tSimultaneous photocatalytic reduction of poisonous Cr(VI) and Ni(II) ions, coupled with pho-tocatalytic oxidation of sodium dodecyl benzene sulfonate (SDBS) were studied with a traceamount of commercial titania nanoparticles and by means of a direct-photo-irradiationreactor. The co-presence of metal ions and SDBS causes metal ions reduction as well asSDBS oxidation to enhance and energy efficiency to improve. XRD, XPS and FTIR analysiswere used to characterize TiO2particles before and after usage with the aim of evaluatingthe mechanism of reactions. The effect of major operating parameters, pH and temper-ature, was investigated. Under conditions of [Cr(VI)]0= [Ni(II)]0= 5 mg/L, [SDBS]0= 10 mg/L,[TiO2] = 40 mg/L, pH 6 and T = 35◦C; the removal efficiencies of 55.4%, 71.2% and 57.2% wereobtained, respectively, for Cr(VI) and Ni(II) reduction, as well as for SDBS oxidation, after110 min operation. The relevant kinetic model jointed with the Arrhenius equation wasintroduced. Pseudo-first-order reactions are relevant. Energy consumption (electrical andthermal) evaluations revealed that operations at higher temperatures provide significantcost reduction. Meantime, a criterion was proposed for a consistent assessment of this kindof processes.
