Converting
sewage sludge into functional environmental materials
has become an attractive sewage sludge disposal route. In this study,
we synthesize a sewage sludge-based material via a facile one-pot
hydrothermal carbonization method and construct a visible light molecular
oxygen activation system with hydrothermally carbonized sewage sludge
(HTC-S) and oxalate to degrade various organic pollutants. It was
found that iron species of HTC-S could chelate with oxalate to generate
H2O2 via molecular oxygen activation under visible
light, and also promote the H2O2 decomposition
to produce •OH for the fast organic pollutants degradation.
Taking sulfadimidine as the example, the apparent degradation rate
of HTC-S/oxalate system was almost 5–20 times that of iron
oxides/oxalate system. This outstanding degradation performance was
attributed to the presence of iron-containing clay minerals in HTC-S,
as confirmed by X-ray diffraction measurements and Mössbauer
spectrometry. In the oxalate solution, these iron-containing clay
minerals could be excited more easily than common iron oxides under
visible light, because the silicon species strongly interacted with
iron species in HTC-S to form Fe–O–Si bond, which lowered
the excitation energy of Fe-oxalate complex. This work provides an
alternative sewage sludge conversion pathway and also sheds light
on the environmental remediation applications of sewage sludge-based
materials.
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