Photodegradation of fenamiphos on the surface of clays and soils

Abstract

International audienceThe photodegradation of the organophosphorus fenamiphos was studied in various clay matrices: montmorillonite, kaolin and the mineral components of two soils collected from two different sites: Settat (S) and Berrechid (B). The degradation was shown to be mainly due to the direct excitation of fenamiphos and was similar for all the matrices with a two-step kinetics : a fast and a slower one. The first step rate obtained at the surface of montmorillonite was slightly lower than that determined at the surface of kaolin. The fenamiphos degradation process clearly depended on the amount of humic substances and iron(III). The latter component accelerated the disappearance of fenamiphos, while humic substances clearly inhibited the process. The degradation rate increased in the presence of water and was mainly due to the involvement of the photohydrolysis process leading to the scission of the P-O bond. The formation of the main by-products, sulfoxide, sulfone and phenol derivatives, were elucidated by HPLC/MS

Fate of Pesticides in Soils: Toward an Integrated Approach of Influential Factors

“…Humic substances tend to decrease direct photolysis through light screening, static quenching (inhibition of the PX* formation through complexation of the ground-state molecule) and dynamic quenching (energy transfer from PX* to humic substance) (Walse et al, 2004). Specific study of direct photolysis in soil is complex because indirect processes may interfere, even if they can theoretically be distinguished through a two-steps kinetic model (Albanis et al, 2002;Hebert & Miller, 1990;Tajeddine et al, 2010). .…”

“…HS may play all those roles, but may also reduce indirect photodegradation by light screening and by scavenging the reactive species. The resulting effect can be a photodegradation increase (Albanis et al, 2002;Besse et al, 2005;Xiaozhen et al, 2005) or decrease (Albanis et al 2002;Tajeddine et al, 2010). Non-transition metal oxides such as aluminium oxide or magnesium oxide can photocatalyze the 1 O 2 generation (Gohre & Miller, 1985).…”

“…However, the global resulting pesticide photodegradation has largely been demonstrated to be slower in dry soils, with half-lives multiplied by a 2-7 factor or more Graebing et al, 2003). Relative importance of the degradation pathways can also be influenced by the presence of water, for instance if a photohydrolysis mechanism is involved (Tajeddine et al, 2010). Drying/rewetting cycles favour indirectly the photodegradation process, because of the movement of the pesticide through condensation and evaporation .…”

Design of ZnCdS Quantum Dots Loaded on Mesoporous Silica as a UV-Light-Sensitive Photocatalyst

“…Organic compounds and toxic pesticides, and manure emission from each industry are polluting drinking water and rivers, which is becoming a worldwide contamination with increased severity. The wide area of water pollution, diversification and nonbiodegradable problems has become a problem that cannot be solved by the natural cleansing cycle [5][6][7]. One of the most important challenges for science is to develop efficient methods to control environmental pollution.…”

Supported TiO2 on Borosilicate Glass Plates for Efficient Photocatalytic Degradation of Fenamiphos

“…In recent years, novel methods for water, soil, and air purification have been developed including chemical, electrochemical, and photochemical processes [1][2][3][4]. Indeed, photocatalytic degradation has been shown to be a promising technology for the treatment of water contaminated with organic and inorganic pollutants [1,2].…”