Abstract

     Two dimensional nanomaterials, such as graphene and MXene, have been widely used to fabricate high performance nanocomposite films owing to their unique structure and excellent physiochemical properties, showing enormous potential applications in many areas. However, the existing voids and wrinkling in the nanocomposite films inevitably impedes realizing the high performance of the nanocomposite films during the assembly process of graphene and MXene nanosheets. Nacre provides an inspiration for fabricating high performance graphene and MXene nanocomposite films through constructing a high alignment structure and strong interface interactions. In this review, we summarize the preparation approaches of graphene and MXene nanocomposite films and discuss the mechanical properties. Then, several effective strategies for assembling graphene and MXene nanosheets have been concluded and discussed. Meanwhile, we also summarize and discuss the applications of graphene and MXene nanocomposite films including electromagnetic interference (EMI) shielding and thermal management. Finally, outlooks and challenges are proposed to promote their progress and applications in the future.

Introduction

     Since the first discovery of graphene in 2004, graphene has gradually aroused widespread attention [1]. Due to the outstanding mechanical, electrical and thermal properties, graphene has been applied in flexible electronic devices, aerospace and thermal management fields in the past decade [2], [3], [4], [5], [6]. For instance, the single-layer graphene has a Young’s modulus of 1.0 TPa [7] and a superhigh thermal conductivity of about 5300 W/mK [8] at room temperature, demonstrating enormous practical potentiality in the above mentioned fields. Before realizing these applications, it is crucial to assemble graphene nanosheets into high performance graphene nanocomposites including one dimensional (1D) fiber, two dimensional (2D) film and three dimensional (3D) bulk. Especially, high performance graphene nanocomposite films have gained enormous attention. However, it is difficult to achieve high performance nanocomposite films due to weak interaction between adjacent graphene nanosheets. Graphene oxide (GO) is a usual precursor for obtaining graphene with plentiful surface terminating groups, which can easily interact with various materials for preparing nanocomposite films [9,10]. Meanwhile, in recent years, MXene, a novel two dimensional (2D) materials, shows promising electrical and thermal properties, which shows promising application in aerospace field [11], [12], [13], [14], [15], [16]. Indeed, compared with graphene, the intrinsic mechanical and thermal conductivity properties and stabilities of MXene is relatively poor. Furthermore, the easily oxidizable characteristics and thermal vulnerability of MXene may restrict its practical applications. However, compared with graphene, MXene has plentiful surface functional groups, which is an ideal building block for fabricating nanocomposite films without chemical modification any more.

Summary and outlook

     In the past several years, two dimensional materials such as graphene and MXene have been widely studied owing to the excellent physiochemical properties. In this review, we have focused on the preparation methods, assembling strategies and mechanical properties of graphene and MXene nanocomposite films. Moreover, we have also discussed the applications of obtained graphene and MXene nanocomposite films such as EMI shielding and thermal conductivity. Various methods such as VAF, blade coating, drop casting and LbL have been used to prepare high performance graphene and MXene nanocomposite films. However, as aforementioned, the existing voids and wrinkling are harmful for the mechanical properties of graphene and MXene nanocomposite films. Hence, several strategies for fabricating high performance graphene and MXene nanocomposite films are proposed.

Highlights

Abstract

Graphical abstract

Keywords

1. Introduction

2. Apparatus

3. Buffer gas cooling considerations

3.1. Buffer gas cell & pumping requirements

3.2. Diffusion and cooling times

3.3. Buffer gas loading of sublimed molecules

4. Spectrometer sensitivity

5. Conclusion

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgements

References

Abstract

High temperatures and associated poor rotational partition functions have hindered the application of high-resolution rotational spectroscopy for detection of molecules desorbing from an ice substrate. Here, an experimental approach is presented which will enable such investigations through incorporation of a buffer gas cooling cell. We discuss design considerations for this apparatus and the expected performance based upon OC34S measurements made with a related spectrometer in a 14.7 K sampled uniform flow. We highlight specific applications of this technique including chiral sensing of molecules generated in an interstellar ice, and the synthesis of exotic species not amenable to generation in the gas-phase.

