1000/1000
Hot
Most Recent
In recent years, the intensification of human activities including rapid urbanization, industrialization, population, and economic growth, led to an increase in waste production and energy demand. Most importantly such activities pose concerns for health, energy security and climate changes. Hazardous volatile organic compounds, VOC, and aromatic organic compounds, AOC, are being generated from the activities of many vital industries like mining and petrochemicals. They are instrumental in the economic growth of many countries and their products are regarded as privileges to modern communities. Nevertheless, they are toxic and carcinogenic thus, these wastes have been classified as “hazardous”. The simultaneous treatment of organic pollutants and energy recovery is an attractive solution to reduce pollution in water, air, and soil as well as provide alternative clean energy sources. Hydrogen could be generated from organic pollutants in water through photocatalysis. Photocatalysis refers to the oxidation and reduction, redox, reactions on semiconductor surfaces, mediated by the valence band holes and conduction band electrons, which are generated by the absorption of ultraviolet or visible light radiation. Compared to traditional oxidation processes, photocatalytic redox reaction operates at ambient conditions without a high temperature or high pressure, and many recalcitrant organic contaminants can be degraded without the addition of chemical oxidants, hence it is fully green process. Among the various photocatalysts, TiO2, as the most widely employed “golden” photocatalyst, has been largely used in photocatalysis, due to its chemical stability, nontoxicity, and low cost. In the last two decades, TiO2 photocatalysis has expanded very quickly, having undergone various development‐related energy issues and environmental issues, such as direct solar H2O splitting into H2 and the decomposition of pollutants in air and H2O at low concentrations. Although great progress has been made in TiO2 photocatalysis, much remains unknown, which raises an interesting challenge not only for engineers but also for basic scientists. a typical photocatalytic reaction in TiO2 photocatalysis contains many fundamental processes, including charge carrier formation, separation, relaxation, trapping, transfer, recombination, and transportation.
Water is essential for the existence of all living beings. However, its pollution with organic and inorganic compounds remains a threat and poses great risks to the environment and human health. The water quality is merely a concept reflecting the kind and quantity of contaminants contained in it. Mining and petrochemical industries are instrumental in the economic growth of many countries and their products are regarded as privileges to modern communities [1]. However, the wastes generated from the activities of these industries are toxic and carcinogenic [2]. Thus, these wastes have been classified as “hazardous” [3], and there is a constant increase in the pollution concerns associated with various petrochemical compounds and their by-products in the form of water, air, and soil pollution. Many of these by-products are still extensively employed, especially in the chemical, medical, and other industrial fields, as irreplaceable and inevitable raw materials [4][5]. Aromatic compounds, such as benzene, phenol, and chlorobenzene, are some of the most encountered volatile organic compounds (VOCs). The primary sources of VOCs are originated from a large number of anthropogenic activities, such as refinery streams, especially from catalytic reforming and cracking, and petroleum refining, petrochemical processing, and solvent use [6]. Other VOCs, such as methane and chlorofluorocarbons, are classified as “greenhouse gases”, which cause global warming.
The aromatic ring is the basic constituent of many organic pollutants, such as polyaromatic hydrocarbons (PAHs), dyes, pesticides, and pharmaceuticals. Aromatic compounds, such as benzene, phenols, and benzoic acid, are the most frequently used model substrates to investigate the photocatalytic mechanism and to test the activity of the photocatalysts [7]]. Detailed studies have been made on the harm caused by the aromatic compounds, for example, the potential relationship between the benzene-related compounds and the risk of hematologic cancers, such as lymphoid malignancies [8]. Moreover, long-term exposure to a low concentration of such compounds could predispose to the development of type 2 diabetes (T2D) and affect human metabolism [9]. Aromatic organic compounds also contribute to serious environmental problems, such as water pollution, which may result in the demise of scarce species, and biological genetic variation, which in many cases is an irreversible problem [10].
Compound Name | Chemical Structure | Chemical Formula |
Number of Rings | Molecular Weight (g\mol) |
Melting Point (°C) |
Boiling Point (°C) |
Aqueous Solubility (mg/L) |
Vapor Pressure (Pa) |
Log Kow |
---|---|---|---|---|---|---|---|---|---|
Naphthalene | C10H8 | 2 | 128.17 | 80.26 | 218 | 31 | 1.0 × 102 | 3.37 | |
Acenaphthene | C12H10 | 3 | 154.21 | 93.4 | 279 | 3.8 | 3.0 × 10−1 | 3.92 | |
Acenaphthylene | C12H8 | 3 | 152.19 | 92–93 | 265–275 | 16 | 9.0 × 10−1 | 4.00 | |
Fluorene | C13H10 | 3 | 166.22 | 116–117 | 295 | 1.9 | 9.0 × 10−2 | 4.18 | |
Anthracene | C14H10 | 3 | 178.23 | 218 | 340–342 | 0.045 | 1.0 × 10−3 | 4.54 | |
Phenanthrene | C14H10 | 3 | 178.23 | 100 | 340 | 1.1 | 2.0 × 10−2 | 4.57 | |
Fluoranthene | C16H10 | 4 | 202.25 | 110.8 | 375 | 0.26 | 1.2 × 10−3 | 5.22 | |
Pyrene | C16H10 | 4 | 202.25 | 156 | 393–404 | 0.13 | 6.0 × 10−4 | 5.18 | |
Benzo[a]anthracene | C20H12 | 4 | 228.29 | 158 | 438 | 0.011 | 2.8 × 10−5 | 5.91 | |
Chrysene | C18H12 | 4 | 228.29 | 254 | 448 | 0.006 | 5.7 × 10−7 | 5.91 | |
Benzo[b]fluoranthene | C20H12 | 5 | 252.31 | 168.3 | No data | 0.0015 | - | 5.80 | |
Benzo[k]fluoranthene | C20H12 | 5 | 252.31 | 215.7 | 480 | 0.0008 | 5.2 × 10−8 | 6.00 | |
Benzo[a]pyrene | C20H12 | 5 | 252.31 | 179–179.3 | 495 | 0.0038 | 7.0 × 10−7 | 5.91 | |
Dibenzo[a,h]anthracene | C22H14 | 6 | 278.35 | 262 | No data | 0.0006 | 3.7 × 10−10 | 6.75 | |
Benzo[ghi]perylene | C22H12 | 6 | 276.33 | 273 | 550 | 0.00026 | 1.4 × 10−8 | 6.50 | |
Indeno[1,2,3-cd]pyrene | C22H12 | 6 | 276.33 | 163.6 | 530 | 0.00019 | - | 6.50 |