Effect of simulated solar light on the autocatalytic degradation of nitrobenzene using Fe3+ and hydrogen peroxide

Synthesis and Characterization of B/NaF and Silicon Phthalocyanine-Modified TiO2 and an Evaluation of Their Photocatalytic Removal of Carbamazepine

This study investigated the synthesis of two different types of photocatalysts, namely, boron/sodium fluoride co-doped titanium dioxide (B/NaF-TiO2), and its analogue, a dye-sensitized form of silicon-based axial methoxy substituted phthalocyanine (B/NaF-TiO2SiPc). Structural and morphological characterizations were performed via X-ray diffraction (XRD); Fourier transform infra-red (FTIR); N2 adsorption–desorption at 77 K by Brunauer–Emmett–Teller (BET) and Barrett, Joyner, and Halenda (BJH) methods; transmission electron microscopy (TEM); X-ray photoelectron spectroscopy (XPS); and UV–visible absorption spectroscopy. The estimated crystallite size of pure TiO2 and pure B/NaF-TiO2 was 24 nm, and that of B/NaF-TiO2SiPc was 29 nm, whereas particle sizes determined by TEM were 25, 28, and 31 nm for pure TiO2, B/NaF-TiO2 and B/NaF-TiO2SiPc respectively. No significant differences between B/NaF-TiO2 and B/NaF-TiO2SiPc were observed for surface area by (BET) analysis (13 m2/g) or total pore volume by the BJH application model (0.05 cm3/g). Energy band gap values obtained for B/NaF-TiO2 and B/NaF-TiO2SiPc were 3.10 and 2.90 eV respectively, lower than pure TiO2 (3.17 eV). The photocatalytic activity of the synthesized materials was tested using carbamazepine (CBZ) as the model substrate. Carbamazepine removal after 4 h of irradiation was almost 100% for B/NaF-TiO2 and 70% for B/NaF-TiO2SiPc; however, the substrate mineralization proceeded slower, suggesting the presence of organic intermediates after the complete disappearance of the pollutant.

Coupling of Nanofiltration and Thermal Fenton Reaction for the Abatement of Carbamazepine in Wastewater

The complete removal of biorecalcitrant xenobiotics, including most notably the pharmaceutical pollutants, by advanced oxidation processes is often difficult to be reached in urban or industrial wastewater because of the high concentration of organic and inorganic scavengers that compete with the xenobiotics for the oxidizing species. This work investigates a coupled treatment train in which wastewater effluents are pretreated with a negatively charged loose nanofiltration (NF) membrane (HydraCoRe70, made up of sulfonated polyethersulfone) to enhance the removal of xenobiotics with the thermal Fenton process. Carbamazepine (CBZ), a drug prescribed mainly for epilepsy treatment, is used here as a model xenobiotic. After optimizing the conditions for separation and degradation, the NF-Fenton approach was applied to both synthetic wastewater and real samples to assess the overall efficiency of CBZ removal. The Fenton degradation of CBZ was drastically enhanced in nanofiltered samples, thanks to the removal by the membrane of nearly all organic matter that would otherwise consume the reactive oxidizing species (e.g., the hydroxyl radical). On the basis of a preliminary treatment cost analysis, it can be concluded that the combined process is potentially applicable to the treatment of several kinds of wastewaters (e.g., industrial ones) to favor the removal of biorecalcitrant contaminants. Key cost savings of NF-Fenton concern the lower amounts of Fenton reagents needed to degrade CBZ and (even more importantly) the decreased levels of acids and bases for pH adjustment before and after the oxidative process because of the lower buffer capacity of the NF permeate compared to feed wastewater, after the removal by the NF of many inorganic ions and most organic carbon.

Application of photo degradation for remediation of cyclic nitramine and nitroaromatic explosives

Photo degradation is a rapid and safe remediation process and advances in continuous-flow photochemistry can scale-up yields of photo degradation.

Syntheses and structures of two gold(i) coordination compounds derived from P–S hybrid ligands and their efficient catalytic performance in the photodegradation of nitroaromatics in water

Two Au–P–S complexes [Au₂(dppatc)₂]Cl₂ and [Au(dppmt)]₂ were prepared and they showed high catalytic activity toward the photodegradation of nitroaromatics in water.

Nitration of nitrobenzene in Fenton's processes

Previous studies of nitrobenzene (NB) degradation by Fenton and photo-Fenton technologies have demonstrated the formation and accumulation of 1,3-dinitrobenzene (1,3-DNB) as a highly toxic reaction intermediate. In the present study, we analyze the conditions that favor 1,3-DNB formation during NB degradation by Fe(2+)/H(2)O(2), Fe(3+)/H(2)O(2), UV/Fe(3+)/H(2)O(2) or UV/H(2)O(2) processes. Nitration yields in Fenton, Fenton-like and photo-Fenton techniques were much higher than those observed in UV/H(2)O(2) systems. Besides, several tests showed that 1,3-DNB formation increases with the initial iron concentration and decreases as the initial H(2)O(2) concentration increases. In order to asses the key species involved in NB nitration mechanism, additional experiments were performed in the presence of NO(2)(-)or NO(3)(-). In dark systems, 1,3-DNB yield significantly increased with increasing [NO(2)(-)]_(0), while it was not affected by the presence of NO(3)(-). In contrast, 1,3-DNB yields were higher and more strongly affected by the additive concentration in UV/NO(3)(-) systems than in UV/HNO(2)/NO(2)(-) systems. Dark experiments performed at pH 1.5 in excess of HNO(2) along with UV/NO(3)(-) tests conducted in the presence of 2-propanol show that hydroxyl radicals play an important role in NB nitration since NB molecule does not react with the nitrating agents ONOOH, .NO or .NO(2). The results indicate that, in the experimental domain tested, the prevailing NB nitration pathway involves the reaction between the .OH-NB adduct and .NO(2) radicals.