Algae decorated TiO2/Ag hybrid nanofiber membrane with enhanced photocatalytic activity for Cr(VI) removal under visible light

Algae as an abundant natural biomass, more attention has been paid to explore its potential application in environmental pollutants treatment. This work prepared the algae-TiO 2 /Ag bionano hybrid material by loading algae cells on the ultrafine TiO 2 /Ag chitosan hybrid nanofiber mat. For the first time, the synergistic photocatalytic effect of fresh algae and TiO 2 /Ag nanomaterial was investigated by removal of Cr(VI). The addition of algae significantly improved the photo-removal of Cr(VI) in the system with TiO 2 /Ag hybrid nanomaterial under visible light irradiation. Meanwhile, the photocatalytic mechanism was studied. The photogenerated reactive oxygen species were quantified and the addition of algae apparently decreased the yields of OH to 31.0   μM, while improved the yields of 1 O 2 and O 2 − in the reaction system with TiO 2 /Ag hybrid nanofiber mats. The change of superoxide dismutase activity and malondialdehyde content in algae indicated that TiO 2 /Ag could impose oxidative stress and cause lipid peroxidation in algae cells. During the course of irradiation, algae released substances could act as scavenger for holes, thus inhibited the recombination of hole/electron and enhanced the photocatalytic reduction of Cr(VI) by electrons on TiO 2 surface. Algae was simultaneously photodegraded in the system and the resulting O 2 − , organic free radicals could promote the reduction of Cr(VI). This functional hybrid nanofiber mat was easily recovered and maintained a great photocatalytic activity on the five successive cycles. This algae-photocatalyst hybrid material has promising applications potential in heavy metal removal and organic pollutants treatment.