The Effect of Thermal Treatment on the Physicochemical Properties of Minerals Applied to Heterogeneous Catalytic Ozonation

Savvina Psaltou, Efthimia Kaprara, Kyriaki Kalaitzidou, Manassis Mitrakas and Anastasios Zouboulis
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Savvina Psaltou: Laboratory of Chemical and Environmental Technology, Department of Chemistry, Aristotle University, 54124 Thessaloniki, Greece
Efthimia Kaprara: Laboratory of Analytical Chemistry, Department of Chemical Engineering, Aristotle University, 54214 Thessaloniki, Greece
Kyriaki Kalaitzidou: Laboratory of Analytical Chemistry, Department of Chemical Engineering, Aristotle University, 54214 Thessaloniki, Greece
Manassis Mitrakas: Laboratory of Analytical Chemistry, Department of Chemical Engineering, Aristotle University, 54214 Thessaloniki, Greece
Anastasios Zouboulis: Laboratory of Chemical and Environmental Technology, Department of Chemistry, Aristotle University, 54124 Thessaloniki, Greece

Sustainability, 2020, vol. 12, issue 24, 1-13

Abstract: In order to enhance the efficiency of heterogeneous catalytic ozonation, the effect of thermal treatment on three commonly used and inexpensive minerals, i.e., zeolite, talc and kaolin (clay), which present different physicochemical properties as potential catalysts, has been examined for the removal of para-chlorobenzoic acid (p-CBA). p-CBA is considered a typical micro-pollutant, usually serving as an indicator (model compound) to evaluate the production of hydroxyl radicals in ozonation systems. The catalytic activity of selected solid catalysts was studied for different pH values (6, 7 and 8) and different temperatures (15 °C, 25 °C and 35 °C). The mechanism of radicals’ production was also verified by the addition of tert-butyl alcohol (TBA). The respective thermal behavior study showed that the point of zero charge (PZC) of these minerals increased with the increase of applied treatment temperature, as it removed crystalline water and hydroxyls, thus improving their hydrophobicity. Circa-neutral surface charge and the presence of hydrophobicity were found to favor the affinity of ozone with solid/catalytic surfaces and the subsequent production of hydroxyl radicals. Therefore, zeolite and talc, presenting PZC 7.2 and 6.5 respectively, showed higher catalytic activity after thermal treatment, while kaolin with PZC equal to 3.1 showed zero to moderate catalytic efficiency. The degradation level of p-CBA by oxidation was favored at 25 °C, while the pH value exerted positive effects when it was increased up to 8.

Keywords: heterogeneous catalytic ozonation; PZC; p-CBA; minerals; thermal treatment; micropollutants removal (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2020
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