Phenolic compounds are known to be present in high concentration
in various of agro industrial wastes such as olive mill wastewater. As
they are highly biorecalcitrant a possible treatment by Advanced
Oxidation Processes has to be investigated.
T
he photocatalytic degradation of the phenolic acids p-Hydroxybenzoic
acid, Dihydroxybenzoic acid, gallic acid, vanillic acid, syringic acid) in the
presence of TiO2 deposit on a glass plate has been reported. A comparison for
the adsorption properties and the kinetics of reaction have been studied. The
kinetics were found to be first order for all compounds and were compared
with the compounds’ structures. The reaction rate for the compounds was
found as the order Di-HBA < GA < p-HBA ≈ SA ≈ VA.
The influence on the photdegradation rate of various parameters as pH, and
substrate’s concentration was studied for p-Hydroxybenzoic acid only. It was
found that the reaction is pH and substrate’s concentration dependence.
A removal efficiency (50-70%) was determined after 5hr using UVlamp
(15W- λ=360nm) and it increased up to 95% when H2O2 was
added.
During the past few years attention has been drawn on chemical techniques
that could be used to discolour textile wastewaters. We have studied the
photocatalytic degradation of various dyes (Methyl orange, Azo carmine B,
Coomassie Brilliant blue G
250, Tartrazine, Calcon, Eriochrome blue SE,
Solamine Red 4BL, Bismarck brown Y(G), Methylen blue, Black 5, Red 120,
Morin) using TiO2 P25 Degussa as catalyst. All dye solutions underwent a
decolourization. The kinetics of reaction have been studied and were found to
be zero or first order with respect to the dye. It was compared with the
adsorption properties. The effect of the addition of hydrogen peroxide has been
studied. An enhancement of the rate has been observed in all cases and the
order with respect to the dye's concentration in presence of the additive seemed
not to change. It is difficult to give general view of the kinetics using these very
different dyes but the process was found to be effective for the decolourization
of textile wastewater.
