Oxidative photodegradation of herbicide fenuron in aqueous solution by natural iron oxide α-Fe2O3, influence of polycarboxylic acids

Two Coordination Polymers Synthesized from Various N-Donor Clusters Spaced by Terephthalic Acid for Efficient Photocatalytic Degradation of Ibuprofen in Water under Solar and Artificial Irradiation

Two coordination polymers CP1 {[Zn(II)(BIPY)(Pht)] _n } and CP2 {[Zn(HYD)(Pht)] _n } (BIPY = 4,4'-bipyridine, Pht = terephthalic acid, and HYD = 8-hydroxyquinoline) have been successfully synthesized by a hydrothermal process using zinc aqueous solution. The so-prepared compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, thermogravimetric analysis (TGA), and cyclic voltammetry. XRD pointed to a crystalline phase for CP1, while CP2 required recrystallization, FTIR spectroscopy established the presence of characteristic bands for all the ligands, and TGA showed thermal stability up to 100 °C. The electrochemical study showed a good charge transfer between the ligands and Zn metal for both materials. The UV-vis spectra displayed a strong absorption band spreading over a wide wavelength range, encompassing UV and visible light, with a band gap of 2.69 eV for CP1 and 2.56 eV for CP2, both of which are smaller than that of ZnO. This provides an advantageous alternative to using ZnO. The 5 × 10^-5 mol L^-1 ibuprofen decomposition kinetics under solar and UV light were studied under different irradiation conditions. Good photocatalytic properties were observed due to their high surface area.

Photodegradation of pesticides using compound-specific isotope analysis (CSIA): a review

Pesticides are commonly applied in agriculture to protect crops from pests, weeds, and harmful pathogens. However, chronic, low-level exposure to pesticides can be toxic to humans. Photochemical degradation of pesticides in water, soil, and other environmental media can alter their environmental fate and toxicity. Compound-specific isotope analysis (CSIA) is an advanced diagnostic tool to quantify the degradation of organic pollutants and provide insight into reaction mechanisms without the need to identify transformation products. CSIA allows for the direct quantification of organic degradation, including pesticides. This review summarizes the recent developments observed in photodegradation studies on different categories of pesticides using CSIA technology. Only seven pesticides have been studied using photodegradation, and these studies have mostly occurred in the last five years. Knowledge gaps in the current literature, as well as potential approaches for CSIA technology for pesticide monitoring, are discussed in this review. Furthermore, the CSIA analytical method is challenged by chemical element types, the accuracy of instrument analysis, reaction conditions, and the stability of degradation products. Finally, future research applications and the operability of this method are also discussed.

Effect of Natural and Artificial Light on Fe(III) Organic Complexes Photolysis: Case of Fe (III)-Malonate and Fe(III)-Malate

The photolysis of iron(III) organic complexes in the presence of natural and simulated light was a concern for the role it plays within the environment in terms of producing hydroxyl radicals able to degrade organic products. In the present work, the study focused on two iron(III) organic complexes. The characterization of these complexes by spectrometry allowed to show their stability in environment with a stability constant equal to Log β = 13.13 for the complex Fe(III)-malonate, and Log β = 20.85 for the Fe(III)-malate complex. Photolysis of these complexes was carried out using a lamp at 365 nm at different pHs, and followed by several assay Fe(II), H2O2 and •OH. The complexes present different photo-reactivities, in the case of Fe(III)-malate, the photolysis is favored by the Fenton process and generates hydroxyl radicals, contrarily to Fe(III)-malonate photolysis which generates an oxidizing •CH2COOH radical without formation of H2O2 nor of •OH. The presence of oxygen and the addition of isopropanol and chloroform show different effects on the complex photolysis. Complexes mineralization at natural irradiation was also studied using chemical oxygen demand (COD).

Catalytic Photodegradation of Rhodamine B in the Presence of Natural Iron Oxide and Oxalic Acid under Artificial and Sunlight Radiation

Natural iron oxide was used as catalyst for a heterogeneous photo-Fenton-like process and it was characterized by X-ray diffraction, X-ray fluorescence, Raman spectroscopy, scanning electron microscopy and N2adsorption volumetry measurement. Natural iron oxide consists mainly of hematite (76 %). Rhodamine B was mineralized by iron oxide/oxalic acid/UV system, involving creation of dissolved Fe-oxalate and adsorption of Fe-oxalate on the iron oxide surface. The effects of the initial concentration of oxalic acid and pH value, amount of natural iron oxide and concentration of dye, temperature and sunlight irradiation on the kinetics of photodegradation of rhodamine B were investigated. Excellent degradation rate was achieved with 5 mmol.L−1of oxalic acid at a pH around 2–4. During the process, the formation of Fe2+, H2O2and the pH of the solution were strongly dependent on the initial concentration of oxalic acid. Use oft-butanol (2.0 %) confirms that hydroxyl radicals are the entities responsible for the rhodamine B photodegradation. The use of the natural iron oxide as a catalyst in wastewater treatment is very interesting; because it is an abundant mineral and easy to separate from the solution in the end of treatment.