Visible-light photoelectrodegradation of diuron on WO3 nanostructures

Using Fe-Cu/HGF composite cathodes for the degradation of Diuron by electro-activated peroxydisulfate

An iron-copper graphite felt (Fe-Cu/HGF) electrode was successfully prepared by heat treatment and impregnation of graphite felt as the support followed by calcination, and an electro-activated peroxydisulfate (E-PDS) system with Fe-Cu/HGF as the cathode was constructed to degrade Diuron. This system synergistically activated PDS through electrochemical processes and transition metal catalysis. High-valence metal ions could be converted into low-valence metal ions by reduction at the cathode, and low-valence metal ions continuously activated PDS to generate more sulfate radicals (SO₄^-) and hydroxyl radicals (OH) to accelerate Diuron degradation. The Fe-Cu/HGF composite cathode exhibited a performance superior to graphite felt (RGF) obtained using pretreatment only, including increased hydrophilicity, significantly increased number of defect sites and larger electroactive surface area. Under optimized experimental degradation conditions, Diuron could be completely removed in 35 min, at which time copper ion leaching was not detected in the solution, while the total iron ion concentration was 0.27 mg L^-1. Extending the reaction time to 6 h, the amount of total organic carbon was reduced to 32.2%. In addition, the free radicals that degraded Diuron were identified as mainly SO₄^- and OH with a slightly higher contribution of SO₄^-. The mechanism and pathways of Diuron degradation in the E-PDS system were determined. The E-PDS system was successfully applied to the degradation of other pollutants and the degradation of Diuron in different simulated water environments. In summary, the E-PDS system using Fe-Cu/HGF as the cathode is a promising treatment method for Diuron-containing wastewater.

Contemporary Techniques for Remediating Endocrine-Disrupting Compounds in Various Water Sources: Advances in Treatment Methods and Their Limitations

Over the years, the persistent occurrence of superfluous endocrine-disrupting compounds (EDCs) (sub µg L⁻¹) in water has led to serious health disorders in human and aquatic lives, as well as undermined the water quality. At present, there are no generally accepted regulatory discharge limits for the EDCs to avert their possible negative impacts. Moreover, the conventional treatment processes have reportedly failed to remove the persistent EDC pollutants, and this has led researchers to develop alternative treatment methods. Comprehensive information on the recent advances in the existing novel treatment processes and their peculiar limitations is still lacking. In this regard, the various treatment methods for the removal of EDCs are critically studied and reported in this paper. Initially, the occurrences of the EDCs and their attributed effects on humans, aquatic life, and wildlife are systematically reviewed, as well as the applied treatments. The most noticeable advances in the treatment methods include adsorption, catalytic degradation, ozonation, membrane separation, and advanced oxidation processes (AOP), as well as hybrid processes. The recent advances in the treatment technologies available for the elimination of EDCs from various water resources alongside with their associated drawbacks are discussed critically. Besides, the application of hybrid adsorption–membrane treatment using several novel nano-precursors is carefully reviewed. The operating factors influencing the EDCs’ remediations via adsorption is also briefly examined. Interestingly, research findings have indicated that some of the contemporary techniques could achieve more than 99% EDCs removal.

Photoelectrocatalyzed degradation of a pesticides mixture solution (chlorfenvinphos and bromacil) by WO3 nanosheets

A photoelectrocatalyst consisting of WO₃ nanosheets or nanorods has been synthesized by electrochemical anodization under hydrodynamic conditions, and has been used for the degradation of two toxic pesticides: chlorfenvinphos and bromacil. Nanostructures have been characterized by FESEM and Raman spectroscopy. Photoelectrochemical degradation tests have been carried out both for individual pesticide solutions and for a mixture solution, and the concentration evolution with time has been followed by UV-Vis spectrophotometry. For individual pesticides, pseudo-first order kinetic coefficients of 0.402h^-1 and 0.324h^-1 have been obtained for chlorfenvinphos and bromacil, respectively, while for the mixture solution, these kinetic coefficients have been 0.162h^-1 and 0.408h^-1. The change in behavior towards pesticide degradation depending on whether individual or mixture solutions were used might be indicative of a competitive process between the two pesticide molecules when interacting with the WO₃ nanostructures surface or when approaching the semiconductor/electrolyte interface.