On chelating surfactants: Molecular perspectives and application prospects

Chelate Complexes of 3d Transition Metal Ions─A Challenge for Electronic-Structure Methods?

Different electronic-structure methods were assessed for their ability to predict two important properties of the industrially relevant chelating agent nitrilotriacetic acid (NTA): its selectivity with respect to six different first-row transition metal ions and the spin-state energetics of its complex with Fe(III). The investigated methods encompassed density functional theory (DFT), the random phase approximation (RPA), coupled cluster (CC) theory, and the auxiliary-field quantum Monte Carlo (AFQMC) method, as well as the complete active space self-consistent field (CASSCF) method and the respective on-top methods: second-order N-electron valence state perturbation theory (NEVPT2) and multiconfiguration pair-density functional theory (MC-PDFT). Different strategies for selecting active spaces were explored, and the density matrix renormalization group (DMRG) approach was used to solve the largest active spaces. Despite somewhat ambiguous multi-reference diagnostics, most methods gave relatively good agreement with experimental data for the chemical reactions connected to the selectivity, which only involved transition-metal complexes in their high-spin state. CC methods yielded the highest accuracy followed by range-separated DFT and AFQMC. We discussed in detail that even higher accuracies can be obtained with NEVPT2, under the prerequisite that consistent active spaces along the entire chemical reaction can be selected, which was not the case for reactions involving Fe(III). A bigger challenge for electronic-structure methods was the prediction of the spin-state energetics, which additionally involved lower spin states that exhibited larger multi-reference diagnostics. Conceptually different, typically accurate methods ranging from CC theory via DMRG-NEVPT2 in combination with large active spaces to AFQMC agreed well that the high-spin state is energetically significantly favored over the other spin states. This was in contrast to most DFT functionals and RPA which yielded a smaller stabilization and some common DFT functionals and MC-PDFT even predicting the low-spin state to be energetically most favorable.

Light Control in Microbial Systems

Light is a key environmental component influencing many biological processes, particularly in prokaryotes such as archaea and bacteria. Light control techniques have revolutionized precise manipulation at molecular and cellular levels in recent years. Bacteria, with adaptability and genetic tractability, are promising candidates for light control studies. This review investigates the mechanisms underlying light activation in bacteria and discusses recent advancements focusing on light control methods and techniques for controlling bacteria. We delve into the mechanisms by which bacteria sense and transduce light signals, including engineered photoreceptors and light-sensitive actuators, and various strategies employed to modulate gene expression, protein function, and bacterial motility. Furthermore, we highlight recent developments in light-integrated methods of controlling microbial responses, such as upconversion nanoparticles and optical tweezers, which can enhance the spatial and temporal control of bacteria and open new horizons for biomedical applications.

Liquid foams: Properties, structures, prevailing phenomena and their applications in chemical/biochemical processes

Liquid foams are gas-liquid dispersions with flexible structures that provide high gas-liquid interfaces. This property nominates liquid foams as excellent gas-liquid contactors, systems that are widely used in the chemical and biochemical industries. However, challenges such as a lack of comprehensive understanding and foam instability have historically hindered their widespread industrial use in most applications. It was not until the recent development of nanofluidics, nanotechnology, surface science, and other related fields that the understanding, analysis, and control of foam phenomena improved. This led to the development of innovative stabilization techniques and foam-based unit operations in chemical and biochemical processes, each of which requires in-depth and exclusive reviews to fully comprehend their potential and limitations and to identify areas for further improvement and innovation. This paper reviews the foams, the common phenomena in them, the characteristics that make them suitable for chemical/biochemical engineering, reports on their current applications and recent developments in this field.

