A new linear form analysis of Redlich–Peterson isotherm equation for the adsorptions of dyes

Many papers report that accuracy of the Redlich–Peterson (R–P) isotherm equation (three parameters) is higher than those of Langmuir and Freundlich isotherm equations (two parameters). This paper first explains why the accuracy of the R–P isotherm equation is equal to or higher than that of two parameters isotherm equations. This study suggests a new exponential linear equation with exponent variable α, and solves the most suitable α value with the aid of Microsoft Excel and Sigma Plot 9.0. This exponential method is quick, simple, and accurate for fitting the R–P isotherm equation to experimental data sets of adsorption systems compared with a logarithmical linear form frequently used previously. This investigation prepares four kinds of pistachio shell activated carbons with various doses of NaOH for studying isotherm equilibrium adsorptions of three dyes. The R–P isotherm equation best fit adsorption system data sets studied in this work.