Removal of hexavalent chromium and methylene blue in aqueous solutions using activated carbon prepared from rubber seed shell

In the present study, the prepared rubber seed shell charcoal (RSS-CH) and activated carbon (RSS-AC) from rubber seed shell (RSS) were used as biosorbent for the removal of Cr(VI) and methylene blue (MB) from aqueous solutions. The surface characterizations of RSS, RSS-CH, and RSS-AC materials were performed using scanning electron microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The adsorption capacity of adsorbents was investigated by varying the pH, initial concentration, contact time, and temperature. The pH value on the solution had significant effect for the adsorption process, in which the optimum pH for adsorption of Cr(VI) and MB was 3 and 7, respectively. The adsorption isotherm of Cr(VI) was described by the Freundlich model while the adsorption process of MB fitted well with Langmuir model. The adsorption behavior of Cr(VI) and MB was described by pseudo-second-order kinetic model with R-2 similar to 0.99. Moreover, the maximum adsorption capacities of Cr(VI) on the RSS-CH and RSS-AC were 75.76 and 125 mg/g, respectively. For MB adsorption, maximum adsorption capacities on the RSS-CH and RSS-AC were 217.39 and 370.37 mg/g, respectively. The adsorption efficiency of Cr(VI) and MB on the RSS-AC showed greater than those of the RSS-CH. Thus, the RSS-AC is a suitable, alternative, and high adsorption efficiency adsorbent for the removal of heavy metal and dye contaminants in wastewater.