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

ABSTRACT

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 (q(m)) 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 TiO(2) 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 TiO(2) hydrosol after 30 h desorption at the first desorption cycle, and the desorbed dye in TiO(2) 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 TiO(2) hydrosol had great potential in practical use.