I. Introduction

Chemistry taking place in ices profoundly impacts atmospheric chemistry and chemistry in astrochemical environments[1,2]. For example, the synthesis of prebiotic amino acids and sugars, as well as the enantiomeric excess observed on Earth may be attributed to chemistry that took place in ice[3,4]. However, current laboratory studies mainly employ mass spectrometric and Fourier-transform infrared spectroscopic detection and do not take advantage of recent tremendous advances of broadband rotational spectroscopy[5,6]. This is largely because of the disadvantage of the rotational partition function associated with molecules desorbing from these ices at typical temperatures from 80-200 K. A means to cool these molecules offers the advantage of rotational spectroscopy for effective probes of chirality, isomer-specificity, complex mixture analysis, and meaningful relative intensities for product branching ratios. There have been, to our knowledge, two reports on the application of millimeter and submillimeter spectroscopy applied to study interstellar ice chemistry. Widicus-Weaver et al. demonstrated the first such experiments in their detection of thermally desorbed H2O, D2O, and CH3OH originating in a solid film created at ~ 12K[7].

Highlights

Abstract

Keywords

1. Introduction

2. Microfluidic devices in analytical chemistry

3. Separation science

4. Extraction

5. Conclusions and future perspectives

Declaration of competing interest

Acknowledgments

References

Abstract

3D printing has attracted the attention of analytical chemists. 3D printing possesses the merits of fast and low-cost fabrication of geometrically complex 3D structures and has been employed in the fields of microfluidic devices, electrochemical sensors and biosensors, separation sciences, sample pretreatment, and wearable sensors. We focus on the applications and materials of 3D printing in microfluidic devices, separation sciences, and extraction over the last three years and we offer outlook. It is clear that the 3D printing in separation science is here to stay and with new materials development, to develop to on demand fabrication of separation tools.

1. Introduction

Recently, three-dimensional (3D) printing, also called “additive manufacturing,” has become a widely used tool for the construction of different devices in analytical chemistry [1]. 3D models are usually created directly by computer-aided design (CAD) and then printed based on layer-by-layer addition [2]. Compared with traditional manufacturing methods, 3D printing has various merits, including fast, low-cost, and fabrication with minimal waste generated [3,4]. Nowadays, 3D printing is an important tool in manufacturing and prototyping [5-7]. Various technologies for 3D printing have been used consisting of fused filament fabrication (FFF), stereolithography (SLA), selective laser melting (SLS), inkjet and Polyjet printing, and laminated object manufacturing (LOM) [8–11]. The techniques of 3D printing have been well-introduced in several reviews [12–14], thus they will not be covered here in detail.

3D printing was first introduced about 40 years ago [15]. Research in 3D printing has exhibited a rapid growth for printing functional parts, such as biomaterials, nanomaterials, metals, and ceramics as well as polymers [16–18]. 3D printing is has been extensively used in the fields of analytical chemistry, environment sciences, biology, medical devices, and other manufacturing fields [19–22]. In analytical chemistry, the main research fields include microfluidic devices, electrochemical sensors and biosensors, separation sciences, sample pretreatment, wearable sensors, and others [23]. A review of 3D printing applications in sensors and biosensors has been published by our group as well as several reviews published in the special area Journal Pre-proof of analytical chemistry [24–27]. A recent comprehensive review on the broader implications for analytical chemistry was published by Spence et al. in 2017 [12]. This review mainly focuses on using 3D printing in the areas of microfluidic devices, 4 separation sciences, and extraction over the last three years, putting in perspective the application of rapidly developing field of printable materials in connections toanalytical chemistry applications (Fig. 1). We discuss recent developments for past 3 years and we provide outlook and future directions. Future impacts and challenges of 3D printing in these areas will be discussed. We hope that the review will guide analytical scientists to further explore 3D printing techniques in order to realize its potential applications in analytical chemistry

Highlights

Abstract

Graphical abstract

Keywords

1. Introduction

2. Apparatus

3. Buffer gas cooling considerations

3.1. Buffer gas cell & pumping requirements

3.2. Diffusion and cooling times

3.3. Buffer gas loading of sublimed molecules

4. Spectrometer sensitivity

5. Conclusion

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgements

References

Abstract

High temperatures and associated poor rotational partition functions have hindered the application of high-resolution rotational spectroscopy for detection of molecules desorbing from an ice substrate. Here, an experimental approach is presented which will enable such investigations through incorporation of a buffer gas cooling cell. We discuss design considerations for this apparatus and the expected performance based upon OC34S measurements made with a related spectrometer in a 14.7 K sampled uniform flow. We highlight specific applications of this technique including chiral sensing of molecules generated in an interstellar ice, and the synthesis of exotic species not amenable to generation in the gas-phase.

