Nano-ZnO film photocatalysts in bench-scale continuous-flow mineralization of olive mill waste contaminants in water

Olive oil milling, widely practiced in Mediterranean countries, including Palestine, yields the so-called olive mill waste water (OMWW) or Zebar (Zibar). The waste contains minerals and organic materials (including phenols and polyphenols) which undergo continuous oxidation and cause environmental hazards if not well managed. This work basically aims at purifying surface waters, intentionally pre-contaminated with OMWW organic contaminants. Fate of other mineral ions present in the contaminated water is also investigated. ZnO nanoparticles, deposited as films onto glass reactor bottom (165 cm 2 area), are described as catalyst for photodegradation of the organic contaminants, in a continuous flow reaction mode (gravity fed, typically at flow rate 3.5 mL/min). Two types of ZnO materials, namely commercial ZnO onto glass (C-ZnO/Glass) and synthetic ZnO supported onto clay and deposited on glass (Syn-ZnO/Clay/Glass), have been examined The Syn-ZnO/Clay/ Glass catalyst is slightly more efficient in removing organic contaminants (similar to 43%), compared to the C-ZnO/Glass (41%) in 30 h. Different reaction parameters have been investigated, such as waste dilution factor, exposure duration, pH and catalyst recovery and reuse.

Automated summary

This study aims to purify surface waters contaminated with organic pollutants by using ZnO nanoparticles as a catalyst for photodegradation. Results showed that the Syn-ZnO/Clay/Glass catalyst is slightly more efficient in removing organic contaminants compared to the C-ZnO/Glass catalyst.