9.

(A) Tartrazine yellow adsorption isotherm on residual yeast at pH 2 and (B) pH 7 (standard deviations magnified 100× for better visualization). For the isotherm tests, solutions containing 0.1 g of dry biomass and varying concentrations of tartrazine (2.5–50 mg·L^–1) were prepared in triplicate (50 mL each), adjusted to pH 2 and pH 7, and maintained at temperatures of 10, 25, 37, and 90 °C. After centrifugation (5000g, 10 min), the samples were analyzed by UV–vis spectrophotometry at 425 nm to determine Q _e and C _e using eq , as described in the Materials and Methods.