Photocatalytic and bactericidal behaviors of Ag/TiO2 doped biochar through Ball–milling approach

Biochar materials derived from various biomass feedstocks have attracted considerable interest as high-performance sorbents for a wide range of contaminants in wastewater. However, the diligence and preoccupation in developing multifunctional materials with interesting properties has prompted researchers worldwide to consider the functionalization of pure biochar for more beneficial applications. In this study, for the first time, a novel ternary photocatalyst was successfully prepared from date palm rachis biochar (BDPR) and silver-doped titanium dioxide (Ag/TiO2) nanoparticles with different Ag/Ti weight ratios using a simple and environmentally friendly ball milling technique. The structural and physicochemical properties of the resulting photocatalysts were investigated by various characterization methods, namely X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA) and UV-diffuse reflectance spectroscopy (UV-DRS). The photocatalytic property of the photocatalysts was evaluated through the degradation of organic dyes, namely, methylene blue (MB) and Congo red (CR). The results show that the photocatalytic activity was greatly enhanced with increasing silver content compared to the neat and TiO2-doped biochars. Complete removal of methylene blue was achieved after 90 and 75 min for 5 %Ag/TiO2-BDPR and 10 %Ag/TiO2-BDPR, respectively, while it took 150 min for 100% photodegradation of Congo red. This was due to the synergistic effect of biochar, silver and TiO2 in trapping electrons and reducing the recombination of e-/h+ pairs. In addition, the photocatalysts could be regenerated and reused for up to 5 cycles without significant degradation of their properties. Furthermore, both 5% and 10% Ag/TiO2 BDPR photocatalysts exhibited high antibacterial activity against E. coli and S. aureus bacteria due to the combined effect of biochar as a sorbent, reactive oxygen species (ROS) and silver.