Application of multivariate calibration for studying competitive adsorption of two problematic colorants on acid-activated-kaolinitic clay

The competitive adsorption of two common colorants (brilliant blue and brilliant black) by activated kaolinite was investigated after fast quantification of dyes by multivariate calibration. Partial least squares, PLS, a common multivariate calibration tool, was effective for dyes quantification with high accuracy 99.4–102.1 %. The novelty of this study is the useful application of PLS for studying competitive adsorption of brilliant blue and brilliant black without the need for advanced analytical methods. Competitive adsorption isotherms of dyes were measured over the concentration range 10–30 mg/L and at 20.0, 30.0, and 40.0 °C. The maximum adsorption capacities (according to the Langmuir model) were 1644 and 1055 mg/kg for brilliant blue and brilliant black at 20.0 °C and pH 7.0, respectively. Thermodynamic analysis indicated that competitive adsorption was exothermic with ΔH° values of −20.9 and −20.3 kJ/mol for brilliant blue and brilliant black, respectively. Competitive adsorption was accomplished with a net reduction in the entropy of the system. The competition factors were 0.67 (brilliant blue) and 0.89 (brilliant black) indicating a negative competition between dyes. This study demonstrated the simple application of PLS calibration for studying competitive adsorption of colorants with minimum analytical efforts.