Equilibrium and Adsorption Studies of Malachite Green onto Melon Seed Shell Activated Carbon

Abstract

The aim of the study is to produce activated carbon using melon seed shell which is harmless, cheaper, and abundant agricultural raw material with HNO3 as an activating agent to remove malachite green from aqueous solution. Two step processes which involve carbonisation of the powder melon seed shell follow by activation of the carbon were used for the production of the activated carbon. Experimental data were analyse using Langmuir, Freundlich, Temkin and Harkin’s-Jura adsorption isotherms. Characteristics of the activated carbon values are: pH = 6.18±0.02, 7.24±0.01, 7.12±0.01; conductivity (μS/cm) = 1.50±0.01, 1.60±0.01, 1.80±0.01; bulk density (g/cm3) = 9.76±0.01, 9.15±0.06, 8.34±0.01; % yield = 56.63±0.02, 22.32±0.01, 13.54±0.03; % burn off = 43.41±0.01, 77.73±0.04, 86.50±0.02; for AC1 (activated carbon 1), AC2 (activated carbon 2) and AC3 (activated carbon 3) respectively. Isothetrm parameters obtained for Langmuir are R2 = 0.9461, 0.9183, 0.9653 and RL= 0.0468, 0.4640, 0.0712 for AC1, AC2 and AC3; for Freundlich are R2 =0.9288, 0.8991, 0.9705 and n = 0.25, 0.41, 0.65 for AC1, AC2 and AC3; for Temkin are R2 = 0.8273, 0.8430, 0.9019 for AC1, AC2 and AC3; for Harkin’s-jura are R2 = 0.8538, 0.8345, 0.8244 for AC1, AC2 and AC3. Adsorption capacity at equilibrium tends to increase as the initial concentration increases. Langmuir adsorption isotherm best described the adsorption processes because of the higher R2 values.