Ball–milled TiO2/biochar hybrid system as a heterogeneous photocatalyst for tannery dyes removal in aqueous solution

TiO2/biochar (C/TiO2)BM hybrid photocatalytic system is prepared, for the first time, by a cost-effective method (ball-milling procedure) and used for the removal of two organic dyes, labeled as Acid Blue 7 and Red RTN, employed in the tanning industry. The physicochemical properties of the (C/TiO2)BM system are investigated by different characterization methods, evidencing the presence of TiO2 in anatase phase in the (C/TiO2)BM composite. The photocatalytic performance of (C/TiO2)BM is evaluated in the degradation of Acid Blue 7 and Red RTN in the presence of UV light irradiation. The photocatalytic results of (C/TiO2)BM show a similar degradation efficiency (about 70 %) for both dyes under UV light at the spontaneous pH of the solution (pH = 6). On the other hand, photocatalytic tests under acidic conditions (pH = 2) indicate higher adsorptive and photocatalytic properties of (C/TiO2)BM composite with an overall removal efficiency of Acid Blue 7 and Red RTN of 86 and 95 %, respectively. Finally, (C/TiO2)BM is reused for up to five cycles without loss of removal performances, underlining the stability of the composite. Therefore, the (C/TiO2)BM composite could be an effective, recyclable, and stable hybrid photocatalytic material for removing tannery dyes from aqueous solutions by adsorption/photocatalysis.