I. Introduction

Chemistry taking place in ices profoundly impacts atmospheric chemistry and chemistry in astrochemical environments[1,2]. For example, the synthesis of prebiotic amino acids and sugars, as well as the enantiomeric excess observed on Earth may be attributed to chemistry that took place in ice[3,4]. However, current laboratory studies mainly employ mass spectrometric and Fourier-transform infrared spectroscopic detection and do not take advantage of recent tremendous advances of broadband rotational spectroscopy[5,6]. This is largely because of the disadvantage of the rotational partition function associated with molecules desorbing from these ices at typical temperatures from 80-200 K. A means to cool these molecules offers the advantage of rotational spectroscopy for effective probes of chirality, isomer-specificity, complex mixture analysis, and meaningful relative intensities for product branching ratios. There have been, to our knowledge, two reports on the application of millimeter and submillimeter spectroscopy applied to study interstellar ice chemistry. Widicus-Weaver et al. demonstrated the first such experiments in their detection of thermally desorbed H2O, D2O, and CH3OH originating in a solid film created at ~ 12K[7].

1- Introduction

2- Experimental method

3- Results and discussion

4- Conclusions

References

Abstract

The deuterium permeation behavior of palladium-coated 316L stainless steel and 430 stainless steel was studied by the gas permeability testing device in this study. The results show that the deuterium permeability of the palladium-coated 316L stainless steel tested at 350 °C∼650 °C was very close to the Forcey’s results. This way, the conformity to some other reported results has been verified for the gas permeability testing device. The deuterium permeability for the oxidized 430 stainless steel was compared with that for the palladium-coated 430 stainless steel at temperature range of 350 °C–600 °C. The deuterium permeability for the oxidized 430 stainless steel was reduced by one order of magnitude compared with that for the palladium-coated 430 stainless steel. However, the activation energy of deuterium permeation as gas form for the oxidized 430 stainless steel was almost the same as that for unoxidized 430 stainless steel.

Introduction

Zirconium hydride is used as the reactor moderator in the thermionic space nuclear power and it easily decomposes hydrogen in the operating environment. The released hydrogen penetrates into the core through the relevant structural components, affecting the physical parameters of the reactor [1]. Compared with 316L austenitic stainless steel, 430 ferritic stainless steel has the advantages of good thermal conductivity, low thermal expansion coefficient and low sensitivity to stress corrosion cracking. It is selected as one of the alternative reactor core materials for structural components of the thermionic space nuclear power. Therefore, investigating the hydrogen permeation behavior of 430 ferritic stainless steel has important engineering application value for the development of thermionic space nuclear power. A lot of research has been carried out on the preparation and properties evaluation of hydrogen isotope permeation barrier coatings for the fusion reactor. However, 316L stainless steel or low-activity ferritic/martensitic steel was used as the substrate material in most of these studies [2–15]. There are few reports on the hydrogen isotope permeation behavior of 430 ferritic stainless steel. In the present study, the deuterium permeability of palladium-plated 316L stainless steel was first tested and compared with the reported values to verify the conformity to other reported results for the gas permeability testing device. Then the deuterium permeation behavior of the palladium-plated 430 stainless steel as well as that with natural oxide film was investigated.

1- Introduction

2- Calculation details

3- Results and discussion

4- Conclusion

References

Abstract

High spin-polarized materials are expected for the development of spintronic devices. In this work, we are aiming to find new spintronic materials in Mn-based binary, ternary and quaternary Heusler alloys by using the first-principles calculations. We investigated structures, electronic properties, magnetic, tetragonal distortion and mechanic properties of Mn3Ga, Mn2YGa (Y = V, Nb, Ta) and ScMnVGa. The results show that Mn3Ga, ScMnVGa type-I, and type-II have lower energy in antiferromagnetic (AFM) states than ferromagnetic (FM) and paramagnetic (NM). Mn2YGa (Y = V, Nb, Ta) compounds are more stable in FM states. The results of electronic and magnetic properties indicate that Mn3Ga is a gapless half-metallic antiferromagnet (Gapless HM-AFM). Mn2VGa and Mn2NbGa belong to gapless half-metallic ferrimagnets (Gapless HM-FE). Mn2TaGa is ferrimagnets. ScMnVGa type-I is half-metallic antiferromagnets (HM-AFM) and type-II belongs to spin gapless semiconductors with AFM (SGSs-AFM). Inspired by Ferromagnetic shape memory alloys (FAMAs), we performed tetragonal deformation of those compounds, and we predicted that Mn3Ga, Mn2YGa (Y = V, Nb, Ta) have possible martensitic transformations. Finally, the mechanical stability and elastic properties of above-mentioned in both cubic and tetragonal structures were discussed in detail.

