The performance of nanofiltration (NF) processes is mainly governed by factors such as the sieving effect (also known as size exclusion) and the Donnan effect (which depends on membrane surface charges). This has encouraged the development of new types of NF membranes using various kinds of polyelectrolytes as they have good pore-sealing effects and are able to improve the membrane surface charge density. Manipulation of the pH, supporting electrolyte concentration, type and concentration of polyelectrolyte solutions can significantly vary the characteristics of polyelectrolyte molecules thus improving their electrostatic interactions with the surrounding compounds. This is highly desired and useful when polyelectrolytes are to be incorporated in membrane surface modification as the charges formed can increase the membrane surface charge density, membrane surface coating stability and membrane selectivity. Most of the research discussed in this paper employed the special features of polyelectrolyte molecules to improve the performance of NF membranes in various applications. Various methods have been used to incorporate polyelectrolytes in order to improve NF membrane performance, such as static deposition, dynamic deposition, single layer coating, layer-by-layer (LbL) coating, and so forth. Some of the suitable devices or instruments used for polyelectrolyte-modified membranes are recommended and evaluated. In conclusion, polyelectrolyte-modified membranes offer significant improvements, can be produced in a short period of time, require less energy during membrane modification or fabrication and incur lower production costs. Thus, a full understanding of the factors affecting polyelectrolyte-modified membranes is very much desired and worth further detailed investigation in the near future.
The fascinating and serendipitous discovery, in 1976, of the characteristic viscoelastic behavior of wormlike micelles of cetyltrimethylammonium salicylate (CTASa) surfactant solution at ~2×10(-4) M CTASa became a catalyst for an increasing interest in both industrial application and mechanism of the origin of micellar growth of this and related wormlike micellar systems. It has been perceived for more than three decades, based upon qualitative evidence, that the extent of the strength of the counterion (X) binding to ionic micelles determines the counterion-induced micellar structural transition from spherical-to-small rodlike-to-linear long stiff/flexible rodlike/wormlike-to-entangled wormlike micelles. This perception predicts the presence of a possible quantitative correlation of counterionic micellar binding constants (KX) with counterion-induced micellar growth. The quantitative estimation of counterion binding affinity to cationic micelles, in terms of the values of the degree of counterion binding (βX), is concluded to be either inefficient or unreliable for moderately hydrophobic counterions (such as substituted benzoate ions). The values of KX, measured in terms of conventional ion exchange constants (KX(Y)), can provide a quantitative correlation between KX or KX(Y) (with a reference counterion Y=Cl(-) or Br(-)) and counterion-induced ionic micellar growth. A recent new semi-empirical kinetic (SEK) method provides the estimation of KX(Y) for Y=Br as well as ratio of counterionic micellar binding constants KX/KBr (= RX(Br)) where the values of KBr and KX have been derived from the kinetic parameters in the presence of cationic spherical and nonspherical micelles, respectively. The SEK method has been used to determine the values of KX(Br) or RX(Br) for X=2-, 3- and 4-ClC6H4CO2(-). Rheometric measurements on aqueous CTABr/MX (MX=2-,3- and 4-ClBzNa) solutions containing 0.015 M CTABr and varying values of [MX] reveal the presence of spherical micelles for MX=2-ClBzNa and long linear as well as entangled wormlike micelles for MX=3- and 4-ClBzNa. The respective values of KX(Br) or RX(Br) of 5.7, 50 and 48 for X=2-, 3- and 4-ClBz(-) give a quantitative correlation with the rheometric measurements of the structural features of micelles of 0.015 M CTABr solutions containing 2-, 3- and 4 ClBzNa.
Water scarcity and pollution rank equal to climate change as the most urgent environmental turmoil for the 21st century. To date, the percolation of textile effluents into the waterways and aquifer systems, remain an intricate conundrum abroad the nations. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of titanium dioxide, a prestigious advanced photo-catalyst which formulates the new growing branch of activated carbon composites for enhancement of adsorption rate and discoloration capacity, has attracted stern consideration and supports worldwide. Confirming the assertion, this paper presents a state of art review of titanium dioxide/activated carbon composites technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbons composites material represents a potentially viable and powerful tool, leading to the plausible improvement of environmental conservation.
