Adsorption isotherm models for basic dye adsorption by peat in single and binary component systems

Colored effluents from textile industries are a problem in many rivers and waterways. Prediction of dye adsorption capacities is important in design considerations. The sorption of three basic dyes, namely Basic blue 3, Basic yellow 21, and Basic red 22, onto peat is reported. Equilibrium sorption isotherms have been measured for the three single-component systems. Equilibrium was achieved after 21 days. The experimental isotherm data were analyzed using Langmuir, Freundlich, Redlich-Peterson, Tempkin, and Toth isotherm equations. A detailed error analysis has been undertaken to investigate the effect of using different error criteria for the determination of the single-component isotherm parameters and hence obtain the best isotherm and isotherm parameters which describe the adsorption process. The linear transform model provided the highest R(2) regression coefficient with the Redlich-Peterson model. The Redlich-Peterson model also yielded the best fit to experimental data for all three dyes using the nonlinear error functions. An extended Langmuir model has been used to predict the isotherm data for the binary systems using the single component data. The correlation between theoretical and experimental data had only limited success due to competitive and interactive effects between the dyes and the dye-surface interactions.