Introduction

Spintronics is considered to be one of the most promising subjects in the information age because spintronic devices use not only the state of charge but electronic spin to transfer and store information, which speeds up information transmission and reduces energy losses. The findings of Giant Magnetoresistance (GMR), Colossal Magnetoresistance (CMR) and Tunnel Magnetoresistance (MGR) accelerate the development of spintronics. Despite great potential advantages, spintronics still faces some challenges, such as, generate high spin injectors. However, the discovery of half-metallic ferrimagnet has improved this problem, which is an ideal semiconductor spin-injection source due to it has 100% spin polarizability. Among different halfmetallic materials, Heusler alloys are prominent especially owing to high Curie temperature and flexible electronic structures [1,2]. Since De Groot et al. [3] discovered the half-metallic ferromagnets of NiMnSb, while they were calculating the energy band using the planewave method, this intermetallic materials with unusual electronic structures arouse people’s attention. In the big family of Heusler alloys, Co-based Heusler alloys [4–6] usually show magnetism, and the source of this property is direct interaction between Co-Co atoms. Cu-based Heusler alloys [7–9] are typical representative of non-magnetic elements show ferromagnetic after high-ordered, Pd-based Heusler alloys [10,11] which contain rareearth elements is superconducting, Ni2Mn-based Heusler alloys [12–17] have both ferromagnetic properties and thermoelastic martensitic transformation, which realizing magnetic-field-induced strain, shape memory effect, magnetoresistance effect and other application functions. At present, most research focuses on ternary Mn-based Heusler alloys, and they usually behave ferromagnetic or ferromagnetic [18–21]. Actually, besides half-metallic ferromagnets and ferrimagnets, half-metallic antiferromagnets also worthy of study. Not only it has 100% spin polarizability, but its total magnetic moment is zero. Thus, it means that when HM-AFMs are applied to spintronic devices, and those alloys will get the feature of the low-stray field and low energy loss. HM-AFMs were discovered in Heusler alloys [22] and perovskite compounds [23]. Besides, the martensitic transformation was found in some Mn-based Heusler alloys [24–26].

1- Introduction

2- Experimental section

3- Results and discussion

4- Conclusion

References

Abstract

A series of hemiphasmidic luminescent liquid crystalline polymers, in which the hemiphasmidic mesogen containing cyanostilbene were linked to the polymethacrylate main-chains via flexible spacers with different lengths, named poly {(Z)-m-(4-(1-cyano-2-(3,4,5-tris(octyloxy)phenyl)vinyl)phenoxy)alkyl methacrylate} (donated as Pr-m, m = 2, 4, 6, 8, 10) were synthesized via free radical polymerization. The phase structures and photophysical properties of Pr-m were investigated in detail by a combination of techniques including differential scanning calorimetry (DSC), polarizing optical microscopy (POM), small-angle X-ray scattering (SAXS), UV–Vis absorption spectra (UV–Vis spectra), photoluminescence spectra (PL spectra) and particle size analyzer. The results revealed that the phase structures of Pr-m transformed from hexagonal columnar phase (m = 2, 4) to smectic A phase (m = 6, 8, 10) with the increasing of flexible spacer length. All of the polymers featured similar AIEE properties, however, the solid state quantum yields of Pr-m decreased with the increasing flexible spacer length, and the solid quantum yields of Pr-m decreased from 8.55 (Pr-2) to 3.71 (Pr-10) with the increasing flexible spacer length.

