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Parasitic Light Absorption, Rate Laws and Heterojunctions in the Photocatalytic Oxidation of Arsenic(III) Using Composite TiO 2 /Fe 2 O 3
Author(s) -
Bullen Jay C.,
Heiba Hany F.,
Kafizas Andreas,
Weiss Dominik J.
Publication year - 2022
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202104181
Subject(s) - photocatalysis , absorption (acoustics) , arsenic , adsorption , kinetics , heterojunction , materials science , langmuir adsorption model , rate equation , arsenite , chemical engineering , inorganic chemistry , chemistry , photochemistry , analytical chemistry (journal) , catalysis , environmental chemistry , optoelectronics , composite material , physics , metallurgy , organic chemistry , quantum mechanics , engineering
Composite photocatalyst‐adsorbents such as TiO 2 /Fe 2 O 3 are promising materials for the one‐step treatment of arsenite contaminated water. However, no previous study has investigated how coupling TiO 2 with Fe 2 O 3 influences the photocatalytic oxidation of arsenic(III). Herein, we develop new hybrid experiment/modelling approaches to study light absorption, charge carrier behaviour and changes in the rate law of the TiO 2 /Fe 2 O 3 system, using UV‐Vis spectroscopy, transient absorption spectroscopy (TAS), and kinetic analysis. Whilst coupling TiO 2 with Fe 2 O 3 improves total arsenic removal by adsorption, oxidation rates significantly decrease (up to a factor of 60), primarily due to the parasitic absorption of light by Fe 2 O 3 (88 % of photons at 368 nm) and secondly due to changes in the rate law from disguised zero‐order kinetics to first‐order kinetics. Charge transfer across this TiO 2 ‐Fe 2 O 3 heterojunction is not observed. Our study demonstrates the first application of a multi‐adsorbate surface complexation model (SCM) towards describing As(III) oxidation kinetics which, unlike Langmuir‐Hinshelwood kinetics, includes the competitive adsorption of As(V). We further highlight the importance of parasitic light absorption and catalyst fouling when designing heterogeneous photocatalysts for As(III) remediation.