A new method, based upon semi-empirical kinetic approach, for the determination of ion exchange constant for ion exchange processes occurring between counterions at the cationic micellar surface is described in this review article. Basically, the method involves a reaction kinetic probe which gives observed pseudo-first-order rate constants (k(obs)) for a nucleophilic substitution reaction between the nonionic and anionic reactants (R and S) in the presence of a constant concentration of both reactants as well as cationic micelles and varying concentrations of an inert inorganic or organic salt (MX). The observed data (k(obs), versus [MX]) fit satisfactorily (in terms of residual errors) to an empirical equation which could be derived from an equation explaining the mechanism of the reaction of the kinetic probe in terms of pseudophase micellar (PM) model coupled with another empirical equation. This (another) empirical equation explains the effect of [MX] on cationic micellar binding constant (K(S)) of the anionic reactant (say S) and gives an empirical constant, K(X/S). The magnitude of K(X/S) is the measure of the ability of X(-) to expel S(-) from a cationic micellar pseudophase to the bulk aqueous phase through ion exchange X(-)/S(-). The values of K(X/S) and K(Y/S) (where Y(-) is another inert counterion) give the ion exchange constant, K(X)(Y) (=K(X)/K(Y) where K(X) and K(Y) represent cationic micellar binding constants of X(-) and Y(-), respectively). The suitability of this method is demonstrated by the use of three different reaction kinetic probes and various MX.
There has been tremendous progress in membrane technology for gas separation, in particular oxygen separation from air in the last 20 years. It provides an alternative route to the existing conventional separation processes such as cryogenic distillation and pressure swing adsorption as well as cheaper production of oxygen with high purity. This review presents the recent advances of ceramic membranes for the separation of oxygen from air at high temperature. It covers the issues and problems with respect to the selectivity and separation performance. The paper also presents different approaches applied to overcome these challenges. The future directions of ceramic-based membranes for oxygen separation from air are also presented.
Over the past couple of years, the resurgence of placing an effective and sustainable amendment to combat against the auxiliary industrial entities, remains a highly contested agenda from a global point. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of zeolite composite, a prestigious advanced catalyst which formulates the enhancement of adsorption rate and hydrogen storage capability, has fore fronted to be a new growing branch in the scientific community. Confirming the assertion, this paper presents a state of art review of activated carbon/zeolite composite technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbon/zeolite composite represents a potentially viable and powerful tool, leading to the plausible improvement of environmental preservation.
Separation of carbon dioxide (CO(2)) from gaseous mixture is an important issue for the removal of CO(2) in natural gas processing and power plants. The ordered mesoporous silicas (OMS) with uniform pore structure and high density of silanol groups, have attracted the interest of researchers for separation of carbon dioxide (CO(2)) using adsorption process. These mesoporous silicas after functionalization with amino groups have been studied for the removal of CO(2). The potential of functionalized ordered mesoporous silica membrane for separation of CO(2) is also recognized. The present paper reviews the synthesis of mesoporous silicas and important issues related to the development of mesoporous silicas. Recent studies on the CO(2) separation using ordered mesoporous silicas (OMS) as adsorbent and membrane are highlighted. The future prospectives of mesoporous silica membrane for CO(2) adsorption and separation are also presented and discussed.
Concern about environmental protection has aroused over the years from a global viewpoint. To date, the ever-increasing importance of biomass as the energy and material resources has lately been accounted by the rising prices for the crude petroleum oil. Rice husk ash, the most appropriate representative of the high ash biomass waste, is currently obtaining sufficient attraction, owning to its wide usefulness and potentiality in environmental conservation. Confirming the assertion, this paper presents a state of the art review of the rice milling industry, its background studies, fundamental properties and industrial applications. Moreover, the key advance on the preparation of novel adsorbents, its major challenges together with the future expectation has been highlighted and discussed. Conclusively, the expanding of rice husk ash in the field of adsorption science represents a viable and powerful tool, leading to the superior improvement of pollution control and environmental preservation.
To date, microwave energy has been widely developed and applied to almost every field of chemistry. In many cases, microwave technology has proven to remarkably reducing costs, accelerating reaction rates, improving yields and selectively activating. This paper presents a state of art review of microwave technology, its background studies, fundamental chemistry and industrial applications. With the renaissance of activated carbon, there has been a steadily growing interest in this research field. The review provides a summary on recent development in preparation and regeneration of activated carbons. The key advance of introducing microwave energy has been highlighted relative to conventional methods. Moreover, the major drawbacks, challenges with its future expectation are presented and discussed. Conclusively, microwave energy is predicted to be a potentially viable and powerful replacement for fuel technology in various areas, while its progress represents an expanding field in the area of adsorption science.