Introduction

Over the past few decades, liquid crystals (LCs) have been widely studied as a type of functional material [1-9]. A substantial number of LCs have been synthesized, and their physical and chemistry properties have been investigated because the LCs show excellent anisotropic physical properties that can be used in many classical fields, such as stimuli-responsive [10-12], information storage [3, 4], and photomechanical materials [13, 14] etc. Among various applications of LCs, display materials is always the most important application direction of LCs. However, the conventional liquid crystal materials are non-self-luminescent, so that a backlight needs to be added in the liquid crystal display device, which violates the development trend of energy saving and thinning of liquid crystal display device [15]. Therefore, new strategy toward more efficient liquid crystal display device is highly desirable. Luminescent liquid crystals (LLCs), which combines optoelectronic characteristics of luminescent materials with the unique properties of anisotropic fluids, is expected to be an effective way to solve those problems mentioned above. LLCs can overcome the shortcomings of traditional liquid crystals as display materials and enjoy tremendous advantages for the construction of linear or circular polarized light emitting materials [16, 17]. In view of the traditional luminogens, researchers have tried to construct fluorescent liquid crystal materials [18-20]. However, due to the aggregation caused quenching (ACQ) effect, these fluorescent liquid crystal materials usually emit strong fluorescence only in dilute solution while hardly emit light in aggregate state, which makes the preparation of LLCs with excellent performance intractable [21-24].

Introduction

Energy band engineering

Z-scheme overall water splitting

Strategies for photocatalytic hydrogen generation activity improvement

Conclusions

References

Abstract

Bismuth-based composite oxides are always considered the best visible-light photocatalysts for oxygen production. However, they are failed to photocatalytic reduce the hydrogen from water, due to their lower conduction band made up by Bi 6p and O 2p. Thus, it is significant to modulate their levels of the conduction and valence bands satisfying the redox potential for both H+/H2 and O2/H2O, which will directly lead to discovering new visible-light materials for photocatalytic hydrogen generation. Recent years, some modified bismuth-based composite oxides have been reported to achieve photocatalytic hydrogen production. In this paper, a review of photocatalytic hydrogen generation by bismuth-based composite oxides is presented, mainly including energy band engineering, Z-scheme overall water splitting, and strategies for photocatalytic activity improvement.

Introduction

Photocatalytic hydrogen generation from pure water, known as the “holy grail” in chemistry, can convert solar energy directly into green storable chemical energy [1,2]. After decades of development, solar-to-hydrogen energy conversion efficiency has exceeded 1% [3]. However, it is still far from the practical application requirement of at least 10% solar energy conversion efficiency. Thus, photocatalytic hydrogen generation is still in the experimental research stage. Discovering new materials (especially visible-light photocatalysts) and improving solar energy conversion efficiency are still two major themes in research.

Introduction

Materials and method

Results and discussion

Conclusion

References

Abstract

Adsorption is one of the most commonly used methods for the wastewaters treatment. In this work, we studied the impact of experimental conditions on the adsorption of heavy metals M(II) (M=Cd, Ni, Cu, Pb and Zn) in batch system using chitin obtained from crab shells. This biomaterial is selected because of its low cost, availability and efciency. The M(II) adsorption was found to be dependent on the initial pH, contact time, initial concentration of M(II) and biomass dose. The kinetic models of Elovich, pseudo-frst-order and pseudo-second-order kinetic models were successfully applied, providing the best ftting of the experimental data. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms and the thermodynamic parameters were also discussed. The adsorption capacity peaks at: 50, 47.61, 43.4, 40 and 38.46 (mg L−1) for Pb(II), Cu(II),Ni(II), Cd(II) and Zn(II), respectively. The negative free energy (∆G°) and positive enthalpy (∆H°) indicated spontaneous and endothermic adsorption.

Introduction

The natural environment is constantly contaminated by various pollutants coming from industrial sectors, which in turn showed a considerable change. Toxic metals are widespread and hazardous and afect the environment with a negative impact on the ecosystem, causing dangerous diseases to both animals and humans. Among toxic metals, one can cite Cd, Hg, Pb, As, Cr and Cu (Salem et al. 2012) which must be removed before discharge to the aquatic environment. Unlike organic pollutants, heavy metals are refractory and cannot be degraded and accumulate in living organisms (Ali and Ateeg 2015). The elimination of metals has been the subject of several works using diferent techniques like ion electrodialysis (Esalah et al. 2000), sedimentation (Gupta et al. 2001), ion exchange (Da̧browski et al. 2004; Kang et al. 2008), biological operations (Rashid et al. 2014), coagulation/focculation (Yue et al. 2009), nanofltration (Hafane et al. 2000), solid-phase extraction (Khezami and Capart 2005), adsorption (Abolhasani and Behbahani 2015; Behbahani et al. 2014) and electrokinetic remediation (Sawada et al. 2004). However, all these techniques sufer from high costs of capital and operations as well as the elimination of metallic sludge (Malairajan 2011). On the other hand, the adsorption has become advantageous for removing toxic metals because of its environmentally friendly characteristic, efciency and low cost. In this regard, many marine wastes were used as adsorbents for both inorganic and organic pollutants (Copat et al. 2012; Izquierdo et al. 2014; Samiey and Ashoori 2012; Vilar et al. 2008).

