Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Abstract

A influência de scavengers de elétrons e de lacunas positivas na digestão fotocatalítica de matéria orgânica na presença de partículas de TiO 2 em suspensão, foi investigada. O processo, que visa a determinação eletroquímica de traços de metais pesados em amostras de água, foi acompanhado mediante observação da recuperação da onda voltamétrica de Cd(II) em presença de EDTA, escolhido como ligante-modelo na simulação do efeito complexante da matéria orgânica natural. Confirmouse o poder acelerador de O 2 , que atua como removedor de elétrons. Na ausência de O 2 , função análoga é exercida pelo íon nitrato, mas não, ao menos aparentemente, pelo analito Cd(II). Já a adição de CH 3 OH apresenta efeito antagônico de scavenger de lacunas positivas, o que pode explicar porque a operação na presença de acetato (usado como tampão de pH), ao mesmo tempo em que proporciona um eficaz controle da acidez do meio, provoca uma certa redução do rendimento da fotodegradação.The influence of electron and hole scavengers in the photocatalytic digestion of organic matter in the presence of suspended particles of TiO 2 was investigated. The process, aiming at the electrochemical determination of traces of heavy metals in water samples, was followed through the recovery of the voltammetric wave of Cd(II) in the presence of EDTA, chosen as model ligand that mimics the complexing effect of natural dissolved organic matter. The accelerating power of O 2 , acting as electron scavenger, was confirmed. In the absence of O 2 , a similar function is played by nitrate ions but not, as it seems, by the analyte, Cd(II). On the other hand, CH 3 OH exhibits an antagonist effect as hole scavenger. This observation may explain why the acetate (from the pH buffer), used to control the medium acidity, leads to a certain reduction in the photocatalytic yield.

Photocatalytic activity of NiS, NiO and coupled NiS–NiO for degradation of pharmaceutical pollutant cephalexin under visible light

“…9). The enhancing effect of dissolved oxygen on the catalysts performance has also been reported by Cavicchioli et al 28 The results obtained in this work were in agreement with those reported by Benacherine et al who studied the photodegradation of amoxicillin by Goethite (a-FeOOH). They reported that dissolved oxygen increased the degradation efficiency.…”

Visible Light Degradation of Naproxen by Enhanced Photocatalytic Activity of NiO and NiS, Scavenger Study and Focus on Catalyst Support and Magnetization

“…Dissolved oxygen was one of the parameters, which had significant effect on the degradation of naproxen. Produced OH° radicals via dissolved oxygen, which ameliorated the degradation process as the following reactions . …”

Kinetic and equilibrium investigation of Cu(II) removal by Co(II)-doped iron oxide nanoparticle-immobilized in PVA–alginate recyclable adsorbent under dark and photo condition

“…The proposed kinetic model bear some similarities with the L-H equation. Since, the organic scavengers were used to minimize the electron-hole recombination during photo-excitation process [46,47], therefore the k d % 0 and the above equation can be simplified into Eq. (10):…”