China
Africa
Explore chapters and articles related to this topic
World Water Crisis and Climate Change
Published in Stanley E. Manahan, Environmental Chemistry, 2022
The use of ultraviolet-irradiated titanium dioxide photocatalysis with titanium dioxide using ultraviolet radiation is an example of several advanced oxidation processes that may be used to treat and disinfect water. Several of these generate highly reactive hydroxyl (HO•). Advanced oxidation processes include Fenton processes that use Fe2+ with H2O2 and can be energized with ultraviolet or ultrasound (sonolysis); sonolysis along with H2O2 or ozone; electrochemical oxidation; wet oxidation; supercritical water oxidation; and electron beam oxidation.
Treatment Technologies
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
William H. DiGuiseppi, James W. Hatton
Sonochemical oxidation of organic contaminants is caused by the production of hydroxyl radicals and other oxidizing species during the collapse of cavitation bubbles formed during high-frequency acoustic stimulation of the aqueous media. High temperatures (up to 4,000°C) and pressures (100,000 kilopascals) can be present in the cavitation bubbles when they collapse. VOCs are degraded through combustion, high-temperature chemical reactions, supercritical water oxidation, and the production of free radicals. Hydroxyl and other free radicals formed during this process are capable of oxidizing organic compounds, such as 1,4-dioxane.
Supercritical Water Gasification of Biomass: Technology and Challenges
Published in Sandeep Kumar, Florin Barla, Sub- and Supercritical Hydrothermal Technology, 2019
Supercritical water is being researched for its application in biomass oxidation as well as gasification. Supercritical water oxidation (SCWO) is generally used for neutralizing toxic organic matter. At supercritical conditions, organic matter and oxygen become fully miscible in water. Organic matter is fully oxidized within one minute at optimum reaction conditions. Supercritical water gasification (SCWG) is carried out in the absence of excess oxygen and the reactions occur in a reductive environment. Though SCWO and SCWG are similar, due to the difference in reaction conditions, reactor design considerations are very different in both the cases. SCWO is an exothermic process while SCWG is endothermic, thus heat recovery is vital in SCWG for process economics. SCWO technology is used for organic waste treatment and SCWG technology is used for fuel generation from organic matter (Kruse, 2009; Marrone & Hong, 2009; Pinkard et al., 2019).
Treatment of wet electrostatic precipitators wastewater by supercritical water oxidation
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Aytuğ Tekbaş, Nihal Bektaş, Mesut Tekbaş, Ercan Gürbulak, Ebubekir Yüksel
Supercritical water oxidation (SCWO) is one of the advanced oxidation methods for the treatment of hazardous wastewater and sludge containing high COD and TN loading (Pervova, Klepalova, and Lipunov 2021). Water reaches the supercritical stage at 374°C temperature and 221 bar above. Supercritical water can serve as a solvent that offers new reaction possibilities for hydrolysis or partial oxidation with excellent transport properties (Jiang et al. 2020) (Wang et al., 2019,). In this phase, organic matter, water, and oxidant homogeneously are mixed as there is no mass transfer resistance, resulting in a high oxidation reaction rate, which ensures complete removal of the pollutants (Jiang et al. 2020). Figure 1 gives a general schematic representation of the SCWO process. Due to changes in water physical properties, supercritical water oxidation has emerged as a treatment method used for hazardous industrial waste removal in recent years (Li and Kumar 2019). Finally, it can be easily said that SCWO is a suitable treatment method for organic wastewaters that contain high toxicity, high concentration, and are refractory in nature (Yao et al. 2018). The supercritical water oxidation process can give complete degradation for WESP wastewater (Li and Kumar 2019).
Municipal Solid Waste Leachates Destruction and Metals Recovery by Supercritical Water Oxidation
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2018
D. A. Zou, Y. Chi, J. Dong, F. Wang, M. J. Ni
Supercritical water oxidation (SCWO) is a novel oxidation process, which occurs in water above its critical point (Tc = 374°C and Pc = 22.1 MPa). Supercritical water (SCW) has a high solubility for both organic compounds and oxygen to form a single and homogeneous phase, and meanwhile the solubility of inorganic salts decreases (Brunner, 2009). As a result, organic compounds can be effectively destructed in a short time. Inorganic materials such as metal salts are insoluble due to the high polarity of ions; therefore, the special characteristic of SCWO could force these inorganic compounds to convert to more stable species, which could decline the mobility of the metals.