Abstract

Introduction

Wastewater in area of focus

Nanotechnology in water purifcation

Nano‑adsorption

Microbial agent

Nanocomposites

Types of nanocomposites

Synthesis modes for nanocomposites

Graphene oxide‑based composites as a disinfectant

Zinc oxide nanocomposites as disinfectant

Copper oxide nanocomposites

Silver/silver oxide nanocomposites

Titanium oxide nanocomposites

Discussion

Conclusion

References

Abstract

     Water is crucial for the existence of life. The world, however, is facing a global water crisis. There are variety of microorganisms, gases and other toxins responsible for water contamination. Various types of nanomaterials exist that have enormous potential to treat contaminated water (water containing metal toxins or specific organic or inorganic impurities) due to their unique properties such as a high surface area and their ability to work effectively even at low concentrations. In recent years, scientists have been giving considerable attention to the application of nanocomposites for water purification, wastewater treatment, microorganism elimination, chemical contaminants, heavy metals removal and so forth. The incorporation of different nanofillers such as carbon nanotubes, graphene oxide, 2D materials, zinc oxide, titanium dioxide, copper and silver nanoparticles into polymeric materials has facilitated important advances, such as suppressing the accumulation of pollutants and foulants, improving the hydrophilicity, increasing the efficiency and improving the mechanical properties. This review discusses leading advances in the development of nanocomposites for antimicrobial and wastewater treatment with the aim of providing an improved understanding of nanocomposites and their applications in antimicrobial and wastewater treatment.

Introduction

     Water is a basic requirement for human life. However, we are far from meeting global requirements for clean water, and this issue will continue to grow over the time (Hillie and Hlophe 2007; Elwakeel et al. 2020b). The demand of clean drinking water is rising as a result of the deterioration of water quality, global climate change and population growth (Tchobanoglous et al. 1991; Elwakeel et al. 2020d). Emissions of organic dyes and heavy metal ions from the paper, leather and textile industries are a serious problem, as they are potentially mutagenic and carcinogenic. To meet environmental requirements, wastewater contaminated with these organic and inorganic species need to be treated before being discharged (Santhosh et al. 2016; Elwakeel et al. 2021). Heavy metals are widely used in various industries for many purposes, including mining and pigment production. Synthetic dyes are also an important type of pollutant, and their sources for water contamination include the textile, pulp and paper, tinting, printing, painting and tanning industries. The removal of dye from such wastewater is a challenging task, as pigments and synthetic dyes are biodegradation-resistant and remain in the environment for a long time. The destruction and handling of organic dyes is therefore an important issue, and a cost-efective method for removing dye substances from wastewater has been developed (Santhosh et al. 2016; Elwakeel et al. 2018).

Conclusion

     This paper explores the existing nanocomposites used to extract heavy metal ions and dyes from wastewater as efective adsorbents. This article addressed recent developments in nanomaterials as economical and environmentally sustainable water purifcation adsorbents. This review highlights fve commonly used nanomaterials/nanoparticles that are used in most existing nanocomposites. In this review, we concluded that TiO2-based nanocomposites have been used for photodegradation activity by most of the researchers in the literature. Silver-based nanocomposites are mostly used for antimicrobial activity. Silver and GO-based nanocomposites were used for the removal of green dye, anionic dye and Cu(II). Copper-based nanocomposites are mostly used for adsorption and photodegradation activity. Zinc oxide nanocomposites are used for adsorption, antimicrobial and photodegradation activity. Finally, we concluded that GO also greatly contributes to the improvement of other materials’ efciency. Further, much needs to be done to control the two-dimensional GO sheets for advanced technologies in the future. There are many challenges and obstacles associated with handling wastewater, and many precautions are required to prevent environmental and health problems. Therefore, new modern wastewater treatment equipment should be versatile, low-cost and commercially efective.

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.

Keywords

1. Introduction

2. Graphene Oxide

3. Aerogels

4. Supercapacitor and Energy Storage

5. Supercapacitor applications of graphene and graphene oxide based aerogels

6. Conclusion

References

Abstract

Graphene and graphene-based materials have a high potential, especially in energy storage technology. Thanks to the three-dimensional (3D) structures developed with this material, their importance in the production and application of energy storage devices has increased. Studies on supercapacitor applications of graphene-based aerogels have begun to arouse interest in recent years. In this study, recent studies on aerogel supercapacitors, in which researchers have shown great interest, have been compiled and collected. In this study, production methods and properties of graphene oxide, properties and production of aerogels, production and applications of graphene/graphene oxide aerogels are discussed. In this way, the data is presented and discussed in an organized way for the researchers who study or who want to study in this field.

