Radiolysis of aqueous 4-nitrophenol solution with Al2O3 or TiO2 nanoparticles

Laser-Assisted Preparation of TiO2/Carbon/Ag Nanocomposite for Degradation of Organic Pollutants

The ever-increasing expansion of chemical industries produces a variety of common pollutants, including colors, which become a global and environmental problem. Using a nanocatalyst is one of the effective ways to reduce these organic contaminants. With this in mind, a straightforward and effective method for the production of a novel nanocatalyst based on lignin-derived carbon, titanium dioxide nanoparticles, and Ag particles (TiO2/C/Ag) is described. The preparation of carbon and Ag particles (in sub-micro and nano size) was carried out by laser ablation in air. The nanocomposite was synthesized using a facile magnetic stirrer of TiO2, C, and Ag. According to characterization methods, a carbon nanostructure was successfully synthesized through the laser irradiation of lignin. According to scanning electron microscope images, spherical Ag particles were agglomerated over the nanocomposite. The catalytic activities of the TiO2/C/Ag nanocomposite were tested for the decolorization of methylene blue (MB) and Congo red (CR), employing NaBH4 in a water-based solution at 25 °C. After adding fresh NaBH4 to the mixture of nanocomposite and dyes, both UV absorption peaks of MB and CR completely disappeared after 10 s and 4 min, respectively. The catalytic activity of the TiO2/C/Ag nanocomposite was also examined for the reduction of 4-nitrophenol (4-NP) using a NaBH4 reducing agent, suggesting the complete reduction of 4-NP to 4-aminophenol (4-AP) after 2.30 min. This shows excellent catalytic behavior of the prepared nanocomposite in the reduction of organic pollutants.

Tailored functional materials as robust candidates to mitigate pesticides in aqueous matrices-a review

Pesticides are among the top-priority contaminants, which significantly contribute to environmental deterioration. Conventional techniques are not efficient enough to remove pollutants from environmental matrices. The development of functional materials has emerged as promising candidates to remove and degrade pesticides and related hazardous compounds. Furthermore, the nanohybrid materials with unique structural and functional characteristics, such as better material anchorage, mass transfer, electron-hole separation, and charged interaction make them a versatile option to treat and reduce pollutants from aqueous matrices. Herein, we present the current progress in the development of functional materials for the abatement of toxic pesticides. The physicochemical characteristics and pesticide-removal functionalities of various metallic functional materials (e.g., zirconium, zinc, titanium, tungsten, and iron), polymer, and carbon-based materials are critically discussed with suitable examples. Finally, the industrial-scale applications of the functional materials, concluding remarks, and future directions in this important arena are given.

Gallic acid degradation by electron beam irradiation under various conditions

In this study, aqueous solutions of gallic acid (GA) were irradiated in an electron beam (EB) accelerator under different experimental conditions (various initial GA concentrations, presence or absence of oxidant and oxygen). For an initial GA concentration of 50 μM, complete GA degradation was achieved with an absorbed dose of 850 Gy in the presence of dissolved oxygen. Both GA removal and mineralization are favored when oxygen is present. The addition of persulfate anions (S₂O₈^2-) or hydrogen peroxide (H₂O₂) also increased the efficiency of GA degradation and mineralization. For an absorbed dose of 14 kGy, GA mineralization reached approximately 45%, 55%, and 72% for the EB, EB/H₂O₂, and EB/S₂O₈^2-systems, respectively. Three transformation products were tentatively identified in the presence of oxygen, these are the result of hydroxylation and ring opening reactions. No specific transformation product was found for the sulfate radical anion (SO₄^-●) reaction. Four additional compounds, including a dimer, were identified in oxygen-free solutions. These findings demonstrate that water radiolysis based on EB irradiation is an efficient process to activate H₂O₂ and S₂O₈^2- anions and is an advanced oxidation process (AOP).

Effect of titanium dioxide nanoparticles on gamma-ray treatment of phenol in different matrices: implications in toxicity toward Daphnia magna

Gamma-ray treatment of phenol was studied in terms of both chemical degradation and toxicological change. About 90% of phenol (5.0 × 10(-4) M) in ultrapure water (UW) was eliminated by gamma-irradiation at a dose of 10 kGy, but acute toxicity was dramatically increased, particularly for dose of 1 kGy, due to the formation of more toxic by-products such as hydroquinone, benzoquinone, resorcinol and catechol. The addition of TiO(2) nanoparticles had little effect on the removal of phenol in UW, but substantially enhanced the mineralization of phenol compared with gamma-irradiation alone. Additionally, degradation of phenol by gamma-irradiation was inhibited in a wastewater effluent (WE) matrix, likely due to the presence of dissolved organic carbon (22.06 mg L(-1)). Furthermore, lower concentrations of toxic by-products were generated both in WE and in the presence of TiO(2) nanoparticles, resulting in reduction of toxicity increase by gamma-irradiation. Meanwhile, the toxicity of gamma-ray treated phenol in WE was well estimated with simple summation of individual toxicity of phenol and by-products (R (2) = 0.9678).

Effect of persulfate on the oxidation of benzotriazole and humic acid by e-beam irradiation

These days, the use of persulfate in advanced oxidation processes (AOPs) has gained more attention as an emerging clean and efficient technology to degrade the organic pollutants. The objective of this study was to investigate the effect of the addition of persulfate on the oxidation of benzotriazole (BT) and humic acids (HAs) by irradiation. The degradation of BT (3.7 μM) was followed under the influence of persulfate addition (200-500 μM) in combination with a fixed radiation dose (15 Gy) in the absence and presence of HA (5 and 20mg/L) in deionized water. The main results obtained in this study on the degradation of BT in the presence of HA showed a different effect of S(2)O(8)(2-) addition during irradiation, depending on whether HA are oxidized or not-oxidized. (1) An inhibitory effect of S(2)O(8)(2-) was observed in the presence of non-oxidized HA. (2) The removal of BT was generally more important during irradiation in the presence of S(2)O(8)(2-) when HA is pre-oxidized. This could be explained by the different structures of humic acids. These differences of structures of HA were identified by physico-chemical parameters such as the absorbance in the UV (254 nm), the fluorescence and the SUVA measurement.

Influence of persulfate ions on the removal of phenol in aqueous solution using electron beam irradiation

The removal of phenol (Co = 100 μM) during electron beam irradiation was studied in pure water and in the presence of HCO(3)(-) and Br(-) ions. It was found that the introduction of S(2)O(8)(2-) ions (1mM), by generating SO(4)(-) radicals increases the radiation yield of phenol removal. 90% removal of phenol was obtained with radiation doses 600 and 1200 Gy with and without S(2)O(8)(2-) ions respectively. This system induced smaller oxygen consumption with smaller concentration of catechol and hydroquinone found in the solution. HCO(3)(-) and Br(-) have an inhibiting effect in the presence as in the absence of S(2)O(8)(2-). In most cases, the introduction of S(2)O(8)(2-) ions in water radiolysis system can advantageously increase the yield of organic compounds removal by oxidation.