Bacillus spp. as Bio-factories for Antifungal Secondary Metabolites: Innovation Beyond Whole Organism Formulations

Several fungi act as parasites for crops causing huge annual crop losses at both pre- and post-harvest stages. For years, chemical fungicides were the solution; however, their wide use has caused environmental contamination and human health problems. For this reason, the use of biofungicides has been in practice as a green solution against fungal phytopathogens. In the context of a more sustainable agriculture, microbial biofungicides have the largest share among the commercial biocontrol products that are available in the market. Precisely, the genus Bacillus has been largely studied for the management of plant pathogenic fungi because they offer a chemically diverse arsenal of antifungal secondary metabolites, which have spawned a heightened industrial engrossment of it as a biopesticide. In this sense, it is indispensable to know the wide arsenal that Bacillus genus has to apply these products for sustainable agriculture. Having this idea in our minds, in this review, secondary metabolites from Bacillus having antifungal activity are chemically and structurally described giving details of their action against several phytopathogens. Knowing the current status of Bacillus secreted antifungals is the base for the goal to apply these in agriculture and it is addressed in depth in the second part of this review.

Removal of hazardous ions from aqueous solutions: Current methods, with a focus on green ion flotation

Hazardous ions, like those of heavy metals, cause significant health and environmental problems when they are discharged into water resources naturally or through various industrial processes. Removing these ions from water is of significant importance in the provision of high-quality water for drinking and agricultural usage. This work discusses current techniques that are frequently used for the removal of heavy-metal ions from aqueous solutions by absorption, particularly the use of biodegradable surfactants in ion flotation. Certain new surfactants promise high efficiency in their use in the ion-flotation process and in their application in industrial-water treatment to remove heavy metals. As an example, this work demonstrates the high efficiency of surfactants based on an amino-acid (L-cysteine) in removing a range of heavy-metal ions in a simple, single-stage ion-flotation process. High foaming ability, the ability to operate in various temperatures and pHs, decomposing into natural products and high binding affinity for heavy-metal ions make the cysteine-based surfactants a highly suitable compound to replace current commercial surfactants in ion- and froth-flotation processes. Removal of particular ions can also be achieved in ion flotation; a suitable choice of parameters, such as pH and surfactant concentration, favours the surfactant binding to those ions. Further intensive work is required to develop an optimal process to recover valuable elements from waste solutions.

Adaptive Synthesis of Functional Amphiphilic Dendrons as a Novel Approach to Artificial Supramolecular Objects

Supramolecular structures, such as micelles, liposomes, polymerosomes or dendrimerosomes, are widely studied and used as drug delivery systems. The behavior of amphiphilic building blocks strongly depends on their spatial distribution and shape of polar and nonpolar component. This report is focused on the development of new versatile synthetic protocols for amphiphilic carbosilane dendrons (amp-CS-DDNs) capable of self-assembly to regular micelles and other supramolecular objects. The presented strategy enables the fine modification of amphiphilic structure in several ways and also enables the facile connection of a desired functionality. DLS experiments demonstrated correlations between structural parameters of amp-CS-DDNs and the size of formed nanoparticles. For detailed information about the organization and spatial distribution of amp-CS-DDNs assemblies, computer simulation models were studied by using molecular dynamics in explicit water.

Heavy Metals Removal from Water by Efficient Adsorbents

Natural occurrence and anthropogenic practices contribute to the release of pollutants, specifically heavy metals, in water over the years. Therefore, this leads to a demand of proper water treatment to minimize the harmful effects of the toxic heavy metals in water, so that a supply of clean water can be distributed into the environment or household. This review highlights several water treatment methods that can be used in removing heavy metal from water. Among various treatment methods, the adsorption process is considered as one of the highly effective treatments of heavy metals and the functionalization of adsorbents can fully enhance the adsorption process. Therefore, four classes of adsorbent sources are highlighted: polymeric, natural mineral, industrial by-product, and carbon nanomaterial adsorbent. The major purpose of this review is to gather up-to-date information on research and development on various adsorbents in the treatment of heavy metal from water by emphasizing the adsorption capability, effect of pH, isotherm and kinetic model, removal efficiency and the contact of time of every adsorbent.

