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Contaminants Dissolved in the Water Film Surrounding Soil Particles in the Unsaturated Zone
Published in Warren J. Lyman, Patrick J. Reidy, Benjamin Levy, Chi-Yuan Fan, Mobility and Degradation of Organic Contaminants in Subsurface Environments, 2020
Warren J. Lyman, Patrick J. Reidy, Benjamin Levy, Chi-Yuan Fan
Hydrolysis. Hydrolysis is the reaction of a compound with water, hydronium or hydroxide ions resulting in bond cleavage. Equation 3.6 is an example of an hydrolysis reaction transforming an epoxide to a diol (Valentine, 1987):
Pyrolysis Gas Chromatography and Mass Spectrometry
Published in Rui Yang, Analytical Methods for Polymer Characterization, 2018
Bond cleavage easily occurs if the elimination of small neutral molecules, such as H2O, CO, NH3, H2S, CH3COOH, and CH3OH, is possible.
Biodegradable textile polymers: a review of current scenario and future opportunities
Published in Environmental Technology Reviews, 2023
PLA is one of the most promising polymers that have sustainable bio-based origin and successful application in the apparel industry [46]. It provides the necessary function and has the ability to biodegrade with the industrial composting method. In contrast to biodegradable polymers that go through continuous surface deterioration by microbes, PLA degrades in a two-step process. In the first step, its chemical bond cleavage occurs due to humidity in the environment which leads to the initial disintegration of the polymer. This process accelerates especially at temperatures > 60 oC [57]. It also lowers the molecular weight to 10 kDa, followed by interaction with the microbes and ultimately assimilation of the fragment residues in the second step of the process [58]. It can degrade completely under thermophilic aerobic conditions in industrial compost, however, only partial degradation of PLA occurs in mesophilic ambient conditions [55,58].
Electrochemical reduction of halogenated organic contaminants using carbon-based cathodes: A review
Published in Critical Reviews in Environmental Science and Technology, 2023
Jacob F. King, William A. Mitch
Concerted and stepwise pathways have been distinguished by fitting electrochemical data from experiments to versions of the Butler-Volmer equation for cathodic reactions (equation 10), which is valid for applied overpotentials > |0.1 V| where the reverse reaction is insignificant (Bard & Faulkner, 2001). Relating experimentally measured values for the current density (j) as a function of the applied overpotential (η) enables the determination of the electron transfer coefficient (α), which represents the fraction of the interfacial potential at the electrode-electrolyte interface that works to lower the free energy barrier for electron transfer; α can also be found by conducting cyclic voltammetry at different scan rates (Lei et al., 2019). Research has indicated that α < 0.3 coincides with a concerted reaction, 0.4 < α < 0.5 suggests a stepwise reaction with electron transfer being rate-limiting and α > 0.5 indicates a stepwise reaction with bond cleavage being rate-limiting (Lei et al., 2019; Rondinini et al., 2001; Totten & Roberts, 2001; Yin et al., 2020). Essentially, increasing α indicates increasing facility of electron transfer compared to carbon-halogen bond cleavage, resulting in electron transfer preceding bond cleavage as a separate step. Other variables in equation 10 include the exchange current density (j0), the surface (Cs) and bulk (Cb) concentrations of the substrate and the number of electrons transferred during the reaction (z).
A strategy for controlling degradation in vitro of carbon fiber-reinforced polylactic acid composites (by combining fiber modification and pulsed electromagnetic fields)
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Di Zhang, Jingang Qi, Sifan Qiao, Liang Liu, Bing Wang, Zuofu Zhao
To clarify the mechanism of fiber modification and PEF degradation during the degradation process, the collision process and location between H＋, influenced by PEF in the model, and ester bonds produced by fiber modification were amplified. The diagram in Figure 6c illustrates the collision of H＋, representing a collision in which an ester bond is broken. As compensation for the chemical bond breakage, H＋was assigned to both ends of the ester bond cleavage. This also reflected the positive role of PEF in early interfacial degradation. However, in late stage degradation, H＋ crossed the ester bond, such that under the action of degradation stress, ester bonds had a self-healing ability, allowing partial recovery (Figure 6d) [14]. Thus, fiber surfaces were still covered with PLA matrix after fiber degradation of C/PLA composite. Also, because of degradation-related ester bond healing, the mechanical properties of the process were stabilized.