Sulfadiazine's photodegradation using a novel magnetic and reusable carbon based photocatalyst: Photocatalytic efficiency and toxic impacts to marine bivalves

In the present study, waste-based biochar functionalized with titanium dioxide (TiO2) and afterwards magnetized by an ex-situ approach, defined as synthetic photosensitizer (SPS), was explored for the photocatalytic degradation of sulfadiazine (SDZ), an antibiotic widely used in the aquaculture industry, under solar irradiation. The use of the SPS enhanced the photodegradation efficiency, with a half-life time (t1/2) reduction from 12.2 ± 0.1 h (without SPS) to 5.6 ± 0.4 h. The applied magnetization procedure allowed to obtain a SPS with good reusability for SDZ photodegradation even after five consecutive cycles. To evaluate the effects on marine bivalves of SDZ, before and after photodegradation and in presence or absence of the SPS, a typical bioindicator species, the mussel Mytilus galloprovincialis, was used and different biochemical markers were analysed. Results obtained indicated that the exposure to SDZbefore irradiation, both in absence and presence of SPS, caused an increase in mussels’ metabolism and defence mechanisms, evidencing great biochemical impacts. However, after irradiation (in the absence and presence of SPS), biochemical responses were similar to those observed in organisms exposed to control conditions, without SDZ. Therefore, this work provided a promising eco-friendly treatment for the removal of SDZ from aquaculture effluents. [Display omitted] •Synthesized photocatalyst (SPS) allowed halving sulfadiazine (SDZ) half-life time.•SPS exhibited excellent recovery and photocatalytic activity during 5 reuse cycles.•Mussels exposed to SDZ contaminated water showed higher metabolism and defenses.•Biochemical results with either irradiated or non-contaminated water were similar.•SPS did not cause toxic effects on mussels.