Abstract
The hydrogen peroxide role in photocatalytic degradation of an anionic azo dye, Acid Orange 7 (AO7), was investigated in a slurry reactor. Commercial ZnO nanoparticles with an average size between 10 to 30 nm were used as catalysts. Optimum conditions for different parameters, including dye concentration (10-100 mg/L), catalyst concentration (0.1-0.5 g/L), and pH (5-10), were determined first in the absence of H2O2. Changes in the COD were measured for the optimum condition. The impact of adding hydrogen peroxide at different concentrations to the system operating at optimum conditions was investigated. It was observed that 0.416 mM hydrogen peroxide increased the system's efficiency and decreased reaction time by 40 min. The reaction followed first-order kinetic. Hydrogen peroxide alone did not contribute to oxidizing the contaminant, and its positive impact was attributed to decreasing electron-hole recombination in the photocatalytic process. Not only can the hydrogen peroxide-assisted photocatalytic process decrease retention time in treatment units, but it can also result in more contaminant degradation. Therefore, it can reduce the treatment cost.
Highlights
Dyes are used in various industries such as textiles, leather, printing, and paper production, to name a few
It is noteworthy to mention that intermediates produced during the process may lead to secondary reactions and consume solution free radicals
Since electron-hole recombination is known to decrease the photocatalytic process’s efficiency, hydrogen peroxide as an electron acceptor was added at different concentrations to address this issue
Summary
Dyes are used in various industries such as textiles, leather, printing, and paper production, to name a few The presence of these recalcitrant compounds in aqueous bodies can have a negative impact on the environment (Naushad et al ). Biological processes produce huge amounts of sludge and are incapable of degrading complex structures; or some adsorbents agglomerate and lose their efficiency They are low-cost and remove a wide range of pollutants (Albadarin et al ; Ahmed et al ). Using nano-scaled materials has attracted researchers’ attention due to the unique charecteristics that these materials possess in nano scale condition These types of materials have been used for different applications such as catalytic hydrogen and oxygen evolution processes (Ahsan et al a; Puente Santiago et al ), and advanced oxidation processes (Ahsan et al , b; Nayebi & Ayati ), photocatalytic degradation of organic pollutants (Islam et al )
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