Graphene is the newest member of the carbon family, and has revolutionized materials science especially in the field of polymer nanocomposites. However, agglomeration and uniform dispersion remains an Achilles' heel (even an elephant in the room), hampering the optimization of this material for practical applications. Chemical functionalization of graphene can overcome these hurdles but is often rather disruptive to the extended pi-conjugation, altering the desired physical and electronic properties. Employing surfactants as stabilizing agents in latex technology circumvents the need for chemical modification allowing for the formation of nanocomposites with retained graphene properties. This article reviews the recent progress in the use of surfactants and polymers to prepare graphene/polymer nanocomposites via latex technology. Of special interest here are surfactant structure-performance relationships, as well as background on the roles surfactant-graphene interactions for promoting stabilization.
The phase behaviour of palm olein (PO) and its derivative oils (palm oil methyl esters and medium chain triglycerides) with Imbentin coco 6.9EO, an ethoxylated C12-14 alcohol, in water has been investigated to identify compositions where microemulsions occur. The techniques used were the optical microscope phase penetration scan and small angle X-ray diffraction (SAXS). Mixed surfactant/oil samples were prepared at wt. ratios of 0.1:1, 0.25:1, 0.5:1 and 1:1 for the phase penetration scan. For SAXS analysis, the initial concentration of surfactant in water (W) was fixed at 38% (w/w), which forms a hexagonal mesophase (H1). Palm oil methyl esters (POME) and medium chain triglycerides (MCT) were added to this at 0.04:1 (or 0.05:1 for MCT), 0.1:1, 0.2:1 (or 0.25:1 for MCT), 0.5:1 and 1:1 ratios of oil to surfactant. Schematic phase diagrams were constructed to document the changes of phase structures using both bulk samples and phase penetration scans techniques. The extent of microemulsion formation (or solubilisation) decreases in the sequence POME > MCT > PO, and increases substantially with temperature, particularly for POME and MCT. All of the oils destabilize the hexagonal phase; for POME and MCT there is an increase in the surfactant cloud point temperature by ca. 10 degrees C or more, but the temperature for the onset of the lamellar (Lalpha) phase dispersion region (W + Lalpha) is hardly affected. There was a pronounced tendency for the lamellar phase formed in the presence of high oil concentrations and low water levels to have a reduced melting point. With the highest MCT levels a bicontinuous cubic phase (probably V2) is present at 25 degrees C, although this phase is not present in the binary surfactant/water system. The X-ray diffraction results show that the average area per head group (ao) at the micelle surface is decreased by the addition of the oils, consistent with the observation of a V2 phase. Possible molecular mechanisms for this observation are discussed.
This is a review article on the rheological properties of mixed solutions of sulfonated methyl esters (SME) and cocamidopropyl betaine (CAPB), which are related to the synergistic growth of giant micelles. Effects of additives, such as fatty alcohols, cocamide monoethanolamine (CMEA) and salt, which are expected to boost the growth of wormlike micelles, are studied. We report and systematize the most significant observed effects with an emphasis on the interpretation at molecular level and understanding the rheological behavior of these systems. The experiments show that the mixing of SME and CAPB produces a significant rise of viscosity, which is greater than in the mixed solutions of sodium dodecyl sulfate and CAPB. The addition of fatty alcohols, CMEA and cationic polymer, leads to broadening of the synergistic peak in viscosity without any pronounced effect on its height. The addition of NaCl leads to a typical salt curve with high maximum, but in the presence of dodecanol this maximum is much lower. At lower salt concentrations, the fatty alcohol acts as a thickener, whereas at higher salt concentrations - as a thinning agent. Depending on the shape of the frequency dependences of the measured storage and loss moduli, G' and G", the investigated micellar solutions behave as systems of standard or nonstandard rheological behavior. The systems with standard behavior obey the Maxwell viscoelastic model (at least) up to the crossover point (G' = G") and can be analyzed in terms of the Cates reptation-reaction model. The systems with nonstandard rheological behavior obey the Maxwell model only in a restricted domain below the crossover frequency; they can be analyzed in the framework of an augmented version of the Maxwell model. The methodology for data analysis and interpretation could be applied to any other viscoelastic micellar system.
