The intimate coupling of photocatalysis and biodegradation for the degradation and mineralization of atrazine in water

Atrazine is one of the most widely used herbicides and a main pollutant of soil and water bodies. Intimately coupled photocatalysis and biodegradation (ICPB) is an attractive technology for the treatment of wastewater, in which the microorganisms can decompose and mineralize the biodegradable intermediates generated by a photocatalytic reaction. A few works have investigated the removal of atrazine through ICPB technology, and in this work a heterojunction Bi₂WO₆/CN was designed and combined with biodegradation to remove atrazine. Bi₂WO₆/CN was adhered on the external section of a sponge carrierviaa powder spraying method and a biofilm was then cultivated in the interior of the sponge carrier. The Bi₂WO₆/CN heterojunction can produce active species like ˙OH, holes and ˙O₂⁻to break atrazine into biodegradable intermediates, which are quickly mineralized by biofilms in the interior of the carrier. The Bi₂WO₆/CN photocatalyst excited by UV-Vis light can take full advantage of the solar energy, and this heterostructure can facilitate the separation of photoinduced electron-hole pairs, hence further improving the generation of ˙OH and ˙O₂⁻. The sponge carrier can not only protect the biofilms inside from the damage of UV light and free radicals, but also can be easily recycled without secondary pollution. This work shows the potential of a Bi₂WO₆/CN based ICPB system for atrazine degradation from a practical point of view.