Enhanced photocatalytic activity of TiO2 with acetylene black and persulfate for degradation of tetracycline hydrochloride under visible light

[Display omitted] •The TiO2, acetylene black and persulfate were combined in the degradation of TH.•The adsorption and activation efficiency of TiO2 was improve by acetylene black.•The TH degradation was increased by 38.5% when persulfate was involved. The photocatalysis and advanced oxidation processes were combined in the degradation of tetracycline hydrochloride (TH). The TiO2 doped with acetylene black (TiO2/AB) was employed with persulfate (PS) to generate reactive radicals. The TiO2/AB-2.5 wt% exhibited the best removal efficiency of TH, compared with TiO2/AB-1.25 wt%, TiO2/AB-5 wt% and TiO2/AB-10 wt%. The TiO2/AB/PS can significantly improve the TH degradation rate by 38.5% compared with the TiO2/AB. The operating conditions such as the PS dosage, TiO2/AB dosage, pH, and initial concentration of TH on the degradation of TH were investigated, and the optimal removal efficiency of TH was obtained when the concentration of PS was 3 mmol/L, TiO2/AB dosage was 0.5 g/L, pH = 4.1 and initial concentration of TH was 10 mg/L. The ethanol and tertiary butanol were used as the radical scavengers to identify the dominant reactive radical species in the TiO2/AB/PS system. The SO4− was demonstrated more important than OH in the degradation of TH. Then the intermediates and possible degradation pathways of TH were discussed. Finally, the stability of TiO2/AB and toxicity of TH were studied. The degradation efficiency was still above 85% after 5 cycles. The toxicity assessment results suggest that the aquatic toxicity of TH was effectively diminished.