Introduction

Today’s rapidly depleted energy resources and the deteriorating ecological balance prioritized the need for energy storage systems. Moreover, the growing popularity of telecommunications equipment, backup storage devices, portable electronic devices, cardiac pacemakers and hybrid electric vehicles has aroused great interest towards energy storage devices. In this context, supercapacitors, which are mostly preferred among various energy storage devices, are electrochemical energy storage devices that cover the gap between batteries and dielectric capacitors with their high-power density, high specific energy and long life (>100,000 cycles) [1]. Furthermore, flexible solidstate supercapacitors are important for wearable electronic devices [[2], [3]].

Graphene, which come into prominence with wide specific surface area (SSA) (2630 m2 g−1 ), high electrical conductivity and chemical stability, as well as excellent mechanical, thermal and optical properties, has become popular especially for supercapacitors. However, a serious loss in surface area is observed due to the re-stacking of graphene layers during chemical reduction. The conversion of graphene nanotubes to graphene aerogel having a stable three-dimensional network solves this problem. The re-stacking problem resulting from π-π interactions between graphene layers and the Van der Waals forces are solved and the layers are chemically bonded together. Thus, the structure is intended to provide better performance in supercapacitors with much higher electronic conductivity, rapid charge transport between the layers and the resulting high surface area. The most interesting feature of GOs is that they are well protected by a hexagonal structure having functional groups such as hydroxyl, epoxide, carboxyl and some randomly distributed alkyl groups in the plane, together with a clear AB stacking order. Hydroxyl and epoxide functional groups are located close to each other in the basal planes, whereas carboxyl and alkyl groups are located at the edges of GO flakes. With longer oxidation times, hydroxyl groups are converted to more epoxide groups in the basal plane.

1- Introduction

2- Mechanism

3- Corrosion inhibitor chemistry

4- Conclusions and prospects

References

Abstract

Corrosion of metals has been a widespread issue in industries for centuries. The use of corrosion inhibitors in rust preventative fluids are commonly employed to provide the temporary corrosion protection to metals. The aim of this review is to summarize the rust inhibition properties, inhibition mechanism, chemistry and development of corrosion inhibitors for rust preventative fluids. Some suggestions for further research on corrosion inhibitors have also been discussed.

Introduction

Corrosion is the degradation of a material’s properties by chemical and/or electrochemical reaction with the environment, and in most cases it means the electrochemical oxidation of metal. The study of National Association of Corrosion Engineers (NACE) estimated that the global cost of corrosion to be $ 2.5 trillion annually, equivalent to about 3.4% of the global Gross Domestic Product (GDP) [1]. It also found that implementing corrosion prevention best practices can save 15–35% of the cost of damage, that is $ 375–875 billion. Among the various methods available to prevent corrosion of metals, rust preventative fluids are extensively used to provide temporary corrosion protection during manufacturing processes, storage and shipment. Rust preventative fluids are prepared by mixing corrosion inhibitors, film-forming agents and other additives into a base fluid, and it can be classified as solvent-based, oil-based and water-based rust preventatives according to the types of base fluid [2]. It is definite that corrosion inhibitors are critical for them to achieving high performance. Inorganic and organic inhibitors are the two main types of corrosion inhibitors. Inorganic inhibitors, such as nitrite, nitrate, chromate, dichromate, phosphate, are widely used in different base fluids and for various metals [3]. On the other hand, organic inhibitors are the compounds containing one or more polar groups (with O, N, P, S atoms, and π electrons), which are effective to prevent corrosion via adsorption on the metal surface [4–6]. Since the polar groups are usually regarded as the reaction centers for the adsorption process, the strength of adsorption is strongly dependent on the electron density and polarizability of the polar groups [7]. Accordingly, organic inhibitors include sulfonates, alcohols, ethers, amines, amides, amine salts, carboxylates, heterocyclic nitrogen compounds, phosphates, polymers, natural products, and others in consideration of polar groups nature. The present article reviews the mechanism and development of corrosion inhibitors for rust preventative fluids.

The advanced synthesis and development of raw graphene based on various significant functionalization has been outstanding in the wastewater treatment compared to the other alternatives such as carbon nanotubes and other carbon nanomaterials. Nano size graphene is known to possess large surface area and some promising properties in terms of mechanical, electrical, chemical and magnetism. Besides, the graphene can be generated via both Top-down and Bottom-up methods such as chemical exfoliation, chemical vapor deposition and other techniques so that it can be further functionalized to form graphene oxide-based nanomaterials. Hence, graphene oxide-based nanomaterials are discovered to be useful in the application of heavy metal removal from wastewater. In short, this paper critically reviewed on the synthesis method of graphene and application of graphene oxidebased nanomaterials in the term of heavy metal removal. The advantages, drawbacks, comparison of the data efficiencies, and research requirements are further highlighted, elaborated and discussed detailly. Lastly, the future challenges of graphene are elaborated. Therefore, it can be guaranteed that the wastewater discharged should be detected with the minimum or none of the heavy metals so that minimum effects on the ecosystem is discovered.

