Photocatalytic Degradation of Paraquat Herbicide Using a Fixed Bed Reactor Containing TiO<sub>2</sub> Nanoparticles Coated onto <i>β-SiC</i> Alveolar Foams

Abstract

Photocatalytic degradation of paraquat (PQ) aqueous solutions was studied in a fixed bed photoreactor under UV irradiation at 368 nm. This contained β-SiC alveolar foams coated with TiO 2 P25 by dip-coating method. SEM analyses revealed that the surface of the film did not exhibit cracks in the presence of TTIP as a binder in the TiO 2 P25 suspension. The following parameters were studied in continuous mode operation: the flow rate in the reactor, the initial concentration of the paraquat, the pH of the solution, the weight of photocatalytic material with the number of foams in the reactor and the weight of the catalyst deposited onto the support. The results showed that by working under optimal operating conditions at natural pH (pH = 6.7), low paraquat (C o = 10 ppm), and flow (26 mL/min), we recorded approximately (43.16 ± 1.00)% oxidation of paraquat and a decrease in total organic carbon (TOC) of (27.13 ± 1.00)% after about 70 minutes. The apparent rate constant is in the order of (0.0656 ± 0.0010) min −1. In addition, by increasing the amount of β-SiC foams coated with TiO 2 , we improve the degradation of paraquat in the same order. The study of aging of the material showed its stability over time. However, photocatalytic activity was limited after 20 minutes of UV irradiation due to the limitation of the diffusion of the paraquat molecules towards the surface of the photocatalyst. As an outcome, we obtained an efficient TiO 2 /β-SiC material for photocatalytic degradation of organic com

Elucidating Synergistic Effect of In-Situ Hybrid Process Towards Paraquat Abatement

“…Similarly, in the case of catalyst; pH greater than pHzpc results in a negatively charged surface of the catalyst and vice-versa (M'Bra et al, 2019). For the given system, pKa of PQ is around 9 resulting in cationic form as dominant while pHzpc of both Fe-PT and S-PT is lower than 6.3 providing a negatively charged catalyst surface (Birben et al, 2016;M'Bra et al, 2019;Moein et al, 2020). This justi es pH 6.3 as the optimum pH since at this pH phenomenon of attraction between catalyst and pollutant surface occurs and several other studies have reported pH in the range of 5.9-6.5 as optimum (Pourzad et al, 2020).…”

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

“…Moreover, the catalyst can be easily recovered and reused, and the SiC-based foams, other than offering a static mixer effect enhancing the molecules/active-phase contact, are prone to be adapted to any reactor geometry. Similar conclusions were drawn by the same group in collaboration with M’Bra, while studying the photocatalytic degradation of Paraquat herbicide (1,1′-dimethyl-4,4′-bipyridinium dichloride) , and Scala fungicide (Pyrimethanil) promoted by TiO 2 NPs coated on β-SiC alveolar foams. Even if the kinetics is lower for the supported photocatalysts with respect to TiO 2 powder suspension, β-SiC support allows conduction of the photodegradation in continuous operational mode for several cycles without the need for any filtration step to separate the catalyst from treated water, thus opening to the large scale development of the process.…”

Adsorption of Paraquat by Poly(Vinyl Alcohol)-Cyclodextrin Nanosponges

“…The appearance of this dangerous herbicide causes different negative effects on the environment [ 3 , 4 ] and heath [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Physical [ 12 , 13 ], biological [ 14 , 15 ], and chemical treatments [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ] have all been reported in the literature for PQ removal. An adsorption process has recently been investigated for PQ removal, which was applied for both organic and inorganic materials such as bio-based material [ 23 , 24 , 25 ], bentonite [ 26 , 27 ], microorganisms [ 28 ], activated carbon [ 29 , 30 ], kaolin [ 31 ], pillararene [ 32 , 33 ], calixarene [ 34 , 35 , 36 ], graphene oxide [ 37 ], carbon nanotubes [ 38 , 39 ], silica [ 40 , 41 ], magnetic adsorbent [ 42 , 43 ], montmorillonite [ 44 , 45 ], cellulose nanofiber [ 46 , 47 ], and cyclodextrin [ 48 ].…”