China
Africa
Explore chapters and articles related to this topic
Summary of Other Remediation Systems
Published in Jimmy H.C. Wong, Chin Hong Lim, Greg L. Nolen, Design of Remediation Systems, 2020
Jimmy H.C. Wong, Chin Hong Lim, Greg L. Nolen
Other factors that affect the success of soil flushing include local soil conditions and surfactants added to the flush water. Flushing works best in soils with high permeability, such as gravel or sand. Soils with high silt and clay content impede movement of the flushing solution through the soils, resulting in less removal. Soils with high organic carbon content and high clay content would tend to have stronger sorption characteristics and thus be less suitable for flushing. The process is enhanced if a surfactant or detergent is added to the flushing solution. Surfactants are either natural or synthetic chemicals that have the ability to promote the wetting, solubilization, or emulsification of various organic chemicals. Cost-effectiveness is improved if biodegradable surfactants are used.
Enhancing Uptake and Translocation of Systemic Active Ingredients
Published in Chester L. Foy, David W. Pritchard, and Adjuvant Technology, 2018
Roger J. Field, Farhad Dasigheib
The development of generalized predictive models that can determine the performance of a wide range of surfactant-active ingredient combinations is a major challenge given the wide range of physicochemical interactions that may occur between particular surfactant-active ingredient partners.86,97 Highly lipophilic, nonpolar active ingredients require solubilization into surfactant micelles.109 Solubilization is influenced by the structure of the surfactant and active ingredient, as well as external conditions, particularly temperature. The site of solubilization in the surfactant micelle is a key factor and demonstrates the structural specificity required.203 For example, highly insoluble active ingredient is typically located either in the core of the micelle or within the hydrophobic portion of the micelle, and solubilization should thus be enhanced by an increase in the alkyl chain length of the surfactant. Where solubilization occurs in the hydrophilic portion of the surfactant, it increases in accordance with the size of the hydrophilic group and may be influenced by polarity, chain branching, and molecular size and configuration.109,203 Highly hydrophilic, polar compounds coexist with surfactant molecules without incorporation into micelle structures.
Formulation Development of Small-Volume Parenteral Products
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Madhav S. Kamat, Patrick P. DeLuca
The CMC can be measured by a variety of techniques, for example, surface tension, light scattering, osmometry, all of which show a characteristic break point in the plot of the operative property as a function of concentration. Figure 10.7, a plot of surface tension against concentration of surfactant, shows a break in the linearity of the curve, indicating the CMC [50]. Many factors such as temperature, pH of the solution, electrolytes, and other ingredients affect micellization and hence solubilization [51,52]. For nonionic surfactants, the CMC value decreases with increasing temperature whereas for ionic surfactants, it increases as the temperature increases [53]. Since the pH can affect the equilibrium between ionized and non-ionized solute species, it can have an effect on the capacity of micellar solubility as shown by De Castro et al., for atenolol, nadolol, midazolam, and nitrazepam [54]. For ionic surfactant micelles, electrolyte addition causes a decrease in the CMC resulting in an increase in the micellar solubilization capacity [55], whereas in the case of nonionic surfactant, polysorbate 80, the solubility of furosemide increases in the presence of sodium chloride due to increased micellar packing and micelle volume [56]. Other ingredients present in the formulation can also have a profound effect on the solubilizing capacity of surfactants. Surfactants may precipitate in the presence of some organic additives or micellization may be abolished, if high enough concentrations of, for example, alcohols are present. Excipients such as phospholipids also affect the CMC. Many water-soluble drugs themselves are remarkably surface active: they lower the surface and interfacial tension of water, promote foaming, and associate into micelles [46].
Comparative solubilization of reactive dyes in single and mixed surfactants
Published in Journal of Dispersion Science and Technology, 2022
Sadia Noor, Muhammad Babar Taj, Senthilkumar M., Iram Naz
Surfactants are amphiphilic substances that facilitate the solubilization of additives and excipient molecules through a partitioning mechanism. These are useful products not only in nature but also in industries.[1,8,9] These molecules get adsorbed at the water–air interface even at very low concentrations and form self-aggregates (micelles). The micelle formation occurs on reaching a threshold level of concentration which is designated as critical micelle concentration (CMC). Quantification of this CMC can be estimated using various techniques: UV–Visible spectroscopy, conductometry, surface tension, and fluorometry.[10–16] The micelles are isotropic motifs of the surfactants having a hydrophilic head and a hydrophobic tail. Micellar solutions play a vital role in enhancing the solubility of less soluble or sparingly substances in aqueous media by the solubilization process.[17] Dye–surfactant aggregation provides useful insight into many industrial and chemical processes and also gives information about dye separation processes. Dye–surfactant interaction depends primarily on the nature and chemical structures of the participating dyes and surfactants.[16,18,19] The intermolecular forces which are dominant during such associations include hydrogen bonding, hydrophobic and electrostatic interactions, Van der Waals forces, and π-stacking.[20–23]
Thermodynamic and solubilization properties of a polynuclear copper complex in ionic surfactants media
Published in Journal of Dispersion Science and Technology, 2021
Muhammad Nadeem Akhtar, Sadia Noor, Muhammad Babar Taj, Muhammad Khalid, Muhammad Imran
Surfactants can facilitate the solubilization behavior of organic molecules (drugs/additives/excipients) through bulk partitioning in micellar and intermolecular bulk phases. Solubilization is a dynamic process that utilizes the amphiphilic micellar media of surfactants to facilitate and enhance the solubilization of less water-soluble species. This process is a useful tool to get an in-vitro understanding of drug-biomembrane interactions which are key events in biological and industrial processes. Micellar solubilization is the most significant and characteristic attribute of the surfactants that expands their viability at biological and industrial studies. The critical micellar concentration (CMC) is the fundamental factor which indicates and influences micellization based on the chemical and structural nature of the surfactants.[3–6]
Micellar-enhanced ultrafiltration (MEUF) for removal of rhodamine B (RhB) from aqueous system
Published in Journal of Dispersion Science and Technology, 2022
Amnah Yusaf, Muhammad Usman, Asim Mansha, Muhammad Saeed, Matloob Ahmad, Muhammad Siddiq
Dyes can be scavenged from water using surfactant solutions. Surfactants are the compounds having hydrophobic and hydrophilic parts in the same molecule. This structural attribute of surfactants enables them to play their part as detergents, emulsifiers, foaming agents, solubilizers, drug delivery agents, wetting agents, flotation agents; etc. in daily life and industry.[2–4] The amphiphilic structure of surfactants enable them to undergo micellization, the ability to form self-aggregates at/after a certain value of concentration called “Critical Micelle Concentration (CMC).”[5,6] The micellization, being widely studied and explored phenomenon is a self-driven process supported by the hydrogen-bonding, van der Waals and other non-covalent forces.[7] Micellization is followed by another very important phenomenon called solubilization[8] being governed by Nernst’s distribution law. Solubilization confers surfactant solution an ability to enhance solubility of insoluble or less soluble solutes.[9–15] Aforesaid characteristics of surfactants have convinced the textile chemists to use these compounds in the textile industry to facilitate the binding of dye on fabric and to remove the remnant dye molecules, from bath, by solubilization.[16,17] The complex structure of dyes makes them resistant to sunlight, oxidants, and microbes. The techniques being used for the removal of the dyes include oxidation, adsorption, biodegradation, catalytic degradation and membrane filtration.[18–21]