Photodegradation of herbicide Metsulfuron-methyl with TiO2 supported on magnetite particles coated with SiO2

Abstract

Natural watercourses may be significantly contaminated due to the increase of agricultural activities, making it necessary to develop new methodologies for the remediation of agrochemicals, including herbicides. To this effect, photodegradation with TiO2 is a very effective process. However, this semiconductor cannot be easily removed from the treated aqueous medium. Supporting the photocatalyst on different materials facilitates its removal by several methods, including magnetic attraction. According to this goal, this work reports the synthesis of TiO2 photocatalysts supported on SiO2-coated magnetite particles (Fe3O4) by a low-temperature sol-gel process (75 °C). By varying the aging time of the TiO2 sol, materials with different structural properties and combinations of anatase-brookite phases were obtained. Of all the synthesized solids, the one with the highest photocatalytic activity in the degradation of model compounds was the TiO2/SiO2/Fe3O4 catalyst with a 47.4/13.6/39.0 wt % respectively. Under optimal working conditions and at a pH value close to neutrality (conditions in which Metsulfuron-methyl is persistent in an aqueous medium) this catalyst degraded 70% of the herbicide initial concentration in three and a half hours of artificial irradiation with an activity similar to the mass TiO2. The aging time significantly influenced on structural properties of supported TiO2. With its increase, the degree of crystallinity of the samples also increased but its specific surface decreased. The catalyst with higher photoactivity blends the best combination of both factors and is, therefore, a good alternative for the remediation of contaminated effluents with commercial formulations of this herbicide. Also, its magnetic support facilitates its subsequent removal from treated water samples.

A Novel Recyclable Magnetic Nano-Catalyst for Fenton-Photodegradation of Methyl Orange and Imidazole Derivatives Catalytic Synthesis

“…Hence, superoxide radicals (O 2 • − ) are generated as a result of the response of the trapped electrons to the dissolved oxygen [ 70 ]. Consequently, these radical anions result in the generation of hydroxyl radicals (OH•) [ 71 ], which oxidise and degrade the target dye ( Figure 15 ).…”

“…Hence, superoxide radicals (O 2 • − ) are generated as a result of the response of the trapped electrons to the dissolved oxygen [70]. Consequently, these radical anions result in the generation of hydroxyl radicals (OH•) [71], which oxidise and degrade the target dye (Figure 15). The immobilisation of iron nanoparticles on the modified surface of cotton fibres (CDC) did not affect the catalytic performance of iron nanoparticles.…”

Photocatalytic removal of 2-chlorophenol from water by using waste eggshell-derived calcium ferrite

“…30 A syringe filter (0.45 μm nylon filter membrane) was used to withdraw the treated 2-CP(aq) from each batch reactor for UV-vis absorption spectrum measurement (GENESYS 10s UV-Vis spectrophotometer). The concentration of 2-CP was monitored by measuring the absorbance at λ = 237 nm, 31–33 following the protocol reported previously. 34–36 The % photocatalytic degradation efficiencies were calculated using the formula below.% Photocatalytic degradation efficiency = [( C 0 − C t )/ C 0 ] × 100where C 0 is the initial concentration of the pollutant model (25 ppm) and C t is the concentration of the pollutant model after treatment after specific treatment times.…”

“…30 A syringe lter (0.45 mm nylon lter membrane) was used to withdraw the treated 2-CP(aq) from each batch reactor for UV-vis absorption spectrum measurement (GENESYS 10s UV-Vis spectrophotometer). The concentration of 2-CP was monitored by measuring the absorbance at l = 237 nm, [31][32][33] following the protocol reported previously. [34][35][36] The % photocatalytic degradation efficiencies were calculated using the formula below.…”

Magnetic Nanoparticles of Fe₃O₄ Biosynthesized by <em>Cnicus Benedictus</em> Extract: Photocatalytic Study of Organic Dye Degradation and Antibacterial Behavior

“…Derivate to the reaction between the trapped electrons and the dissolved oxygen in the system, superoxide radical anions (O2 •−) are generated[50,51]. Consequently, this superoxide radicals anions give has result the hydroxyl radicals (OH•) formation[52][53][54], which are responsible to the oxidation and degradations of the organic dye compound presents in the CR (figure 8).…”