Introduction

Graphene can be extracted from graphite and it is merely a sheet of graphite. It is defined as a single layer of sp2 bonded carbon atoms in hexagonal lattice arrangement. At the same time, graphene possesses few promising properties such as good electronic properties caused by the bonding and anti-bonding of the pi orbitals. Furthermore, graphene is clarified to be the strongest substance in terms of mechanical strength since it possesses high tensile strength and it is light in weight. For instance, it is more than 40 times stronger than diamond and more than 300 times stronger than A36 structural steel, at 130 GPa[1]. Meanwhile, for the optical properties, high absorption of white light up to 2.3% is capable to be observed from graphene. Besides of the impressive properties, appropriate method to produce graphene must be taken into consideration. There are two different type of methods to produce graphene which are exfoliation methods and direct growth of graphene layer which can be known as Top-down and Bottom-up methods respectively[2]. Methods to generate graphene include “Scotch Tape Method”, dispersion of graphite, exfoliation of graphite oxide, epitaxial growth and lastly chemical vapor deposition (CVD)[3]. However, improved Hummers method which falls under method of dispersion of graphite is widely used since it is an improved method which excludes the usage of toxic chemical and at the same time enhances the reaction performance[4].

چکیده

توسعه و سنتز پیشرفته ی گرافن خام بر اساس عملکردهای مختلف و قابل توجه در زمینه ی تصفيه فاضلاب، در مقایسه با سایر راهکارهاي جايگزين (مانند نانولوله هاي كربني و ساير نانو مواد كربني)،بسيار چشمگير بوده است. گرافن در ابعاد نانو داراي مساحت سطح بزرگ و برخي ويژگي هاي نويد بخش از نظر مكانيكي، شيميايي،الكتريكي و مغناطيسي است.علاوه بر اين گرافن مي تواند از هر دو روش پايين به بالا و بالا به پايين ،مانند لايه برداري شيميايي،رسوب دهی شیمیایی بخار و روش های دیگر تولید شود بنابراین ، بنابراین نانو‌مواد بر پایه ی اکسید گرافن برای حذف فلزات سنگین از فاضلاب مفید در نظر گرفته شده اند . به طور خلاصه این مقاله مروری است بر روی روش های سنتز گرافن وکاربرد نانو مواد برپایه ی اکسید گرافن د رحذف فلزات سنگین. در این مقاله فواید،نقص ها و مقایسه ی بازده ی داده ها و تحقیقات مورد نیاز، بیشتر برجسته شده و با جزییات توضیح داده شده و مورد بحث قرارگرفته است. در آخر چالش های آینده ی گرافن مورد بررسی قرار گرفته است. بنابراین می توان تضمین کرد که تخلیه ی فاضلاب باید با حداقل مقدار فلز سنگین یا بدون آن در نظر گرفته شود تا کمترین اثر را روی اکو سیستم بگذارد.

Introduction

Magnetic fluids are specific subset of smart materials that can adaptively change their physical properties due to external magnetic field. Magnetic control of the properties and behavior of liquids are promising fields for advanced applications and a challenge for basic research. Two main types of magnetic fluids are known since the middle of the 20th century; magnetorheological (MR) fluids and ferrofluids. The former are suspensions of micrometer-sized particles of magnetizable materials dispersed in a liquid carrier. On the other hand, ideal ferrofluids are colloidal suspensions of ultrafine (5–10 nm) single domain magnetic nano-particles such as iron oxide (g-Fe2O3, Fe3O4), MnZn ferrites, and Fe and Co in either polar or non-polar liquid carriers [1,2]. Between 15 and 40 nm, the magnetic fluid is still considered as ferrofluids. Above thislimit, the fluid goesinto the limits of the MR fluids. Although conventional or real ferrofluids synthesized by various scientists are in the order of 5–15 nm, Lopez-Lopez and coworkers developed 2 new kinds of ferrofluids. The features that differentiate them from a conventional ferrofluid is that one of them is composed of spherical particles with larger particle size (diameter = 24 nm) and the other one is composed of fibers. Figure 1 gives their classification of the particles. These fluids have proved to be an advantage from the point of view of the intensity of the MR effect. As a result they develop a larger yield stress and viscosities upon application. However, the stability of these new ferrofluids is worse than the conventional ferrofluids. The reason for this is the magnetostatic forces dominating over Brownian motion. Although they have worse stabilities, these ferrofluids have propertiesintermediate between conventional ferrofluids and MR fluids. These new fluids could be good candidates for applications with moderate MR effect and stability [3].

