Desorption behavior of methylene blue on pyromellitic dianhydride modified biosorbent by a novel eluent: Acid TiO2 hydrosol

In this study, waste beer yeast powder was modified by pyromellitic dianhydride to improve its adsorption capacities for cationic dye: methylene blue (MB). According to the Langmuir equation, the maximum uptake capacities (qm) of the modified biomass for MB was 830.8 mg g−1, which was about five times than that obtained on the unmodified biomass. Adsorption mechanism was investigated by FTIR. Desorption kinetics of methylene blue in six solvents: HCl (0.1 mol L−1), ethanol, mixtures of HCl (0.1 mol L−1) and ethanol with different volume ratio and a self-clean eluent: acid TiO2 were studied in details. Results showed that desorption kinetics curve fit the two-step kinetic model, and methylene blue release process was distinctly divided into two steps: rapid and slow desorption steps. 52.2% of the methylene blue could be desorbed into TiO2 hydrosol after 30 h desorption at the first desorption cycle, and the desorbed dye in TiO2 hydrosol could be degrade completely under sunlight irradiation. After three desorption-photodegradation cycles, 80.0% of the absorbed dyes could be desorbed from the surface of the modified biomass. Although there was much work to do, the self-clean eluent: TiO2 hydrosol had great potential in practical use.