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<p>The photocatalytic degradation of caffeine has been investigated in aqueous suspensions of titanium dioxide (TiO<sub>2</sub>) by monitoring process efficiency at varying TiO<sub>2</sub> (25 - 175 mg l<sup>-1</sup>) and initial drug concentrations (0.5 - 9.5 mg l<sup>-1</sup>). The use of the response surface methodology (RSM) allowed to fit the optimal regions of the parameters leading to the degradation of the pollutant. Also, a single polynomial expression modelling the reaction was obtained. In parallel a set of bioassays (<em>Daphnia magna</em>, <em>Pseudokirchneriella subcapitata </em>and <em>Lactuca sativa)</em> was performed to evaluate the process in terms of detoxification of caffeine oxidation by-products under chronic and acute tests. Results clearly demonstrate that caffeine is quickly degraded, but not mineralized as quickly, and that persistent toxic organic intermediates resist further oxidation.</p>
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