Adsorption of methylene blue and rhodamine B on baker's yeast and photocatalytic regeneration of the biosorbent

Biomass of baker's yeast was used as biosorbent for the removal of methylene blue and rhodamine B, and the dyes-loaded biomass was regenerated by acid TiO2 hydrosol. Adsorption experiments showed that the uptake of the two dyes followed the Langmuir monolayer adsorption models, and the kinetics of dyes adsorption fit better to the pseudo-second-order equation than to the pseudo-first-order equation. Since biosorption cannot detoxify the dyes, regeneration of the biosorbent and simultaneous photodegradation of the desorbed dyes by acid TiO2 hydrosol were attempted at the first time. The acid TiO2 hydrosol was prepared by sol–gel method. The photocatalytic regeneration experiments showed that the two dyes could be desorbed at the acid condition, and the time for degradation of methylene blue and rhodamine B was 100 and 50 min, respectively. The treatment for dyes by integrating biosorption and photocatalytic degradation results in no secondary pollution in the form of any concentrated wastes, which is an environmentally acceptable option.