Application of surfactants in papermaking industry and future development trend of green surfactants

In this work, the application of chemical surfactants, including cooking aids, detergents, surface sizing agents, and deinking agents as core components, is introduced in the wet end of pulping and papermaking. This method for the combined application of enzymes and surfactants has expanded, promoting technological updates and improving the effect of surfactants in practical applications. Finally, the potential substitution of green surfactants for chemical surfactants is discussed. The source, classification, and natural functions of green surfactants are introduced, including plant extracts, biobased surfactants, fermentation products, and woody biomass. These green surfactants have advantages over their chemically synthesized counterparts, such as their low toxicity and biodegradability. This article reviews the latest developments in the application of surfactants in different paper industry processes and extends the methods of use. Additionally, the application potential of green surfactants in the field of papermaking is discussed. KEY POINTS: • Surfactants as important chemical additives in papermaking process are reviewed. • Deinking technologies by combined of surfactants and enzymes are reviewed. • Applications of green surfactant in papermaking industry are prospected.

Chelation-Assisted Ion-Exchange Leaching of Rare Earths from Clay Minerals

The effect of biodegradable chelating agents on the recovery of rare earth elements (REE) from clay minerals via ion-exchange leaching was investigated, with the aim of proposing a cost-effective, enhanced procedure that is environmentally benign and allows high REE recovery while reducing/eliminating ammonium sulfate usage. A processing route employing a lixiviant system consisting of simulated sea water (equivalent to about 0.5 mol/L NaCl) in conjunction with chelating agents was also explored, in order to offer a process alternative for situations with restricted access to fresh water (either due to remote location or to lower the operating costs). Screening criteria for the selection of chelating agents were established and experiments were conducted to assess the efficiency of selected reagents in terms of REE recovery. The results were compared to extraction levels obtained during conventional ion-exchange leaching procedures with ammonium sulfate and simulated sea water only. It was found that stoichiometric addition of N,N′-ethylenediaminedisuccinic acid (EDDS) and nitrilotriacetic acid-trisodium form (NTA-Na3) resulted in 10–20% increased REE extraction when compared to lixiviant only, while achieving moderate Al co-desorption and maintaining neutral pH values in the final solution.

Magnetic nanocomposites for sustainable water purification-a comprehensive review

Numerous contaminants in huge amounts are discharged to the environment from various anthropogenic activities. Waterbodies are one of the major receivers of these contaminants. The contaminated water can pose serious threats to humans and animals, by distrubing the ecosystem. In treating the contaminated water, adsorption processes have attained significant maturity due to lower cost, easy operation and environmental friendliness. The adsorption process uses various adsorbent materials and some of emerging adsorbent materials include carbon- and polymer-based magnetic nanocomposites. These hybrid magnetic nanocomposites have attained extensive applications in water treatment technologies due to their magnetic properties as well as combination of unique characteristics of organic and inorganic elements. Carbon- and polymer-related magnetic nanocomposites are more adapted materials for the removal of various kinds of contaminants from waterbodies. These nanocomposites can be produced via different approaches such as filling, pulse-laser irradiation, ball milling, and electro-spinning. This comprehensive review is compiled by reviewing published work of last the latest recent 3 years. The review article extensively focuses on different approaches for producing various carbon- and polymer-based magnetic nanocomposites, their merits and demerits and applications for sustainable water purification. More specifically, use of carbon- and polymer-based magnetic nanocomposites for removal of heavy metal ions and dyes is discussed in detail, critically analyzed and compared with other technologies. In addition, commercial viability in terms of regeneration of adsorbents is also reviewed. Furthermore, the future challenges and prospects in employing magnetic nanocomposites for contaminant removal from various water sources are presented.

The Surfactin-Like Lipopeptides From Bacillus spp.: Natural Biodiversity and Synthetic Biology for a Broader Application Range

Surfactin is a lipoheptapeptide produced by several Bacillus species and identified for the first time in 1969. At first, the biosynthesis of this remarkable biosurfactant was described in this review. The peptide moiety of the surfactin is synthesized using huge multienzymatic proteins called NonRibosomal Peptide Synthetases. This mechanism is responsible for the peptide biodiversity of the members of the surfactin family. In addition, on the fatty acid side, fifteen different isoforms (from C12 to C17) can be incorporated so increasing the number of the surfactin-like biomolecules. The review also highlights the last development in metabolic modeling and engineering and in synthetic biology to direct surfactin biosynthesis but also to generate novel derivatives. This large set of different biomolecules leads to a broad spectrum of physico-chemical properties and biological activities. The last parts of the review summarized the numerous studies related to the production processes optimization as well as the approaches developed to increase the surfactin productivity of Bacillus cells taking into account the different steps of its biosynthesis from gene transcription to surfactin degradation in the culture medium.