Material and methods

Results and discussion

Conclusion

References

Introduction

The diversity of distilled spirits consumed around the world is large. In Europe, the definition, description, labelling and protection of geographical indications of spirit drinks are specified in regulation 110/2008 (1). The standard unit for ethanol concentration is the alcoholic strength by volume (annex I point 11), or ABV (alcohol by volume) in % v/v. The distillation process concentrates the ethanol and volatile aroma compounds from the fermented must, as well as those formed in situ through chemical reactions (2). The quality and specific characteristics of a spirit beverage are highly dependent on the nature and concentration of the volatile compounds and, to a lesser extent, its ethanol concentration. The volatile compounds responsible for the overall aroma perception of spirit beverages belong to many chemical families, such as alcohols, carboxylic acids, esters and aldehydes (2). The precise relationship between volatile compounds and aroma perception is still difficult to assess, owing to the variable nature of volatile compounds, concentration relative to sensory threshold and possible synergies. The diversity of volatile compounds and differences in concentration is mainly due to the raw materials, fermentation method and the distillation process, which includes both the apparatus and the method (3,4). Three main methods are commonly used with a typical distillation apparatus: (a) continuous distillation in a multistage distillation column (e.g. rum, vodka, Armagnac, Calvados, neutral alcohol), (b) batch (simple discontinuous) distillation involving recycling (e.g. Cognac, Armagnac, Auge, Calvados, rum) and (c) batch distillation in a column involving recycling (fruit brandies). The preferred method depends on the organoleptic qualities desired. For instance, full-bodied, single malt whiskies are produced with a batch method in traditional pot stills, while lighter grain whiskies are produced in multistage distillation columns (5). According to Ferrari et al. (6), the behaviour of volatile compounds is different during distillation in pot stills and rectification columns. Indeed, in contrast to esters, it was observed that larger quantities of higher alcohols were recovered in the distillate in continuous distillation than in the simple batch process. This study focused on the behaviour of volatile compounds during simple batch distillation. This method is generally conducted in a traditional copper still, known as an ‘alambic charentais’ (Fig. 1) (3,7–9). Distillation is carried out in two successive cycles. During the first cycle, known as ‘wine distillation’, the wine is introduced into the boiler. An initial small fraction of distillate (‘heads’) is collected and separated. Distillation then continues until the ABV of the distillate reaches ~2% v/v. This second fraction constitutes the low wine, with ethanol concentration between 27 and 30% v/v. The second cycle is the low wine distillation. In analogy with wine distillation, the first fraction of distillate (‘heads’) with the highest ethanol concentration is removed.

1- Introduction

2- Experimental

3- Results and discussion

4- Conclusion

References

Abstract

Petroleum coke is the waste from the delay coking process during petroleum refining. It is urgent to solve the problem of the effective and environmental utilization of high-sulfur petroleum coke. Chemical looping gasification (CLG) is employed in the application of petroleum coke for syngas production and sulfur recovery for the first time. The conventional steam gasification was for comparison to have a better understanding of the chemical looping process of petroleum coke. The presence of hematite improved the carbon conversion efficiency to 70.13%, although the fraction of the effective syngas decreased slightly. Experiments are conducted to evaluate the effects of temperature, steam flow rate and the sizes of fuel and hematite on the conversion of carbon and sulfur in a batch fluidized bed. The data shows that the effective syngas accounts for 83.51% and the molar fraction of H2S/SO2 is about 2, when the fuel size was 0.1–0.3 mm, and the hematite size was 0.3–0.4 mm at the steam flow rate of 1 g/min at 900 °C. Moreover, that condition is advantageous to the further utilization of the flue gas stream for sulfur recovery via Claus process. The size of oxygen carrier has a significant influence on distribution of sulfur species releasing. The high-content sulfur in the petroleum coke did not remain on the surface of hematite and the oxygen carriers were not poisoned. As a consequence, chemical looping gasification with hematite as oxygen carrier is an excellent technique for petroleum coke conversion coupled with sulfur recovery.

