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Preformulation
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
N. Murti Vemuri, Abira Pyne Ramakrishnan
Photodegradation depends on wavelength of the incident light as well as the intensity. Primary photochemical reactions usually occur at wavelengths where the drug absorbs light, that is, in regions where the UV-visible (VIS) absorption spectrum of the drug overlaps with the spectrum of incident radiation. In some instances, it is possible that the energy absorbed by a nondrug molecule (photosensitizer) in the formulation is transferred to the drug molecule which eventually degrades. Examples of some common drugs that undergo photolytic degradation include methotrexate, furosemide, and tetracyclines. For many drug substances, the kinetics of photodegradation vary significantly with the ionization state of the molecule. Examples would include ciprofloxacin, midazolam, mefloquine, and amiloride.24
Ill Degradable Packaging
Published in Susan E. M. Selke, Packaging and the Environment, 1994
We will define degradation in this book to mean the chemical breakdown of a material into smaller molecules, or the incorporation of materials into living organisms. Biodegradation is, then, degradation resulting from the action of living organisms, of which microorganisms are generally the most significant. Photodegradation is degradation resulting from the action of light, the most significant component being ultraviolet light. Photodegradation, most commonly, is actually an oxidative process. Oxidation can also occur in the absence of light, but is typically much slower under those conditions. For some materials, hydrolytic degradation, degradation resulting from the action of water, is also important. All materials are subject to thermal degradation, the breaking down of chemical structures on exposure to heat.
Instrumentation and Test Methods
Published in Paul N. Cheremisinoff, Handbook of Water and Wastewater Treatment Technology, 2019
Chemical substances also become deposited on various surfaces through such processes as condensation, rainfall, and atmospheric dispersion. These surfaces provide an inert medium for photodegradation. Again such factors as light intensity, temperature, and the presence of other substances will be important in determining whether photodegradation will occur.
A comprehensive review on photocatalytic removal of heavy metal ions by polyaniline-based nanocomposites
Published in Chemical Engineering Communications, 2023
Ai Ling Pang, Agus Arsad, Muhammad Abbas Ahmad Zaini, Renuka Garg, Muhammad Saqlain Iqbal, Ujjwal Pal, Muhammad Aniq Shazni Mohammad Haniff, Azrul Azlan Hamzah, Swee-Yong Pung, Mohsen Ahmadipour
The reaction temperature is another factor that can influence the photocatalytic removal efficiency of Cr(VI) ions under irradiation (Luo et al. 2017; Zhao et al. 2018; Hasanpour and Hatami 2020). Generally, the photodegradation rate tends to increase with reaction temperature (Gusain et al. 2020; Kumar et al. 2020). Interestingly, photocatalytic reactions in semiconductors occur rapidly, and these materials become less sensitive to temperature changes (Kumar et al. 2020). However, Zhao et al. discovered that increasing the temperature (from 25 °C to 45 °C) enhanced the interfacial transfer of electrons to the Cr(VI) ions, thereby increasing the Cr(VI) ion removal percentage using PANI/W18O49 hybrid nanocomposites by about 4% (i.e., from ∼82% to ∼86%) (Zhao et al. 2018).
General Path Models for Degradation Data With Multiple Characteristics and Covariates
Published in Technometrics, 2021
Lu Lu, Bingxing Wang, Yili Hong, Zhisheng Ye
Scientists at NIST conducted laboratory accelerated tests to collect degradation data for polymeric material under controlled environmental conditions. The design of the accelerated tests was based on the physical and chemical understanding of the photodegradation process. In particular, the UV spectrum and intensity, and environmental conditions such as temperature and relative humidity are among the key factors that are likely to affect the photodegradation process. The test specimens were exposed under a variety of designed test conditions for an extended period of time with the chemical degradation of the samples measured every few days using Fourier transform infrared (FTIR) spectroscopy.
Ag–Co oxides nanoparticles supported on carbon nanotubes as an effective catalyst for the photodegradation of Congo red dye in aqueous medium
Published in Inorganic and Nano-Metal Chemistry, 2020
Noor Zada, Idrees Khan, Tariq Shah, Tamanna Gul, Nasib Khan, Khalid Saeed
Currently photodegradation as an eco-friendly technique that is used as an alternative treatment method for wastewater containing toxic organic compounds.[16] This is powerful technique and an advance oxidation process for degradation of dyes and has the ability to completely mineralize the target organic pollutants into to carbon dioxide, water and mineral ions.[17,18] It has advantages over other conventional methods due to its effective, simple instrumental technique, easy controlled operation, nonselective oxidation, low expensive, complete mineralization and degradation of synthetic organic dyes.[11] This process is effectively carried in the presence of semiconductor photocatalyst activated by adsorbing photon and has the capability of accelerating a reaction without being consumed.[18] The most common photocatalysts are metal nanoparticles that show different properties which are directly relevant and depend on their particle shape, size, geometry and morphology.[19,20] Nanoparticles are small grains with size below 100 nm and have received great attention by their unique chemical and physical properties and also by their potential application in different fields[21] such as medical,[22] solar cells, nanodevices[23] etc. These metal nanopartices are used as photocatalysts in suspension form due to their large surface area, high efficiency and chemical reactivity and green nature for water cleaning and environmental remediation.[24–26] Various metal nanoparticles and nanocomposites are employed as photocatalysts such as ZrO2,[27] Nd2Sn2O7–SnO2,[28] MnO2/AC composites[29] etc.