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Global Abatement of Air Pollution Through Green Technology Routes
Published in Shrikaant Kulkarni, Ann Rose Abraham, A. K. Haghi, Renewable Materials and Green Technology Products, 2021
Sijo Francis, Remya Vijayan, Ebey P. Koshy, Beena Mathew
Montreal Protocol is an international agreement made in 1987. This is a result of serious discussions made by 28 countries at the Vienna convention for the protection of ozone layer. This protocol controls the production of chemicals that depletes ozone concentration in the atmosphere. Chloro-fluorocarbons from refrigerators, coolants, aerosol sprays produce chlorine atoms that are the major ozone-depleting gases. This treaty entreats countries to reduce the production of ozone-depleting gases.
Chlorinated Solvents and Solvent Stabilizers
Published in Thomas K.G. Mohr, William H. DiGuiseppi, Janet K. Anderson, James W. Hatton, Jeremy Bishop, Barrie Selcoe, William B. Kappleman, Environmental Investigation and Remediation, 2020
The primary use of PCE is dry cleaning; about 60% of the 1991 PCE production was used for dry cleaning, whereas only 15% of that year's production was used for vapor degreasing (USEPA, 1994b). A minor use of PCE was as a dielectric fluid (e.g., to insulate electrical transformers). Improvements in dry cleaning machinery to minimize solvent losses, in response to increasing regulatory oversight of PCE use in dry cleaning operations, have greatly curtailed PCE consumption. Compared to other solvents, the solvent losses from PCE vapor degreasers were more easily controlled because of PCE's higher vapor density (Dow Chemical Company, 2006d). By 1998, the total annual U.S. production of PCE had declined to 341 million pounds; the total consumption by dry cleaners had fallen to 40% of the total PCE production, and only 10% was used for metal degreasing. The rest was used as a feedstock for the production of fluorocarbons (chlorofluorocarbons and HFCs) for refrigerant, blowing agent, and fluoropolymer applications.
Solar Collectors and Reactors for Environmental Applications
Published in Sampa Chakrabarti, Solar Photocatalysis for Environmental Remediation, 2019
Generally, these reactors are batch type, but an array of reactors can be used for the continuous treatment. The material for the construction of flat plates should be permeable to UV radiation, but it should not be damaged by the radiation. Owing to the absorption of the part of solar radiation having larger wavelengths, temperature inside the reactor may rise to 50–60°C. The material should not be damaged at this temperature. Moreover, the material should resist chemical attack at acidic or alkaline pH. Quartz has an excellent UV permeability as well as temperature and chemical resistance, but its use is too costly in a large volume reactor. Standard glass is not suitable as a flat plate material, owing to its iron content, it absorbs a significant portion of the solar UV radiation. Most of the common low-cost polymers are not suitable owing to their poor UV permeability and chemical resistance. Fluorocarbons are a good choice because of their UV transmittance, UV stability, and chemical resistance. However, the major problem with fluoropolymer is that a thick plate is to be used for mechanical strength and this reduces its ability of UV transmittance. Ethylene tetrafluoroethylene (ETFE) and fluorinated ethylene propylene (FEP) are good candidates, of which the former has higher tensile strength, and, hence, a thinner plate with more UV permeability is possible.
Synthesis and application of cationic fluorocarbon surfactants
Published in Journal of Dispersion Science and Technology, 2023
Saipeng Zhang, Mingxin Zhang, Xingjiang Liu, Liuhe Wei
Surfactants consist of two parts, the hydrophilic end and the hydrophobic end, which can change the surface properties of aqueous solutions, such as reducing surface tension and changing contact angles. The performance of fluorinated surfactants is much better than that of hydrocarbon surfactants, and fluorinated surfactants exhibit excellent surface activity, high thermal and chemical stability at low concentrations.[1] This is due to the high electronegativity and low polarity of fluorine atoms and the hydrophobic and oleophobic nature of fluorocarbon chains.[2] It exhibits excellent reduction of interfacial tension at very low concentrations, and when the solution concentration is higher than the critical micelle concentration, excess surfactant spontaneously aggregates to form micelles.[3]
Synthesis and properties of novel betaine fluorocarbon surfactants
Published in Journal of Dispersion Science and Technology, 2023
Wen Ren, Shuixiang Xie, Yuanpeng Cheng, Mingdong Zhang, Chunyang Wang, Jialuo Rong, Zongkun Li
Surfactants are essential chemicals with a range of applications and varieties, widely used in industrial and agricultural production, scientific research, national defense and daily life.[1] The traditional surfactants are hydrocarbon surfactants, whose molecular structures are the hydrophilic groups at one end and lipophilic groups at the other end. Fluorocarbon surfactants replace part of the hydrogen atoms in the hydrophobic carbon chain of conventional surfactants with fluorine atoms, and the fluorocarbon chain has superior water-oil repellency. Because of their unique structure, fluorocarbon surfactants have high surface activity, adsorption, foaming, and the ability to change wettability, so they have become a research hotspot in the fields of petrochemical industry, fire protection and coatings.[2,3]
Flow condensing heat transfer of R410A, R22, and R32 inside a micro-fin tube
Published in Experimental Heat Transfer, 2019
Quang Vu Pham, Kwang-Il Choi, Jong-Taek Oh, Honggi Cho
According to the Montreal Protocol, R22 systems can still be sold in developing countries such as China, Vietnam, and India until 2020; however, new systems using R22 are restricted in developed countries. The phase-out of R22 obligated manufacturers to find alternative refrigerants. R410A is a hydro-fluorocarbon refrigerant, which does not contribute to the ozone depletion. The air conditioning systems using R410A offer greater efficiency, lower energy costs, and are more friendly than those using R22. Therefore, R410A has recently been employed as an alternative working fluid in residential air conditioning systems. However, the global warming potential (GWP) of R410 is relatively high and may not be suitable in the future. The R32 has been considered as the alternative refrigerant for R410A in Japan and China because R32 also has an Ozone depletion potential of 0, the GWP of R32 is only around one-third that of R410A, and vaporization heat for R32 is greater than that of R410A. Currently, R410A is the most common refrigerant used in developed countries, but if all of systems were changed to R32 the global warming potential will be reduced. So, in this study, the condensation of refrigerants was considered and analyzed, aiming to create the premise for the research and evolution of ecosystems.