The main aim of the study was to find out the influence of pH and the molecular weight of the dye molecules on adsorption isotherm models using activated carbon in a single solid–liquid system. In this study we derived activated carbon from the waste biomass of wood apple rind. Batch mode experiments were carried out in order to assess the influence of the initial pH and molecular weight of the dye on adsorption capacity of the carbon. Two basic dyes namely Methylene blue and Crystal violet having different molecular structures have been chosen. To find out the pH effect on the adsorption capacity of the activated carbon, the equilibrium isotherm experiments were carried out by varying the pH of the dye solutions by fixing the carbon dose as constant. A separate study was carried out to note down the change in pH of the dye solution during the adsorption of cationic dye molecules on the activated carbon surface. The adsorption capacity of the activated carbon increased while increasing the pH of the dye solution. The structure of the dye molecules and the nature of pores present on the surface of the activated carbon also decide the adsorption capacity of the carbon.
