Removal of basic dyes from aqueous solutions by dimethyl terephthalate distillation residue

In this study the removal of basic dyes from aqueous solutions by residue acid mixture (RAM) obtained from dimethyl terephthalate distillation residue was investigated. Adsorption experiments were carried out at ambient temperature. A fixed amount of sample was immersed in 50 mL basic dye (500 mg/L) solutions. The amount of residual dye concentrations was determined using UV/Vis Spectrophotometer at wavelength 530 nm Safranine-T (ST), 622 nm Brilliant Cresyl Blue (BCB), 638 nm Nile Blue (NB) and 618 nm Brilliant Green (BG). Adsorption capacities of RAM for basic dyes decrease with the following order: BG > ST > NB > BCB. The maximum adsorption capacities for BG, NB, ST and BCB onto RAM were found to be 107, 22, 17, 13 mg/g, respectively. Adsorption kinetic data were tested using pseudo-first-order and pseudo-second-order models. The results show that the pseudo-second-order kinetic model fitted better than the data obtained from pseudo-first-order model for the adsorption of basic dyes onto RAM. Adsorption data were modeled using Langmuir and Freundlich adsorption isotherms. The result revealed that the adsorption of basic dyes onto RAM fit very well with the Langmuir isotherm model.