OPTIMIZATION OF THE CATALYTIC DEGRADATION OF WASTES IN THE OIL AND GAS INDUSTRY BY COUPLING PHOTOCATALYSIS AND FENTON PROCESS

Wastewater effluents from petroleum refineries and petrochemical plants pass through a
train of treatment processes. Primary, secondary and tertiary treatments are employed for
the sake of removing a wide range of pollutants. However, they are limited by treatment
efficiency for certain pollutants, specifically recalcitrant organic pollutants. Effluents
containing such pollutants can't be treated using the old conventional methods.
Adopting Advanced oxidation processes such as photocatalysis and Fenton processes as
innovative, environmentally friendly, facile, and cost-effective technologies shall provide
the route of an effective treatment. The main purpose of this project is to optimize the
essential parameters influencing the activity of each process: photocatalysis and Fenton.
This will be followed by the examination of the coupling between these two processes.
For the aim of the proposed project, zinc oxide was chosen as the photocatalyst material. It
was synthesized and prepared by the sol-gel method followed by dip-coating on a glass
substrate to create 𝑍𝑛𝑂 thin film. To test the effect of the photoactivity of the prepared
photocatalyst on the kinetics of the photodegradation three parameters were altered and
observed, the precursor’s concentration, post-heat treatment temperature, and the number
of coated layers. The best configuration obtained for this photocatalyst according to its
photodegradation efficiency and the rate was the thin film prepared using a sol of
[𝑍𝐴𝐷] = 0.1𝑀, and by coating three layers, such that after each layer pre-heat treatment
temperature applied is 150°𝐶 for seven minutes, and finally post-heat treatment at 450°𝐶
for one hour.
For the Fenton process section, the tested parameters were 𝐻2𝑂2 concentration, catalyst
(𝐹𝑒3+) concentration and chelating agent (𝐸𝐷𝑇𝐴 ) addition at neutral 𝑝𝐻. The optimized
configuration was to use 59 𝑝𝑝𝑚 𝐻2𝑂2, 10 𝑝𝑝𝑚 𝐹𝑒3+ and a 1: 1 molar ratio of
𝐹𝑒3+: 𝐸𝐷𝑇𝐴.
Finally, comparison between all the optimized processes: three layers 𝑍𝑛𝑂 thin-film,
photo Fenton-like process, photo Fenton-like process modified with 𝐸𝐷𝑇𝐴, photo Fentonlike
process coupled with three layers 𝑍𝑛𝑂 thin-film and photo Fenton-like process
modified with 𝐸𝐷𝑇𝐴 coupled with three layers 𝑍𝑛𝑂 thin-film.
The photocatalytic degradation process experimented on 10 𝑝𝑝𝑚 methylene blue while
the Fenton process and the coupling experimented on 20 𝑝𝑝𝑚 of the same probe
molecule. 𝑈𝑉 rays (𝜆 = 366𝑛𝑚) are used as the light source in all experiments. The
experimental time was monitored at an interval of 30 minutes and 10 minutes in some
cases.
As a final result, the photo Fenton process modified with the chelating agent showed the
greatest degradation efficiency and rate, followed by the coupling of the photo Fenton
process and three layers 𝑍𝑛𝑂 thin film which has shown a degradation activity greater
than each process alone.