Recent Progress in Solution-Based Metal Oxide Resistive Switching Devices

Metal oxide resistive switching memories have been a crucial component for the requirements of the Internet of Things, which demands ultra-low power and high-density devices with new computing principles, exploiting low cost green products and technologies. Most of the reported resistive switching devices use conventional methods (physical and chemical vapor deposition), which are quite expensive due to their up-scale production. Solution-processing methods have been improved, being now a reliable technology that offers many advantages for resistive random-access memory (RRAM) such as high versatility, large area uniformity, transparency, low-cost and a simple fabrication of two-terminal structures. Solution-based metal oxide RRAM devices are emergent and promising non-volatile memories for future electronics. In this review, a brief history of non-volatile memories is highlighted as well as the present status of solution-based metal oxide resistive random-access memory (S-RRAM). Then, a focus on describing the solution synthesis parameters of S-RRAMs which induce a massive influence in the overall performance of these devices is discussed. Next, a precise analysis is performed on the metal oxide thin film and electrode interface and the recent advances on S-RRAM that will allow their large-area manufacturing. Finally, the figures of merit and the main challenges in S-RRAMs are discussed and future trends are proposed.

Rare Earths (La, Y, and Nd) Adsorption Behaviour towards Mineral Clays and Organoclays: Monoionic and Trionic Solutions

Metals from electric and electronic waste equipment (WEEE) can be recovered by dissolution with acids followed by liquid–liquid extraction. A possible alternative to liquid–liquid extraction is liquid–solid adsorption, where sorbents efficiency is the key factor for process efficiency. In this respect, aim of this paper is the study of the behaviour of two solid sorbents for the recovery of Rare Earths (REs)—in particular, La, Nd, and Y—from scraps of end-of-Life (EOL) electronic equipment. Two solid matrices were considered: a pristine montmorillonite clay and a modified-montmorillonite clay intercalated with a commercial pentaethylen-hexamine. The capture ability of the solids was tested towards single-ion La, Nd, and Y solutions and a multi-element solution containing the three ions. Before and after the uptake step, samples of both the solid and liquid phases were analysed. For both sorbents, at lower metal initial concentrations, the ions were captured in similar amount. At higher concentrations, pure clay showed a high total uptake towards La ions, likely due to surface interactions with clay sites. The organoclay preferentially interacts with Nd and Y. Considering the presence of the polyamine, this behaviour was related to ion coordination with the amino groups. The capture behaviour of the two sorbents was related to the different physicochemical properties of the ions, as well as to the ionic radius.

Feasibility and mechanism of enhanced 17β-estradiol degradation by the nano Zero Valent Iron-citrate system

17β-Estradiol (17β-E2) as a non-conventional pollutant with high damage, the effective removal of 17β-E2 had been studied wildly. In recent years, nano materials application enabled the rapid removal of 17β-E2. Nano zero valent iron (nZVI) as one of the most widely used nano materials could also be used to degrade 17β-E2. But, the degradation performance of nZVI was limited by oxidation and aggregation. Therefore, this study explored the degradation mechanisms of 17β-E2 by nZVI and the enhancement mechanisms of nZVI by citrate. Firstly, 17β-E2 could be effectively degraded under acidic conditions without the addition of citrate. Citrate had protective effect on nZVI, so the degradation efficiency in neutral condition and degradation rate at all pH values of 17β-E2 were enhanced greatly in nZVI-citrate system. 17β-E2 degradation was mainly about group change and cleavage of ring A, as well as dominated by O₂^-▪ and OH∙ in the absence and presence of citrate. The formation of dimers and trimers proved the existence of laccase-like reaction during the 17β-E2 degradation process by nZVI. In nZVI-citrate system, the laccase-like reaction was replaced by specific cross-coupling of 17β-E2, E1, and citrate. Overall, the study proved that citrate could enhance the degradation of 17β-E2 by nZVI.

