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Adsorption and Desorption Aspects of Carbon-Based Nanomaterials: Recent Applications for Water Treatments and Toxic Effects
Published in Uma Shanker, Manviri Rani, Liquid and Crystal Nanomaterials for Water Pollutants Remediation, 2022
Patricia Prediger, Melissa Gurgel Adeodato Vieira, Natália Gabriele Camparotto, Tauany de Figueiredo Neves, Paula Mayara Morais da Silva, Giani de Vargas Brião
Desorption is often described as a surface phenomenon whereby the adsorbed molecules are detached from a solid surface. It can occur by the release of molecules, without chemical modifications, merely by breaking the bonds with surface atoms or by the detachment of new molecules that underwent chemical modifications, such as association or decomposition. A successful desorption step requires optimized conditions whereby the best elutants are chosen, which strongly depends on the nature of the adsorbent and adsorbate and the related adsorption mechanism. The elutant must not damage the adsorbent and should be cost-effective and eco-friendly (Das 2010). The most widely adopted desorption protocols involve the use of strong acids or bases. However, some desorption procedures apply chelating or oxidizing agents, salts, ultrasound or irradiation-assistance, thermal treatments, microbial activities, or simple washing with organic solvents or water (Hu et al. 2017). Low pH may favor the desorption and/or dissolution of metal cations and organic molecules. There is a strong competition between H+ ions and adsorbates for adsorption sites causing the displacement of adsorbed ions/molecules into the acid solution. At basic conditions, adsorbents usually became negatively charged and the attraction interactions are replaced by electrostatic repulsions, favoring the desorption process (Hou et al. 2020). Desorption is crucial to adsorbent reuse that reduces operating costs.
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Published in J. Russell Boulding, Epa Environmental Engineering Sourcebook, 2019
Thermal desorption is a process that uses either indirect or direct heat exchange to heat organic contaminants to a temperature high enough to volatilize and separate them from a contaminated solid medium. Air, combustion gas, or an inert gas is used as the transfer medium for the vaporized components. Thermal desorption systems are physical separation processes that transfer contaminants from one phase to another. They are not designed to provide high levels of organic destruction, although the higher temperature of some systems will result in localized oxidation or pyrolysis. Thermal desorption is not incineration, since the destruction of organic contaminants is not the desired result. The bed temperatures achieved and residence times used by thermal desorption systems will volatilize selected contaminants, but usually not oxidize or destroy them. System performance is usually measured by the comparison of untreated solid contaminant levels with those of the processed solids. The contaminated medium is typically heated to 300 to 1,000°F, based on the thermal desorption system selected.
Fundamental Principles
Published in Martyn V. Twigg, Catalyst Handbook, 2018
Table 1.3shows that adsorption and desorption are both essential and critical stages of the overall catalytic process. In the act of adsorption, a molecule approaches the solid surface from the gas phase and is held close to (or in) the surface. This is different from the collision and rebound that occurs at all solid surfaces in contact with gases. Thus, a molecule which stays on the surface for a time longer than that of a collision is said to be adsorbed. The removal of an adsorbed molecule is known as desorption. A distinction is drawn between adsorption, where the adsorbed material stays on (or at least close to) the solid surface, and absorption, where the absorbed material “soaks” into the bulk of the solid.
Removal and recovery of phosphonates from wastewater via adsorption
Published in Critical Reviews in Environmental Science and Technology, 2023
Rubina Altaf, Bo Sun, Huijie Lu, Heping Zhao, Dezhao Liu
Desorption is the reversal of adsorption, in which the adsorbed compounds are desorbed from the surface of adsorbent (Havlik, 2008). The most important aspects of adsorption are regeneration and desorption, and desorption can be accomplished with either thermal treatment or desorbing reagents (Sorokhaibam & Ahmaruzzaman, 2014). Desorption contributes to sustainability in two ways: (1) reuse of the adsorbent, making it reusable across a variety of effective adsorption or desorption cycles, and (2) retrieval of the adsorbate (Piol et al., 2019). Coherent desorption depends on particular circumstances and interfaces among adsorbent, adsorbate, and the adsorbent substance's nature (Volesky, 2004). The desorption study of kinetics and equilibrium are dominant for understanding the desorption features from adsorbents. In addition, for the study of desorption kinetics different models can be used including Freundlich, two constant rates, Elovich, third order model, parabolic diffusion, zero order, pseudo first order, and pseudo second order (Bashiri, 2011). The desorption rate depends on the species, bonding strength on the adsorbent surfaces, temperature, and sometimes highly dependent on the atomic response from the adsorbents. Thus, desorption should be characterized by the kinetics dealing with the desorption rate (Matsushima, 2018). The desorption solutions could relieve the problems of discharge and storage of solution (Canedo-Arguelles et al., 2013).
Nickel adsorption from waters onto Fe3O4/sugar beet pulp nanocomposite
Published in International Journal of Phytoremediation, 2023
Sayed Mohammad Osman Sadat, Sezen Kucukcongar, Mehmet Turkyilmaz
The desorption process consists of important studies for the recovery of heavy metals, reuse of the adsorbent material in adsorption, lowering the cost of processing, preventing the formation of secondary wastes or bringing them to a minimum. In this study, the results of the study for desorption of Fe3O4-SBP material, which was adsorbed Ni(II) using pure water, HCl and HNO3 solutions at different concentrations, are given in Table 7. With increasing HNO3 concentration, the desorption efficiency of Ni(II) adsorbed to the Fe3O4-SBP increased. Considering desorption results, 1 N for HNO3 and 0.5 N for HCl solution were chosen as the optimum solution concentration. When Fe3O4-SBP nanocomposite was reused for Ni(II) adsorption process, 40.4% and 36.8% Ni(II) removal results were obtained for 0.5 N HCl and 1 N HNO3, respectively. When the results were examined, a decrease of approximately 55% was observed in the second cycle. In general, it was observed that the recovery of the synthesized nanocomposite was high, but lower efficiency was obtained in its reuse. Decreasing the efficiency of the elimination process can be linked to damage and alteration in adsorption active places (Foroutan et al.2021). Due to the organic content of the material, it is thought that it would be beneficial to apply different desorption solutions and/or techniques to increase the reuse performance.
Low-cost adsorbents for environmental pollution control: a concise systematic review from the prospective of principles, mechanism and their applications
Published in Journal of Dispersion Science and Technology, 2022
Desorption process is termed as the technique in which the adsorbed substance is released from the bulk or surface of the adsorbent material. Developing techniques for adsorbents regeneration after use is necessary to decrease waste besides maximizing the sustainability of the materials. The ideal regeneration technique is not only based on desorption, but also recovers the adsorbent materials which enables collection of the adsorbate in a way to not be destroyed.[190] Thus, both the adsorbent and adsorbate materials could be available for reuse. Literature suggested various desorption methods based on the thermal treatments or using appropriate desorbing agents, however, the nondestructive techniques are still limited since a drastic destruction of the adsorbate, adsorbent, or both could occur.[191] The adsorption and desorption mechanism could be summarized in Figure 4. The adsorbents surfaces have active sites, which is the responsible of the adsorption process. Such sites are the responsible of the binding forces between the individual atoms of the solid structure. The adsorption process took place at those active sites and the cavitation will be saturated with the foreign adorbate molecules.[8,26] On contrary, for the desorption process activation took place to recover the adsorbate molecules and reuse the adsorbent materials.