Carbon quantum dots (CQDs) are a fascinating class of carbon nanoparticles with sizes around 10 nm. The unique properties of CQDs are low toxicity, chemical inertness, excellent biocompatibility, photo-induced electron transfer and highly tunable photoluminescence behaviour. Sustainable raw materials are commonly used for the fabrication of CQDs because they are cost-effective, eco-friendly and effective to minimise waste production. CQDs can be fabricated using laser ablation, microwave irradiation, hydrothermal reaction, electrochemical oxidation, reflux method and ultrasonication. These methods undergo several chemical reactions such as oxidation, carbonisation, pyrolysis and polymerisation processes to produce CQDs. Due to small particle sizes of CQDs, they possess strong tunable fluorescent properties and highly photo-luminescent emissions. It also contains oxygen-based functional groups and highly desired properties as semiconductor nanoparticles. Therefore, CQDs are promising nanomaterials for photo-catalysis, ions sensing, biological imaging, heavy metal detection, adsorption treatment, supercapacitor, membrane fabrication and water pollution treatment. This review paper will discuss the physical and chemical properties of CQDs, raw materials and methods used in the fabrication of CQDs, the stability of CQDs as well as their potential applications in wastewater treatment and biomedical field.
Recently, there have been increasing demand for the application of Pickering emulsions in various industries due to its combined advantage in terms of cost, quality and sustainability. This review aims to provide a complete overview of the available methodology for the physical characterization of emulsions that are stabilized by solid particles (known as Pickering emulsion). Current approaches and techniques for the analysis of the formation and properties of the Pickering emulsion were outlined along with the expected results of these methods on the emulsions. Besides, the application of modelling techniques has also been elaborated for the effective characterization of Pickering emulsions. Additionally, approaches to assess the stability of Pickering emulsions against physical deformation such as coalescence and gravitational separation were reviewed. Potential future developments of these characterization techniques were also briefly discussed. This review can act as a guide to researchers to better understand the standard procedures of Pickering emulsion assessment and the advanced methods available to date to study these emulsions, down to the minute details.
The present article evaluates the composition and synthesis of hydrogel beads. Hydrogels, owing to their known biocompatibility, are widely used in drug delivery as a host (or drug carrier). Hydrogels, owing to their physical, chemical and biological properties, are popular in many aspects. Hydrogels are crosslinked-hydrophilic polymers and commercialized/synthesized in both natural and synthetic forms. These polymers are compatible with human tissues, therefore can be potentially used for biomedical treatments. Hydrogels in drug delivery offer several points of interest such as sustainability, and sensitivity without any side-effects as compared to traditional methods in this field. Drugs can encapsulate and release continuously into the targets when hydrogels are activated/modified magnetically or by fluorescent materials. It is crucial to develop new crosslinked polymers in terms of "biocompatibility" and "biodegradability" for novel drug delivery platforms. In the event that the accomplishments of the past can be used into the longer terms, it is exceedingly likely that hydrogels with a wide cluster of alluring properties can be synthesized. The current review, offers an updated summary of latest developments in the nanomedicines field as well as nanobased drug delivery systems over broad study of the discovery/ application of nanomaterials in improving both the efficacy of drugs and targeted delivery of them. The challenges/opportunities of nanomedicine in drug delivery also discussed. SCOPE OF THE RESEARCH: Although several reviews have been published in the field of hydrogels, however many of them have just centralized on the general overviews in terms of "synthesis" and "properties". The utilization of hydrogels and hydrogel-based composites in vital applications have been achieved a great interest. In this review, our aim is to recap of the key points in the field of hydrogels such as; a) hydrogel nanocomposites, b) magnetic beads, c) biomedical applications, and d) drug delivery. In the same vein, these outlines will be expanded with emphasizing on the boon of magnetic beads and recent developments in this area.