Recent designer surfactants for catalysis in water

Recent development of new designer surfactants further spurs the development of micellar catalysis in water for chemical transformations and catalysis, providing reliable alternatives to the employment of organic solvents.

Biosurfactants, natural alternatives to synthetic surfactants: Physicochemical properties and applications

Biosurfactants comprise a wide array of amphiphilic molecules synthesized by plants, animals, and microbes. The synthesis route dictates their molecular characteristics, leading to broad structural diversity and ensuing functional properties. We focus here on low molecular weight (LMW) and high molecular weight (HMW) biosurfactants of microbial origin. These are environmentally safe and biodegradable, making them attractive candidates for applications spanning cosmetics to oil recovery. Biosurfactants spontaneously adsorb at various interfaces and self-assemble in aqueous solution, resulting in useful physicochemical properties such as decreased surface and interfacial tension, low critical micellization concentrations (CMCs), and ability to solubilize hydrophobic compounds. This review highlights the relationships between biosurfactant molecular composition, structure, and their interfacial behavior. It also describes how environmental factors such as temperature, pH, and ionic strength can impact physicochemical properties and self-assembly behavior of biosurfactant-containing solutions and dispersions. Comparison between biosurfactants and their synthetic counterparts are drawn to illustrate differences in their structure-property relationships and potential benefits. Knowledge of biosurfactant properties organized along these lines is useful for those seeking to formulate so-called green or natural products with novel and useful properties.

Co-solvent Effect on Spontaneous Formation of Large Nanoscale Structures in Catanionic Mixtures in the Anionic-Rich Region

The aggregation behavior was investigated in mixtures of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) (anionic-rich catanionic) solutions. The study was conducted in solutions of water–ethylene glycol (EG) by means of surface tension, conductometry, cyclic voltammetry, zeta potential measurements, transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. The degree of counterion dissociation (α), critical micelle concentration, aggregation numbers, interfacial properties, interparticle interaction parameters, and morphology of aggregates were determined. Based on regular solution theory, the cosolvent effects between SDS and CTAB as surfactants were also analyzed for both mixed monolayers at mixed micelles (βM) and the air/liquid interface (βσ). It was shown that the formation of large aggregates occurred in the presence of an excess of anionic surfactant. A phase transition from cylindrical micelles to spherical micelles in the anionic-rich regime was observed with an increase in the EG volume fraction. The inter particle interactions were assessed in terms of cosolvent effects on the micellar surface charge density and the cylindrical-to-spherical morphology change. Zeta potential and size of the aggregates were determined using dynamic light scattering and confirmed the models suggested for the processes taking place in each system.

Removal of chelated heavy metals from aqueous solution: A review of current methods and mechanisms

Water contamination with heavy metal ions and organic compounds such as citrate, ethylenediaminetetraacetic acid, tartrate, pharmaceuticals, surfactants and natural organic matter, is a serious problem in the natural environment. Although many methods have been effectively applied to the removal of heavy metal complexes from aqueous solution, there is a lack of information available on the mechanisms, advantages and disadvantages of these various methods. This review summarizes the various treatment methods applied to the removal of heavy metal complexes, with a summary of the mechanisms of action and recent research progress. The methods reviewed in detail include electrolysis, membrane separation, adsorption, precipitation, replacement-coprecipitation, TiO₂ photocatalysis and Fenton oxidation-precipitation, with the advantages and disadvantages of each method discussed. Furthermore, the heavy metal complex removal mechanisms are analyzed comprehensively. Results show that the adsorption method exhibited unique merits, showing much promise for future development. Finally, this review comprehensively analyzes future prospects and developments in methods for removal of chelated heavy metals.