Removal of methylene blue from aqueous solution by adsorption onto NaOH-treated rambutan peel

Adsorption of methylene blue (MB) by NaOH-treated rambutan peel (N-RP) was examined. The adsorption experiments were carried out under different conditions of initial concentration (25-500 mg/L), solution pH 2-12 and N-RP dose (0.05-1.0 g). The influence of these parameters on the adsorption capacity was studied using the batch process. MB adsorption uptake was found to increase with increase in initial concentration and contact time. The MB adsorption was unfavourable at pH<;4. Langmuir, Freundlich and Temkin isotherm models were used to illustrate the experimental isotherms and isotherms constant. The equilibrium data were best represented by Langmuir isothem model, showing maximum monolayer adsorption capacity of 231.34 mg/g. The rates of adsorption were found to obey the rules of pseudo-second order model with good correlation. The result suggested that the N-RP would be an excellent alternative for the removal of MB by adsorption process.