Kinetic and isotherm studies of Malachite green dye removal using onion peel

Abstract

The utilization of onion peel is introduced as a new absorbent for the removal of cationic dye, Green Malachite from the aqueous solution. Various parameters, including pH (5-9), initial solution concentration (100-700 mg L-1), adsorbent dosage (2.5-20 mg), were used to study the effects on Green Malachite biosorption. The results appeared that the adsorption process took place well in alkaline condition with optimum pH 9. The adsorption rate decreased when the temperature increases showing the adsorption process is exothermic. The adsorption will see with increase in adsorbent dosage and initial dye concentration. However the percentage of removal decreased once the amount of dosage reaches more than 10 mg. The equilibrium data fitted better in Langmuir model, although it also can fit into Freundlich model demonstrate that the adsorption occurs at heterogeneous sites and multilayer biosorption. The adsorption process followed the pseudo-first order kinetic model showing chemisorption was involved during adsorption process.