectively adsorbed arsenic.•The significant arsenic re-adsorption capacity after regeneration was observed.
Since graphene-based materials have been investigated to adsorb many kinds of contaminants such as heavy metals especially arsenic, the fabrication costs of them are critically important for their application to the practical adsorption process. Here, we fabricate a non-oxidative graphene with mass production and synthesis magnetite/non-oxidative graphene (M-nOG) composites for arsenic removal. The M-nOG showed great capacity for adsorption of arsenic against its low material cost. We found that the arsenite was more influenced by surface complexation and the arsenate was favorable for intraparticle diffusion in the adsorption process using M-nOG. To confirm the feasibility of M-nOG as adsorbents for arsenic removal, the effect of various conditions such as pH, temperature, competing anions, and humic acid on the arsenic removal were evaluated. Moreover, the repetitive reuse and regeneration of M-nOG were performed. In conclusion, the M-nOG was cost-effective and feasible to use practically as adsorbents for arsenic removal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This review highlights scientific and advances of carbon-based functional materials, such as graphene, biochar, activated carbon, carbon cloth and nano-tube, maghemite and magnetite carbons in ...improving anaerobic digestion performance. Moreover, it focuses on some important mechanisms like microbial immobilization, syntrophic communities, interspecies electron transfer, buffering capacity, biogas upgrading, and nutrient retention, as well as current challenges and future perspectives of different carbon materials in bio-H2 and CH4 processes. Further attention should be paid to carbon-microbe interactions and the effects in continuous-feed digesters.
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•Carbon supplementation improves anaerobic digestion performance.•Carbons favor microbial activity and electron transfer among anaerobes.•Carbons facilitate microbial immobilization and metabolism.•Carbons may raise fertilizer nutrient retention and biogas quality.•Future perspectives and challenges for carbon-amended digestion are enlightened.
Carbon-based materials such as graphite, graphene, biochar, activated carbon, carbon cloth and nano-tube, and maghemite and magnetite carbons are capable for adsorbing chemicals onto their surfaces. Currently, this review is to highlight the relevance of carbons in enhancing hydrogen or methane production. Some key roles of carbons in improving cell growth, enrichment and activity, and accelerating their co-metabolisms were elaborated with regard to their effects on syntrophic communities, interspecies electron transfer, buffering capacity, biogas upgrading, and fertilizer nutrient retention and land application. Carbons can serve as a habitation for microbial immobilization, and a provision for bioelectrical connections among cells, and provide some essential elements for anaerobes. Besides, an outlook on the possible options towards the large scale and improvement solutions has been provided. Further studies in this area could be encouraged to intend and operate continuous mode by designing carbon-amended bioreactor with stability and reliability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
At present, high-solids anaerobic digestion of sewage sludge has drawn great attention due to the superiority of its small land area footprint and low energy consumption. However, a high organic ...loading rate may cause acids accumulation and ammonia inhibition, thus leading to an inhibited pseudo-steady state in which electron transfer through interspecies hydrogen transfer (IHT) between acetogens and methanogens is blocked. In this study, adding 50 mg/g TS (total solid) magnetite clearly reduced the accumulation of short-chain fatty acids and accelerated methane production by 26.6%. As demonstrated, the individual processes of anaerobic digestion could not be improved by magnetite when methanogenesis was interrupted. Analyzing stable carbon isotopes and investigating the methanogenesis pathways using acetate and H2/CO2 as substrates together proved that direct interspecies electron transfer (DIET) was enhanced by magnetite. Metatranscriptomic analysis and determination of key enzymes showed that IHT could be partially substituted by enhanced DIET, and acetate-dependent methanogenesis was improved after the blockage of electron transfer was scavenged. Additionally, the expression of both pili and c-type cytochromes was found to decrease, indicating that magnetite could replace their roles for efficient electron transfer between acetogens and methanogens; thus, a robust chain of electron transfer was established.
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IJS, KILJ, NUK, PNG, UL, UM
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