Introduction

Petroleum coke is the waste from the delayed coking process in the petroleum refining industry with high calorific value and low ash content. It is classified to high and low sulfur petroleum coke depending on the sulfur content. The low sulfur one can be used in many fields such as fuel, anode and electrode. However, the high sulfur petroleum coke faces a great challenge to be utilized because of the pollution [1,2]. Moreover, the production yield of high sulfur coke is overstocked with a high increasing rate, while the low sulfur one is in short supply [3]. Therefore, the utilization of high sulfur petroleum coke in a benign environmental and effective method is being solved urgently [4]. Gasification is considered as a cleaner and economic process to convert solid fuels in comparison with combustion [5e7]. When petroleum coke is used in the gasification technology, the sulfur compounds in the raw gas product would be converted into elemental sulfur in the Claus plant. But the gasification reactivity of petroleum coke is rather low due to its carbon structure and low combustibility [8,9]. Chemical looping gasification (CLG) is a promising gasification technology to produce syngas, sharing the same principle with chemical looping combustion (CLC) [10]. Generally, the system involves two reactors, a fuel reactor and an air reactor, with the oxygen carrier circulating between the two reactors as shown in Fig. 1. The oxygen carrier transfers lattice oxygen and heat to achieve the fuel partial oxidation and gasification in the fuel reactor, while the reductive oxygen carrier is transported for regeneration in the air reactor. Compared with the traditional gasification technology, CLG has several advantages [11,12]. The regeneration of oxygen carrier can supply heat for gasification, thus balancing the heat in the system with less extra energy input.

1- Introduction

2- Materials and methods

3- Results and discussion

4- Conclusions

References

Abstract

Traditional wastewater treatment plants cannot completely remove trace pharmaceutical and personal care products. In particular, quinolone antibiotics are mainly adsorbed on microbial cell surfaces in excess sludge and are released into the water environment during agricultural supplementation, mainly due to the exfoliation of extracellular polymeric substances (EPS) caused by changes in environmental conditions. Here, the occurrence of seven typical quinolone antibiotics from three generations in excess sludge was investigated at trace concentrations using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). EPS facilitated adsorption independent of pH and quinolone antibiotic type, and the solid-liquid distribution coefficient decreased markedly as pH increased (pH 5–9, range of municipal wastewater). Metal ions bound in EPS were predominantly responsible for the adsorption of antibiotics in sludge, rather than the macroscopic size of the sludge floc. pH affected patterns of quinolone antibiotics, the zeta potential of sludge floc, and the contents of metal ions contained in sludge. The adsorption capacity of antibiotics first increased and then decreased with increasing pH in the range of pH 3–11, reaching a maximum (20,506, 14,458, 10,689, 22,854, 20,302, 8494, and 29,547 L/kg for CIP, ENR, LOM, MOX, NOR, OFL, and SAR, respectively) near pH 5, at which the cationic bridging of Ca2+ and Mg2+ bound in EPS played a major role owing to their larger ion radius and higher contents in excess sludge. Due to high surface heterogeneity of sludge, the Freundlich model was more suitable than the Langmuir model for describing the adsorption behavior of quinolone antibiotics. These results provide further insight into the release of quinolone antibiotics adsorbed in excess sludge, with potential implications for the agricultural use of sludge.

Introduction

Trace pharmaceutical and personal care products (PPCPs) have been detected in environmental media such as surface water, groundwater, and soil. Although the concentration of PPCPs related to human activities is usually on the order of nanograms to micrograms per liter in the water environment [1–5], many PPCPs are discharged continuously into the environment, causing potential risks for human health and the environment due to their ongoing utilization [6–9]. Wastewater treatment plants (WWTPs) are one of the main point sources of PPCP discharge into the environment [10], as it is difficult to biochemically degrade these substances during the conventional wastewater treatment process [11]. As a result, except for a small amount of PPCPs that are released into the atmosphere by escape, some portion of PPCPs remains in the effluent of the wastewater treatment plant, with the remainder present in excess sludge due to adsorption or dissolution [12]. The Water Pollution Prevention Action Plan promulgated in April 2015 in China stipulates that treated sludge cannot contain potential environmental pollutants [13]. When excess sludge containing PPCPs is used for land use and agricultural production activities such as fertilization, PPCPs in the sludge may be released into the environment as the external environment changes [10,14–19], thereby contaminating surface water and groundwater [4,12,18–20]. In recent years, quinolone antibiotics have been one of the most widely used antibiotics in veterinary and medical applications [21]. In China, they are widely used in human clinical settings and livestock breeding for disease prevention, with livestock and poultry farming accounting for about 50% of their use [22]. Moreover, the consumption of quinolone antibiotics has increased significantly; for example, the annual consumption of quinolone antibiotics in humans and animals in 1998 was 1,350 and 470 tons respectively [23], while the annual consumption of ciprofloxacin, norfloxacin, ofloxacin, lomefloxacin, and enrofloxacin in China in 2013 for both humans and animals reached 5340, 5440, 5110, 1250, and 5180 tons, respectively [22].

