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Green Materials for Waterborne Polyurethanes
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Felipe M. de Souza, Prashant Kote, Ram K. Gupta
Surfactants are another important component used during the formulation of polyurethanes to improve the mixability of polyols with isocyanates and allow a good foaming process. Surfactants can be divided into four different types: anionic, cationic, nonionic, and amphoteric. Cationic and anionic surfactants are commonly used in polyurethanes. The first one is used for better emulsification action, while the second provides stability against corrosion [1]. For polyurethane foams, surfactants play an important role in forming and stabilizing the cellular structure, air permeability, and prevention of coalescence, while for WPU, surfactants improve dispersibility. Surfactants can be introduced externally or internally during the synthesis of WPU. External surfactants are blended into the reaction mixture to create the emulsion. Internal emulsifiers are chemically bonded to the starting chemicals to improve the dispersion of the polyurethanes in water. The second approach is a preferred method as it leads to a more stable WPU dispersion. With the basics of polyurethanes discussed above, the second part of this chapter addresses the main points in terms of materials and chemistries for WPU, showing the vast number of materials that can be employed as well as the chemical process for their synthesis. The third session covers many green approaches used for WPU, along with other important characteristics.
Applications and Future Prospects of Biosurfactants
Published in R.Z. Sayyed, Microbial Surfactants, 2022
Anita V. Handore, Sharad R. Khandelwal, Rajib Karmakar, Divya L. Gupta, Vinita S. Jagtap
Although, surfactants are extensively used in numerous applications, they show various adverse impacts on the environment and society health . On the other hand, biosurfactants exhibit numerous benefits over synthetic surfactants such as high biodegradability, low toxicity, low irritancy and compatibility with human skin and ecological acceptance. These biomolecules synthesized by microorganisms like bacteria, fungi and yeast possess identical characteristics to reduce the surface and interfacial tensions by similar mechanisms of synthetic surfactants. They exhibit numerous benefits over synthetic surfactants like high biodegradability, low toxicity, low irritancy and compatibility with human skin and ecological acceptance. They tends to show some special properties like selectivity, specific activity at extreme temperatures, pH and salinity. In spite of extensive research in respect of cost effective production of biosurfactants, there is still an economic challenge with respect to their commercial success in comparison with their synthetic counterparts. In such circumstances these potent biomolecules can come up as ‘Green and economically viable safe products’ as per increasing demand of consumers by implementing some promising prospects and strategies for economizing their sustainable production as well as promoting their diverse applications for remarkable growth in the global market.
Activated Sludge Process for Refractory Pollutants Removal
Published in Maulin P. Shah, Removal of Refractory Pollutants from Wastewater Treatment Plants, 2021
Reyhan Ata, Gökçe Faika Merdan, Günay Yıldız Töre
Perfluorooctane sulfonic acid (PFOS), its salts, and perfluorooctane sulfonyl fluoride (PFOS-F) fulfills the criteria of the Stockholm Convention Annex B (Restriction) list as refractory (persistent, bio-accumulative, and toxic) chemicals with extensive industrial application. They are man-made (synthetic), non-biodegradable, and striking in terms of the strength of organic pollution created in the receiving environment where it is discharged without treatment. They do not occur naturally in the environment and are known as surfactants or fluorosurfactants [perfluorooctanoic acid (PFOA)]. Surfactants are compounds that reduce the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants have the ability to play the role of detergent, wetting agent, emulsifier, foaming agent, and dispersant. The volume of surfactants (through detergents, cleaning agents, and PPCPs) released into the environment at a rising rate are becoming an increasing concern. Linear alkylbenzene sulfonates (LAS) (used for detergent production) and alkyl phenol ethoxylates (APE) (used for detergent-like compounds production), known as the two basic surfactants, break down into nonylphenol, which is considered an endocrine disruptor in sewage treatment plants and soil (Rebello et al. 2014).
Remediation of organic contaminated soil by Fe-based nanoparticles and surfactants: a review
Published in Environmental Technology Reviews, 2023
Kien A. Vu, Catherine N. Mulligan
Surface-active agents or surfactants are heterogeneous and long-chain organic molecules that contain both hydrophilic and hydrophobic parts. The hydrophilic groups (head), such as amino acid, alkylphenols, make them soluble in water, while the hydrophobic groups (tail), for example, fatty acids, lipopeptides, make them likely concentrated at the interfaces [105]. Due to the capacity to decrease surface tension, improve solubility, detergency strength, wetting and foaming performance, surfactants are generally used as additives in cleaning agents, household detergents, wetting or foaming agents [106,107]. Based on the properties of the hydrophilic group, surfactants may be distinguished as anionic, cationic, zwitterionic, and nonionic [108]. One of the most critical properties of surfactants is the ability to form micelles. If the surfactant concentration exceeds a specific value, called the critical micelle concentration (CMC), the monomer molecules may agglomerate in an aqueous solution to form large micelles. The CMC value for each surfactant varies. Surfactants may be produced chemically or biologically, equivalent to synthetic surfactants or biosurfactants, respectively.
Review on performance analysis in diffusion absorption refrigeration system (DARS) using different working fluids
Published in International Journal of Ambient Energy, 2023
Sreenesh Valiyandi, Gireeshkumaran Thampi
Wu et al. (2020) addressed the Comparative analysis of conventional and low-GWP refrigerants with the ionic liquid used for assisted-compression absorption cooling cycles. Problems of conventional absorption methods, hydrofluorolofins/hydrofluorocarbons with low global warming potential, and ionic fluids at low temperatures for two assisted absorption-compression are numerically investigated. Surfactant is one of the temporary chemical treatment methods for improving absorption. Surfactants are known as compounds that reduce surface tension between two liquids. Kim et al. (2006) used a shadow graphic technique to inspect surfactants’ effects and analyse the bubble behaviour. 2-Ethyl-1 Hexanol was the most effective because its absorption rate was 4.81 times more. The addition of surfactant (2-ethyl-1-hexanol 700 ppm) and Nano-particle (Cu, 0.1%) improved the absorption efficiency up to 5.32 times through their continued research.
TX-100 adsorption from aqueous solution using modified graphene oxide; optimization by response surface methodology and one factor at a time techniques
Published in Journal of Dispersion Science and Technology, 2023
Najmeh Rezazadeh, Shahnaz Danesh, Mohammad Eftekhari
Surfactants are organic compounds that are used in various industries like agriculture, textile, petrochemicals, leather, cement and food industry.[1–3] Due to their toxicity, the wastewater treatment for removing of surfactants is a challenging research field.[4] One of the most commonly used methods for the removal of surfactants is the adsorption-based techniques which have advantages, such as various types of adsorbents, high efficiency and relatively low costs.[5] Researchers have used many natural and synthetic adsorbents for adsorption of surfactants from wastewater samples, such as fly ash,[2,6] activated carbon,[7–9] chitosan,[10] soil,[11–13] zeolite[14–16] and silica.[17] Other techniques were used for the removal of surfactants are including electrochemical,[18] flocculation and advanced oxidation process,[19] biological treatment[20–24] and filtration.[25–27]