Regeneration of Rhodamine B Loaded Modified Biosorbent by a Self-Cleaning Eluent: TiO2 Hydrosol

Waste beer yeast was modified by pyromellitic dianhydride to improve its adsorption capacity for rhodamine B (RhB). Results showed that the adsorption capacity of the modified biomass for RhB was 600mgg(-1), which was about five times than that obtained on the unmodified biomass. Dye loaded modified biomass was regenerated by (1) a common eluent: HNO3 solution and (2) a self-cleaning eluent: TiO2 hydrosol, while the pH of both systems varied from 1 to 4. Desorption experimental results showed that low desorption rates were obtained in both systems after the first desorption cycle. A large volume of HNO3 solution was needed to obtain high desorption rate, and a concentrated solution of RhB was left, which brought a secondary pollution. As a self-cleaning eluent, acid TiO2 hydrosol acted both as eluent and photocatalyst. The desorbed RhB could be photodegraded under sunlight irradiation and the same hydrosol could be used in the next desorption cycle without losing its activity, which could economize large volumes of solvent. The results showed an adsorption capacity of the regenerated biosorbent for RhB of 450mgg(-1) by using hydrosol with pH 2 as eluent after four desorption/photodegradation cycles.