An overview of capacitive technologies based on carbon materials (energy storage in electrical double-layer capacitors (EDLCs), capacitive deionization (CDI), energy harvesting, capacitive actuation, and potential controlled chromatography) is presented. The review reveals the role of carbon for these scientific and industrial purposes with disclosing the benefits and limitations of various nanostructured carbons for a certain application. A special attention is placed on the electrical double-layer (EDL) formation mechanisms affected by the porous texture of carbon and the electrode architecture. The importance of a careful selection of the electrolytic solution for the EDL formation inside the intraparticle pores of carbon electrodes is also enlightened.

Introduction

During the last fifty years, the worldwide industrial development accompanied by improving wealth in emerging markets and growth of the human population have driven a steadily increasing demand for new energy and fresh water supplies. The emission of noxious gases during fossil fuel consumption and the depletion of their reserves have led to introduce renewables (sun and wind) in the energy mix. Unfortunately, due to their intermittent character, the renewable technologies are not able to ensure a real-time balance of electricity supply.[1] Therefore, in order to adapt the energy delivery to the demand and improve the energy efficiency, current researches are focused on introducing energy-storage technologies which would meet sustainability, environmental requirements and be cost-effective. What is more, the automotive industry faces the challenge to reduce the exhaust gases emission and amount of energy dissipated in urban areas by internal combustion engine powered vehicles. Encouraging efficient energy management should accelerate commercialization of the powertrain technologies to be applied in low carbon vehicles (LCV), fast-charging infrastructures in the stations, wireless monitoring systems or electricity load leveling in stationary and transportation systems. Apart from energy related issues, another critical problem worldwide concerns the shrinking access to potable water sources. It is commonly known that sea or brackish water is not suitable to drink without being desalinated. Therefore, alternative options to i.e. expensive vacuum distillation processes, reverse osmosis and cogeneration desalination plants, using either fossil fuels or nuclear power, are still highly sought in order to meet the global needs for clean water with reduced carbon footprint. Electrochemical technologies are able to bring some response to the issues related with efficient energy management, reduction of greenhouse gases emissions and water desalination by utilizing the concept of electrical double-layer (EDL) created at the surface of nanoporous electrodes.[2-4] When an electrode is polarized, the ions of opposite charge present in the electrolyte migrate to the electrode surface, where they create an EDL.[5] The double-layer capacitance depends on the electrode surface area able to accumulate electrical charge by pure electrostatic forces and on the charge separation distance imposed by dimensions of the charge carriers. Therefore, electrodes made from nanostructured carbon materials (also called carbons further in the text), characterized by a highly extended surface area and pores which match with the size of electrolyte ions, are generally considered to be capacitive.[4, 6-13] The capacitive technologies include: i) capacitive energy storage in electrical double-layer capacitors (EDLCs);[14, 15] ii) capacitive energy harvesting where small amount of ambient energy is captured, accumulated, and converted into electrical energy;[16, 17] and iii) capacitive deionization (CDI) of sea or brackish water where the salt ions are removed from the feed water, electrostatically held in the EDL and released in a brine stream during discharge.[18-20] Besides, the chargedependent ions separation can be also employed in a new type of liquid chromatography (called potentialcontrolled chromatography) to enhance the anolyte concentration or to introduce withholding of certain species.[21] What is more, the distribution of electric charges within the porosity of carbon material entails changes of geometric surface area of the electrodes triggered by charging and discharging, so-called capacitive actuation. The flexible capacitive devices where the electrodes deformation is controlled by a voltage stimulation can be used in soft robotics to make shape-changing robots.[22] In this context, the paper reveals the benefits and limitations of various nanostructured carbons, with a special attention to the charge storage mechanism in EDLCs affected by the porous texture of carbon electrodes. It then reviews the state-of-the-art of capacitive technologies based on carbon materials with discussing in some detail how the double-layer concept is being utilized for their development.