Characteristics of cationic Red X-GRL biosorption by anaerobic activated sludge

Anaerobic activated sludge (AAS) was employed for the adsorption of cationic Red X-GRL (X-GRL) from aqueous solutions. The X-GRL uptakes decreased with increases in temperature and salinity, while it was improved with increase in pH. The adsorption of X-GRL by AAS had a better agreement with a fractal-like Langmuir isotherm than a typical Langmuir isotherm. The adsorption rate coefficients at different time had a power-law relationship with time. The surface dimension was positively related to the X-GRL uptakes. The X-GRL uptake by the EPS accounted for only ∼19% of the total adsorption. The X-GRL adsorption was therefore largely attributed to the active groups on the cell wall. FTIR analysis showed that –CH2 and –NH2 groups were not responsible for the adsorption, which indicated chemical adsorption was negligible.