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Introduction to Inorganic Chemistry
Published in Caroline Desgranges, Jerome Delhommelle, A Mole of Chemistry, 2020
Caroline Desgranges, Jerome Delhommelle
Chemisorption refers to the formation of bonds between the adsorbed molecules and the metal atoms of the surface. In the case of physisorption, there is no chemical bonds formation (the interaction with the surface atoms is much weaker). Chemisorption is what Sabatier (see Figure 6.12) had postulated for the reactions of the hydrogenation of alkenes (for example, ethylene) on nickel columns. Indeed, experiments in the 1940s show that when ethylene undergoes chemisorption on a catalyst, its double bond becomes “open”, meaning that an “attachment” takes place between the carbon atoms and the metal atoms of the catalyst. They establish this through an exchange reaction between ethylene and a heavy hydrogen atom known as deuterium (D2). Deuterium is an isotope of hydrogen with a nucleus composed of one proton and one neutron. The opening of the double bond coupled with the dissociative chemisorption of H2 molecules on Ni paves the way for the formation and release of ethane molecules (H3C–CH3). This reaction mechanism is later proved to be correct by experiments, known as high-resolution electron energy loss spectra of adsorbed molecules, and by quantum chemistry calculations.
Surface and Interfacial Phenomena
Published in Mary Anne White, Physical Properties of Materials, 2018
Understanding the properties of surfaces can be very important in chemistry. For example, many reactions are catalyzed on surfaces that allow energetically favorable reaction pathways, primarily through chemisorption of reactants.
Industrial Odor Control
Published in Paul N. Cheremisinoff, Air Pollution Control and Design for Industry, 2018
Chemical adsorption, or chemisorption, involves formation of chemical bonds between the gas and surface molecules. The strength of the chemical bond may vary considerably, and identifiable chemical compounds in the usual sense may not actually form. However, the adhesive force is much greater than found in physical adsorption. The heat liberated during chemisorption is usually large, of the order of the heat of chemical reaction.
The adsorptive removal of lead ions in aquatic media: Performance comparison between advanced functional materials and conventional materials
Published in Critical Reviews in Environmental Science and Technology, 2020
Botao Liu, Azmatullah Khan, Ki-Hyun Kim, Deepak Kukkar, Ming Zhang
As aforementioned, adsorption-based removal of Pb2+ has been one of the preferable options due to various advantages (e.g., facile operation, recovery of adsorbent/adsorbate, and cost-efficiency). The adsorption mechanism involves physisorption and chemisorption (Ho, Ng, & McKay, 2001; Unuabonah, Adebowale, & Olu-Owolabi, 2007). Physisorption, also known as van der Waals adsorption, is the adsorption between adsorbate and adsorbent based on intermolecular forces, including electrostatic and dispersive forces, between the solid surface and adsorbate molecules. Chemisorption is the adsorption in which adsorbate and adsorbent interact to generate chemical bonds (e.g., metal organic complexes or cation exchange reactions). For more detailed contents about the adsorption mechanism, readers may refer to SM 2.2.2.
Endocrine disrupting chemicals (EDCs): chemical fate, distribution, analytical methods and promising remediation strategies – a critical review
Published in Environmental Technology Reviews, 2023
Mridula Chaturvedi, Sam Joy, Rinkoo Devi Gupta, Sangeeta Pandey, Shashi Sharma
Adsorption is a surface phenomenon and is defined as the increase of concentration of a component (the absorbate) at the surface of substrate (the absorbent) due to molecular interaction between the adsorbate and the adsorbent. According to the interaction between adsorbates and adsorbents, the process can be classified into two categories: physisorption and chemisorption [51]. Chemisorption is a chemical adsorption process which involves a chemical reaction between the surface and the adsorbate whereas physisorption is a physical adsorption process of mechanically locking up molecules in other solid material. Choong et al. [52] reported adsorption behaviour of bisphenol-A (83.53 mg g−1) and ibuprofen (34.96 mg g−1) via chemisorption. Rakhym et al. [53] reported adsorption of propranolol hydrochloride via physisorption. Due to its high efficiency and low cost, adsorption serves as the most preferential method besides its drawbacks as disposal of desorbing agents to the sink causing secondary pollution [54]. Hence, recycle options should be developed to regenerate desorbing solvents and recollect desorbed pollutants that may be removed or returned to the manufacturing industry [55]. Some alternative solution to the present dilemma was addressed by Zbair et al. [56] reporting incineration of exhausted adsorbents and conversion of retained pollutants to less harmful byproducts. But, such a study requires proper waste management techniques and transport facilities that should be considered by environmental protection agencies. The percentage removal of EDCs by various adsorbents has been summarized in Table 2.
Sorption of organic pollutants frequently detected in stormwater: evaluation of five potential sorbents
Published in Environmental Technology, 2018
The Langmuir model assumes monolayer molecular adsorption and is said to better describe chemisorption, while the Freundlich model describes equilibrium on heterogeneous surfaces where monolayer and multilayer adsorption may occur [45,46]. Chemisorption implies covalent, ionic and metallic bonds that are highly specific, whereas physisorption is attributed mainly to van der Waals forces. However, because of the negative qmax-values for the Langmuir model (Table 2), the Langmuir isotherm is not appropriate and physisorption should not be ruled out.