New packaging materials are an emerging field in the food industry. Poor thermal, mechanical, chemical, and physical properties of biopolymers, and also their inherent permeability to gases and vapor have increased this interest. Biopolymeric materials (matrix) require fillers, which can react/interact with available matrix in order to provide new formulations with improved properties. Many studies have shown the potential use of metal nanoparticles in biopolymeric packaging and edible coatings for improving their properties. The current review summarizes the characterization of bio-nanocomposite films and edible coatings incorporated with metal nanoparticles on the shelf life and quality of tropical fruits, berries, climacteric/non-climacteric fruits and vegetables. It also provides a brief description of some advantages of bio-nanocomposite films and edible coatings applied to fruits and vegetables such as decreasing the color changes, respiration rate, weight loss and extended shelf life, delaying ripening and being environmentally friendly. The results of recent reports provide a better understanding of the impact of metal nanoparticles incorporated in biopolymers on the shelf life and the quality of fruits and vegetables.
Among the various electrically conducting polymers, polyaniline (PANI) has gained attentions due to its unique properties and doping chemistry. A number of electrically conducting biodegradable polymers has been synthesized by incorporating a biodegradable content of cellulose, chitin, chitosan, etc. in the matrix of PANI. The hybrid materials are also employed as photocatalysts, antibacterial agents, sensors, fuel cells and as materials in biomedical applications. Furthermore, these biodegradable and biocompatible conducting polymers are employed in tissue engineering, dental implants and targeted drug delivery. This review presents state of the art of PANI based biodegradable polymers along with their synthesis routes and unique applications in diverse fields. In future, the synthesis of PANI-grafted biodegradable nanocomposite material is expected to open innovative ways for their outstanding applications.
The modern eco-friendly materials used in research and innovation today consist of nanocomposites and bio-nanocomposite polymers. Their unique composite properties make them suitable for various industrial, medicinal, and energy applications. Bio-nanocomposite polymers are made of biopolymer matrices that have nanofillers dispersed throughout them. There are several types of fillers that can be added to polymers to enhance their quality, such as cellulose-based fillers, clay nanomaterials, carbon black, talc, carbon quantum dots, and many others. Biopolymer-based nanocomposites are considered a superior alternative to traditional materials as they reduce reliance on fossil fuels and promote the use of renewable resources. This review covers the current state-of-the-art in nanocomposite and bio-nanocomposite materials, focusing on ways to improve their features and the various applications they can be used for. The review article also investigates the utilization of diverse nanocomposites as a viable approach for developing bio-nanocomposites. It delves into the underlying principles that govern the synthesis of these materials and explores their prospective applications in the biomedical field, food packaging, sensing (Immunosensors), and energy storage devices. Lastly, the review discusses the future outlook and current challenges of these materials, with a focus on sustainability.
Carbon dots (CDs) are a recent addition to the nanocarbon family, encompassing both crystalline and amorphous phases. They have sparked significant research interest due to their unique electrical and optical properties, remarkable biocompatibility, outstanding mechanical characteristics, customizable surface chemistry, and negligible cytotoxicity. Their current applications are mainly limited to flexible photonic and biomedical devices, but they have also garnered attention for their potential use in intelligent packaging. The conversion of food waste into CDs further contributes to the concept of the circular economy. It provides a comprehensive overview of emerging green technologies, energy-saving reactions, and cost-effective starting materials involved in the synthesis of CDs. It also highlights the unique properties of biomass-derived CDs, focusing on their structural performance, cellular toxicity, and functional characteristics. The application of CDs in the food industry, including food packaging, is summarized in a concise manner. This paper sheds light on the current challenges and prospects of utilizing CDs in the packaging industry. It aims to provide researchers with a roadmap to tailor the properties of CDs to suit specific applications in the food industry, particularly in food packaging.
Ti-MXene allows a range of possibilities to tune their compositional stoichiometry due to their electronic and electrochemical properties. Other than conventionally explored Ti-MXene, there have been ample opportunities for the non-Ti-based MXenes, especially the emerging Mo-based MXenes. Mo-MXenes are established to be remarkable with optoelectronic and electrochemical properties, tuned energy, catalysis, and sensing applications. In this timely review, we systematically discuss the various organized synthesis procedures, associated experimental tunning parameters, physiochemical properties, structural evaluation, stability challenges, key findings, and a wide range of applications of emerging Mo-MXene over Ti-MXenes. We also critically examined the precise control of Mo-MXenes to cater to advanced applications by comprehensively evaluating the summary of recent studies using artificial intelligence and machine learning tools. The critical future perspectives, significant challenges, and possible outlooks for successfully developing and using Mo-MXenes for various practical applications are highlighted.