Abstract

We review the present state of polymer nanocomposites research in which the fillers are singlewall or multiwall carbon nanotubes. By way of background we provide a brief synopsis about carbon nanotube materials and their suspensions. We summarize and critique various nanotube/polymer composite fabrication methods including solution mixing, melt mixing, and in situ polymerization with a particular emphasis on evaluating the dispersion state of the nanotubes. We discuss mechanical, electrical, rheological, thermal, and flammability properties separately and how these physical properties depend on the size, aspect ratio, loading, dispersion state, and alignment of nanotubes within polymer nanocomposites. Finally, we summarize the current challenges to and opportunities for efficiently translating the extraordinary properties of carbon nanotubes to polymer matrices in hopes of facilitating progress in this emerging area.

Introduction

Carbon nanotubes (CNT) were first reported by Iijima1 in 1991, and the first polymer nanocomposites using carbon nanotubes as a filler were reported in 1994 by Ajayan et al.2 Earlier nanocomposites used nanoscale fillers such as carbon blacks, silicas, clays, and carbon nanofibers (CNF) to improve the mechanical, electrical, and thermal properties of polymers. Carbon nanotubes possess high flexibility,3 low mass density,4 and large aspect ratio (typically ca. 300-1000). CNT have a unique combination of mechanical, electrical, and thermal properties that make nanotubes excellent candidates to substitute or complement the conventional nanofillers in the fabrication of multifunctional polymer nanocomposites. Some nanotubes are stronger than steel, lighter than aluminum, and more conductive than copper. For example, theoretical and experimental results on individual single-wall carbon nanotubes (SWNT) show extremely high tensile modulus5 (640 GPa to 1 TPa) and tensile strength6 (150-180 GPa). Depending on their structural parameters, SWNT can be metallic or semiconducting, which further expands their range of applications. Because of the nearly one-dimensional electronic structures, metallic nanotubes can transport electrons over long tube lengths without significant scattering (electronic mean free path for metallic SWNT is on the order of several microns7). Similarly, SWNT exhibit large phonon mean free path lengths that result in high thermal conductivity (theoretically8 >6000 W/(m K)). Because of these extraordinary properties of isolated carbon nanotubes, great enthusiasm exists among researchers around the world as they explore the immense potential of these nanofillers. The level of activity is illustrated by the number of journal articles and patents published within a short period of time (Figure 1).

In many countries using nuclear energy high-level wastes resulting from the reprocessing of nuclear spent fuel is being confined in a highly-resistant glass matrix. In France, the resulting highly radioactive glass, named R7T7, is cooled in stainless steel canisters and stored on-site waiting for final geological disposal. For geological disposal the waste package will be encapsulated in carbon steel container and then sent to a multi-barrier underground disposal facility located in an argillaceous Callovo-Oxfordian (COx) layer. This confinement system should limit both the glass alteration by surrounding ground waters and the release of the radioactive elements from the glass matrix, although the alteration of the glass by surrounding ground waters cannot be excluded for long-term. It is expected after closure of the disposal facility that the glass will be firstly in contact with water vapour before complete saturation of the void spaces. In fact, the anoxic corrosion of metallic components will lead to a massive production of hydrogen that will probably prevent a fast saturation of the glass container with the surrounding ground waters. Consequently, a phenomenon of glass vapour hydration may occur for several thousands of years before the glass becomes completely submerged by groundwater. Various studies have been conducted to better understand the hydration of nuclear glasses [1−5] and their natural analogues such as obsidian [6−11]. During the hydration process, a thin film of water is firstly sorbed or condensed on the surface of the glass [12]. The thickness of the sorbed film of water mainly depends on the temperature and relative humidity (RH), the latter was controlled by varying the concentration of NaCl in the solution [13]. The condensed water diffuses and reacts via a hydrolysis and ion exchange mechanism. This leads to the transfer of glass components to the glass surface. The glass surface-area-to-liquid volume (S/V) ratio is estimated to be high under water vapour hydration (in the order of 108 m-1 ) [12]. This estimation is based on the sorption curve of water on the SRL glass as a function of the relative humidity. The thin film of water became rapidly saturated with dissolved glass constituents leading for certain glass compositions to higher local pH values and then the increase of solubility of the silicate glasses network. An alteration layer grows on the corroded glass surface; it is mainly composed of hydration gel, pore water and crystalline alteration products. The thickness of the alteration layer and the nature of secondary phases precipitated on the external surface depend on experimental conditions (time, temperature, RH, pH) and glass composition.